SWODY1
SPC AC 020554
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT SUN AUG 02 2009
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CAROLINAS TO LOWER
HUDSON VALLEY REGION...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN ORE...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NRN PLAINS/UPPER
MIDWEST...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS S-CENTRAL HIGH
PLAINS...
...SYNOPSIS...
LARGE SCALE PATTERN WILL CONTINUE TO INCLUDE WRN CONUS RIDGE AND
TROUGHING OVER GREAT LAKES/MS VALLEY...BUT TRENDING SOMEWHAT TOWARD
LOWER AMPLITUDE BEGINNING THIS PERIOD. PERSISTENT...LARGE AND
QUASISTATIONARY CYCLONE IN MID-UPPER LEVELS WILL REMAIN OFFSHORE
CA...ITS CENTER DRIFTING ERRATICALLY INVOF 36N130W. SHORTWAVE
TROUGH -- NOW EVIDENT OVER SRN BC -- IS FCST TO MOVE SEWD ACROSS NRN
ROCKIES...REACHING NRN HIGH PLAINS BY AROUND 3/00Z AND NRN IA 12
HOURS LATER. PERTURBATION NOW EVIDENT OVER TN VALLEY REGION AND KY
SHOULD LIFT NEWD ACROSS CENTRAL APPALACHIANS NEAR BEGINNING OF
PERIOD...THEN NNEWD OVER CENTRAL NY DURING DAY...MERGING WITH
INITIALLY SEPARATE VORTICITY LOBE ACCOMPANYING STG SHORTWAVE TROUGH
NOW OVER WI/UPPER MI.
AT SFC...COLD FRONT NOW ANALYZED FROM LOWER MI TO SRN IL...NRN AR
AND N-CENTRAL TX...IS EXACTED TO MOVE EWD ACROSS LOWER GREAT LAKES
AND NRN/CENTRAL APPALACHIANS...BECOMING DIFFUSE AND QUASISTATIONARY
FARTHER SWWD OVER SRN APPALACHIANS...TN VALLEY AND ARKLATEX REGIONS.
MEANWHILE...SFC LOW PRECEDING NWRN CONUS SHORTWAVE TROUGH SHOULD
MOVE SEWD FROM SERN SASK TO CENTRAL/SERN MN BY 3/00Z...THEN ENEWD
OVER UPPER MI. TRAILING COLD FRONT SHOULD BE POSITIONED ACROSS
E-CENTRAL THROUGH SWRN SD INTO NERN WY BY LATE AFTERNOON...REACHING
NRN WI...NWRN IA AND CENTRAL NEB BY 3/12Z.
...CAROLINAS TO LOWER HUDSON VALLEY REGION...
SVR POTENTIAL FCST TO INCREASE FROM MID-DAY THROUGH MID-AFTERNOON
OVER THIS REGION AS DIURNAL HEATING AND WAA CONTRIBUTE TO WEAK
MLCINH. AFTERNOON DESTABILIZATION BECOMES MORE UNCERTAIN AND MRGL
WITH NWD EXTENT FROM DE VALLEY REGION BECAUSE OF LIKELIHOOD OF
ANTECEDENT CLOUD COVER AND PRECIP...COMBINED WITH WEAK MIDLEVEL
LAPSE RATES. MEANWHILE DEEP-LAYER WIND PROFILES AND SHEAR VALUES
WILL STRENGTHEN FROM THAT AREA NWD...IN INCREASING PROXIMITY TO
MID-UPPER LEVEL JET MAXIMA. LOW LEVEL SHEAR AND HODOGRAPH SIZE EACH
SHOULD BE MAXIMIZED ALONG AND E OF SFC TROUGH AND WIND SHIFT LINE
FROM VA PIEDMONT NNEWD TOWARD ALB AREA. MOST PROBABLE JUXTAPOSITION
OF SHEAR AND BUOYANCY SUPPORTING SUPERCELL POTENTIAL CURRENTLY
APPEARS TO BE BETWEEN DE VALLEY AND SERN NY...WHERE LOW LEVEL THETAE
AXIS AND SFC TROUGH ARE PROGGED IN CLOSE PROXIMITY.
