SPC AC 010532
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 AM CDT WED JUL 01 2009
VALID 011200Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NRN AND CNTRL
HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE LOWER HUDSON
VALLEY...SRN NEW ENGLAND AND THE MID ATLANTIC STATES...
...SYNOPSIS...
SYNOPTIC PATTERN WILL REMAIN LARGELY UNCHANGED...FEATURING
MID/UPPER-LEVEL LOWS OVER THE GREAT LAKES AND WRN CANADA. WITHIN
THIS REGIME...WELL-DEFINED VORTICITY MAXIMUM NOW OVER THE LOWER OH
VALLEY WILL ROTATE NEWD AROUND UPPER LOW THROUGH THE MID ATLANTIC
STATES AND NEW ENGLAND. A SECONDARY IMPULSE IMMEDIATELY UPSTREAM
FROM THE FORMER WILL MOVE THROUGH THE MID ATLANTIC STATES LATER
TODAY INTO TONIGHT. IN THE WEST...SHORT WAVE TROUGH CURRENTLY
CRESTING RIDGE AXIS OVER NV WILL TURN MORE EWD TODAY EMERGING OVER
THE NRN HIGH PLAINS NEAR PEAK HEATING.
AT THE SURFACE...A LOW-LEVEL CONVERGENCE ZONE WILL BE MAINTAINED
FROM THE HUDSON VALLEY TO MID ATLANTIC COAST WITH A SECONDARY
FRONTAL SURGE MOVING THROUGH THE BLUE RIDGE THIS AFTERNOON INTO
EVENING. FARTHER W...A WEAK SURFACE LOW IS FORECAST TO DEVELOP SEWD
THROUGH THE NRN HIGH PLAINS IN CONJUNCTION WITH A SIMILARLY-MOVING
COLD FRONT. THIS FRONT WILL GRADUALLY OVERTAKE STATIONARY BOUNDARY
WHICH WILL BE ORIENTED NNW-SSE OVER WRN PARTS OF THE DAKOTAS AND
NEB.
...NRN/CNTRL HIGH PLAINS...
OVERALL PATTERN WILL BE SOMEWHAT SIMILAR TO TUESDAY/S WITH SCATTERED
TSTMS ANTICIPATED BY AFTERNOON ALONG BOTH COLD AND STATIONARY
BOUNDARIES IN ADVANCE OF SHORT WAVE TROUGH. THE STRONGEST AIR MASS
DESTABILIZATION IS FORECAST ALONG STATIONARY BOUNDARY WHERE
DEWPOINTS IN THE 50S COUPLED WITH STEEP MIDLEVEL LAPSE RATES AND
DIABATIC HEATING WILL CONTRIBUTE TO MLCAPE OF 1000-2000 J/KG.
FORECAST HODOGRAPHS ALONG IMMEDIATE COOL SIDE OF BOUNDARY FEATURE
VEERING WINDS WITH HEIGHT...RESULTING IN MODEST LOW AND DEEP-LAYER
SHEAR...SUPPORTIVE OF SUPERCELLS. WHILE LARGE HAIL AND DAMAGING
WINDS GUSTS WILL BE THE PRIMARY SEVERE WEATHER THREATS...A TORNADO
OR TWO IS POSSIBLE WITH ANY STORMS THAT CAN FAVORABLY INTERACT WITH
SURFACE BOUNDARY.
STORMS SHOULD GROW UPSCALE INTO CLUSTERS OR AN MCS TONIGHT OVER WRN
OR CNTRL NEB WITH A CONTINUED POTENTIAL FOR LARGE HAIL AND DAMAGING
WIND GUSTS.
...HUDSON VALLEY/NEW ENGLAND INTO THE MID ATLANTIC STATES...
HERE TOO...SYNOPTIC SETUP WILL REMAIN QUITE SIMILAR TO THAT OF
TUESDAY. HOWEVER...TODAY IT APPEARS THAT CLOUDS AND THE EARLY ONSET
OF PRECIPITATION MAY IMPEDE THE DESTABILIZATION PROCESS OVER PARTS
OF THE HUDSON VALLEY AND NEW ENGLAND. LATEST MODEL GUIDANCE DOES
SUGGEST THAT STRONGER DAYTIME HEATING AND RESULTANT AIR MASS
DESTABILIZATION WILL OCCUR FROM THE PIEDMONT NEWD THROUGH THE DE
RIVER VALLEY INTO LOWER HUDSON VALLEY. THEREFORE...THE HIGHER
WIND/HAIL PROBABILITIES HAVE BEEN ADJUSTED SLIGHTLY S FROM INITIAL
DAY TWO OUTLOOKS.
TSTMS SHOULD INCREASE IN COVERAGE AND INTENSITY THROUGH THE
AFTERNOON IN ADVANCE OF SHORT WAVE TROUGH/PV ANOMALY WHICH WILL BE
LIFTING NEWD THROUGH THE REGION. THE COMBINATION OF MLCAPE
APPROACHING 500-1500 J/KG AND 30-35 KT OF DEEP LAYER SHEAR MAY
SUPPORT A FEW STRONGER/MORE ORGANIZED STORMS CAPABLE OF DAMAGING
WIND GUSTS AND HAIL THROUGH THIS EVENING.
ADDITIONAL STORMS WILL BE POSSIBLE THIS AFTERNOON ALONG SECONDARY
FRONT EMERGING FROM THE BLUE RIDGE OVER WRN/CNTRL VA. FORECAST
HODOGRAPHS INDICATE LARGELY UNIDIRECTIONAL WLY TROPOSPHERIC FLOW
ALONG THIS FRONT WITH THE POTENTIAL FOR A FEW DAMAGING WIND GUSTS
AND PERHAPS SOME HAIL EWD TOWARD CHESAPEAKE BAY LATER THIS AFTERNOON
INTO THIS EVENING.
...AZ...
THE COMBINATION OF PW VALUES OF 1.2-1.5 INCHES AND MODESTLY STEEP
LAPSE RATES WILL YIELD POCKETS OF MODERATE INSTABILITY TODAY OVER
THE LOWER DESERTS. SCATTERED TSTMS WILL AGAIN BE POSSIBLE ALONG THE
HIGHER TERRAIN WITH ELY WINDS THROUGH THE LOWEST 5-6 KM SUPPORTING
THE SWWD MOVEMENT/PROPAGATION OF STORMS CAPABLE OF LOCALLY DAMAGING
WIND GUSTS THROUGH THIS EVENING.
..MEAD/GARNER.. 07/01/2009
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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