SPC AC 030508
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1208 AM CDT THU SEP 03 2009
VALID 031200Z - 041200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PATTERN ALOFT IS FCST TO FEATURE MEAN RIDGING OVER WRN CONUS AND
TROUGHING E OF MS RIVER THROUGH PERIOD. WRN SYNOPTIC RIDGE WILL BE
BREACHED BY STG SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY AS CYCLONE CENTERED INVOF 45N130W -- FCST TO MOVE INLAND
AROUND 3/12Z. THIS PERTURBATION WILL MOVE NEWD ACROSS PAC NW EARLY
IN PERIOD...AND ACROSS CANADIAN ROCKIES FROM ABOUT
4/00Z-4/06Z...REACHING TO NEAR S-CENTRAL AB/SK BORDER BY END OF
PERIOD. MEANWHILE...EACH OF A PAIR OF 500 MB LOWS -- NOW EVIDENT
OVER SERN SD AND SWRN IL -- IS FCST TO PIVOT CYCLONICALLY...LEADING
LOW REACHING OH/WV BORDER AREA AND WRN LOW MOVING ACROSS ERN NEB
TOWARD NERN KS BY 4/12Z.
AT SFC...DIFFUSE FRONTAL ZONE NOW OVER WRN OK/SWRN KS SHOULD BECOME
QUASISTATIONARY...EXTENDING NWWD TO WEAK SFC LOW OVER W-CENTRAL/NW
KS BY 4/00Z...THEN MERGING WITH ANOTHER FRONTAL ZONE NEAR THAT LOW
AND EXTENDING FARTHER NW INTO E-CENTRAL/SERN WY AS COLD FRONT.
PERSISTENT/RESIDUAL LOW-LEVEL FRONTAL ZONE ALSO WILL LINGER ACROSS
CENTRAL/SWRN FL PENINSULA...ALMOST DIRECTLY BENEATH AND PARALLEL TO
QUASISTATIONARY/MID-UPPER LEVEL VORTICITY LOBE...IN SUPPORT OF GEN
TSTM POTENTIAL IN THAT AREA.
...SRN OK TO N-CENTRAL/NE TX...
WIDELY SCATTERED TO SCATTERED TSTMS MAY BE ONGOING AT BEGINNING OF
PERIOD NEAR NRN FRINGE OF THIS AREA...ACROSS PORTIONS ERN OK AND/OR
NE TX...WHICH SHOULD WEAKEN DURING MID-LATE MORNING.
ADDITIONAL/AFTERNOON DEVELOPMENT IS POSSIBLE MAINLY ALONG AND E OF
SFC FRONTAL ZONE...AS STG SFC HEATING AND WEAK CONVERGENCE
CONTRIBUTE TO LOCALLY MINIMIZED MLCINH. MODIFIED FCST SOUNDINGS
SUGGEST SUFFICIENTLY STEEP MIDLEVEL LAPSE RATES TO SUPPORT MLCAPE
1500-2000 J/KG WITH SFC DEW POINTS ONLY IN LOW-MID 60S F. BOUNDARY
LAYER AIR MASS WILL BE SIGNIFICANTLY DRIER AND MORE DEEPLY MIXED
WITH SSWWD EXTENT FROM FRONTAL ZONE...SUPPORTING GUST POTENTIAL BUT
ALSO REDUCING CAPE. LOW LEVEL WINDS WILL BE WEAK ACROSS
REGION...LIMITING BOTH HODOGRAPH SIZE AND CONVERGENCE.
HOWEVER...PRONOUNCED VEERING OF WINDS WITH HEIGHT AND STRONGER
MID-UPPER LEVEL WINDS -- INCLUDING PROJECTED ANVIL-LEVEL SPEEDS
50-55 KT -- MAY AID IN MULTICELLULAR ORGANIZATION. ISOLATED SVR
HAIL AND DAMAGING GUSTS ARE POSSIBLE.
...S-CENTRAL HIGH PLAINS TO SW OK/NW TX...
DIURNAL DEVELOPMENT OF WIDELY SCATTERED TSTMS IS EXPECTED FROM
S-CENTRAL NEB SWWD ACROSS SERN CO/NERN NM...INVOF SFC TROUGH/FRONTAL
ZONE AND HIGHER TERRAIN OF SRN CO/NERN NM. SFC DEW POINTS MID 50S
TO LOW 60S WILL BE COMMON AWAY FROM HIGHER ELEVATIONS. THIS
MOISTURE...COMBINED WITH DIURNAL HEATING...WILL HELP TO YIELD
1500-2000 J/KG MLCAPE. STG DIRECTIONAL SHEAR IS FCST ACROSS MOST OF
THIS REGION...IN ADDITION TO SOMEWHAT MORE ROBUST SPEED SHEAR OVER
NRN KS/SRN NEB IN SUPPORT OF AT LEAST MRGL/TRANSIENT SUPERCELL
POTENTIAL OVER LATTER AREA.
NOCTURNAL CONVECTIVE COMPLEX MAY PERSIST SEWD ACROSS TX
PANHANDLE...PORTIONS WRN OK AND/OR NW TX AS UPSCALE/EVOLUTIONARY
EXTENSION OF AFTERNOON/EARLY EVENING TSTMS MOVING SEWD OFF S-CENTRAL
HIGH PLAINS. THIS SCENARIO IS SUPPORTED BY OPERATIONAL SPECTRAL AND
SOME SREF MEMBERS...ANY SUCH ACTIVITY WOULD MOVE PARALLEL TO AND
VERY NEAR INSTABILITY/MOISTURE GRADIENT RELATED TO FRONTAL
ZONE...WITH POTENTIAL FOR ISOLATED HAIL OR STG/DAMAGING GUSTS. LACK
OF MORE ROBUST SPEEDS ALOFT...AND OF RELATED DEEP-LAYER
SHEAR...SHOULD MITIGATE ORGANIZATION OF SVR POTENTIAL...BUT MRGL
THREAT MAY PERSIST SEWD INTO WRN RED RIVER VALLEY REGION....HENCE
SOME SPATIAL OVERLAP WITH AREA COVERED BY ABOVE REGIME EARLIER IN
PERIOD.
..EDWARDS/HURLBUT.. 09/03/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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