SPC MD 1786

MD 1786 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR SOUTHWEST LOWER MICHIGAN...NORTHWEST INDIANA

Mesoscale Discussion 1786
NWS Storm Prediction Center Norman OK
0604 PM CST Tue Nov 10 2020

Areas affected...Southwest Lower Michigan...Northwest Indiana

Concerning...Severe potential...Watch possible 

Valid 110004Z - 110200Z

Probability of Watch Issuance...60 percent

SUMMARY...Damaging winds are possible with convection this evening.

DISCUSSION...Strongly forced squall line remains organized as it
progresses across southern lake Michigan this evening. Northern
portions of this line have been efficient in producing severe wind
gusts in excess of 50kt. While buoyancy is not as great over lower
MI, lower 60s surface dew points have crept north along the
southeastern shore of LM. With time this linear MCS should begin to
diminish; however, strength of upper support and forward propagation
speed in excess of 40kt suggests the risk of damaging winds is
increasing across southwestern lower MI and northwestern IN.

..Darrow/Guyer.. 11/11/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...IWX...GRR...LOT...

LAT...LON   41608754 43868644 43688524 42008590 41168685 41608754 

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SPC MD 1768

MD 1768 CONCERNING TORNADO WATCH 502... FOR PARTS OF SOUTHEASTERN MISSISSIPPI THOUGH MUCH OF SOUTHWESTERN ALABAMA

Mesoscale Discussion 1768
NWS Storm Prediction Center Norman OK
0623 PM CDT Wed Oct 28 2020

Areas affected...Parts of southeastern Mississippi though much of
southwestern Alabama

Concerning...Tornado Watch 502...

Valid 282323Z - 290130Z

The severe weather threat for Tornado Watch 502 continues.

SUMMARY...The risk for storms capable of producing tornadoes is
beginning to increase, and likely will maximize across and northeast
of the Mobile AL area by around 8-9 PM CDT.

DISCUSSION...The low-level circulation center of Zeta is migrating
northeastward at 20-25 kt, inland of the southeastern Louisiana
coast, and appears likely to continue rapidly across the New Orleans
vicinity into southeastern Mississippi through 01-03Z.  Although it
will probably undergo at least some weakening, southeasterly to
southerly flow on its eastern/northeastern periphery around the 850
mb level may be maintained at 50-80+ kt.  This will contribute to
considerable enlargement of clockwise curved low-level hodographs
inland of coastal areas during the next few hours. 

Latest NAM and Rapid Refresh forecast soundings indicate that
low-level hodographs will become maximized across the Mobile through
Evergreen AL vicinity, where mid 70s F surface dew points are
already present and contributing to modest boundary-layer CAPE ahead
of the mid-level warm core.  A number of storms with embedded
low-level mesocyclones are evident within the corridor of stronger
low-level shear, in outer bands offshore, but already beginning to
pivot inland of far southeastern Mississippi coastal areas.  As
these continue to spread and/or develop inland, occasional
intensification probably will be accompanied by a risk for
tornadoes.  One or two of these could be briefly strong.

..Kerr.. 10/28/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...TAE...BMX...MOB...LIX...

LAT...LON   31158862 32418772 32438671 31128612 30578663 30418782
            30288853 31158862 

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SPC MD 1759

MD 1759 CONCERNING WINTER MIXED PRECIPITATION FOR NORTHWEST TX...WESTERN/CENTRAL OK

Mesoscale Discussion 1759
NWS Storm Prediction Center Norman OK
0419 AM CDT Tue Oct 27 2020

Areas affected...Northwest TX...Western/Central OK

Concerning...Winter mixed precipitation 

Valid 270919Z - 271315Z

SUMMARY...Freezing rain and sleet will increase across far northwest
TX and western/central OK over the next few hours. Relatively high
precipitation rates and lightning are possible within the deeper
convective cells.

