Mesoscale Discussion 0806
NWS Storm Prediction Center Norman OK
0222 PM CDT Sun May 21 2017
Areas affected...Portions of far east TX...LA...and western/central
MS
Concerning...Severe potential...Watch unlikely
Valid 211922Z - 212115Z
Probability of Watch Issuance...20 percent
SUMMARY...Strong to locally damaging winds and perhaps some large
hail may occur on an isolated basis this afternoon. Watch issuance
is unlikely.
DISCUSSION...Thunderstorms have increased in coverage and intensity
over the past hour or so along a southeastward-moving cold front in
northern/central LA, and along a sea breeze boundary across southern
LA. Even through scattered to numerous thunderstorms moved across
parts of this region yesterday and early this morning, strong
diurnal heating from mostly sunny skies and a rich low-level airmass
have allowed for moderate to locally strong instability to redevelop
as of 19Z. Latest RAP Mesoanalysis indicates MLCAPE has increased to
around 1500-2500 J/kg along and ahead of the front, as well as along
the sea breeze boundary, with lapse rates generally 6.5-7.0 C/km in
the 700-500 mb layer.
Although low-level winds remain weak, they do strengthen slightly to
35-40 kt at 500 mb, and veer to westerly with height. Resultant
effective bulk shear values of 35-45 kt (locally 50 kt) should
support some updraft organization, and this has been noted in recent
radar imagery from KDGX/KPOE. There are some indications that a weak
MCV may have developed in northeastern LA, and convection is
expected to continue developing along the cold front and then move
mostly east-southeastward across the discussion area. Isolated
strong/gusty winds may produce localized damage through this
afternoon, and the strongest thunderstorm cores may also be capable
of large hail. Several recent runs of the operational HRRR indicate
one or more line segments may consolidate along or just ahead of the
front across portions of southeastern LA and southern/central MS
over the next several hours. If this were to occur, then the
damaging wind threat could increase. Still, the overall severe
weather threat should remain isolated, and watch issuance is
unlikely.
..Gleason/Weiss.. 05/21/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LIX...LCH...SHV...
LAT...LON 30209320 30159389 30189456 30499446 30819376 31319289
31769240 31969185 32529143 32959111 32949059 32848997
32498956 31468955 30479026 29949115 30139200 30209320
Read morefrom SPC Forecast Products http://ift.tt/JV6uqo
No comments:
Post a Comment