744  
FXUS01 KWBC 212001  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
401 PM EDT TUE AUG 21 2018  
 
VALID 00Z WED AUG 22 2018 - 00Z FRI AUG 24 2018  
 
...HEAVY RAIN AND SEVERE WEATHER EXPECTED ACROSS THE OHIO VALLEY  
AND MID-ATLANTIC TODAY...  
 
...FIRE WEATHER AND AIR QUALITY CONCERNS CONTINUE FOR PORTIONS OF  
THE WESTERN U.S...  
 
THUNDERSTORMS ALONG WITH EMBEDDED HEAVY RAINFALL IS SPREADING  
ACROSS PORTIONS OF THE OHIO VALLEY AND MID-ATLANTIC REGION TODAY  
AS A SLOW MOVING FRONTAL SYSTEM MOVES TO THE EAST. A LARGE PORTION  
OF THE OHIO VALLEY, CENTRAL APPALACHIANS AND THE MID-ATLANTIC WILL  
CONTINUE TO HAVE FAVORABLE CONDITIONS FOR STRONG TO SEVERE  
THUNDERSTORMS THROUGH WEDNESDAY MORNING. WITHIN THIS SAME REGION,  
SLOW CELL MOTION WILL FAVOR HIGH RAINFALL RATES AND INCREASE THE  
RISK FOR FLASH FLOODING. ALTHOUGH NOT AS HIGH OF A RISK, THE  
FAVORED AREA FOR HIGHER RAINFALL ON WEDNESDAY WILL BE OVER PARTS  
OF NEW ENGLAND. THIS SYSTEM IS EXPECTED TO CONTINUE MOVING EAST  
AND EXIT THE EAST COAST BY THURSDAY. MEANWHILE, BEHIND THIS  
SYSTEM, A LARGE AREA OF HIGH PRESSURE WILL SET IN ACROSS THE  
EASTERN U.S., RESULTING IN MUCH DRIER WEATHER TO FINISH OUT THE  
WORK WEEK.  
 
MUCH OF THE WEST WILL REMAIN IN A DRIER AIRMASS THAT WILL BE  
CONDUCIVE FOR ELEVATED FIRE DANGER. RED FLAG WARNINGS ARE IN  
EFFECT FOR A SMALL AREA OF NORTHEAST CALIFORNIA AND NORTHEAST  
NEVADA. THE PACIFIC NORTHWEST AND PORTIONS OF THE INTERMOUNTAIN  
WEST CONTINUES TO HAVE WIDESPREAD, POOR AIR QUALITY DUE TO THE  
SMOKE FROM ONGOING FIRES. AIR QUALITY ALERTS ARE IN EFFECT FOR ALL  
OF THE PACIFIC NORTHWEST, NORTHERN IDAHO, AND WESTERN MONTANA.  
FURTHERMORE, FIRES BURNING IN BRITISH COLUMBIA, CANADA ARE  
TRANSPORTING SMOKE SOUTHWARD INTO PORTIONS OF MINNESOTA.  
 
SCATTERED TO WIDESPREAD CONVECTION WILL STEADILY INCREASE OVER THE  
NEXT FEW DAYS FOR THE GREAT BASIN AND SOUTHERN/CENTRAL ROCKIES AS  
MONSOONAL MOISTURE RETURNS TO THE REGION. INDIVIDUAL STORMS WILL  
HAVE THE POTENTIAL TO PRODUCE HEAVY RAIN. THE AREA OF CONVECTION  
IS EXPECTED TO SHIFT TOWARD THE SOUTHERN PLAINS AS THE WEEK  
PROGRESSES. SOME OF THESE STORMS COULD PRODUCE FLASH FLOODING,  
ESPECIALLY IN FAVORABLE TERRAIN AND URBAN AREAS, AS WELL AS ACROSS  
BURN SCAR REGIONS. FLASH FLOODING WILL ALSO BE A CONCERN IN THE  
HIGH PLAINS, WHERE ABOVE NORMAL RAINFALL HAS ALREADY OCCURRED OVER  
THE PAST WEEK.  
 
CAMPBELL/REINHART  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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