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.
SPC AC 291958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0158 PM CST TUE NOV 29 2016
VALID 292000Z - 301200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF NORTHERN AND
CENTRAL MISSISSIPPI...
...THERE IS AN ENH RISK OF SVR TSTMS FROM EASTERN LOUISIANA TO
NORTHWESTERN ALABAMA AND SOUTHERN MIDDLE TENNESSEE...
...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM SOUTHEAST TEXAS
TO SOUTH-CENTRAL KENTUCKY AND CENTRAL/NORTHERN ALABAMA...
...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK...
...SUMMARY...
SCATTERED SEVERE STORMS ARE EXPECTED MAINLY THIS EVENING AND TONIGHT
ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY AND ADJACENT GULF
COASTAL AREAS...EXTENDING NORTHEASTWARD INTO TENNESSEE AND KENTUCKY.
MULTIPLE STRONG TORNADOES APPEAR LIKELY ACROSS NORTHERN AND CENTRAL
MISSISSIPPI. DAMAGING WINDS...ISOLATED LARGE HAIL...AND AND A FEW
TORNADOES WILL ALL BE POSSIBLE ACROSS THE REMAINDER OF THESE
REGIONS.
...20Z UPDATE...
CONFIDENCE HAS INCREASED IN A NARROW CORRIDOR OF RELATIVELY HIGHER
STRONG TORNADO POTENTIAL ACROSS NORTHERN AND CENTRAL MS THIS EVENING
INTO THE EARLY OVERNIGHT HOURS...AND A SMALL MODERATE RISK HAS BEEN
INTRODUCED WITHIN THE BROADER ENHANCED RISK ACROSS THE LOWER MS
VALLEY. THERE STILL REMAINS SOME UNCERTAINTY IN THE EXACT PLACEMENT
OF THE STRONGEST WINDS ASSOCIATED WITH LOW-LEVEL JET IN LATEST
SHORT-TERM GUIDANCE...BUT LARGE CLOCKWISE-TURNING HODOGRAPHS AND
SUFFICIENT INSTABILITY WILL BE FAVORABLE FOR DISCRETE SUPERCELL
STRUCTURES AND STRONG LOW-LEVEL ROTATION ACROSS NORTHERN/CENTRAL MS...
MAINLY IN THE 00-04Z TIME FRAME. CONSENSUS OF RECENT
CONVECTION-ALLOWING MODEL GUIDANCE INDICATES ACTIVITY WILL LIKELY
DEVELOP NORTHEASTWARD FROM ONGOING STRONG TO SEVERE THUNDERSTORMS IN
NORTHERN LA/SOUTHERN AR INTO MS...WITH LOW-LEVEL MOISTURE RAPIDLY
MOVING NORTHWARD (CHARACTERIZED BY SURFACE DEWPOINTS IN THE UPPER
60S TO LOWER 70S). AFTER ABOUT 04Z...INCREASING CONVECTIVE COVERAGE
SUGGESTS THE SEVERE RISK MAY TRANSITION TO MORE OF A DAMAGING WIND
THREAT...ALTHOUGH ISOLATED TORNADOES WILL REMAIN POSSIBLE INTO
WESTERN AL OVERNIGHT. NO OTHER CHANGES HAVE BEEN MADE TO THE
OUTLOOK.
..GLEASON/THOMPSON.. 11/29/2016
.PREV DISCUSSION.../ISSUED 1030 AM CST TUE NOV 29 2016/
...SYNOPSIS...
A CLOSED MID/UPPER-LEVEL LOW OVER EASTERN ND/SD AND WESTERN MN
SHOULD MOVE LITTLE TODAY INTO TONIGHT. STRONG MID-LEVEL CYCLONIC
FLOW EXTENDS FROM THE WESTERN CONUS INTO THE SOUTHERN PLAINS/MS
VALLEY...AND CONTINUES NORTHEASTWARD OVER MUCH OF THE EASTERN CONUS.