DISCUSSION...A large precipitation shield, with numerous embedded
convective elements, continues to spread northeastward ahead of the
shortwave trough moving into the southern High Plains. Recent
surface observations place the freezing line from near BKD in North
Texas northeastward through south-central OK to just north of TUL in
northeast OK. The majority of the precipitation spreading
northeastward will remain north of this line. 06Z regional soundings
as well as the latest RAP forecast soundings also show a
well-defined warm layer between 850 mb and 700 mb, with maximum
temperatures from 4 to 8 deg C. Some modest instability also exists
above this layer between the warm nose and the cold mid-level
temperatures. These thermal profiles support a mix of sleet and
freezing rain, as well as lightning within the deep cores. Based on
recent radar and lightning trends, the highest precipitation rates
over the next few hours are expected from parts of northwest TX into
central OK.

..Mosier.. 10/27/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FWD...OUN...LUB...AMA...

LAT...LON   34450045 36310000 36779853 36229735 35279692 33849795
            33509866 33579971 34450045 

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SPC Oct 27, 2020 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0332 AM CDT Tue Oct 27 2020

Valid 301200Z - 041200Z

...DISCUSSION...
A quiescent period for severe thunderstorms will begin on Friday
(day 4) and continue through next Tuesday (day 8) as the large-scale
upper-air pattern features a mean trough over the eastern U.S. for
much of the extended period.  Dry offshore flow will occur over the
Gulf of Mexico through the period and lead to hostile conditions for
thunderstorm development.

Read more

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SPC Oct 27, 2020 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0208 AM CDT Tue Oct 27 2020

Valid 291200Z - 301200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
SOUTHEAST AND VIRGINIA...

...SUMMARY...
A conditional risk for a tornado may exist Thursday morning for
adjacent parts of Alabama, Georgia, and the Florida Panhandle in
association with tropical cyclone Zeta.  An isolated threat for
damaging thunderstorm gusts may develop over the Carolinas and
southern Virginia Thursday night.

...Synopsis...
A fairly complex scenario with relative higher uncertainty is
forecast for the day 3 period over the Southeast into the Carolinas
and VA.  Tropical cyclone Zeta will move from the AL/GA vicinity
west of Atlanta and accelerate rapidly northeastward reaching
Chesapeake Bay by early Thursday evening according to the latest
National Hurricane Center forecast.  The risk for a tornado may
linger during the morning from parts of the FL Panhandle
northeastward into central GA before low-level flow veers as Zeta
becomes increasingly displaced from the region.  Only marginal
instability is expected to penetrate the areas north of the
immediate coastal counties with less-available instability farther
north into southwest GA.  Nonetheless, a conditional risk for a
supercell or two capable of a tornado could continue from the late
Day 2 period into Day 3 across this region.  

By early evening, a mid-level low will open and feature a
strengthening jet (100 kt at 500 mb) moving from northern AL
northeastward across the Carolinas into southeast VA by early Friday
morning.  Significant mid-level height falls (120-180 m at 500 mb)
will overspread central NC Thursday night.  Concurrently, a cold
front is forecast to sweep eastward across the southern Appalachians
with intensifying frontal forcing in lee of the higher terrain. 
Model guidance currently indicates a moist boundary layer will
become conditionally unstable with a cluster or band of storms
potentially developing after dark.  The transport of higher momentum
aloft to the surface could materialize with a risk for damaging
gusts.

..Smith.. 10/27/2020

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SPC MD 1758

MD 1758 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF WEST TEXAS AND FAR WESTERN OKLAHOMA

Mesoscale Discussion 1758
NWS Storm Prediction Center Norman OK
1222 AM CDT Tue Oct 27 2020

Areas affected...portions of west Texas and far western Oklahoma

Concerning...Winter mixed precipitation 

Valid 270522Z - 271115Z

SUMMARY...Forcing for ascent will gradually overspread the
discussion area from west to east, resulting in a broad area of
icing through 11Z Tuesday.

