562
FXUS01 KWBC 240736
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
335 AM EDT WED SEP 24 2008
VALID 12Z WED SEP 24 2008 - 00Z FRI SEP 26 2008
CURRENTLY...THERE IS A STRONG FRONTAL BOUNDARY THAT BISECTS CANADA
AND EXTENDS SOUTHWARD OVER THE WESTERN GREAT LAKES REGION AND
WESTWARD INTO EASTERN COLORADO. OVER THE UPPER MIDWEST AND CENTRAL
PLAINS...ORGANIZED CONVECTION HAS BEEN AND WILL CONTINUE TO FIRE
UP AT OR JUST AHEAD OF THE FRONTAL ZONE IN THE WARM SECTOR. A SLUG
OF UPPER LEVEL ENERGY WHICH HAS BEEN GENERATING PERSISTENT
DIFFLUENCE ALOFT WILL MOVE ACROSS MINNESOTA EARLY WEDNESDAY AND
THEN ITS TRAJECTORY WILL RECURVE ABRUPTLY NORTHEASTWARD INTO
ONTARIO...BRINGING THREAT OF ORGANIZED CONVECTION WITH IT.
HOWEVER...SCATTERED SHOWERS/THUNDERSTORMS MAY LINGER LATER INTO
THE PERIOD ALONG THE FRONTAL BOUNDARY AS IT MOVES EASTWARD ACROSS
THE GREAT LAKES REGION.
HEADING WEST...A PACIFIC CYCLONE THAT IS LESS THAN 200 NAUTICAL
MILES FROM THE SHORES OF WASHINGTON STATE WILL CONTINUE TO DEEPEN
AS IT MARCHES FORWARD INTO BRITISH COLUMBIA AND THE PACIFIC
NORTHWEST. IN ADDITION TO RAIN AND LOW CEILINGS...AS THE LOW
DEEPENS...THE PRESSURE GRADIENT FORCES WILL INCREASE RESULTING IN
STRONG WINDS. RADAR DATA INDICATES THAT THE PRECIPITATION SHIELD
IS ALREADY IN STRIKING DISTANCE OF THE OLYMPIC PENNINSULA...AND
SHOWERS WILL PERSIST LATE INTO THURSDAY FOR PORTIONS OF WASHINGTON
AND OREGON. ALTHOUGH BRITISH COLUMBIA CAN ANTICIPATE THE LION'S
SHARE OF THIS UNSETTLED WEATHER...ENHANCED PRECIPITATION IS
FORECAST FOR BOTH THE OLYMPIC AND CASCADE MOUNTAIN RANGES DUE TO
MESOCALE TERRAIN INFLUENCES. ADDITIONALLY...AS THE MID TO UPPER
LEVEL TROUGH MOVES OVER THE PACIFIC NORTHWEST...COOLER
TEMPERATURES WILL SETTLE INTO THE REGION.
HEADING SOUTH...THE UPPER LEVEL RIDGE WILL RETAIN ITS STRONGHOLD
OVER THE DESERT SOUTHWEST...KEEPING THE TEMPERATURES TOASTY AND
DRY OVER MUCH OF THE REGION. MOVING EAST ALONG THE U.S./MEXICAN
BORDER...THE DEWPOINTS OVER TEXAS WILL STEADILY CLIMB...AS
EASTERLY FLOW OFF THE GULF OF MEXICO HAS BEEN CHURNING MOISTURE
INTO EASTERN MEXICO AND THE LONE STAR STATE. SOUTHERN TEXAS AND
THE LOWER RIO GRANDE BASIN WILL SEE SCATTERED TO NUMEROUS
SHOWERS/THUNDERSTORMS ON WEDNESDAY...WHICH WILL TAPER OFF LATER IN
THE PERIOD. LAST BUT NOT LEAST...A LOW PRESSURE SYSTEM OFF THE
SOUTHEAST COAST WILL GET BETTER ORGANIZED AND MOVE NORTH ALONG THE
ATLANTIC SEABOARD. THE LATEST 00Z RUNS OF NCEP AND EUROPEAN MODELS
AREN'T EXACTLY IN LOCK STEP YET...AS TO HOW EXACTLY THIS SYSTEM
WILL EVOLVE. HOWEVER...IT IS APPARENT THAT ONSHORE FLOW WILL
SUBSTANTIALLY INCREASE RESULTING IN SCATTERED PRECIPITATION
ACTIVITY ALONG THE SOUTHEAST COAST EARLY IN THE PERIOD...AND LATER
THIS CYCLONE WILL BECOME A SIGNIFICANT WEATHER PRODUCER FOR
PORTIONS OF THE MID-ATLANTIC.
SZATANEK
GRAPHICS AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
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