SWODY2
SPC AC 281728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT SUN JUN 28 2009
VALID 291200Z - 301200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
UPPER TROUGH/CLOSED LOW CURRENTLY OVER NRN ONTARIO/WRN GREAT LAKES
WILL AMPLIFY SEWD ACROSS MUCH OF THE ERN U.S. WITH THE ATTENDANT
CLOSED LOW REACHING THE LOWER GREAT LAKES BY 12Z TUESDAY. AN UPPER
RIDGE WILL REMAIN ANCHORED OVER THE SWRN STATES WITH THE NERN
EXTENSION OF THIS FEATURE OVER THE NRN PLAINS/MANITOBA SHARPENING
SOME AS AN UPSTREAM LARGE CLOSED LOW ALONG BC COAST MOVES INLAND.
...GULF COASTAL AREA THROUGH TX...
A COLD FRONT WILL CONTINUE SEWD INTO THE GULF COAST REGION WHERE IT
SHOULD EVENTUALLY STALL AND EXTEND WWD THROUGH TX. MODERATE
INSTABILITY IS EXPECTED AS THE BOUNDARY LAYER WARMS MONDAY AFTERNOON
FROM THE GULF COAST WWD THROUGH A PORTION OF CNTRL AND NRN TX.
STORMS WILL REDEVELOP IN VICINITY OF THIS BOUNDARY...BUT WARM SECTOR
WILL HAVE BEEN SHUNTED S OF STRONGER WINDS ALOFT WITH MODEST NWLY
DEEP LAYER FLOW SUPPORTIVE OF MULTICELLS. ISOLATED WET DOWNBURSTS
AND MARGINALLY SEVERE HAIL WILL BE POSSIBLE WITH THE STRONGER
STORMS...PRIMARILY FROM SRN LA TO SRN GA WHERE INSTABILITY WILL BE
GREATER GIVEN HIGHER SURFACE DEWPOINTS /LOWER-MID 70S/ THAN FARTHER
W ACROSS TX. ACTIVITY SHOULD DIMINISH DURING THE EVENING WITH LOSS
OF DIABATIC HEATING.
...ROCKY MOUNTAINS/NRN AND CENTRAL HIGH PLAINS...
ISOLATED TO WIDELY SCATTERED STORMS SHOULD DEVELOP OVER THE ROCKIES
AS HEATING COMMENCES OVER THE HIGHER TERRAIN. MUCH OF THIS REGION
WILL REMAIN EMBEDDED WITHIN WEAK FLOW ALOFT ATTENDANT TO PROXIMITY
OF UPPER RIDGE.
MODELS MAINTAIN AN EXCEPTION OVER THE NRN ROCKIES WHERE A BELT OF
STRONGER WINDS WILL EXIST ALONG NRN PERIPHERY OF UPPER RIDGE. STEEP
LAPSE RATES WITH AN INVERTED-V BOUNDARY LAYER WILL SUPPORT A THREAT
OF MAINLY ISOLATED DOWNBURSTS BEFORE ACTIVITY DIMINISHES TOWARD MID
EVENING. ANY SEVERE EVENTS ARE EXPECTED TO REMAIN SOMEWHAT ISOLATED
/NO MORE THAN 5% SEVERE PROBABILITIES/...GIVEN GENERALLY WEAK
INSTABILITY DUE TO LIMITED LOW LEVEL MOISTURE. A CLUSTER OF STORMS
MAY ALSO DEVELOP OVER SERN WY/NERN CO GIVEN SLIGHTLY GREATER
INSTABILITY THAN FARTHER N...BUT WEAK EFFECTIVE BULK SHEAR PRECLUDES
THE INTRODUCTION OF SEVERE PROBABILITIES GREATER THAN 5%.
...LOWER GREAT LAKES TO SRN NEW ENGLAND...
MODELS ARE IN AGREEMENT SHOWING THE DEVELOPMENT OF WEAK INSTABILITY
ACROSS THIS REGION...AS COLD MID LEVEL TEMPERATURES /-14 TO -16 C AT
500 MB/ SPREAD ACROSS SRN ONTARIO AND LOWER GREAT LAKES. FARTHER E
ACROSS SRN NEW ENGLAND...GREATER LOW LEVEL MOISTURE AND SURFACE
HEATING WILL OFFSET WEAKER MID LEVEL LAPSE RATES SUPPORTING WEAK
INSTABILITY. ALTHOUGH TSTMS ARE EXPECTED TO DEVELOP ACROSS THE
LOWER GREAT LAKES/UPPER OH VALLEY TO SRN NEW ENGLAND ON MONDAY...
WEAK DEEP LAYER SHEAR IS EXPECTED TO PRECLUDE THE THREAT FOR
ORGANIZED SEVERE STORMS. DESPITE THE WEAK SHEAR...GREATER POTENTIAL
FOR MARGINALLY SEVERE HAIL SHOULD REMAIN OVER SRN ONTARIO WHERE MID
LEVEL TEMPERATURES ARE FORECAST TO BE COLDER.
..PETERS.. 06/28/2009
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