DISCUSSION...At 05Z, mid-level frontogenetical forcing was beginning
to induce areas of light to moderate precipitation in western
portions of the discussion area.  The forcing was occurring atop a
cold, yet moist low-level airmass, with an appreciable warm nose
(4-7C at 700 hPa) favoring a mix of sleet and freezing rain as the
precipitation shield continues to expand.  Resultant profiles also
suggest potential for robust, lightning-producing convection that
may also enhance precipitation rates in a few areas.  Over the next
several hours, models indicate that this precipitation shield will
expand while migrating northeastward.  Freezing-rain rates should
exceed 0.05-0.1 inch per hour for several hours on the southern and
eastern extent of the discussion area (generally from Midland to
Abilene to Altus) where shallower cold air should limit the amount
of refreezing of precipitation.  Farther north, deeper cold air
should tend to support more sleet, with accumulations of 0.25 to 0.5
inch sleet per three hours possible in a few areas.

..Cook.. 10/27/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...OUN...SJT...LUB...AMA...MAF...ABQ...

LAT...LON   35020302 35620272 36280184 36580014 36249947 35499922
            34439927 33839934 32429937 31389960 30789996 30510071
            30290171 30310248 30750297 31590341 32440341 35020302 

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SPC Oct 27, 2020 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1240 AM CDT Tue Oct 27 2020

Valid 271200Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected across the contiguous United
States on Tuesday.

...Discussion...

Early-morning water-vapor imagery depicts a well-defined upper low
moving south toward the AZ/Mexico border. This feature is forecast
to begin advancing east along the international border later this
morning, then into extreme southwest NM by late afternoon. Very cold
continental surface high has settled into the central Plains with
the leading edge of this air mass now to the coastal plain of TX.
Latest model guidance continues to suggest low-level warm advection
will focus along a corridor from the Edwards Plateau-northwest
TX-central OK. This zone will be the primary area of concern for
elevated convection through the period.

Currently, the leading edge of large-scale forcing for ascent
appears to be spreading across the southern Rockies into far west
TX, per moistening observed at mid levels in water vapor imagery.
Scattered showers are now developing across the southern High Plains
in response, and these showers should eventually deepen sufficiently
for lightning. Much of this activity will develop atop sub-freezing
boundary-layer temperatures and significant icing may ultimately be
noted along the aforementioned corridor.

Farther southeast across the Gulf Coast region, a strong mid-level
Bermuda high will forcing deep southerly trajectories across the
Gulf Basin ahead of Hurricane Zeta. While Zeta will not reach the
central Gulf Coast during the day1 period, moisture will begin to
spread inland such that isolated thunderstorms will be possible,
despite the poor low-level lapse rates and overall weak buoyancy.

..Darrow.. 10/27/2020

Read more

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SPC Oct 27, 2020 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1226 AM CDT Tue Oct 27 2020

Valid 281200Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR FAR SOUTHERN
ALABAMA AND THE WESTERN FLORIDA PANHANDLE...

...SUMMARY...
A couple tornadoes are possible beginning Wednesday afternoon
through Wednesday night over parts of the central Gulf Coast states
in association with Zeta.

...Central Gulf Coast...
Tropical cyclone Zeta will approach the coast and subsequently move
inland during the period.  The influx of a tropical airmass
(characterized by mid 70s surface dewpoints) will gradually spread
inland over southeast LA and the immediate coastal areas of MS/AL/FL
Panhandle during the day.  Forecast soundings show hodographs
enlarging initially over southeast LA and later along the MS/AL/FL
Panhandle coasts by late afternoon.  Sufficient buoyancy and
enlarged hodographs (0-1 km SRH 300-600 m2/s2) will probably yield
the development of several mini supercells in the outer bands of
Zeta.  It appears the greatest tornado risk will be confined to far
southern AL and the FL Panhandle where larger CAPE (500-1000 J/kg)
and SRH will spatiotemporally overlap.  Considerable uncertainty
remains how far inland a low/conditional supercell-tornado risk will
develop late overnight (i.e., east-central AL and adjacent parts of
GA).

..Smith.. 10/27/2020

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SPC Oct 27, 2020 0100 UTC Day 1 Convective Outlook

SPC 0100Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0740 PM CDT Mon Oct 26 2020

Valid 270100Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not expected across the
contiguous U.S. through tonight.

