SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1254 AM CDT Wed Mar 30 2022
Valid 301200Z - 311200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
MISSISSIPPI VALLEY INTO ALABAMA...AND INTO THE FAR WESTERN FLORIDA
PANHANDLE...
...SUMMARY...
A regional outbreak of severe thunderstorms is expected from the
Lower Mississippi Valley into parts of the Ohio and Tennessee
Valleys today, and over portions of the central Gulf Coast states
later today into tonight. Widespread damaging winds with gusts over
75 mph and several strong tornadoes (EF2+) appear likely.
...Synopsis...
A large-scale upper trough will exist over the central U.S. today,
with an intense leading wave moving across OK and TX through midday.
This feature will then take on a negative tilt as it moves across
the lower MS Valley and into the OH Valley after 00Z, providing
large-scale lift with rapid height falls. Midlevel wind speeds of
70+ kt will be common across the region, with a compact speed max to
100 kt possible with the ejecting wave. Just off the surface, 850 mb
flow will already average 60-70 kt at 12Z Wednesday from eastern TX
into AR and LA, and speeds will only increase with time, possibly as
high as 85 kt out of the south across TN and KY by 00Z.
As a surface low deepens over MO and IL during the day, low-level
moisture advection will occur quickly across the warm sector, with
upper 60s F dewpoints across LA, southern MS and AL, and mid 60s F
as far north as western TN. Two primary severe-weather regimes
appear evident today, one in association with the negative-tilt wave
as it ejects northeastward, and another farther south late in the
period ahead of the trailing cold front as it sweeps east along the
Gulf Coast.
...Eastern AR/northern LA northeastward into KY and TN...
Storms are likely to be ongoing near a cold front early in the day,
roughly from central MO into eastern OK, and near a developing
dryline pushing east of I-35 in TX. While instability will be
relatively weak at this juncture, shear will be extreme with large
looping hodographs. This may favor QLCS structures within any
ongoing lines of storms. By midday, the combination of cooling aloft
and strong low-level moisture advection will lead to destabilization
near the cold front, with a rapid increase in storm coverage and
intensity. Most CAMs suggest this will occur around 18Z, focused
over northern LA, central and eastern AR, and southeast MO. The bulk
of this activity is expected become severe as it quickly crosses the
MS River into MS, western TN and KY.
Extreme shear is forecast, with effective SRH of 500-800 m2/s2
common as MLCAPE increases to 1000-1500 J/kg over LA/AR/MS and
southwest TN. Supercells are likely, with strong tornadoes possible
as well as particularly damaging outflow surges. As outflows merge,
QLCS tornadoes may occur as well. Although CAPE values will be lower
across the OH Valley, strong lift may sustain a severe-wind threat
there through about 03Z.
...Parts of eastern LA...much of MS...AL...FL Panhandle...
Southern portions of the front/dryline will move much slower
compared to farther north, resulting in a longer duration of
boundary-layer moistening. A line of convection should become
evident by 21Z from southwest MS into parts of southern LA, moving
across MS and into north-central AL by about 03Z. The subtle lift,
combined with ample low-level moisture beneath an intense low-level
jet, will favor tornadic supercells which may peak during the night.
Effective SRH will remain high, averaging 400-500 m2/s2, with proper
hodograph elongation in the mid and high levels. Given the long
duration and slow eastward movement of this line of supercells, and
the magnitude of the forecast hodographs, a few intense tornadoes
could occur. However, the threat will become limited late in the
period due to decreasing instability to the east of about longitude
86W.
..Jewell/Bentley.. 03/30/2022
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/SMcw71