MID-ATLANTIC STORM MODE SHOULD BE DOMINATED BY LINEAR AND CLUSTERED
CONFIGURATIONS WITH DAMAGING GUSTS BEING MAIN THREAT. HOWEVER...ANY
RELATIVELY DISCRETE/SUSTAINED STORMS COULD BECOME SUPERCELLS...WITH
POTENTIAL FOR A FEW TORNADOES IN WHAT SHOULD BE RICHLY
MOIST...LOW-LCL ENVIRONMENT NEAR SFC TROUGH. SHEAR SHOULD BECOME
QUITE WEAK SWD ACROSS CAROLINAS. NEBULOUSLY DEFINED TRANSITION
EXISTS FROM ORGANIZED SVR POTENTIAL OVER MID-ATLANTIC REGION TO
DISORGANIZED MULTICELL/SVR POTENTIAL INVOF SEA BREEZES...SFC TROUGHS
AND OUTFLOW BOUNDARIES BETWEEN SRN ATLANTIC COAST AND E TX.
...SRN ORE...
SCATTERED TSTMS FCST TO DEVELOP AGAIN THIS AFTERNOON WITHIN
PERIPHERAL BELT OF SE FLOW ALOFT ENCIRCLING PACIFIC CYCLONE.
ACTIVITY SHOULD FORM INITIALLY OVER HIGHER TERRAIN...WITH PRIMARY
CONCERN BEING LARGE HAIL...AND ISOLATED DAMAGING GUSTS ALSO
POSSIBLE. STG SFC HEATING AND RELATIVELY RICH LOW LEVEL MOISTURE --
SUPPORTING .75-1.25 INCH PW -- SHOULD AID AIR MASS RECOVERY FROM
PRIOR DAY'S CONVECTION...AND BOOST PRECONVECTIVE MLCAPE INTO
1000-1500 J/KG RANGE IN SOME LOCALES...SIMILAR TO 02/00Z MFR RAOB.
ACTIVITY MOVING OVER LOWER ELEVATIONS ALSO WILL ENCOUNTER
DEEP/WELL-MIXED BOUNDARY LAYER SUPPORTING POTENTIAL FOR HAIL/GUSTS
GENERATED ALOFT TO REACH SFC.
...NRN PLAINS/UPPER MIDWEST...
SCATTERED AFTERNOON TSTM DEVELOPMENT OVER THIS AREA WILL BE
SUPPORTED BY CONVERGENCE INVOF SFC LOW AND COLD FRONT...ALONG WITH
DIURNAL HEATING AND AT LEAST MRGL LOW LEVEL MOISTURE. SVR HAIL AND
STG-SVR GUSTS ARE POSSIBLE. GIVEN AMBIENT SFC DEW POINT GENERALLY
50S F...COVERAGE OF MID-UPPER 60S DEW POINTS PROGGED BY OPERATIONAL
WRF AND ETA-KF APPEARS UNREASONABLY LARGE. STILL...50S TO LOW 60S
DEW POINTS WILL SUPPORT 1000-2000 J/KG MLCAPE IN MODIFIED FCST
SOUNDINGS. SHEAR WILL BE LIMITED BY SW FLOW ALONG/AHEAD OF SFC COLD
FRONT...BUT SOME FAVORABLE DEEP-LAYER SHEAR AND HODOGRAPH CURVATURE
FOR SUPERCELLS MAY EXIST NEAR AND JUST S THROUGH SE OF SFC LOW.
...S-CENTRAL HIGH PLAINS...
RELATIVELY MAXIMIZED SVR POTENTIAL IS EXPECTED OVER THIS REGION AS
CONCENTRATION OF TSTMS DEVELOPS IN LEE TROUGH/CONVERGENCE ZONE.
FCST SHEAR/BUOYANCY PROFILES MAY SUPPORT A SUPERCELL OR TWO WITH
ATTENDANT HAIL/SVR GUST RISK. STG SFC HEATING IS FCST INVOF MOIST
AXIS THAT WILL BE CHARACTERIZED BY 50S TO LOW 60S F SFC DEW POINTS.
THIS WILL SUPPORT MLCAPE 1500-2500 J/KG...ATOP WELL-MIXED SUBCLOUD
LAYERS THAT ENCOURAGE STG-SVR GUSTS AND HAIL TO REACH SFC. ALTHOUGH
SFC WINDS WILL BE SSWLY TO SWLY ACROSS MUCH OF THIS
REGION...WRF/ETA-KF FCST SOUNDINGS STILL SUGGEST ENOUGH
VEERING/STRENGTHENING OF FLOW WITH HEIGHT IN BOUNDARY LAYER TO
SUPPORT CURVED HODOGRAPHS AND 150-250 J/KG OF 0-3 KM SRH BY
03/00Z...WITH AROUND 35 KT EFFECTIVE SHEAR MAGNITUDES AND 50-60 KT
ANVIL LEVEL STORM-RELATIVE WINDS.
..EDWARDS/HURLBUT.. 08/02/2009
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