...01z Update...

Minor changes have been made to the 20z outlook this evening, namely
to lower thunder probabilities across most of the FL Peninsula.
Earlier convection that developed across the southwestern portions
of the Peninsula have propagated northwest with most lightning now
offshore. 01z product will reflect this evolution.

Farther west across the south-central US, isentropic ascent atop
cold boundary layer will be the primary forcing mechanism for
elevated convection later tonight. Earlier thunderstorm activity
that developed across the southern Plains has moved into the Ozark
Plateau region and weakened with minimal lightning observed.
However, buoyancy remains across the southern Plains and the next
short-wave trough will approach this region after midnight. At that
time, renewed thunderstorm activity is expected.

..Darrow.. 10/27/2020

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SPC MD 1756

MD 1756 CONCERNING WINTER MIXED PRECIPITATION FOR TX PANHANDLE...WESTERN/CENTRAL OK...SOUTH-CENTRAL/SOUTHEAST KS

Mesoscale Discussion 1756
NWS Storm Prediction Center Norman OK
0541 AM CDT Mon Oct 26 2020

Areas affected...TX Panhandle...Western/Central
OK...South-Central/Southeast KS

Concerning...Winter mixed precipitation 

Valid 261041Z - 261445Z

SUMMARY...Mixed winter precipitation, including sleet, will continue
for the next several hours from the southern TX Panhandle through
western/central OK and into south-central KS. Lightning and
relatively high precipitation may occur within the stronger cells.

DISCUSSION...Regional radar imagery has shown an increase in
precipitation coverage over the last few hours. This increase is
likely the result of persistent isentropic ascent across the shallow
front as well as strengthening large-scale ascent attendant to an
approaching shortwave trough. Thus far, a predominantly banded
precipitation structure has been observed, but radar trends across
the east-central and southeast TX Panhandle suggest a transition to
a more uniform precipitation shield may be occurring. Elevated
instability has contributed to lightning within a few of these
bands, particularly on the leading edge of the precipitation
(currently from SNK northeastward through TUL and into far southeast
KS).

Given the expectation for continued ascent across the front and the
radar trends suggesting higher precipitation coverage, the potential
for freezing rain and sleet will continue from the southern TX
Panhandle across western/central OK into south-central/southeast KS.
Modest instability will contribute to occasionally stronger
convection capable of lightning and relatively high precipitation
rates throughout the morning.

..Mosier.. 10/26/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...TSA...ICT...OUN...DDC...LUB...AMA...

LAT...LON   35210211 37039936 37999711 36859597 35389806 33900070
            33120218 35210211 

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SPC MD 1755

MD 1755 CONCERNING WINTER MIXED PRECIPITATION FOR FAR EAST-CENTRAL NM...MUCH OF THE TX PANHANDLE...WESTERN OK/EASTERN OK PANHANDLE

Mesoscale Discussion 1755
NWS Storm Prediction Center Norman OK
0117 AM CDT Mon Oct 26 2020

Areas affected...Far East-Central NM...Much of the TX
Panhandle...Western OK/Eastern OK Panhandle

Concerning...Winter mixed precipitation 

Valid 260617Z - 261015Z

SUMMARY...Mixed winter precipitation, predominantly sleet, is
expected this morning from far east-central NM across the TX
Panhandle into western OK.

DISCUSSION...Regional radar imagery has shown an increase in
precipitation coverage during the past few hours as isentropic
ascent persists across the southern Plains/southern High Plains. 00Z
AMA sounding sampled a shallow cold layer well, revealing a cold
layer extending to 850 mb (about 1 km deep). Above this cold layer,
warm temperatures associated with the persistent southwesterly flow
aloft resulted in a strong inversion, with 700 mb temperatures near
7 to 8 deg C. This results in a thermodynamic profile supporting
mixed precipitation, predominantly sleet, once the mid-level layer
moistens enough to erode the dry layer in place. The increase in
precipitation coverage noted in regional radars is likely evidence
of that ongoing moistening process, which is expected to continue
and will soon support precipitation reaching the surface over much
of this region. 

