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)The SPC is forecasting ...severe thunderstorms expected over parts of the lower mississippi and tennessee valleys today through tonight.... Please read the latest public statement about this event. View What is a Watch? clip.
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| Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point. |
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| Probabilistic Damaging Wind Graphic | |||||||||||||
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| 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. |
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| Probabilistic Large Hail Graphic | |||||||||||||
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| Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point. |
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SPC AC 211246 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0646 AM CST SAT DEC 21 2013 VALID 211300Z - 221200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF THE LWR MS AND LWR TN VLYS... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA...FROM E TX AND THE CNTRL GULF CST NE INTO THE OH VLY... ...SYNOPSIS... AN OUTBREAK OF SVR TSTMS IS POSSIBLE TODAY INTO TNGT OVER THE LWR MS AND LWR TN VLYS. THE POTENTIAL WILL EXIST FOR A FEW STRONG TORNADOES...IN ADDITION TO SWATHS OF DMGG WINDS. POTENT SHORTWAVE TROUGH NOW ENTERING W TX SHOULD PIVOT NE ACROSS THE RED RVR VLY LATER TODAY/EARLY TNGT...AND ACCELERATE NE INTO IL EARLY SUN...AS LARGE-SCALE/HIGH-AMPLITUDE TROUGH REMAINS CENTERED OVER THE PLAINS. THE SHORTWAVE WILL ASSUME A SLIGHTLY NEGATIVE TILT BEFORE IT BECOMES ABSORBED WITHIN DOWNSTREAM CONFLUENT FLOW OVER THE OH VLY LATER SUN. AHEAD OF THE IMPULSE...STRENGTHENING/DEEPENING SWLY FLOW WILL ALLOW A SWATH OF SEASONABLY WARM/MOIST AIR TO SURGE NE ACROSS THE LWR MS VLY INTO MUCH OF THE OH VLY TODAY THROUGH EARLY SUN. COUPLED WITH THE VERY STRONG WIND FIELD ACCOMPANYING THE UPR IMPULSE...SETUP WILL BE FAVORABLE FOR BANDS OF TSTMS/SUPERCELLS CAPABLE OF BOTH DMGG WIND AND POTENTIALLY STRONG TORNADOES LATER TODAY INTO TNGT. ...WRN/CNTRL GULF CST INTO THE OH VLY TODAY/TNGT... SFC OBS SHOW STRONG/BROAD CURRENT OF VERY MOIST AIR SURGING N FROM THE WRN GULF OF MEXICO ATTM INTO THE LWR MS VLY...AHEAD OF SLOWLY-PROGRESSIVE COLD FRONT ASSOCIATED WITH W TX SHORTWAVE TROUGH. NUMEROUS BUOYS REPORT 30 KT SLY FLOW WITH DEWPOINTS AOA 70 F IN AREA WITH PW AOA 1.50 INCHES. THE MOIST PLUME WILL SPREAD FARTHER NE ACROSS THE OH VLY THROUGH EARLY SUN...AND LARGELY DELINEATE THE NRN/ERN EXTENT OF SFC-BASED INSTABILITY ACROSS THE REGION. CLOUDS WILL LIMIT DIURNAL STEEPENING OF LOW-LVL LAPSE RATES OVER MOST AREAS. BUT QUALITY OF MOISTURE INFLOW AND PRESENCE OF RESIDUAL EML LIKELY WILL YIELD SUFFICIENT BUOYANCY /MLCAPE OF 500-1000 J PER KG/ FOR SUSTAINED TSTMS...ESPECIALLY OVER THE LWR MS VLY/DEEP SOUTH. WIDESPREAD SHOWERS/STORMS NOW OCCURRING ALONG AND W OF THE COLD FRONT SHOULD GRADUALLY INCREASE IN STRENGTH/COVERAGE THROUGH LATER THIS MORNING AS STRONGER FORCING FOR ASCENT ASSOCIATED WITH THE UPR IMPULSE APPROACHES THE WARM SECTOR. TOGETHER WITH CONTINUED MOISTENING OF CONFLUENT LWR TROPOSPHERIC FLOW...SETUP ALSO MAY SUPPORT DEVELOPMENT OF BANDS/CLUSTERS OF STORMS AHEAD OF THE FRONT OVER FAR E TX...LA...ERN AR...AND MS BY EARLY AFTN. ALTHOUGH THE INTENSITY AND NEGATIVE-TILT NATURE OF THE SHORTWAVE IMPULSE MAY RESULT IN WIND PROFILES WITH A SLIGHT VEER-BACK PATTERN IN THE VERTICAL...STRENGTH OF THE WIND FIELD /WITH 60-70 KT 850-700 MB WINDS BENEATH 100 KT FLOW AT 250 MB/ WILL BE VERY FAVORABLE FOR ROTATING UPDRAFTS. THE GREATEST RISK FOR DISCRETE OR SEMI-DISCRETE STORMS WITH POTENTIAL FOR TORNADOES /SOME OF WHICH COULD BE STRONG/...SHOULD EXIST OVER PARTS OF LA...AR...MS...AND WRN TN THIS AFTN/EARLY TNGT. CONTINUED NE MOTION OF THE SHORTWAVE IMPULSE SHOULD FOSTER CONSOLIDATION OF THE FRONTAL AND PRE-FRONTAL STORMS INTO A FAIRLY LENGTHY SQLN BY MID-LATE AFTN. ATTENDANT FAST-MOVING BOW/LEWP STRUCTURES WILL MAINTAIN A RISK FOR SWATHS OF DMGG WIND...IN ADDITION TO A FEW TORNADOES...INTO THE NIGHT FROM WRN/CNTRL KY SSW THROUGH TN INTO MS...AL...AND LA. IN ADDITION...ALTHOUGH BUOYANCY WILL DECREASE WITH NEWD EXTENT...THE STRONGEST LOW-LVL MASS CONVERGENCE/WAA WILL FOCUS ON THE OH VLY BY LATE EVE. COUPLED WITH THE INTENSITY OF THE WIND FIELD...AND THE LIKELIHOOD FOR MODEST SFC DEVELOPMENT ALONG THAT PART OF THE FRONTAL ZONE STRADDLING THE OH VLY...ISOLD TORNADOES AND DMGG WIND GUSTS MAY OCCUR AS FAR N AS PARTS OF IND...OH...AND WV THROUGH SUN MORNING. ..CORFIDI/MOSIER.. 12/21/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z |