The SPC is forecasting ...tornadoes large hail and damaging winds over parts of eastern texas northern and western louisiana as well as southern and eastern arkansas this afternoon and tonight.... Please read the latest public statement about this event.
| Categorical Graphic |
|---|
|
| Probabilistic Tornado Graphic |
 |
 |
| Probabilistic Damaging Wind Graphic |
 |
 |
| Probabilistic Large Hail Graphic |
 |
 |
SPC AC 181618 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1118 AM CDT TUE MAR 18 2008 VALID 181630Z - 191200Z ...THERE IS A MDT RISK OF SVR TSTMS ERN TX...SRN AND ERN AR...AND NRN/WRN LA...... ...THERE IS A SLGT RISK OF SVR TSTMS SRN PLAINS NEWD ACROSS THE LOWER MS/ WRN TN AND LOWER OH VALLEYS... ...CENTRAL/ERN TX/LA AND SRN AR... AT MID MORNING...A SW-NE ORIENTED FRONT STRETCHED FROM THE MIDDLE RIO GRANDE VALLEY NEWD INTO NWRN AR/SERN MO. A WEAK SURFACE LOW WAS LOCATED NEAR SAT...WITH DRYLINE EXTENDING N-S FROM THIS FEATURE. THE SRN TX SURFACE LOW IS FORECAST TO DEEPEN AS IT SHIFTS NEWD INTO THE ARKLATEX THIS EVENING...AND WRN TN BY WEDNESDAY MORNING...IN RESPONSE TO UPPER LOW AND ASSOCIATED JET MAX LIFTING NEWD FROM SRN TX INTO AR. MOST OF THE CONVECTION SO FAR THIS MORNING HAS BEEN ELEVATED AND LOCATED NORTHWEST OF THE FRONT/DRYLINE. HOWEVER...INCREASING LARGE SCALE LIFT HAD RECENTLY RESULTED IN STORMS DEVELOPING IN THE WARM SECTOR FROM CENTRAL TX NEWD INTO AR. AS THE FORCING OVERSPREADS THE AREA THROUGH THE PERIOD...THIS SHOULD AID IN WEAKENING THE CAP...WITH STORMS INTENSIFYING AND INCREASING IN NUMBER THROUGH THE AFTERNOON/EVENING HOURS. EAST OF THE FRONT/DRYLINE ACROSS TX AND LA/SERN AR AND SWRN AR... TEMPERATURES HAD WARMED INTO 70S WITH DEW POINTS RANGING FROM 65 TO 70 DEGREES. THIS WAS RESULTING IN MODERATE INSTABILITY WITH MLCAPES NEAR 1000 J/KG...AND THESE VALUES ARE EXPECTED TO INCREASE TO NEAR 2000 J/KG BY MID AFTERNOON...ESPECIALLY ACROSS ERN TX/LA. MORNING SOUNDINGS AND WIND PROFILERS SHOW STRONG DEEP LAYER SHEAR SUPPORTIVE OF SUPERCELLS...AND WIND PROFILES WILL STRENGTHEN MORE SO THIS AFTERNOON AND TONIGHT AS 100+ KT MID LEVEL JET MAX SPREADS INTO THE REGION. LARGE LOW LEVEL CLOCKWISE TURNING HODOGRAPHS... WITH 1 KM SRH FROM 300-500 M2/S2...WILL BE SUPPORTIVE OF STORMS WITH STRONG ROTATION AND TORNADOES...SOME STRONG. ALSO...SEVERE HAIL AND DAMAGING WIND GUSTS ARE EXPECTED WITH THESE STORMS. THE SEVERE STORMS...ESPECIALLY ACROSS SERN TX THIS AFTERNOON... SHOULD EVOLVE INTO A FAST MOVING LINEAR SYSTEM AS THE 100 KT SSWLY ORIENTED JET MAX LIFTS INTO THE AREA ALONG DRYLINE/COLD FRONT. THE STRENGTH OF THE SHEAR WILL BE SUPPORTIVE OF EMBEDDED BOW ECHOES/SUPERCELLS WITHIN THE LINE. THOUGH WIND DAMAGE SHOULD BE THE PRIMARY THREAT...THE MAGNITUDE OF THE LOW/DEEP LAYER SHEAR WILL ALSO FAVOR ISOLATED TORNADOES WITHIN BOW ECHO STRUCTURES. THE LINE IS EXPECTED TO SWEEP RAPIDLY EWD INTO SRN LA/MS OVERNIGHT. ALTHOUGH INSTABILITY IS FORECAST TO DIMINISH WITH EASTWARD EXTENT OVER THE LOWER MS VALLEY THIS EVENING...THE STRENGTH OF UPPER SYSTEM AND WIND FIELDS WILL BE SUPPORTIVE OF WIND DAMAGE AND ISOLATED TORNADOES AS THE LINE SHIFTS EWD INTO THE CENTRAL GULF COASTAL STATES OVERNIGHT. ...MID MS AND TN VALLEY THROUGH SRN PARTS OF THE OH VALLEY... AN AXIS OF LOWER TO MID 60S DEWPOINTS IS LOCATED ON THE WARM SIDE OF THE STATIONARY FRONT...BUT INSTABILITY WILL BE WEAKER THAN IN TX/LA DUE TO EXPANSIVE CLOUD COVER AND WEAK MID LEVEL LAPSE RATES. HOWEVER...EVEN WITH WEAK INSTABILITY...EFFECTIVE SHEAR OF 60 KT AND 1KM SRH FROM 400 TO 500 M2/S2 WILL BE FAVORABLE FOR BOW ECHOES AND SUPERCELLS...WITH DAMAGING WINDS AND A FEW TORNADOES. THE SEVERE THREAT APPEARS MORE MARGINAL INTO THE TN AND LOWER OH VALLEYS WHERE INSTABILITY WILL BE WEAKER. ..IMY.. 03/18/2008 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z