Given the anticipated persistence of the southwesterly flow aloft
and resulting maintenance of the warm layer aloft, the expectation
is for an area of mixed winter precipitation to develop from far
east-central NM across the TX Panhandle in western OK/eastern OK
Panhandle. Sleet is expected to be the dominant precipitation type.
Additionally, elevated instability, based the at the top of the warm
layer around 700 mb, could contribute to higher precipitation rates
as well as occasional lightning. Current observations show lightning
within the precipitation band from Potter County TX into Harper
County OK.

..Mosier.. 10/26/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...OUN...DDC...LUB...AMA...ABQ...

LAT...LON   35500332 36190236 37200002 36959882 36039911 35399962
            34630075 34150235 34130337 34390375 34850375 35500332 

Read more

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SPC MD 1754

MD 1754 CONCERNING HEAVY SNOW FOR WEST-CENTRAL TO SOUTH-CENTRAL CO

Mesoscale Discussion 1754
NWS Storm Prediction Center Norman OK
0617 PM CDT Sun Oct 25 2020

Areas affected...West-central to south-central CO

Concerning...Heavy snow 

Valid 252317Z - 260315Z

SUMMARY...Heavy snow that has affected portions of the Upper CO
Valley along the I-70 corridor should shift south and may subside,
while a separate band of heavy snow likely forms across portions of
the Upper AR Valley, including the I-25 corridor near Pueblo.
Snowfall rates of 2-3 inches/hour are expected in the stronger
bursts.

DISCUSSION...Intense frontogenetic forcing for ascent associated
with a very tight thermal gradient arcing in a zigzag pattern across
west-central to south-central CO has supported a persistent band of
heavy snow just to the cold side of the slowly-southward shifting
surface front. This band of heavy snow has recently affected the
I-70 corridor in the Upper CO Valley. Radar/satellite imagery
suggest a separate band of probable heavy snow is beginning to form
off the northern Sangre de Cristos as elevated convection with CG
lightning that formed farther west-southwest overspreads this
portion of the baroclinic zone. Both convection allowing and
parameterized guidance are largely consistent in suggesting that
this will be the favored corridor for persistent heavy snow through
the evening. Rates should reach 2-3 inches/hour in the stronger
convective bursts that affect lower terrain across the Upper AR
Valley across portions of I-25 from near Pueblo to Trinidad.

..Grams.. 10/25/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...PUB...BOU...GJT...

LAT...LON   38590514 38560478 38530422 38280413 37790414 37240433
            37090476 37500510 37910555 38090613 38370654 38500702
            38430785 38520834 38710861 39130865 39390814 39560775
            39560713 39580659 38700555 38590514 

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SPC MD 1748

MD 1748 CONCERNING HEAVY SNOW FOR NORTH CENTRAL SOUTH DAKOTA...SOUTHERN NORTH DAKOTA AND WEST CENTRAL MINNESOTA

Mesoscale Discussion 1748
NWS Storm Prediction Center Norman OK
0956 PM CDT Wed Oct 21 2020

Areas affected...north central South Dakota...southern North Dakota
and west central Minnesota

Concerning...Heavy snow 

Valid 220256Z - 220600Z

SUMMARY...Periods of heavy snow with rates of 1 to 2 inches per hour
appear likely across portions of the Dakotas and western Minnesota
tonight.

DISCUSSION...00z observed soundings and evening water vapor imagery
showed a mid-level shortwave trough and jet streak amplifying across
the northern Rockies. Downstream of the trough across western South
Dakota, radar showed a broad area of stratiform precipitation
developing from increasing synoptic lift ahead of the trough. Model
soundings show widespread isentropic ascent with strong low and
mid-level warm advection across much of South Dakota. This strong
lift will support mesoscale banding in the precip shield late this
evening and overnight. Heavy snowfall rates of 1 to 2 inches per
hour will be likely as these bands develop and move northeastward.
Current model guidance suggests the most likely time frame for the
heaviest snowfall rates will be between 6 and 9 UTC across north
central South Dakota. With time, the heavier snow axis should shift
northeastward and weaken as it moves into portions of southeast
North Dakota and perhaps west central Minnesota.

