Post by SKYSUMMIT on May 17, 2019 5:28:20 GMT -6
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Fri May 17 2019
Valid 181200Z - 191200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
CENTRAL/NORTHEAST TX...FAR SOUTHEAST OK...WESTERN AR...FAR SOUTHWEST
MO...AND FAR NORTHWEST LA...
...SUMMARY...
Severe storms are possible over a large area Saturday, from Texas to
Iowa, with the greatest threat across central/northeast Texas toward
the Arklatex and through western Arkansas, where a few tornadoes
along with hail and damaging wind gusts are possible.
...Synopsis...
A shortwave trough is expected to eject northeastward through the
central Plains and into the middle MS Valley on Saturday, while
accompanying strong flow aloft spreads over the southern Plains and
lower MO and middle MS valleys. Surface pattern at the beginning of
the period will likely consist of a low near the SD/NE/IA border
intersection with a cold front extending southwestward across
eastern NE and central KS to another low over northwest OK. A
dryline will likely extend from this northwest OK low southwestward
into southwest TX.
Northern portion of this front is expected to move gradually
eastward during the day while central/southern portion will remain
stationary (or perhaps move slightly westward) through the early
afternoon as surface pressure deepens across the southeast
CO/southwest KS/OK Panhandle vicinity. Resulting surface low is then
expected to progress northeastward along the front during the second
half of the period.
...TX/OK/AR/LA...
Global/region model guidance and convection-allowing guidance is in
good agreement that thunderstorms will initiate across southwest TX
Friday night and quickly grow upscale into a convective line. The
resulting progression of this convective line will have a major
influence on the location of the greatest severe potential. Current
expectation is for this line to extend from north-central TX
southwestward into the TX Hill Country at the beginning of the
period with gradual eastward progression anticipated. Despite being
displaced from the stronger flow aloft, strong instability across
central/east/southeast TX will lead to the potential for damaging
wind gusts and occasional hail within the line as it moves
eastward/southeastward.
Some reintensification of the line is anticipated as it moves into
the Arklatex, eastern OK and western AR during the afternoon. Here,
diurnal destabilization will overlap favorably with strengthening
deep-layer shear to increase the severe potential.
A separate threat for severe thunderstorms is likely later in the
late afternoon/early evening as the shortwave moves into western
OK/central KS. Current guidance indicates there will be enough air
mass recovery to support strong/severe thunderstorms along the
leading edge of the upper trough/cold temperatures aloft. There is
still some uncertainty regarding air mass recovery but the strong
vertical shear and steep lapse rates support a conditional risk of
very large hail and strong wind gusts.
...KS/MO/IA...
Thunderstorm are possible Saturday morning along the front extending
from central KS into IA. Deep-layer shear is supportive of a few
stronger storms capable of hail. Additional surface-based
thunderstorm activity is expected later in the day as forcing for
ascent attendant to the approaching shortwave trough, diurnal
destabilization and lift along the front all align to support
convective initiation. Environment is supportive of strong,
organized updrafts capable of hail and strong wind gusts. Backed
surface winds may also develop within the warm sector ahead of the
front, contributing to a tornado risk with any discrete, warm-sector
storms. The cold front across KS and MO may provide a favored
corridor for potential upscale growth, although uncertainties are
currently too high to outlook higher probabilities with this
outlook.
...MAXIMUM RISK BY HAZARD...
Tornado: 5% - Slight
Wind: 30% - Enhanced
Hail: 15% SIG - Slight
