SWODY2
SPC AC 310522
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1222 AM CDT FRI OCT 31 2008
VALID 011200Z - 021200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS INDICATE THAT A SERIES OF SPEED MAXIMA WILL CONTINUE TO
PROGRESS THROUGH A MID/HIGH LEVEL POLAR JET...ARCING SOUTH OF THE
ALEUTIANS TOWARD THE CALIFORNIA COAST...TODAY THROUGH 12Z SUNDAY.
THIS IS PROGGED TO MAINTAIN BROAD UPPER TROUGHING ACROSS THE EASTERN
PACIFIC INTO PACIFIC COASTAL AREAS. DOWNSTREAM...THE POLAR
WESTERLIES APPEAR LIKELY TO REMAIN SPLIT EAST OF THE ROCKIES THROUGH
THE WESTERN ATLANTIC...WITH A LARGE-SCALE NORTHERN STREAM SHORT WAVE
TROUGH EXPECTED TO SHIFT ACROSS THE CANADIAN MARITIMES/NORTHERN
ATLANTIC COAST SATURDAY/SATURDAY NIGHT. AT THE SAME TIME...A
VIGOROUS IMPULSE WITHIN THE WEAKER SOUTHERN STREAM IS FORECAST TO
DIG ACROSS THE GULF COAST...BEFORE EVOLVING INTO A CLOSED LOW OVER
THE NORTHEASTERN GULF OF MEXICO.
...EAST OF THE ROCKIES...
IN RESPONSE TO THE EVOLVING UPPER PATTERN...SURFACE RIDGING...
INITIALLY OVER MUCH OF THE SOUTHEASTERN STATES AT 12Z SATURDAY... IS
EXPECTED TO WEAKEN THROUGH THE PERIOD. BUT...ANOTHER COLD SURFACE
HIGH...MIGRATING SOUTHEAST OF THE GREAT LAKES REGION IN ASSOCIATION
WITH THE NORTHERN BRANCH TROUGH...IS PROGGED TO BEGIN TO BUILD
SOUTHWARD TO THE LEE OF THE APPALACHIANS. AND...SURFACE FLOW WILL
LIKELY MAINTAIN A LARGELY OFFSHORE COMPONENT ACROSS MUCH OF THE GULF
COAST THROUGH THIS PERIOD AND BEYOND. SREF GUIDANCE IS SUGGESTIVE
THAT LINGERING MOISTURE ACROSS EASTERN TEXAS COULD SUPPORT WEAK
BOUNDARY LAYER BASED INSTABILITY AND POTENTIAL FOR THUNDERSTORMS
SATURDAY AFTERNOON. HOWEVER...IT SEEMS PROBABLE THAT WARM MID-LEVEL
TEMPERATURES/LARGE-SCALE SUBSIDENCE WILL MINIMIZE THE RISK...WITH
PROBABILITIES FOR THUNDERSTORMS ELSEWHERE ACROSS THE CENTRAL/EASTERN
U.S. EVEN MORE NEGLIGIBLE.
...WEST OF THE ROCKIES...
STRONG FORCING ASSOCIATED WITH A SHORT WAVE TROUGH OFF THE PACIFIC
COAST AT 12Z SATURDAY IS EXPECTED TO REMAIN OFFSHORE THROUGH THE
PERIOD AS IT LIFTS TOWARD THE BRITISH COLUMBIA COAST...AND MERGES
WITH ANOTHER DIGGING SHORT WAVE IMPULSE. HOWEVER...MODELS INDICATE
THAT ANOTHER SIGNIFICANT IMPULSE WILL PIVOT INLAND TO THE SOUTH OF
THE DEVELOPING LARGER SCALE FEATURE...ACROSS THE CALIFORNIA COAST
SATURDAY EVENING. AS AN ASSOCIATED MID-LEVEL FRONTAL BAND ADVANCES
ACROSS CENTRAL/NORTHERN COASTAL AREAS INTO THE SACRAMENTO/SAN
JOAQUIN VALLEYS...COOLING/DRYING ALOFT IS EXPECTED TO DESTABILIZE
INITIALLY SATURATED THERMODYNAMIC PROFILES WITH WEAK LAPSE RATES.
THIS MAY CONTRIBUTE TO A MORE CONDUCIVE ENVIRONMENT FOR CHARGE
SEPARATION AND EMBEDDED WEAK THUNDERSTORM ACTIVITY.
..KERR.. 10/31/2008
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