..Lyons/Grams.. 10/22/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FGF...ABR...BIS...UNR...

LAT...LON   45199812 44969963 44950097 45170170 45460201 45740218
            46020192 46310036 46529857 46419714 46269612 45889618
            45539702 45339748 45199812 

Read more

from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1748.html

SPC MD 1747

MD 1747 CONCERNING HEAVY SNOW FOR NORTHEAST WI/CENTRAL UPPER MI

Mesoscale Discussion 1747
NWS Storm Prediction Center Norman OK
0706 PM CDT Tue Oct 20 2020

Areas affected...Northeast WI/central Upper MI

Concerning...Heavy snow 

Valid 210006Z - 210400Z

SUMMARY...Hourly snowfall rates approaching 1" will be possible
through about 05z, with a diminishing threat for locally heavy snow
thereafter.

DISCUSSION...In advance of a midlevel shortwave trough crossing the
upper MS Valley, a zone of strong low-midlevel warm advection is
ongoing across central/northern WI.  Ascent is resulting in
saturation and widespread precipitation formation from central WI
northward, and the combination of wet bulk cooling/melting has
resulted in surface temperatures near 32 F across northwest and
north central WI.  The zone of ascent and modest low-level cooling
will spread northeastward toward central Upper MI this evening in
tandem with the heavier precipitation rates, where snow is the
likely precipitation type.  The warm advection will tend to support
a broad zone of precipitation formation given the stable midlevel
lapse rates, with the heavier precipitation rates (and greater
snowfall potential) expected along and 1-2 counties north of the
surface 32 F line.  Though focused banding is not expected given
only weak frontogenesis, local snowfall rates could approach 1"/hour
before the snow diminishes from southwest-to-northeast across
central Upper MI toward about 05z.

..Thompson.. 10/21/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MQT...GRB...ARX...

LAT...LON   46828776 46458769 46108776 45738786 45258825 44768889
            44508965 44769004 45309004 45778939 46898802 46828776 

Read more

from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1747.html

SPC MD 1743

MD 1743 CONCERNING SEVERE THUNDERSTORM WATCH 500... FOR EASTERN NEBRASKA AND FAR WESTERN IOWA

Mesoscale Discussion 1743
NWS Storm Prediction Center Norman OK
0902 PM CDT Sun Oct 11 2020

Areas affected...eastern Nebraska and far western Iowa

Concerning...Severe Thunderstorm Watch 500...

Valid 120202Z - 120400Z

The severe weather threat for Severe Thunderstorm Watch 500
continues.

SUMMARY...The potential for severe wind will continue for portions
of central Minnesota as well as eastern Nebraska and far western
Iowa through at least 03 UTC.

DISCUSSION...Recent radar trends from MN show an organized squall
line, which suggests that 40-45 knot effective bulk shear is
compensating for relatively weak (around 500 J/kg MLCAPE)
instability. Convection will likely begin to diminish as it moves
eastward into the cool side of a diffuse surface warm front, but
will continue to pose a severe wind potential in the near term
(through at least 03 UTC) for central MN. With temperatures in the
mid 60s (and dewpoints in the 40s) across eastern MN, a downstream
watch is not anticipated at this time. 

Further south, the cold front has overtaken the main line of storms
per recent surface and radar observations from KOAX. This will
further favor a linear storm mode for the rest of the evening.
Despite increasing inhibition from nocturnal cooling, stronger
ascent associated with the cold front should maintain convection for
the next few hours. Downward trends in MRMS vertically integrated
ice and warming IR cloud top temperatures, combined with a
transition to a linear storm mode, suggest a downward trend in the
hail potential overall, though a few instances of severe hail can
not be ruled out with any stronger updraft pulses. Although severe
wind is possible along the entirety of the line, portions of
southeast NE may see a locally higher wind threat associated with
accelerating convection along the cold frontal surge.

