639
FXUS01 KWBC 202046
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
446 PM EDT SAT SEP 20 2008
VALID 00Z SUN SEP 21 2008 - 12Z MON SEP 22 2008
THE MAIN FOCUS FOR PRECIPITATION THROUGH THE REMAINDER OF THE
WEEKEND AND INTO MONDAY WILL BE ACROSS THE PACIFIC NORTHWEST ALONG
WITH MUCH OF THE UPPER INTERMOUNTAIN WEST AND NORTHERN ROCKIES. A
SERIES OF DISTURBANCES WILL TRAVERSE ALONG A BROAD UPPER-LEVEL
TROUGH WHICH WILL HELP KEEP THE WEATHER UNSETTLED ACROSS THE
NORTHWESTERN QUADRANT OF THE NATION. CLOUDY...RAINY CONDITIONS
WILL LIMIT THE AMOUNT OF SURFACE HEATING WHICH WILL RESTRICT HIGH
TEMPERATURES BOTH SUNDAY AND MONDAY TO THE 60S ACROSS LOWER
ELEVATIONS WITH 50S IN THE HIGHER TERRAIN. GIVEN THE ORIGIN OF THE
AIR MASS IN PLACE...THE MARITIME PACIFIC AIR WILL NOT
SIGNIFICANTLY COOL THE AIR ENOUGH TO SPAWN SNOW AT THIS POINT IN
TIME. AS THIS SYSTEM GRADUALLY MOVES TOWARD THE EAST...SCATTERED
SHOWERS AND THUNDERSTORMS WILL BREAKOUT OVER THE NORTHERN PLAINS
BY SUNDAY EVENING AND PROGRESS INTO THE UPPER MIDWEST BY DAYBREAK
THE FOLLOWING DAY.
OVER MUCH OF THE NORTHEASTERN QUARTER OF THE U.S...A LARGE SURFACE
ANTICYCLONE WILL COVER THE REGION ALLOWING COOL...AUTUMN-LIKE
WEATHER TO SETTLE IN. HUMIDITY WILL BE ON THE LOWER SIDE AS MUCH
OF THE GULF MOISTURE WILL BE TUCKED CLOSER TO THE GULF COASTLINE.
IN ADDITION...OVERNIGHT LOWS WILL BE ON THE CHILLY SIDE AS NEARLY
CLOUDLESS NIGHTS COMBINED WITH GENTLE WINDS WILL MAXIMIZE THE
NOCTURNAL COOLING. IN TERMS OF RAINFALL...SOME LIGHT PRECIPITATION
IS IN THE FORECAST ACROSS THE SOUTHERN GREAT LAKES EASTWARD INTO
THE INTERIOR NORTHEAST AS A FRONTAL BOUNDARY DRAGS SOUTHEASTWARD
ACROSS THE AREA TONIGHT INTO SUNDAY MORNING.
SCATTERED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED ACROSS THE
LOWER AND MIDDLE MISSISSIPPI VALLEYS AS A SERIES OF WEAK MID-LEVEL
DISTURBANCES WILL HELP DESTABILIZE THE ATMOSPHERE. THE LACK OF
ORGANIZATION ALONG WITH ANY DISCERNIBLE SURFACE FEATURE WILL KEEP
THE CONVECTION DISORGANIZED WITH RAINFALL AMOUNTS REMAINING ON THE
LIGHTER SIDE. FARTHER TO THE EAST...SCATTERED THUNDERSTORMS ARE
POSSIBLE ACROSS COASTAL NORTH CAROLINA AS A SURFACE BOUNDARY
REMAINS CLOSE TO THE EASTERN SEABOARD. THIS AREA OF LOW PRESSURE
WILL ALSO PROMOTE BREEZY CONDITIONS AS AN ANTICYCLONE TO THE NORTH
WILL INCREASE THE PRESSURE GRADIENT WHICH WILL DRIVE A STRONGER
WIND ALONG THE COAST.
RUBIN-OSTER
GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
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