SPC Jul 12, 2020 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1251 AM CDT Sun Jul 12 2020

Valid 121200Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
EASTERN COLORADO...NORTHEAST NEW MEXICO...AND PARTS OF THE OKLAHOMA
AND TEXAS PANHANDLES...

...SUMMARY...
Isolated to widely scattered severe thunderstorms are forecast this
afternoon through the late evening across parts of the central and
southern High Plains.  Severe gusts and large hail are the primary
hazards.

...Synopsis...
A mid-level anticyclone will remain over the Desert Southwest today
with a mid-level shortwave trough moving through the base of a
larger scale trough over the eastern third of the U.S.  A
disturbance is forecast to move across the northwestern CONUS during
the period.  A few remnant MCVs originating from early morning
thunderstorm activity may serve as features focusing
showers/thunderstorms.  In the low levels, a composite front/outflow
will become draped from the Arklatex westward across the southern
Great Plains and extend north in lee of the central Rockies.  A
surface low and associated lee trough are forecast to develop over
the parts of the northern High Plains.

...Central-southern High Plains...
Forecast model guidance indicates a weak disturbance will move
through the central Rockies during the day and into the
south-central High Plains late.  Strong heating and appreciable
boundary layer moisture (surface dewpoints in the 50s near I-25 to
the 60s over far eastern CO), will contribute to strong
destabilization.  Easterly upslope flow veering to
west-northwesterly will result in 25-45 kt effective shear. 
Forecast soundings over southeastern CO show large CAPE in the -10
to -30 deg C layer.  Supercells and severe multicells will be the
preferred storm mode with a cluster or two likely evolving as
outflow mergers lead to storms developing south-southeast into the
OK/TX Panhandles during the evening.  

...East TX into the lower MS Valley...
Overnight thunderstorm activity over parts of the southern Plains
will move south into a moisture-rich boundary layer over the Sabine
Valley during the morning.  It is uncertain whether a risk for
damaging gusts will persist into the early morning over the
northwest Gulf Coast.  With that stated, additional storms may
develop during peak heating farther east over the lower MS Valley
within a weakly capped airmass.  Isolated downbursts capable of wind
damage are the primary severe threat.  

...OH Valley and central-southern Appalachians...
Convective outflow from thunderstorm activity prior to the period
will lead to some uncertainty regarding the quality of the airmass
across parts of the OH Valley ahead of the mid-level disturbance. 
Nonetheless, isolated to scattered thunderstorms are forecast to
develop by early afternoon and gradually spread east/downstream
across parts of the central-southern Appalachians during the
afternoon/early evening.  Moderate destabilization/deep-layer shear
will likely result in organized storm structures with isolated
damaging gusts/marginally severe hail the primary hazard
accompanying the strong multicells/marginal supercells.  It is
possible a portion of this region may require a probability upgrade
in later outlooks if confidence increases for a concentrated area of
storms/wind damage potential.

...Northern Great Plains...
Upper forcing for ascent is expected to gradually overspread the
region late in the day and overnight as a mid-level shortwave trough
approaches the region.  Strong heating and steep lapse rates will
yield 1000-2000 J/kg MLCAPE by late afternoon.  Models generally
indicate only isolated thunderstorm coverage.  The stronger storms
will potentially be capable of severe gusts/large hail beginning
during the early evening and perhaps persisting on an isolated basis
into the overnight.

..Smith/Lyons.. 07/12/2020

Read more

from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html