SWODY2
SPC AC 081712
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1212 PM CDT WED OCT 08 2008
VALID 091200Z - 101200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
SIGNIFICANT AMPLIFICATION OF THE LARGE-SCALE UPPER FLOW PATTERN FROM
THE EASTERN PACIFIC INTO THE WESTERN U.S. APPEARS LIKELY LATER
TODAY/TONIGHT INTO THURSDAY. THIS WILL INCLUDE A BUILDING RIDGE
OVER THE EASTERN PACIFIC...WITH A DEEPENING TROUGH OVER THE PACIFIC
COAST STATES INTO THE ROCKIES. DOWNSTREAM...MODELS INDICATE ANOTHER
RIDGE WILL BEGIN BUILDING EAST OF THE MISSISSIPPI VALLEY INTO THE
LOWER GREAT LAKES/UPPER OHIO VALLEY REGION. AND...AS THIS
OCCURS...THE MID/UPPER CLOSED LOW OVER THE SOUTHEAST STATES WILL
BECOME INCREASINGLY CUT-OFF FROM THE WESTERLIES. GUIDANCE HAS BEEN
GENERALLY SUGGESTIVE OF A CONTINUED EASTWARD PROGRESSION OF THIS
SYSTEM...BUT THIS SHOULD BE SLOW...AND THE MID-LEVEL CIRCULATION
SEEMS LIKELY TO LINGER ACROSS PARTS OF SOUTHERN GEORGIA/NORTHERN
FLORIDA THROUGH MUCH OF THE PERIOD.
...SOUTHEAST...
LOW/MID-LEVEL WIND FIELDS ASSOCIATED WITH THE CLOSED LOW ARE
EXPECTED TO WEAKEN...WITH MODELS SUGGESTIVE OF THE STRONGEST
MID-LEVEL FLOW BECOMING CONCENTRATED ON THE SOUTHWESTERN PERIPHERY
OF THE CIRCULATION...MOSTLY OVER THE NORTHEASTERN GULF OF MEXICO.
THIS SHOULD MINIMIZE DEEP LAYER SHEAR OVER THE FLORIDA PENINSULA AND
SOUTH ATLANTIC COASTAL AREAS...WHERE LOW-LEVELS WILL REMAIN VERY
MOIST BENEATH A 500 MB COLD POCKET WITH TEMPERATURES AS LOW AS -12C.
WITH ENOUGH SURFACE HEATING THIS MAY SUPPORT SUFFICIENT
DESTABILIZATION FOR VIGOROUS STORM DEVELOPMENT CAPABLE OF PRODUCING
SOME HAIL/LOCALLY DAMAGING WIND GUSTS...PERHAPS AN ISOLATED TORNADO.
IT IS POSSIBLE THAT A CONCENTRATED SEVERE THREAT SUPPORTIVE OF
HIGHER SEVERE PROBABILITIES MAY EVENTUALLY DEVELOP...BUT IT IS STILL
UNCLEAR WHERE...DUE TO POTENTIAL FOR CONSIDERABLE CLOUD COVER/EARLY
DAY CONVECTION...AND MODEL VARIABILITY CONCERNING THE MOVEMENT OF
THE UPPER SYSTEM. IT COULD BE THAT THE SEA BREEZES ACROSS THE
CENTRAL FLORIDA PENINSULA PROVIDE THE FOCUS FOR THE STRONGEST STORMS
THURSDAY AFTERNOON.
...PLAINS...
LEE CYCLOGENESIS IS PROGGED ACROSS THE CENTRAL PLAINS IN RESPONSE TO
THE DEVELOPING UPPER PATTERN. LACK OF A LOW-LEVEL RETURN FLOW OF
MOISTURE FROM THE GULF OF MEXICO SHOULD MINIMIZE THE CONVECTIVE
POTENTIAL THROUGH THIS PERIOD. BUT...ENOUGH MOISTURE IS EXPECTED TO
EXIST TO SUPPORT INCREASING SCATTERED STORMS THURSDAY NIGHT... BASED
IN A STRENGTHENING LOWER/MID TROPOSPHERIC WARM ADVECTION
REGIME...FROM PARTS OF NORTHEAST WYOMING INTO PARTS OF THE DAKOTAS.
...SOUTHERN PLATEAU...
MOISTURE RETURN FROM THE GULF OF CALIFORNIA/LOWER LATITUDE EASTERN
PACIFIC MAY BECOME SUPPORTIVE OF AN INCREASING RISK FOR
THUNDERSTORMS. PRIMARY ACTIVITY THROUGH THIS PERIOD PROBABLY WILL
BE MOSTLY CONFINED TO THE MEXICO PLATEAU. BUT...ISOLATED TO WIDELY
SCATTERED STORMS APPEAR POSSIBLE ACROSS THE MOUNTAINS OF PARTS OF
SOUTHEAST ARIZONA/SOUTHWEST NEW MEXICO.
...PACIFIC NORTHWEST...
THE COLD MID-LEVEL AIR MASS...WITH 500 MB TEMPERATURES AT OR BELOW
-30C...ASSOCIATED WITH THE DEVELOPING WESTERN U.S. TROUGH MAY
CONTRIBUTE TO SUFFICIENT DESTABILIZATION FOR SCATTERED THUNDERSTORM
ACTIVITY WEST OF THE CASCADES THURSDAY.
..KERR.. 10/08/2008
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