..Moore/Dial.. 10/12/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MPX...DMX...FSD...OAX...GID...

LAT...LON   40979791 42009666 42409634 42849593 43769563 44629550
            45269523 45759511 45929479 45859429 45329389 44969383
            44489390 43889416 43149459 42549494 41999520 41659539
            41169556 40739560 40459611 40429688 40569759 40979791 

Read more

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SPC MD 1742

MD 1742 CONCERNING SEVERE THUNDERSTORM WATCH 500... FOR THE EAST CENTRAL AND NORTHERN PLAINS INTO THE UPPER MIDWEST

Mesoscale Discussion 1742
NWS Storm Prediction Center Norman OK
0650 PM CDT Sun Oct 11 2020

Areas affected...the east central and northern Plains into the upper
Midwest

Concerning...Severe Thunderstorm Watch 500...

Valid 112350Z - 120145Z

The severe weather threat for Severe Thunderstorm Watch 500
continues.

SUMMARY...The threat for severe wind and hail will continue across
WW 500 for the next 1-2 hours, especially across southeast South
Dakota, eastern Nebraska, and adjacent areas of Iowa and Minnesota.
A transition to primarily a wind threat is expected heading into the
late evening.

DISCUSSION...Thunderstorm coverage continues to increase from
northwest MN southward into eastern NE as an east/southeast surging
cold front begins to overtake the leading surface trough that has
acted as the focus for initial convection. Deep layer flow
orientated along this boundary has lead to largely broken line
segments and transient discrete modes across the eastern Dakotas and
west/southwest MN. Storm interactions and a narrow axis of
instability has largely limited the severe potential thus far, and
will likely continue to do so into the late evening hours. However,
a brief severe wind, and perhaps severe hail, threat will remain
possible with any stronger convection that can remain organized as
storms moves into central MN where effective bulk shear is slightly
stronger due to backed low-level flow in the vicinity of a diffuse
surface warm front.

Further south into the SD/NE/IA/MN region, a stronger zonal
component to upper-level winds has allowed for more persistent
discrete modes. Effective bulk shear values on the order of 30-40
knots will continue to favor supercellular characteristics and
support the potential for severe hail and strong winds in the near
term. Eventual upscale growth into linear modes (and an associated
increase in severe wind potential) is still expected as the cold
front catches up with the primary convective line through the
evening.

..Moore/Dial.. 10/11/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MPX...DMX...FGF...FSD...OAX...ABR...GID...

LAT...LON   46239670 46549611 46359541 45309477 44469478 43149499
            41929540 41249584 41029672 40979727 41059772 41299779
            41959748 42919708 43649691 44229682 45069677 46239670 

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SPC MD 1730

MD 1730 CONCERNING TORNADO WATCH 497... FOR PARTS OF SOUTHERN ALABAMA AND INTO WESTERN PORTIONS OF THE FLORIDA PANHANDLE

Mesoscale Discussion 1730
NWS Storm Prediction Center Norman OK
0709 AM CDT Sat Oct 10 2020

Areas affected...parts of southern Alabama and into western portions
of the Florida Panhandle

Concerning...Tornado Watch 497...

Valid 101209Z - 101415Z

The severe weather threat for Tornado Watch 497 continues.

SUMMARY...Risk for brief tornadoes continues across Tornado Watch
497, in conjunction with Tropical Storm Delta.

DISCUSSION...Latest radar loop shows the center of Tropical Storm
Delta near the intersection of the Arkansas/Louisiana/Mississippi
borders.  A primary band of convection east/southeast of Delta's
center continues advancing eastward across southwestern Alabama,
while individual convective elements move quickly northward.

Within this band of low-topped convection, occasional cells have
exhibited low-level rotation, with at least one confirmed tornado
earlier this morning.  While a moist boundary layer resides ahead of
the convective band, CAPE remains limited, particularly with
northward extent into central Alabama.  Still, low-level flow
veering/increasing with height is yielding shear quite favorable for
occasional low-level rotation within sustained updrafts.  As such,
the risk for brief tornadoes will continue across the watch area.

