SWODY2
SPC AC 010523
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1223 AM CDT WED OCT 01 2008
VALID 021200Z - 031200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
THE TRANSITION TO A LESS AMPLIFIED SPLIT UPPER FLOW PATTERN MAY
COMMENCE AS EARLY AS THURSDAY...AS THE EXIT REGION OF A STRONG ZONAL
MID LATITUDE PACIFIC JET NOSES TOWARD THE NORTHERN PACIFIC COAST.
CONSIDERABLE MODEL GUIDANCE INDICATES THAT WEAKENING OF THE
LARGE-SCALE WESTERN NORTH AMERICAN RIDGE WILL CONTINUE...AS THE
REMNANTS OF THE CLOSED LOW/UPPER TROUGH...NOW OVER THE EASTERN
PACIFIC...LIFT INLAND ACROSS THE CANADIAN ROCKIES AND NORTHWESTERN
STATES. WHILE MID-LEVEL HEIGHTS FALL ACROSS MUCH OF THE WESTERN
U.S....A BROAD DEEP CLOSED LOW WITHIN THE NORTHERN STREAM IS PROGGED
TO LIFT AWAY FROM THE GREAT LAKES REGION INTO THE EASTERN CANADIAN
PROVINCES BY 12Z FRIDAY. BUT...WEAK TROUGHING WITHIN THE SOUTHERN
STREAM APPEARS LIKELY TO LINGER FROM THE LOWER RIO GRANDE VALLEY
INTO THE GULF OF MEXICO.
THIS REGIME PROBABLY WILL SUPPORT THE MAINTENANCE OF HIGH MOISTURE
LEVELS ALONG A STALLED FRONTAL ZONE NEAR THE FLORIDA PENINSULA...BUT
THE DEVELOPMENT OF A MOIST SOUTHERLY RETURN FLOW OFF THE GULF OF
MEXICO SHOULD REMAIN IMPEDED. COUPLED WITH ONLY MODEST POST-FRONTAL
MOISTENING ACROSS PARTS OF THE NORTHERN INTERMOUNTAIN
REGION...CONVECTIVE POTENTIAL ACROSS MUCH OF THE U.S. THROUGH THIS
PERIOD IS EXPECTED TO BE LOW.
...GREAT LAKES REGION...
ROTATING AROUND A COLD CORE LOW...WITH 500 MB TEMPERATURES AT OR
BELOW -30C...ONE MID-LEVEL IMPULSE MAY CONTRIBUTE TO SCATTERED WEAK
THUNDERSTORM ACTIVITY THURSDAY ACROSS SOUTHERN ONTARIO... PERHAPS
INTO THE LEE OF THE LOWER GREAT LAKES...WHILE ANOTHER SUPPORTS THE
POTENTIAL FOR SIMILAR CONVECTION ACROSS PARTS OF UPPER INTO NORTHERN
LOWER MICHIGAN.
...FLORIDA...
SREF GUIDANCE SUGGESTS THAT IT MAY BE MOST PROBABLE THAT A SURFACE
FRONT WILL REMAIN STALLED JUST OFF SOUTHEAST COASTAL AREAS THROUGH
THE PERIOD. BUT...THE CLOSE PROXIMITY OF THIS BOUNDARY AND AN
ASSOCIATED NARROW TONGUE OF HIGH PRECIPITABLE WATER...AT OR ABOVE 2
INCHES...SUPPORTS AT LEAST LOW THUNDERSTORM PROBABILITIES ACROSS THE
SOUTHERN PENINSULA.
...CENTRAL HIGH PLAINS...
DESPITE LOW MOISTURE LEVELS...SREF GUIDANCE INDICATES THAT
STEEPENING LAPSE RATES AND WEAK FORCING NEAR A DEEPENING LEE SURFACE
TROUGH/LOW CENTER MAY BECOME SUFFICIENT FOR FEW HIGH BASED
THUNDERSTORMS THURSDAY AFTERNOON. BUT...EVEN WITH NOCTURNAL
STRENGTHENING OF A LOW-LEVEL JET LIKELY ACROSS THE TEXAS PANHANDLE
INTO WESTERN KANSAS...THE RISK OF STORMS PROBABLY WILL DIMINISH
AFTER DARK.
...NORTHERN INTERMOUNTAIN REGION...
POST-FRONTAL MOISTENING AND WEAK MID-LEVEL COOLING MAY SUPPORT
ISOLATED TO SCATTERED STORMS FROM PARTS OF EASTERN WASHINGTON...
PERHAPS NORTHEAST OREGON...INTO THE MOUNTAINS OF NORTHERN IDAHO LATE
THURSDAY AFTERNOON AND EVENING. OTHERWISE...DUE TO THE LACK OF
MOISTURE...PRE-FRONTAL STORMS ARE EXPECTED TO BE SPARSE IN COVERAGE
AND CONFINED TO AREAS OF STRONGER AFTERNOON HEATING...ACROSS THE
MOUNTAINS OF NORTHEAST IDAHO INTO WESTERN MONTANA.
..KERR.. 10/01/2008
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