A SHORTWAVE TROUGH EVIDENT ON WATER VAPOR SATELLITE IMAGERY OVER
AZ/NM THIS MORNING WILL MOVE EASTWARD ACROSS THE SOUTHERN PLAINS
TODAY INTO TONIGHT. AT THE SURFACE...AN OUTFLOW BOUNDARY FROM PRIOR
CONVECTION WAS ANALYZED AT 16Z FROM SOUTHERN GA/AL TO CENTRAL MS AND
NORTHERN LA. THIS BOUNDARY WILL LIFT NORTHWARD AS AN EFFECTIVE WARM
FRONT THROUGH TONIGHT AS LOW-LEVEL FLOW STRENGTHENS OVER THE LOWER
MS VALLEY BEGINNING THIS EVENING. A MOIST LOW-LEVEL AIRMASS PRESENT
ALONG AND SOUTH OF THE OUTFLOW BOUNDARY WILL ALSO DEVELOP NORTHWARD
ACROSS THE LOWER MS VALLEY INTO THE TN VALLEY AND WESTERN GULF COAST
STATES TONIGHT. A COLD FRONT LOCATED FROM CENTRAL OK INTO WESTERN
NORTH TEXAS WILL ADVANCE EASTWARD TO THE LOWER MS VALLEY BY LATE
TONIGHT.
...LOWER MS VALLEY TO TN/KY...
ELEVATED CONVECTION HAS DEVELOPED THIS MORNING ACROSS EASTERN TX...
MOST LIKELY RELATED TO LOW-LEVEL WARM AIR ADVECTION OCCURRING TO THE
NORTH OF OUTFLOW BOUNDARY. THIS ACTIVITY MAY POSE SOME HAIL RISK IN
THE SHORT TERM...AND IT REMAINS UNCLEAR IF THIS ONGOING ACTIVITY WILL
BECOME SURFACE BASED LATER THIS AFTERNOON AS THE BOUNDARY ACROSS THE
LOWER MS VALLEY MOVES NORTHWARD. FOR ADDITIONAL INFORMATION ON THIS
SHORT-TERM THREAT (THROUGH ABOUT 1715Z)...SEE MESOSCALE DISCUSSION
1838.
EVEN WITH THE LACK OF AN OBVIOUS LARGE-SCALE FORCING MECHANISM...SOME
NEAR-TERM CONVECTION-ALLOWING MODEL GUIDANCE SUGGESTS SURFACE-BASED
THUNDERSTORMS MAY DEVELOP THIS AFTERNOON ACROSS PARTS OF
NORTHEASTERN LA INTO CENTRAL MS WITHIN THE WARM SECTOR. MLCAPE OF
1500-2000 J/KG AND EFFECTIVE BULK SHEAR IN EXCESS OF 50 KT WOULD
FAVOR SUPERCELL STRUCTURES...WITH AN ATTENDANT DAMAGING WIND...LARGE
HAIL...AND ISOLATED TORNADO THREAT. THIS AFTERNOON SEVERE THREAT IS
CONDITIONAL UPON CONVECTION DEVELOPING.
A MORE SUBSTANTIAL SEVERE THREAT WILL LIKELY DEVELOP LATE THIS
EVENING INTO TONIGHT ACROSS THE LOWER MS VALLEY AS A 40-50 KT
LOW-LEVEL JET DEVELOPS AND WEAK SURFACE CYCLOGENESIS OCCURS ALONG
THE BAROCLINIC ZONE. A VERY FAVORABLE LOW-LEVEL WIND PROFILE...WITH
EFFECTIVE SRH RANGING FROM 300-400 M2/S2...AND MLCAPE REMAINING
GENERALLY IN THE 1000-1500 J/KG RANGE SHOULD SUPPORT A TORNADO RISK
WITH ANY SUPERCELLS THAT FORM IN THE WARM SECTOR. ONE OR TWO OF
THESE TORNADOES COULD BE STRONG GIVEN THE DEGREE OF LOW-LEVEL SHEAR.
LATEST GUIDANCE INDICATES THE BEST TORNADIC POTENTIAL REMAINS ACROSS
NORTHEASTERN LA INTO MOST OF MS AND NORTHWESTERN AL/SOUTHERN TN.
DEPENDING ON OBSERVATIONAL AND MODEL TRENDS TODAY...A SMALL MODERATE
RISK AREA MAY BE CONSIDERED WITH THE 20Z UPDATE ACROSS NORTH-CENTRAL
MS.
MORE LIMITED INSTABILITY WITH NORTHWARD EXTENT PRECLUDES HIGHER
PROBABILITIES INTO TN/KY...ALTHOUGH DAMAGING WINDS MAY OCCUR AS
CONVECTION EVENTUALLY GROWS UPSCALE. FARTHER SOUTH ACROSS MS/AL...A
TRANSITION TO A BROKEN SQUALL LINE WITH A WIND DAMAGE AND CONTINUED
ISOLATED TORNADO THREAT SHOULD OCCUR LATE TONIGHT INTO THE WESTERN
GULF COAST STATES...ALTHOUGH INSTABILITY WILL BECOME MORE MARGINAL
WITH EASTWARD EXTENT.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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