..Goss.. 10/10/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...TAE...MOB...

LAT...LON   31798779 31808703 31678656 30438638 29638700 29868775
            29948800 31798779 

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SPC Tornado Watch 497 Status Reports

WW 0497 Status Updates

STATUS FOR WATCH 0497 HAS NOT BEEN ISSUED YET

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SPC MD 1729

MD 1729 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF SOUTHEASTERN MISSISSIPPI...SOUTHWESTERN ALABAMA...AND WESTERN PORTIONS OF THE FLORIDA PANHANDLE

Mesoscale Discussion 1729
NWS Storm Prediction Center Norman OK
0223 AM CDT Sat Oct 10 2020

Areas affected...parts of southeastern Mississippi...southwestern
Alabama...and western portions of the Florida Panhandle

Concerning...Severe potential...Watch possible 

Valid 100723Z - 100930Z

Probability of Watch Issuance...60 percent

SUMMARY...Potential for brief tornadoes may increase over the next
few hours, within north-south convective bands east of the center of
tropical cyclone Delta.  A tornado watch may become necessary.

DISCUSSION...Latest radar data shows the center of gradually
weakening tropical system Delta over east-central Louisiana, moving
slowly north-northeastward with time.  East of the center, two
primary bands of convection are evident -- one extending northward
across southeastern Mississippi, and the other extending
north-northwestward across western portions of the Florida Panhandle
into southwestern Alabama.  

Inland convection within these two bands remains weak/disorganized,
with no lightning observed with convection within either of these
two bands.  However, hints of slightly better organization have been
observed within a few of the offshore cells, along with some very
weak low-level rotation.

A zone of low-level confluence is indicated in the vicinity of these
convective bands, and resulting ascent suggests a continuation of
this convection -- which may consolidate with time into a single,
more pronounced band per recent CAM guidance.  Given the tropical
boundary layer streaming northward/inland (dewpoints in the upper
70s) possibly permitting some minimal degree of increase in CAPE, a
corresponding, small increase in updraft strength/organization may
occur within a few stronger cells.  Given the observed
veering/increasing flow with height yielding 0-1km shear supportive
of updraft rotation, potential for brief tornadoes may increase with
time, possibly warranting tornado watch consideration.

..Goss/Guyer.. 10/10/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...TAE...BMX...MOB...JAN...LIX...

LAT...LON   29398878 29898903 30668909 31548952 32158950 32868866
            32648760 32248706 30888648 29658616 29138827 29398878 

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SPC MD 1725

MD 1725 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHEAST NEW ENGLAND

Mesoscale Discussion 1725
NWS Storm Prediction Center Norman OK
0409 AM CDT Wed Sep 30 2020

Areas affected...Southeast New England

Concerning...Severe potential...Watch unlikely 

Valid 300909Z - 301045Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated damaging gusts will be possible this morning,
prior to frontal passage.

DISCUSSION...A narrow band of shallow frontal convection (without
lightning) is moving eastward into western MA/CT and Long Island. 
The convection is focused along a surface cold front that will move
eastward across southern New England this morning, as a surface low
near the NY/MA border moves north-northeastward and deepens in
advance of an ejecting shortwave trough over VA/MD/PA.  The primary
limiting factor for a severe-storm threat will be poor lapse rates
aloft and near the surface, leading to very weak buoyancy despite
boundary-layer dewpoints of 68-70 F.  Still, the near moist neutral
profiles, strong forcing for ascent along the front, and 60-70 kt
flow to within a km of the ground will support some potential for
downward momentum transfer in the stronger convective elements.  The
threat for isolated damaging winds will persist until frontal
passage occurs across eastern MA/Cape Cod around 14z.

..Thompson.. 09/30/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...GYX...BOX...OKX...ALY...

LAT...LON   40677307 41567317 42457295 43167248 43277170 43027075
            42197050 41577073 41147115 40677307 

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