SPC AC 180100
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0800 PM CDT MON MAR 17 2008
VALID 180100Z - 181200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM PARTS OF S CNTRL THROUGH
CNTRL TX...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PART OF THE SRN
PLAINS INTO THE LOWER MS VALLEY...
...TX...
A COLD FRONT EXTENDS FROM SRN MO SWWD THROUGH CNTRL OK INTO THE
TRANS-PECOS REGION. A DRYLINE EXTENDS FROM THE RIO GRANDE NWD TO
JUST NORTH OF SAN ANGELO WHERE IT INTERSECTS THE COLD FRONT. A WARM
FRONT EXTENDS FROM SRN AR NWWD THROUGH S CNTRL OK. THE COLD FRONT
WILL ADVANCE SLOWLY SEWD THROUGH THE MID MS VALLEY AND SRN PLAINS AS
NRN STREAM UPPER TROUGH MIGRATES TOWARD THE UPPER MS VALLEY. THE
WARM FRONT WILL LIFT SLOWLY NWD THROUGH ARKANSAS AND ERN OK TONIGHT
AS THE LOW LEVEL JET STRENGTHENS ACROSS ERN TX INTO THE LOWER MS
VALLEY.
THUNDERSTORMS ARE INITIATING IN WARM SECTOR BETWEEN JUNCTION AND
HONDO WHERE THE TEMPERATURES NEAR 90 AND DEWPOINTS AROUND 60
INDICATE SUFFICIENT BOUNDARY LAYER MIXING HAS OCCURRED TO WEAKEN THE
CAP. THESE STORMS ARE NOW INTERCEPTING RICHER LOW LEVEL MOISTURE
WITH DEWPOINTS IN THE UPPER 60S RETURNING NWWD THROUGH SRN TX.
LATEST VWP DATA SHOW PRONOUNCED 0-2 KM DIRECTIONAL SHEAR. THE LOW
LEVEL JET WILL GRADUALLY STRENGTHEN IN THIS REGION TONIGHT WITHIN
INCREASING DIVERGENT UPPER FLOW REGIME AS EXIT REGION OF MID LEVEL
JET ROTATES THROUGH BASE OF UPPER TROUGH AND INTO SW TX. THIS WILL
ENHANCE LOW LEVEL HODOGRAPHS...AND WITH MODERATE INSTABILITY AND
STEEP LAPSE RATES IN PLACE...THE ENVIRONMENT WILL BECOME
INCREASINGLY FAVORABLE FOR SUPERCELLS TO DEVELOP LOW LEVEL
MESOCYCLONES WITH VERY LARGE HAIL AND A FEW TORNADOES THIS EVENING.
OTHER STORMS ARE DEVELOPING FARTHER WEST ALONG THE PACIFIC FRONT
OVER ERN PORTIONS OF WRN TX. STRONG BULK SHEAR WILL CONTINUE TO
SUPPORT SUPERCELLS STRUCTURES THIS EVENING WITH LARGE HAIL THE MAIN
THREAT. ISOLATED TORNADOES WILL ALSO REMAIN POSSIBLE. HOWEVER...LOW
LEVEL FLOW AND HODOGRAPHS ARE MUCH WEAKER IN THIS REGION. THIS ALONG
WITH LARGER BOUNDARY LAYER TEMPERATURE-DEWPOINT SPREADS SUGGESTS THE
TORNADO THREAT WILL PROBABLY NOT BE AS HIGH AS IN AREAS FARTHER
EAST. AS THE LOW LEVEL JET STRENGTHENS OVERNIGHT...CONVERGENCE ALONG
THE FRONT WILL INCREASE. THIS COUPLED WITH A TENDENCY FOR THE UPPER
FLOW TO BACK WITH TIME SUGGEST STORMS SHOULD EVENTUALLY EVOLVE INTO
MORE LINEAR STRUCTURES. HOWEVER...EMBEDDED ORGANIZED STORMS
INCLUDING SUPERCELLS WILL REMAIN POSSIBLE AS ACTIVITY DEVELOPS EWD
OVERNIGHT.
......ERN OK...NERN TX THROUGH WRN AR...
THUNDERSTORMS HAVE DEVELOPED WITHIN ZONE OF LOW LEVEL WARM ADVECTION
IN VICINITY OF THE WARM FRONT FROM NERN TX...SERN OK INTO SWRN AR.
LOW LEVEL HODOGRAPHS AND BULK SHEAR REMAIN FAVORABLE FOR SUPERCELLS
WITH ISOLATED TORNADOES AND LARGE HAIL. THE BOUNDARY LAYER WILL
SLOWLY DESTABILIZE NWD WITH TIME AS THE WARM FRONT RETREATS.
HOWEVER...THE ONSET OF NOCTURNAL COOLING AND ONGOING CONVECTION ON
COOL SIDE OF FRONT WILL SLOW ITS NWD PROGRESS. CURRENT THINKING IS
THAT TORNADO THREAT WILL REMAIN CONFINED TO NERN TX...WRN AR AND ERN
OK WITH HAIL THE MAIN THREAT FARTHER NORTH.
...WRN AND CNTRL OK...
STORMS CONTINUE DEVELOPING ALONG AND JUST BEHIND THE COLD FRONT FROM
SWRN THROUGH W CNTRL OK. THE 00Z RAOB SHOWS WEAK LOW LEVEL SHEAR AND
SMALL HODOGRAPHS. HOWEVER...BULK SHEAR IS SUPPORTIVE OF SUPERCELL
STRUCTURES. STORMS WILL LIKELY INCREASE IN COVERAGE DURING THE
EVENING AS THIS BOUNDARY ADVANCES SEWD. LARGE HAIL AND ISOLATED
STRONG WIND GUSTS ARE EXPECTED TO REMAIN THE PRIMARY THREATS IN THIS
REGION.
..DIAL.. 03/18/2008
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
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