High Risk for Today Includes Parts of 6 Different States



Upgrade Map Showing Risk for Severe Weather. Courtesy of the Storm Prediction Center.

As I mentioned in an earlier blog post, some parts of 6 states, which includes southeastern Oklahoma, northeastern Texas, most of Arkansas, far northwestern Mississippi, far northwestern Louisiana, and southwestern Tennessee, has been included in a high risk area. This includes in Oklahoma, Idabel & Hugo; in Texas, Greenville, Commerce, Sulphur Springs, Texarkana, areas just east of Dallas, Tyler and Longview; in Louisiana, areas just north of Sherveport; in Mississippi, Tunica; in Tennessee, Memphis and just south of Dyersburg; and Arkansas, Little Rock, Hot Springs, areas along I-30, US-67 near Jonesboro.

What does this mean? The potential for life-threatening weather conditions, including long-track, violent, deadly tornado, massive sized hail to grapefruit sized and damaging, straight-line winds. Here is the discussion on this event by the Storm Prediction Center.

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1127 AM CDT TUE APR 26 2011

VALID 261630Z – 271200Z

…THERE IS A HIGH RISK OF SVR TSTMS LATE THIS AFTERNOON INTO
TONIGHT FOR NE TX…FAR SE OK…EXTREME NW LA…THE SRN HALF OF
AR…SOUTHWEST TN…AND NORTHWEST MS…

…THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK…FROM
NE TX/SE OK TO THE CONFLUENCE OF THE MS/OH RIVERS…

…THERE IS A SLGT RISK OF SVR TSTMS FROM SRN OK/EAST TX INTO MUCH
OF THE LOWER/MID MS VALLEY…TN AND OH VALLEYS…AND INTO PA/NY…

…AN OUTBREAK OF SEVERE THUNDERSTORMS INCLUDING STRONG TORNADOES
AND WIDESPREAD DAMAGING WINDS IS FORECAST TO OCCUR LATER TODAY AND
TONIGHT…

MORNING WATER VAPOR LOOPS SHOW A BROAD UPPER TROUGH OVER MUCH OF THE
UNITED STATES…WITH TWO SIGNIFICANT SHORTWAVE FEATURES TRACKING
ACROSS THE NATION. THE FIRST TROUGH IS CURRENTLY OVER THE MID MS
AND OH VALLEY AND WILL EJECT NORTHEASTWARD TODAY INTO THE NORTHEAST
STATES. THIS WILL LEAD TO A RELATIVELY LARGE AREA OF POTENTIAL FOR
ISOLATED SEVERE THUNDERSTORMS AS FAR NORTHEAST AS PORTIONS OF NY/PA.
ANOTHER SHORTWAVE TROUGH IS OVER CO/NM AND WILL QUICKLY TRANSLATE
INTO OK/TX BY EVENING. THIS FEATURE IS EXPECTED TO RESULT IN
SIGNIFICANT SEVERE WEATHER OVER THE ARKLATEX AND LOWER/MID MS
VALLEY.

…OK/TX INTO THE LOWER/MID MS VALLEY…
LOW LEVEL MOISTURE IS RAPIDLY RETURNING NORTHWARD THIS MORNING
ACROSS THIS REGION…WITH MID/UPPER 60S DEWPOINTS NOW AS FAR NORTH
AS SOUTHERN AR. THE 12Z FWD RAOB SHOWED A PRONOUNCED CAPPING
INVERSION…WHICH SHOULD INHIBIT STRONG CONVECTIVE DEVELOPMENT UNTIL
MID AFTERNOON. BY THAT TIME…STRONG DAYTIME HEATING AND CONTINUED
MOISTENING OF THE BOUNDARY LAYER WILL YIELD MLCAPE VALUES OF
3000-4000 J/KG AND A WEAKENED CAP OVER NORTHEAST TX/NORTHWEST
LA/SOUTHWEST AR. ISOLATED DISCRETE SUPERCELL THUNDERSTORMS ARE
EXPECTED TO FORM IN THIS REGION…WHICH SHOULD TRACK NORTHEASTWARD
ACROSS SOUTHERN AR/NORTHERN LA DURING THE EVENING. LOW LEVEL WINDS
WILL BE STRENGTHENING DURING THIS PERIOD AS SURFACE CYCLOGENESIS
OCCURS OVER TX…LEADING TO INCREASINGLY FAVORABLE SHEAR PROFILES
FOR TORNADIC ACTIVITY.

MOST MODEL SOLUTIONS SUGGEST A SECOND ROUND OF INTENSE SUPERCELLS
DEVELOP NEAR THE DRYLINE ACROSS NORTH TX AND SOUTHEAST OK BY EARLY
EVENING. THESE STORMS WILL ALSO TRACK EAST-NORTHEASTWARD INTO AR/LA
/ROUGHLY THE SAME AXIS AS THE FIRST WAVE OF STORMS/ AND WILL BE IN A
MUCH MORE FAVORABLE VERTICAL SHEAR PROFILE FOR RISKS OF
STRONG/DAMAGING TORNADOES.

TONIGHT…VERY STRONG LOW LEVEL WINDS ARE FORECAST TO DEVELOP OVER
EASTERN AR/NORTHWEST MS/WEST TN NORTHWARD INTO IL/IND. THERE IS
CONSIDERABLE UNCERTAINTY REGARDING THE EVOLUTION OF STORMS AS THEY
PROGRESS INTO THIS ENVIRONMENT. THE STORMS MAY REMAIN DISCRETE
ACROSS AR WITH A RISK OF STRONG/VIOLENT TORNADOES…OR THEY MAY GROW
UPSCALE INTO A FAST-MOVING BOW ECHO WITH THE RISK OF WIDESPREAD
SIGNIFICANT WIND DAMAGE AND ISOLATED TORNADOES. IN EITHER
CASE…CONDITIONS ARE CLEARLY FAVORABLE A HIGH-END SEVERE WEATHER
EVENT WELL INTO THE NIGHT. FOR THESE REASONS…HAVE EXTENDED THE
HIGH RISK FARTHER EAST.

…TN/OH VALLEY INTO THE NORTHEAST STATES…
THE LEAD SHORTWAVE TROUGH EXTENDS FROM IL/IND INTO MS/AL. A BAND OF
THUNDERSTORMS ASSOCIATED WITH THIS TROUGH HAS BEEN SLOWLY
DIMINISHING THIS MORNING…BUT IS LIKELY TO REJUVENATE BY EARLY
AFTERNOON. WIDESPREAD STRONG MID LEVEL WINDS AND MODERATE CAPE WILL
LEAD TO A RISK OF HAIL AND LOCALLY DAMAGING WINDS OVER A RELATIVELY
BROAD AREA FROM AL/GA NORTHEASTWARD INTO PA/NY. DETAILS ON SPECIFIC
AREAS OF THIS THREAT WILL BE ADDRESSED THROUGH THE DAY IN
FORTHCOMING MESOSCALE DISCUSSIONS

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