921
FXUS01 KWBC 052038
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
337 PM EST THU NOV 05 2009
VALID 00Z FRI NOV 06 2009 - 12Z SAT NOV 07 2009
A LARGE PACIFIC SYSTEM CURRENTLY PUSHING INTO THE PACIFIC
NORTHWEST WILL BRING PLENTY OF RAIN AND SNOW TO MUCH OF THE REGION
TO CONCLUDE THE WORK WEEK AND INTO THE WEEKEND. SEVERAL
DISTURBANCES SWINGING AROUND A CLOSED LOW OVER THE GULF OF ALASKA
WILL ALLOW A STRONG ONSHORE FLOW TO PERSIST PROVIDING AMPLE
MOISTURE FOR WIDESPREAD PRECIPITATION ACROSS THE NORTHWESTERN U.S.
THE BEST FOCUS FOR EMBEDDED HEAVIER AMOUNTS WILL BE ALONG THE
WINDWARD SIDE OF THE COASTAL OLYMPICS AND CASCADES.
INITIALLY...THE PRECIPITATION ACROSS THESE PEAKS WILL BE IN THE
FORM OF RAIN...BEFORE A CHANGEOVER TO SNOW BY FRIDAY MORNING AS
COLDER AIR STREAMS IN BEHIND THE FRONTAL BOUNDARY. WHILE THE FRONT
WILL QUICKLY RACE OFF TO THE EAST REACHING THE NORTHERN HIGH
PLAINS BY LATE FRIDAY...UNSETTLED CONDITIONS WILL PERSIST ACROSS
THE NORTHWESTERN TIER STATES AS A SERIES OF UPPER-LEVEL
DISTURBANCES CONTINUE TO BOMBARD THE REGION.
AN UPPER TROUGH EXITING THE NORTHEASTERN U.S. LATER TODAY WILL
GRADUALLY BRING AN END TO THE SCATTERED PRECIPITATION CURRENTLY
FALLING ACROSS THE REGION. HOWEVER..SOME LINGERING RAIN/SNOW
SHOWERS CANNOT BE RULED OUT THROUGH EARLY FRIDAY MORNING. AS THE
UPPER TROUGH REACHES COASTAL NEW ENGLAND...RAPID CYCLOGENESIS IS
EXPECTED TO TAKE PLACE OFFSHORE WHICH WILL BRING ABOUT A QUICK
STRENGTHENING OF THE SURFACE LOW. THE ENHANCED PRESSURE GRADIENT
WILL INCREASE THE WINDS ACROSS THE REGION...BUT THE STRONGEST WIND
FIELD SHOULD REMAIN FARTHER OFFSHORE. IN THE WAKE OF THIS
DEEPENING WEATHER SYSTEM...A LARGE SURFACE ANTICYCLONE WILL BUILD
ACROSS THE EASTERN U.S. WHICH WILL BRING VERY COOL CONDITIONS TO
THE REGION ON FRIDAY. HIGHS TO CONCLUDE THE WORK WEEK WILL
STRUGGLE TO REACH ABOVE THE 40S ACROSS THE MID-ATLANTIC AND NEW
ENGLAND STATES...WHILE LOWS WILL PLUNGE BELOW THE FREEZING MARK
GIVEN CLEAR SKIES AND CALM WINDS.
ACROSS THE CENTRAL U.S...A LARGE UPPER RIDGE WILL PROMOTE WARM
CONDITIONS INTO FRIDAY WITH WIDESPREAD HIGHS IN THE 70S ACROSS THE
CENTRAL PLAINS. EVEN SOME ISOLATED 80S CANNOT BE RULED OUT OVER
EASTERN COLORADO/WESTERN KANSAS WHERE A DOWNSLOPING FLOW OFF THE
LEE OF THE ROCKIES WILL FURTHER ENHANCE THE WARMING. BY LATE
FRIDAY AND INTO SATURDAY...COOLER WEATHER WILL BE ON ITS WAY AS
THE UPPER RIDGE ADVANCES EASTWARD INTO THE OHIO/TENNESSEE RIVER
VALLEYS.
RUBIN-OSTER
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