SPC AC 090556
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT MON MAR 09 2009
VALID 091200Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF N TX NEWD
ACROSS OK/SERN KS/NWRN AR AND INTO MO/SRN IL...
...SYNOPSIS...
NRN STREAM UPPER TROUGH IS FORECAST TO DIG SEWD ACROSS THE ROCKIES
THIS PERIOD...WHILE WEAKER SRN STREAM DISTURBANCES EJECT NEWD AHEAD
OF THIS TROUGH IN FAST SWLY MID-LEVEL FLOW.
AT THE SURFACE...LOW-LEVEL MOISTURE NOW ACROSS CENTRAL AND ERN TX
WILL CONTINUE SPREADING NWWD ACROSS N TX AND INTO OK...AS LOW
PRESSURE REMAINS INVOF SERN CO THROUGH THE DAY AND A WEAK WARM FRONT
SHIFTS NWD. MEANWHILE...A DRYLINE IS FORECAST TO MIX EWD INTO WRN
OK/WRN N TX THROUGH THE AFTERNOON.
AS THE UPPER TROUGH CONTINUES ACROSS THE ROCKIES YIELDING WEAK
PRESSURE FALLS ACROSS THE CENTRAL CONUS...A WEAK SURFACE WAVE OR
WAVES SHOULD SHIFT EWD ALONG THE RETREATING WARM FRONT. BY THE END
OF THE PERIOD...IT APPEARS THAT AN ELONGATED AREA OF LOW PRESSURE
WILL EXTEND FROM IL WWD ACROSS MO AND INTO THE KS/OK VICINITY.
...PARTS OF TX INTO OK/SERN KS AND EWD INTO THE MID MS VALLEY...
THUNDERSTORMS WILL LIKELY INCREASE EARLY IN THE PERIOD ACROSS N
TX/OK AND VICINITY...IN AREA OF INCREASING WARM ADVECTION INVOF THE
RETREATING WARM FRONT. ELEVATED INSTABILITY MAY BE SUFFICIENT TO
SUPPORT A FEW STRONGER CELLS...THOUGH WEAK LAPSE RATES SUGGEST ONLY
A MARGINAL HAIL THREAT.
WITH TIME...LOW-LEVEL MOISTENING WILL SPREAD NWD ACROSS OK...THOUGH
HIGH CLOUDINESS SHOULD HINDER HEATING TO SOME DEGREE. BY
AFTERNOON...MARGINAL INSTABILITY /AROUND 500 J/KG MIXED-LAYER CAPE/
IS EXPECTED...WITH ADDITIONAL CONVECTION FORECAST TO DEVELOP ACROSS
OK INVOF THE RETREATING FRONT...AND EVENTUALLY FARTHER W ACROSS OK
AND SWD INTO TX ALONG THE DRYLINE MIXING EWD THROUGH THE AFTERNOON.
WHILE DEGREE OF INSTABILITY SHOULD BE A LIMITING FACTOR...THE
DEEP-LAYER WIND FIELD WILL BE QUITE SUPPORTIVE OF SEVERE/SUPERCELL
STORMS...WITH SLY WARM SECTOR BOUNDARY-LAYER FLOW VEERING/INCREASING
TO 70 TO 80 KT FROM THE WSW AT MID LEVELS. ALONG WITH THE POTENTIAL
FOR HAIL...LOCALLY-DAMAGING WINDS WILL ALSO BE POSSIBLE. THE
GREATEST TORNADO THREAT SHOULD OCCUR DURING THE LATE AFTERNOON/EARLY
EVENING FROM CENTRAL OK NEWD INTO SWRN MO INVOF THE WARM
FRONT...WHERE THE MOST FAVORABLE LOW-LEVEL SHEAR IS ANTICIPATED.
HOWEVER...AN ISOLATED TORNADO THREAT WILL ALSO EXIST WITH STORMS
DEVELOPING INVOF THE DRYLINE ACROSS WRN OK AND INTO WRN N TX.
LATER IN THE EVENING/OVERNIGHT...STORMS MAY EVOLVE INTO ONE OR MORE
MCS/S...AS CONVECTION SPREADS INTO MO. WIND THREAT MAY THUS
INCREASE...WHILE SOME HAIL AND ISOLATED TORNADOES WILL REMAIN
POSSIBLE. THE POTENTIAL FOR HAIL WITH ELEVATED STORMS N OF THE
SURFACE FRONT MAY EXTEND INTO NRN MO...AND EWD INTO IL/IN LATE IN
THE PERIOD.
STORMS ARE ALSO FORECAST TO PERSIST INVOF THE DRYLINE ACROSS TX
THROUGH THE EVENING AND INTO THE OVERNIGHT HOURS -- AS WEAK SRN
STREAM DISTURBANCES CONTINUE SHIFTING SW-NE ACROSS NWRN TX. WHILE A
LESSER TORNADO THREAT APPEARS TO EXIST WITH SWD
EXTENT...LOCALLY-DAMAGING WINDS AND HAIL WILL BE POSSIBLE.
..GOSS.. 03/09/2009
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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