Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
Memphis, TN...Birmingham, AL...Montgomery, AL...Shreveport, LA...Little Rock, AR...
Atlanta, GA...Chattanooga, TN...Clarksville, TN...Beaumont, TX...Sandy Springs, GA...
Houston, TX...Nashville, TN...Kansas City, MO...Tulsa, OK...Wichita, KS...
SPC AC 170552
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1252 AM CDT Wed Mar 17 2021
Valid 171200Z - 181200Z
...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
LOUISIANA ACROSS NORTHERN MISSISSIPPI INTO NORTHWEST ALABAMA...
A regional outbreak of severe storms is expected today and tonight
across portions of the lower Mississippi Valley into Alabama.
Widespread severe storms capable of producing tornadoes (several of
which may be intense), very large hail and intense damaging wind
gusts are expected. More than one round of severe storms are
possible across parts of Mississippi into Alabama during the
afternoon into the overnight hours.
...Lower Mississippi Valley to Alabama...
Early-morning water-vapor imagery depicts a well-defined upper low
over central NM moving east toward the TX Panhandle. This feature
will eject across OK into the Ozark Plateau by the end of the
period. Intense large-scale forcing for ascent is currently
spreading across the southern High Plains region where deep
convection is currently expanding in areal coverage along the dry
line/Pacific front as it encounters western edge of moisture plume.
This boundary will remain active leading into the start of the day1
Strongly diffluent flow aloft will overspread the lower MS
Valley/central Gulf States during the day as 80kt+ 500mb flow
overspreads increasingly moist/buoyant warm sector. Latest model
guidance suggests several LLJ segments will increase ahead of the
trough, each likely modulating bouts of organized severe
thunderstorm clusters/supercells. The primary synoptic low is
forecast to track across northeastern OK into southern MO.
Significant elevated convection will be noted north of the warm
front but ample surface-based buoyancy/shear south of the front
should prove favorable for supercells as one LLJ segment focuses
across AR into southeast MO ahead of this feature. At the same time,
a secondary LLJ will strengthen across MS during the day and become
the primary LLJ into the overnight hours over northwestern AL/middle
TN. This secondary LLJ appears to be responding to a mid-level speed
max that will translate across south-central TX into southern LA
during the late evening hours.
Of particular interest is the boundary-layer moisture that is now
present along the Gulf Coast where lower 70s surface dew points are
observed. This air mass will advance north during the day and
diurnal heating will allow moderate instability to develop along a
corridor from southern LA through central MS into western AL where
SBCAPE should be on the order of 2500 J/kg. While the primary 500mb
speed max will likely maintain convection along the surging Pacific
front over southeast TX, an uncapped, buoyant air mass downstream
over MS/AL should prove favorable for discrete supercell development
ahead of the primary short wave. Forecast soundings across the HIGH
Risk exhibit profiles favorable for strong, long-track tornadoes,
and this is especially true from northeast LA through northern MS
into northwest AL.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z