668  
FXUS01 KWBC 172001  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
400 PM EDT FRI AUG 17 2018  
 
VALID 00Z SAT AUG 18 2018 - 00Z MON AUG 20 2018  
 
...SLIGHT RISK OF SEVERE THUNDERSTORMS AND FLASH FLOODING FOR THE  
NORTHEAST WITH HEAVY RAINFALL IMPACTING AREAS FROM THE  
MID-ATLANTIC TO THE SOUTHERN PLAINS...  
 
...HEAVY RAINFALL WILL BEGIN IMPACTING PORTIONS OF THE PLAINS THIS  
WEEKEND...  
 
...AIR QUALITY WILL REMAIN A CONCERN THIS WEEKEND ACROSS MUCH OF  
THE NORTHWESTERN U.S. AND ALSO PARTS OF THE UPPER MISSISSIPPI  
VALLEY...  
 
ACTIVE WEATHER WILL IMPACT LOCATIONS FROM THE NORTHEAST TO THE  
SOUTHERN PLAINS THIS EVENING AS A FRONTAL BOUNDARY DRIFTS SLOWLY  
EASTWARD. DEEP SOUTHERLY FLOW AHEAD OF THIS SYSTEM WILL PULL  
ANOMALOUS MOISTURE NORTHWARD TO CREATE AN ENVIRONMENT CONDUCIVE TO  
HEAVY RAINFALL AND POSSIBLE SEVERE WEATHER. EXPECT WIDESPREAD  
SCATTERED SHOWERS AND THUNDERSTORMS TO CONTINUE ALL ACROSS MUCH OF  
THE EASTERN STATES AND BACK INTO THE LOWER MISSISSIPPI VALLEY AND  
SOUTHERN PLAINS. THE BEST CHANCE FOR SEVERE WEATHER AND EXCESSIVE  
RAINFALL/FLASH FLOODING WILL BE IN THE NORTHEAST AS THE MAIN  
SURFACE LOW MOVES THROUGH THIS REGION. WHILE THE COLD FRONT SHOULD  
EXIT THE NORTHEAST EARLY SATURDAY, THE BOUNDARY SHOULD LINGER  
ACROSS THE MID-ATLANTIC, THE TENNESSEE VALLEY, AND THE SOUTHERN  
PLAINS. THIS WILL CONTINUE THE THREAT FOR SHOWERS AND  
THUNDERSTORMS, ALONG WITH LOCALIZED HEAVY RAINFALL AND SEVERE  
WEATHER, ACROSS THE MID-ATLANTIC AND MUCH OF THE SOUTHERN TIER  
STATES. BOTH SPC AND WPC HAVE MARGINAL RISKS HIGHLIGHTED ON THEIR  
CONVECTIVE AND EXCESSIVE RAINFALL GRAPHICS, RESPECTIVELY.  
 
MONSOONAL MOISTURE WILL CONTINUE ACROSS THE SOUTHWEST WITH  
DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS LEADING TO A DAILY,  
MARGINAL TO SLIGHT, THREAT FOR HEAVY TO EXCESSIVE RAINFALL AND  
FLASH FLOODING. TO THE NORTH, A SYSTEM PUSHING INTO THE CENTRAL  
U.S. WILL INCREASE THE HEAVY RAINFALL THREAT FOR THE CENTRAL AND  
SOUTHERN HIGH PLAINS AND PLAINS. WITH SIGNIFICANT MOISTURE IN  
PLACE, EXCESSIVE RAINFALL AND FLASH FLOODING WILL BE A CONCERN,  
AND WPC HAS PORTIONS OF THE HIGH PLAINS IN A SLIGHT RISK FOR  
SATURDAY, PUSHING EASTWARD ON SUNDAY.  
 
OUT WEST, DRY THUNDERSTORMS AND ACTIVE FIRE WEATHER WILL CONTINUE  
THIS EVENING, WITH NUMEROUS RED FLAG WARNINGS IN EFFECT ACROSS THE  
NORTHERN INTERMOUNTAIN WEST. AIR QUALITY WILL REMAIN A CONCERN  
THROUGH THE WEEKEND AS WELL WITH HEAVY SMOKE FROM ONGOING FIRES  
LINGERING ACROSS THE NORTHWEST AND CALIFORNIA. THE LATEST  
SATELLITE IMAGERY INDICATES SMOKE FROM THESE FIRES PROPAGATING  
DOWNSTREAM INTO PARTS OF THE FAR NORTHERN PLAINS AND THE UPPER  
MISSISSIPPI VALLEY. AIR QUALITY ALERTS ARE ALSO IN EFFECT FOR MUCH  
OF MINNESOTA.  
 
SANTORELLI  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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