339
FXUS01 KWBC 212006
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
406 PM EDT SUN SEP 21 2008
VALID 00Z MON SEP 22 2008 - 12Z TUE SEP 23 2008
MOST OF THE ACTION IN THE UNITED STATES WILL BE ACROSS THE
NORTHWESTERN QUARTER OF THE NATION WHERE A BROAD UPPER-LEVEL
TROUGH WILL SLOWLY MOVE THROUGH THE REGION. THIS WILL PROMOTE
COOL...WET CONDITIONS AS THE SURFACE BOUNDARY GRADUALLY MOVES
TOWARD THE EAST. MUCH OF THE FOCUS FOR THE RAINFALL WILL BE IN
ADVANCE OF THIS FRONT WHERE A MOIST...SOUTHERLY FLOW WILL COMBINE
WITH WARM TEMPERATURES TO ALLOW UNSETTLED CONDITIONS TO PERSIST
ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY. A
NOTICEABLE DIFFERENCE IN THE SENSIBLE WEATHER WILL BE APPARENT AS
HIGH TEMPERATURES BY TUESDAY SHOULD FALL FROM THE LOWER 80S DOWN
INTO THE UPPER 60S UPON FRONTAL PASSAGE ACROSS THE NORTHERN HIGH
PLAINS.
A PERSISTENT AREA OF SHOWERS AND THUNDERSTORMS WILL HIT A
SIGNIFICANT PORTION OF THE EASTERN GULF COAST STATES ALONG WITH
THE SOUTHEASTERN U.S. COASTLINE THROUGH TUESDAY AFTERNOON. A
CONTINUAL NORTHEASTERLY FLOW AT THE SURFACE WILL BRING
MOISTURE-LADEN AIR INLAND WHICH WILL HELP SPAWN CLUSTERS OF
THUNDERSTORMS...ESPECIALLY ALONG THE IMMEDIATE COASTLINE WHERE THE
BEST SURFACE CONVERGENCE WILL RESIDE. MUCH OF THE REGION CAN
EXPECT TEMPERATURES TO PUNCH INTO THE MIDDLE 80S BOTH MONDAY AND
TUESDAY WITH RELATIVE HUMIDITY VALUES ON THE HIGHER SIDE.
ELSEWHERE...A LARGE DOME OF SURFACE HIGH PRESSURE WILL SET UP OVER
EASTERN CANADA KEEPING THE WEATHER QUIET OVER THE NORTHEASTERN
UNITED STATES INTO EARLY NEXT WEEK. WITH THE CALENDAR MARKING THE
START OF AUTUMN...THE WEATHER WILL COOPERATE WITH THE CHANGE OF
SEASON BRINGING COOL...DRY AIR OVER THE REGION. AFTERNOON HIGHS TO
START THE WORK WEEK WILL BE IN THE 60S ACROSS THE NEW ENGLAND
STATES WITH SOME LOWER 70S OVER THE MAJOR METROPOLITAN CITIES IN
THE MID-ATLANTIC REGION. AS THE RIDGE OF HIGH PRESSURE SETTLES IN
OVER THE REGION ON MONDAY...OPTIMAL RADIATIONAL COOLING WILL TAKE
PLACE DRAWING OVERNIGHT TEMPERATURES INTO THE 30S WITH SPOTTED 20S
OVER MAINE.
AS THE AXIS OF THE UPPER-LEVEL TROUGH OVER THE WESTERN U.S. IS
POSITIONED JUST TO THE EAST OF THE DESERT SOUTHWEST...THIS
CORRIDOR OF THE NATION CAN EXPECT TRANQUIL WEATHER CONDITIONS TO
PERSIST. TEMPERATURES OVER THE DESERTS WILL NEAR THE CENTURY MARK
WHILE CLOSER TO THE SOUTHERN CALIFORNIA COAST...MARINE AIR WILL
SETTLE IN OVER THE COASTLINE RESTRICTING DAYTIME HIGHS TO THE
UPPER 60S TO LOWER 70S.
RUBIN-OSTER
GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
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