295  
FXUS01 KWBC 250804  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
403 AM EDT TUE SEP 25 2018  
 
VALID 12Z TUE SEP 25 2018 - 12Z THU SEP 27 2018  
 
...HEAVY TO EXCESSIVE RAINFALL POSSIBLE FROM THE TENNESSEE VALLEY  
TO THE NORTHEAST...  
 
...STRONG TO SEVERE THUNDERSTORMS EXPECTED WITH A STRONG COLD  
FRONT PUSHING FROM THE MIDWEST TO THE NORTHEAST TUESDAY AND  
WEDNESDAY...  
 
THE UPPER-LEVEL PATTERN ACROSS THE U.S. CONTINUES TO FAVOR A WET  
PATTERN ACROSS MUCH OF THE EASTERN HALF OF THE COUNTRY THE NEXT  
COUPLE OF DAYS. MOISTURE OVERRIDING A REMNANT SURFACE BOUNDARY  
DRAPED ACROSS THE MID-SOUTH CONTINUES THE THREAT FOR HEAVY TO  
EXCESSIVE RAINFALL ACROSS PORTIONS OF THE TENNESSEE AND OHIO  
VALLEYS ON TUESDAY BUT THE FOCUS SHOULD BEGIN SHIFTING INTO NEW  
ENGLAND AS THIS BOUNDARY LIFTS NORTHWARD AS A WARM FRONT. AS A  
RESULT, WPC HAS MUCH OF THE REGION FROM THE TENNESSEE VALLEY TO  
THE NORTHEAST WITHIN A MARGINAL TO SLIGHT RISK FOR EXCESSIVE  
RAINFALL/FLASH FLOODING ON TUESDAY. THE TEMPERATURE PATTERN ACROSS  
THE EAST IS ALSO CHANGING, AS THIS WARM FRONT ERODES AWAY A WEDGE  
OF SURFACE HIGH PRESSURE AND SUMMERY HEAT AND HUMIDITY RETURNS BY  
WEDNESDAY. A NUMBER OF RECORD WARM OVERNIGHT TEMPERATURES ARE  
FORECAST FROM THE GULF COAST TO THE OHIO VALLEY AND MID-ATLANTIC.  
 
A STRONG COLD FRONT WILL SWEEP QUICKLY EASTWARD FROM THE  
MISSISSIPPI VALLEY TO THE SOUTHERN PLAINS ON TUESDAY, REACHING THE  
OHIO VALLEY AND NORTHEAST BY WEDNESDAY. THUNDERSTORMS DEVELOPING  
ALONG THE BOUNDARY COULD BE STRONG TO SEVERE ACROSS THE MIDWEST ON  
TUESDAY, AND THE NORTHEAST/MID-ATLANTIC STATES ON WEDNESDAY WHERE  
THE STORM PREDICTION CENTER HAS SLIGHT RISKS ON THEIR LATEST  
CONVECTIVE OUTLOOKS. A THREAT FOR HEAVY RAINFALL IS ALSO POSSIBLE  
ALONG THE FRONT, ESPECIALLY ACROSS THE CENTRAL GULF STATES TO THE  
SOUTHERN APPALACHIANS ON WEDNESDAY AND WPC HAS HIGHLIGHTED THIS  
REGION IN MARGINAL TO SLIGHT RISK FOR EXCESSIVE RAINFALL/FLASH  
FLOODING. ON THE BACKSIDE OF THE FRONT, MUCH COOLER AIR FILTERS IN  
FROM CANADA WITH WELL BELOW NORMAL TEMPERATURES (ON THE ORDER OF  
10 TO 20 DEGREES BELOW AVERAGE) REACHING THE SOUTHERN PLAINS BY  
WEDNESDAY.  
 
ELSEWHERE, SURFACE HIGH PRESSURE ACROSS THE WESTERN U.S. WILL  
RESULT IN WARM AND DRY CONDITIONS AND A CONTINUED ELEVATED TO  
CRITICAL FIRE WEATHER THREAT FOR PORTIONS OF NORTHERN CALIFORNIA  
WHERE RED FLAG WARNINGS ARE IN EFFECT. ADDITIONALLY, A BROAD AREA  
OF LOW PRESSURE IS EXPECTED TO SKIRT THE OUTER BANKS ON TUESDAY  
WHICH MAY BRING SOME LOCALLY HEAVY RAINFALL TO THE AREA.  
 
SANTORELLI  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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