000
FXUS01 KWBC 250816
PMDSPD
 
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
315 AM EST WED NOV 25 2009
 
VALID 12Z WED NOV 25 2009 - 00Z FRI NOV 27 2009
 
AS THANKSGIVING NEARS...A TOUCH OF WINTER WILL BE IN THE AIR AS A
SERIES OF DISTURBANCES SURGE DOWN FROM CENTRAL CANADA INTO THE
NORTHERN TIER STATES AND SPREADING EASTWARD THROUGH THE GREAT
LAKES REGION. WHILE THE COVERAGE OF PRECIPITATION WITH THESE
WEATHER SYSTEMS WILL BE WIDESPREAD ACROSS THE UPPER MIDWEST AND
INTO MUCH OF THE GREAT LAKES...THE INTENSITY WILL GENERALLY BE
LIGHT. NOT ENOUGH MOISTURE WILL BE AVAILABLE TO PRODUCE HEAVY
RAIN/SNOW AMOUNTS...BUT THE PRESENCE OF THE CANADIAN AIR MASS WILL
BRING SIGNIFICANT CHANGES TO THE SENSIBLE WEATHER. IN
PARTICULAR...BY THANKSGIVING DAY...HIGH TEMPERATURES ACROSS MUCH
OF THE MAJOR GREAT LAKES AND DOWN INTO THE OHIO RIVER VALLEY WILL
LINGER IN THE LOWER 40S UNDERNEATH A THICK LAYER OF CLOUDS WITH AN
ACCOMPANIED WIND WHICH WILL MAKE IT FEEL AT LEAST 10 DEGREES
COLDER. AS THIS ENTIRE SYSTEM ADVANCES EASTWARD...TEMPERATURES
WILL BEGIN TO PLUMMET ALONG THE EAST COAST WHICH HAD BEEN ENJOYING
A RATHER MILD NOVEMBER THUS FAR.

WHILE A MAJORITY OF THE PACIFIC NORTHWEST HAS SEEN THE COVERAGE OF
PRECIPITATION DIMINISH IN PAST DAYS...AN UPPER TROUGH OFFSHORE
WILL BRING AN END TO THIS BY LATE WEDNESDAY EVENING. AS THE
DISTURBANCE TAKES A MORE SOUTHWARD TRACK INTO THE PACIFIC
NORTHWEST...THE SHIELD OF LIGHT TO MODERATE RAIN SHOWERS WILL DROP
DOWN INTO MUCH OF OREGON AND PORTIONS OF EXTREME NORTHWESTERN
CALIFORNIA BY THE LATE AFTERNOON ON THANKSGIVING. THIS PARTICULAR
SYSTEM WILL PRIMARILY BE A RAIN EVENT AS IT WILL BE DOMINATED BY
WARM AIR ADVECTION OFF THE RELATIVELY MILD OFFSHORE PACIFIC
WATERS. FARTHER INLAND...INTERIOR PORTIONS OF THE MOUNTAINOUS WEST
CAN EXPECT TRANQUIL CONDITIONS AS A SURFACE DOME OF HIGH PRESSURE
CONTINUES TO DOMINATE THE REGION. THE RESULT OF THIS RIDGE AXIS
WILL ALSO BE CHILLY OVERNIGHT TEMPERATURES AS CLEAR SKIES AND CALM
WINDS WILL ENHANCE THE RADIATIONAL COOLING EFFECTS. THE RESULT
WILL BE LOWS THAT REMAIN IN THE UPPER TEENS TO MID 20S THE NEXT
COUPLE OF NIGHTS.

MUCH OF WEDNESDAY WILL BE QUITE STORMY ACROSS THE SOUTHERN HALF OF
FLORIDA AS A SLOW MOVING FRONTAL BOUNDARY WILL KEEP CONDITIONS
UNSETTLED. EVENTUALLY THE SYSTEM WILL BECOME MORE PROGRESSIVE IN
NATURE EXITING THE NATION BY LATE THURSDAY NIGHT AS THE BOUNDARY
REACHES CUBA. THEREFORE...MUCH OF THE RAINFALL SHOULD COME TO AN
END BY LATE THAT NIGHT.

ELSEWHERE...ONE OF THE WARMER SPOTS IN THE NATION ON THANKSGIVING
WILL BE ALONG THE LEE SIDE OF THE ROCKIES. DOWNSLOPING FLOW WILL
RAISE THE MERCURY WELL INTO THE 50S WITH SOME READINGS EVEN INTO
THE LOWER-MID 60S ON THANKSGIVING.


RUBIN-OSTER

GRAPHIC AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
$$