SPC AC 051248
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0748 AM CDT THU JUL 05 2007
VALID 051300Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT LAKES AND OHIO
VALLEY INTO THE MID ATLANTIC STATES AND SRN NEW ENGLAND...
...SYNOPSIS...
HIGH AMPLITUDE FLOW PATTERN WILL PERSIST THROUGH THE PERIOD WITH
MAJOR LONG WAVE TROUGH OVER THE ERN STATES AND UPPER RIDGE AXIS FROM
THE SOUTHWEST US INTO THE CANADIAN ROCKIES. ERN TROUGH IS EXPECTED
TO DEEPEN AS SERIES OF SHORT WAVE TROUGHS/VORTICITY MAXIMA MOVE SEWD
ACROSS THE GREAT LAKES INTO THE MIDDLE ATLANTIC STATES.
AT THE SURFACE...PRIMARY LOW WILL MOVE SLOWLY EWD OVER CENTRAL
QUEBEC WHILE A SOMEWHAT DIFFUSE COLD FRONT TRAILING SWWD FROM THE
LOW MOVES SEWD ACROSS THE LOWER GREAT LAKES AND MIDDLE MS VALLEY
TODAY...REACHING A NRN ATLANTIC COAST/DELMARVA/NRN AR LINE LATE
TONIGHT.
...OH VALLEY...MIDDLE ATLANTIC STATES INTO SRN NEW ENGLAND...
CLOUD COVER ACROSS MUCH OF THE REGION WILL LIKELY IMPACT THE
THERMODYNAMIC ENVIRONMENT TODAY BY LIMITING HEATING AND
DESTABILIZATION. LATEST VISIBLE SATELLITE IMAGERY SHOWS WIDESPREAD
CLOUDS ACROSS THE AREA...ALTHOUGH A CORRIDOR OF MAINLY CLEAR SKIES
FROM NRN INDIANA ACROSS NRN OH/LAKE ERIE INTO WRN NY/NWRN PA IS
EXPECTED TO SPREAD EWD/ESEWD TODAY AND PROVIDE AN AXIS OF STRONGER
HEATING AND DESTABILIZATION. IN ADDITION...SOME BREAKS IN THE CLOUD
COVER ARE EXPECTED TO DEVELOP AND LOCALLY ENHANCE HEATING.
CONTINUING CONVECTION FROM KY ACROSS NRN VA MAY MAINTAIN CLOUD
SHIELD ACROSS THIS REGION AND LIMIT SEVERE POTENTIAL...SO SRN EDGE
OF SLIGHT RISK HAS BEEN ADJUSTED NWD IN LATEST OUTLOOK.
WITH SURFACE DEW POINTS IN THE LOW-UPPER 60S...AIR MASS IS EXPECTED
TO BECOME INCREASINGLY UNSTABLE WITH MLCAPE RANGING FROM 500-1000
J/KG OVER SRN NEW ENGLAND TO 2000 J/KG INTO PARTS OF THE OH VALLEY.
DYNAMIC FORCING FOR LARGE SCALE ASCENT IS EXPECTED TO INCREASE AS
VORTICITY MAXIMA CURRENTLY OVER LAKE HURON AND WRN LAKE SUPERIOR
MOVE SEWD ACROSS THE GREAT LAKES...AND MID LEVEL JET CORES OF 40-50
KT PROGRESS ACROSS OH TOWARD SRN NEW ENGLAND. THESE WILL CONTRIBUTE
TO AN INCREASE IN DEEP LAYER SHEAR TO AROUND 40 KT ACROSS THIS
REGION.
CONVECTION HAS BEEN SLOWLY INCREASING THIS MORNING ACROSS OH AND
ADDITIONAL STORMS ARE LIKELY TO FORM DOWNSTREAM OVER PARTS OF PA/SRN
NY AND SRN NEW ENGLAND THROUGH THE EVENING HOURS. THE LACK OF A
DOMINANT LOW LEVEL CONVERGENCE ZONE INDICATES THAT MULTIPLE CELLS
AND BANDS OF STORMS WILL BE POSSIBLE GIVEN THE WEAKLY CAPPED
ENVIRONMENT AND LARGELY UNIDIRECTIONAL SHEAR ABOVE THE SURFACE.
UPDRAFT INTENSITY WILL BE PARTIALLY DEPENDENT ON DEGREE OF
HEATING/INSTABILITY THAT CAN OCCUR...ALTHOUGH GRADUAL COOLING ALOFT
ASSOCIATED WITH THE DEEPENING TROUGH MAY COMPENSATE IN AREAS WHERE
CLOUD COVER IS GREATER. THE FAVORABLE VERTICAL SHEAR COUPLED WITH
INCREASING DYNAMIC FORCING SUGGEST POTENTIAL FOR A FEW SEVERE
THUNDERSTORMS TO DEVELOP WITH PRIMARY THREAT FOR DAMAGING WIND GUSTS
AND OCCASIONAL HAIL. THE SEVERE POTENTIAL SHOULD CONTINUE THROUGH
THE EVENING HOURS WITH ISOLATED SEVERE STORMS POSSIBLY PERSISTING
OVER SRN NEW ENGLAND AND THE MID ATLANTIC REGION THROUGH 06Z.
...UPPER GREAT LAKES...
RESIDUAL LOW LEVEL MOISTURE WITH SURFACE DEW POINTS IN THE UPPER 50S
AND LOWER 60S IS OVER PARTS OF WI AND MI. VISIBLE IMAGERY SHOWS
REGIONS OF CLEAR SKIES WHICH WILL ALLOW AREAS OF STRONG DIABATIC
HEATING TO OCCUR TODAY. A MID LEVEL THERMAL TROUGH WITH
TEMPERATURES OF -14 TO -16C IS FORECAST TO SPREAD SEWD ACROSS WI
INTO MI THIS AFTERNOON WHICH WILL STEEPEN LAPSE RATES AND CONTRIBUTE
TO MLCAPE OF 500-1000 J/KG. LOW TOP THUNDERSTORMS ARE MOVING SEWD
ACROSS WRN PARTS OF LAKE SUPERIOR/UPPER MI INTO NRN WI AND
ADDITIONAL CONVECTION IS LIKELY TO DEVELOP SEWD BY THIS AFTERNOON IN
ASSOCIATION WITH VORTICITY MAX CROSSING NERN MN. STRONGER CELLS
WILL BE CAPABLE OF PRODUCING LARGE HAIL AND STRONG WIND GUSTS INTO
THE EVENING.
...SRN ROCKIES AREA...
NNELY MID LEVEL FLOW IS EXPECTED TO CONTINUE OVER NM AND ADJACENT
PARTS OF W TX...ENHANCED BY SSWWD MOVING MCV CURRENTLY OVER THE ERN
TX PANHANDLE. AMPLE MOISTURE WITH GPS PRECIPITABLE WATER VALUES
AROUND 1 INCH WILL SUPPORT THUNDERSTORM DEVELOPMENT AGAIN TODAY.
STORMS ARE LIKELY TO DEVELOP INITIALLY OVER THE HIGHER TERRAIN OF NM
BY EARLY AFTERNOON AND MOVE SSWWD WITH TIME. FORECAST SOUNDINGS
SHOW THE DEVELOPMENT OF A WELL-MIXED BOUNDARY LAYER TO ABOVE 700 MB
WITH DRY ADIABATIC LOW LEVEL LAPSE RATES...SUGGESTING POTENTIAL FOR
ISOLATED STRONG WIND GUSTS AND MARGINAL HAIL TO OCCUR.
..WEISS/GUYER.. 07/05/2007
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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