Post by Randy - Brandon, MS on Feb 9, 2009 13:13:25 GMT -6
Like I posted yesterday, the primary threat with this system in our area should be very strong winds associated with the squall line. 50-60kt 925mb winds are nothing to sneeze at.
As far as those winds are concerned, here is today's 12z GFS 925mb (2,500-3,500 ft in atmosphere) wind chart. If a squall line forms and mixes those winds down to the surface, that will be our primary severe threat, I think.
Day 2 Moderate Risk for NE TX, extreme NW LA, SW AR, and SE OK:
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CST MON FEB 09 2009
VALID 101200Z - 111200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF NERN
TX...SERN OK AND SWRN AR...
...THERE IS A SLGT RISK OF SVR TSTMS FROM TX/OK EAST-NORTHEASTWARD
INTO PORTIONS OF THE LOWER/MID MS VALLEY...
ACTIVE AND WIDESPREAD SEVERE WEATHER IS EXPECTED LATE TUESDAY
AFTERNOON AND NIGHT FROM PORTIONS OF OK/TX EWD INTO PORTIONS OF THE
LOWER/MID VS VALLEY. EVOLUTION OF CONVECTION APPEARS
COMPLICATED...AND THIS PRECLUDES A LARGER MODERATE RISK AREA.
MONITOR TUESDAY/S DAY 1 OUTLOOKS FOR UPDATES ON THIS SITUATION.
...SYNOPSIS...
LONGWAVE TROUGH WILL REMAIN SITUATED ACROSS THE WRN/CENTRAL
CONUS...AS A FAST MOVING SHORTWAVE TROUGH SHIFTS EWD FROM THE SWRN
STATES INTO THE ARKLATEX AREA BY EARLY WED MORNING. A 90-100 KT MID
LEVEL IS FORECAST TO ACCOMPANY THE UPPER SYSTEM AND MOVE INTO SWRN
TX BY LATE AFTERNOON...AND AR OVERNIGHT. WHILE NAM/GFS SHOW A
DEEPENING SURFACE LOW LOCATED NEAR THE MO/AR BY 11/12Z... NAM MOVES
THE DEVELOPING SURFACE LOW EWD ACROSS NRN OK AND THE GFS THOUGH NRN
TX TUESDAY.
TX/OK NEWD INTO THE MID MS VALLEY...
CURRENTLY PREFER GFS SURFACE LOW SOLUTION AS THE MAIN UPPER FORCING
SPREADS FROM SWRN TX TOWARD THE ARKLATEX DURING THE
AFTERNOON/EVENING HOURS. HOWEVER...SURFACE LOW LIKELY WILL NOT
DEVELOP UNTIL LATE UNTIL MAIN UPPER SYSTEM SHIFTS EWD INTO FAR WRN
TX. SINCE THE COLD FRONT CURRENTLY MOVING THROUGH SRN TX IS EXPECTED
TO STALL LATER TODAY...THIS SHOULD ALLOWING CURRENT LOWER/MID 60S TO
RETURN NWWD INTO SJT/ABI/SPS AREAS OF WRN TX AND NWD INTO
OK...MAINLY ALONG AND S OF I-44...TUESDAY. THESE DEWPOINTS COMBINED
WITH DIURNAL HEATING AND STRONG COOLING ALOFT...500 MB TEMPERATURES
FROM -18C TO -20C...SHOULD YIELD MLCAPES FROM 1000-1500 J/KG BY LATE
TUESDAY.
STRONG 850 MB FRONTOGENESIS AND INCREASING FORCING IS SUGGESTIVE OF
THE INITIAL CONVECTION DEVELOPING AS A SQUALL IN THE SPS/ABI/SJT
AREA...IN ASSOCIATION WITH THE DEVELOPING SURFACE LOW/TRAILING
FRONT. VERY STRONG ENVIRONMENTAL WINDS AND THE EXPECTED FAST
TRANSLATIONAL MOTION OF THE LINE SHOULD FAVOR WIND DAMAGE.
HOWEVER...FURTHER EAST ACROSS NRN TEXAS...SRN/ERN OK AND WRN
ARKANSAS...DISCRETE STORMS ARE ALSO LIKELY TO DEVELOP
BY LATE AFTERNOON IN STRENGTHENING DIFFLUENCE ALOFT AND CONSEQUENT
LOW-LEVEL CONVERGENCE/WARM ADVECTION WITHIN INTENSIFYING /50-70 KT/
850 JET CORE. EFFECTIVE SHEAR AT 40-60 KT AND STRONG FORCING WILL BE
SUPPORTIVE OF SUPERCELLS. THERMODYNAMIC PROFILES AND ROTATING STORMS
INDICATE THE MAIN THREAT WILL BE LARGE HAIL. HOWEVER...20-30 KT LOW
LEVEL SHEAR AND LARGE CLOCKWISE CURVED LOW LEVEL HODOGRAPHS WILL
FAVOR TORNADOES...SOME STRONG. HOWEVER...WARM ADVECTION DURING THE
DAY MAY RESULT IN WEAKER CONVECTION THROUGHOUT THE DAY AND
COMPLICATE THE LOCATION AND EVOLUTION OF STRONG CONVECTION LATER IN
THE DAY.
STORMS AND SQUALL WILL SPREAD ENEWD INTO AR/LA/SRN MO OVERNIGHT
...AND POSSIBLY AS FAR EAST AS WRN TN/NWRN MS BY DAYBREAK WED.
DESPITE SOME WEAK NOCTURNAL COOLING VERY STRONG KINEMATICS AND UPPER
SYSTEM FAVOR A HIGH POTENTIAL FOR SEVERE WEATHER... INCLUDING
TORNADOES...TUESDAY NIGHT.
