SWODY3
SPC AC 280617
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0117 AM CDT TUE OCT 28 2008
VALID 301200Z - 311200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS AND FORECAST...
LARGE-SCALE PATTERN WILL BECOME MORE PROGRESSIVE DURING THE DAY
THREE PERIOD AS STRONG POLAR BRANCH SHORT WAVE TROUGH MOVING THROUGH
CNTRL CANADA REMAINS LOOSELY PHASED WITH WEAKER...LOWER LATITUDE
IMPULSE SHIFTING FROM THE CNTRL PLAINS INTO THE CNTRL MS VALLEY.
THE ERN PROGRESSION OF THESE TWO SYSTEMS WILL RESULT IN THE MOVEMENT
OF WEAKENING UPPER TROUGH OFF THE NEW ENGLAND COAST. MEANWHILE...A
LARGE-SCALE TROUGH IS FORECAST TO INTENSIFY OVER THE ERN PACIFIC
WITH AN EMBEDDED SHORT WAVE TROUGH MOVING ONTO THE CA COAST LATE IN
THE PERIOD.
IN THE LOW LEVELS...A SURFACE FRONT WILL PUSH EWD FROM THE DAKOTAS
INTO THE UPPER GREAT LAKES WITH THE WRN EXTENSION OF THIS BOUNDARY
PUSHING MORE SWD THROUGH THE CNTRL AND SRN HIGH PLAINS. FARTHER
E...A RIDGE OF HIGH PRESSURE WILL BE MAINTAINED ALONG THE EAST COAST
SWWD INTO THE GULF OF MEXICO.
SLY/SWLY LOW-LEVEL FLOW ON THE BACKSIDE OF SURFACE HIGH WILL SUPPORT
THE NWD RETURN OF A MODIFIED CP AIR MASS THROUGH THE SRN PLAINS IN
ADVANCE OF APPROACHING COLD FRONT. STRENGTHENING NOCTURNAL LLJ
THURSDAY NIGHT OVER THE SRN PLAINS INTO OZARK PLATEAU WILL SERVE TO
ENHANCE A NARROW CORRIDOR OF ISENTROPIC ASCENT WITH ENVIRONMENT
BECOMING WEAKLY UNSTABLE FOR ELEVATED PARCELS. WHILE ISOLATED TSTMS
WILL BE POSSIBLE WITHIN THIS REGIME...FORECAST SOUNDINGS SUGGEST
THAT THE MARGINAL MOISTURE AND RELATIVELY WARM TEMPERATURES IN THE
850-600 MB LAYER WILL MAINTAIN SOME DEGREE OF CAPPING AND
EFFECTIVELY LIMIT THE DEGREE OF CONVECTIVE INSTABILITY.
ELSEWHERE...INCREASING MIDLEVEL MOISTURE AND LARGE-SCALE FORCING FOR
ASCENT IN ADVANCE OF APPROACHING UPPER TROUGH MAY SUPPORT A FEW
TSTMS OVER PARTS OF SRN CA. HERE TOO...INSTABILITY WILL REMAIN
QUITE MARGINAL AND NO SEVERE WEATHER IS EXPECTED.
..MEAD.. 10/28/2008
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