As far as those winds are concerned, here is today's 12z GFS 925mb (2,500-3,500 ft in atmosphere) wind chart. If a squall line forms and mixes those winds down to the surface, that will be our primary severe threat, I think.
Day 2 Moderate Risk for NE TX, extreme NW LA, SW AR, and SE OK:
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CST MON FEB 09 2009
VALID 101200Z - 111200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF NERN
TX...SERN OK AND SWRN AR...
...THERE IS A SLGT RISK OF SVR TSTMS FROM TX/OK EAST-NORTHEASTWARD
INTO PORTIONS OF THE LOWER/MID MS VALLEY...
ACTIVE AND WIDESPREAD SEVERE WEATHER IS EXPECTED LATE TUESDAY
AFTERNOON AND NIGHT FROM PORTIONS OF OK/TX EWD INTO PORTIONS OF THE
LOWER/MID VS VALLEY. EVOLUTION OF CONVECTION APPEARS
COMPLICATED...AND THIS PRECLUDES A LARGER MODERATE RISK AREA.
MONITOR TUESDAY/S DAY 1 OUTLOOKS FOR UPDATES ON THIS SITUATION.
...SYNOPSIS...
LONGWAVE TROUGH WILL REMAIN SITUATED ACROSS THE WRN/CENTRAL
CONUS...AS A FAST MOVING SHORTWAVE TROUGH SHIFTS EWD FROM THE SWRN
STATES INTO THE ARKLATEX AREA BY EARLY WED MORNING. A 90-100 KT MID
LEVEL IS FORECAST TO ACCOMPANY THE UPPER SYSTEM AND MOVE INTO SWRN
TX BY LATE AFTERNOON...AND AR OVERNIGHT. WHILE NAM/GFS SHOW A
DEEPENING SURFACE LOW LOCATED NEAR THE MO/AR BY 11/12Z... NAM MOVES
THE DEVELOPING SURFACE LOW EWD ACROSS NRN OK AND THE GFS THOUGH NRN
TX TUESDAY.
TX/OK NEWD INTO THE MID MS VALLEY...
CURRENTLY PREFER GFS SURFACE LOW SOLUTION AS THE MAIN UPPER FORCING
SPREADS FROM SWRN TX TOWARD THE ARKLATEX DURING THE
AFTERNOON/EVENING HOURS. HOWEVER...SURFACE LOW LIKELY WILL NOT
DEVELOP UNTIL LATE UNTIL MAIN UPPER SYSTEM SHIFTS EWD INTO FAR WRN
TX. SINCE THE COLD FRONT CURRENTLY MOVING THROUGH SRN TX IS EXPECTED
TO STALL LATER TODAY...THIS SHOULD ALLOWING CURRENT LOWER/MID 60S TO
RETURN NWWD INTO SJT/ABI/SPS AREAS OF WRN TX AND NWD INTO
OK...MAINLY ALONG AND S OF I-44...TUESDAY. THESE DEWPOINTS COMBINED
WITH DIURNAL HEATING AND STRONG COOLING ALOFT...500 MB TEMPERATURES
FROM -18C TO -20C...SHOULD YIELD MLCAPES FROM 1000-1500 J/KG BY LATE
TUESDAY.
STRONG 850 MB FRONTOGENESIS AND INCREASING FORCING IS SUGGESTIVE OF
THE INITIAL CONVECTION DEVELOPING AS A SQUALL IN THE SPS/ABI/SJT
AREA...IN ASSOCIATION WITH THE DEVELOPING SURFACE LOW/TRAILING
FRONT. VERY STRONG ENVIRONMENTAL WINDS AND THE EXPECTED FAST
TRANSLATIONAL MOTION OF THE LINE SHOULD FAVOR WIND DAMAGE.
HOWEVER...FURTHER EAST ACROSS NRN TEXAS...SRN/ERN OK AND WRN
ARKANSAS...DISCRETE STORMS ARE ALSO LIKELY TO DEVELOP
BY LATE AFTERNOON IN STRENGTHENING DIFFLUENCE ALOFT AND CONSEQUENT
LOW-LEVEL CONVERGENCE/WARM ADVECTION WITHIN INTENSIFYING /50-70 KT/
850 JET CORE. EFFECTIVE SHEAR AT 40-60 KT AND STRONG FORCING WILL BE
SUPPORTIVE OF SUPERCELLS. THERMODYNAMIC PROFILES AND ROTATING STORMS
INDICATE THE MAIN THREAT WILL BE LARGE HAIL. HOWEVER...20-30 KT LOW
LEVEL SHEAR AND LARGE CLOCKWISE CURVED LOW LEVEL HODOGRAPHS WILL
FAVOR TORNADOES...SOME STRONG. HOWEVER...WARM ADVECTION DURING THE
DAY MAY RESULT IN WEAKER CONVECTION THROUGHOUT THE DAY AND
COMPLICATE THE LOCATION AND EVOLUTION OF STRONG CONVECTION LATER IN
THE DAY.
STORMS AND SQUALL WILL SPREAD ENEWD INTO AR/LA/SRN MO OVERNIGHT
...AND POSSIBLY AS FAR EAST AS WRN TN/NWRN MS BY DAYBREAK WED.
DESPITE SOME WEAK NOCTURNAL COOLING VERY STRONG KINEMATICS AND UPPER
SYSTEM FAVOR A HIGH POTENTIAL FOR SEVERE WEATHER... INCLUDING
TORNADOES...TUESDAY NIGHT.
