653  
FXUS01 KWBC 202000  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
359 PM EDT MON AUG 20 2018  
 
VALID 00Z TUE AUG 21 2018 - 00Z THU AUG 23 2018  
 
...HEAVY RAIN AND SEVERE WEATHER EXPECTED ACROSS THE MISSISSIPPI  
VALLEY TODAY...  
   
..ACTIVE WEATHER RETURNS FOR THE EAST COAST THIS WEEK
 
 
   
..AIR QUALITY REMAINS A CONCERN FOR PARTS OF THE WESTERN U.S
 
 
A VERY STRONG LOW PRESSURE SYSTEM WILL CONTINUE TO LIFT ACROSS THE  
MID AND UPPER MISSSIPI VALLEY THIS EVENING, REACHING THE OHIO  
VALLEY AND LOWER GREAT LAKES BY OVERNIGHT. FROM THIS WILL STRETCH  
A ROBUST COLD FRONT WHICH WILL DRAPE SOUTWARD INTO THE SOUTHERN  
PLAINS. AHEAD OF THE FRONTAL SYSTEM, WARM AND MOIST AIR WILL BE  
TRANSPORTED FROM THE GULF OF MEXICO SPAWNING WIDESPREAD SHOWERS  
AND THUNDERSTORMS ACROSS MUCH OF THE EASTERN U.S. AND SOUTHEAST.  
THE HEAVIEST RAINFALL AND BEST THUNDERSTORM POTENTIAL WILL BE  
LOCATED ALONG THE FRONTAL BOUNDARY AND CLOSE TO THE CENTER OF LOW  
PERSSURE. THE STORM PREDICTION CENTER HAS OUTLINED A PORTION OF  
THE MID/LOWER MISSISSIPPI RIVER AS BEING IN AN ENHANCED RISK OF  
SEVERE THUNDERSTORMS THROUGH TONIGHT. A SLIGHT RISK OF SEVERE  
WEATHER IS ALSO IN EFFECT FOR THE SURROUNDING AREAS. A SEVERE  
THUNDERSTORM WATCH IS IN EFFECT FOR NORTHEAST ARKANSAS, SOUTHEAST  
MISSOURI, AND SOUTHERN ILLINOIS. THE WEATHER PREDICTION CENTER HAS  
ALSO OUTLINED A LARGE SLIGHT RISK AREA FOR EXCESSIVE RAINFALL  
STRETCHING FROM THE LOWER MISSIPPI RIVER NORTHWARD TO LAKE  
MICHIGAN AND WESTWARD INTO IOWA THROUGH TONIGHT. AS THIS SYSTEM  
CONTINUES TO PROGRESS EASTWARD OVER THE COMING DAYS, SO TO WILL  
THE SEVERE WEATHER AND EXCESSIVE RAINFALL/FLASH FLOODING THREATS.  
MEANWHILE A STRONG AREA OF HIGH PRESSURE WILL MOVE INTO MUCH OF  
THE UNITED STATES BEHIND THIS FRONTAL FEATURE.  
 
FIRE WEATHER RISKS CONTINUE TO BE ELEVATED ACROSS THE WESTERN  
U.S., ESPECIALLY FOR THE PACIFIC NORTHWEST, INTERMOUNTAIN WEST,  
GREAT BASIN, AND PORTIONS OF THE NORTHERN ROCKIES THROUGH TUESDAY.  
RED FLAG WARNINGS ARE IN EFFECT FOR PARTS OF THESE AREAS DUE TO  
HIGH WINDS AND LOW RELATIVE HUMIDITIES. AIR QUALITY ALSO REMAINS A  
CONCERN DUE TO THE SMOKE FROM ONGOING FIRES. AIR QUALITY ALERTS  
CONTINUE TO BE IN EFFECT FOR ALL OF WASHINGTON, OREGON, NORTHERN  
IDAHO, AND WESTERN MONTANA. FURTHERMORE, FIRES BURNING IN BRITISH  
COLUMBIA, CANADA ARE TRANSPORTING SMOKE SOUTHWARD INTO PORTIONS OF  
MINNESOTA, WHERE AN AIR QUALITY ALERT IS ALSO IN EFFECT.  
 
MONSOONAL MOISTURE WILL SURGE BACK INTO THE SOUTHWEST BY TUESDAY.  
LATE AFTERNOON AND EARLY EVENING THUNDERSTORMS WILL RETURN ACROSS  
THE SOUTHWEST AND GREAT BASIN ON TUESDAY AND WEDNESDAY. SOME OF  
THESE STORMS COULD PRODUCE FLASH FLOODING ESPECIALLY IN FAVORABLE  
TERRAIN AND URBAN AREAS, AS WELL AS ACROSS BURN SCAR REGIONS. ON  
TUESDAY NIGHT AND INTO WEDNESDAY, THUNDERSTORMS ARE EXPECTED TO  
DEVELOP IN THE HIGH PLAINS OF COLORADO AND KANSAS AND MOVE INTO  
THE SOUTHERN PLAINS. SOME OF THESE AREAS HAVE RECEIVED ABOVE  
NORMAL RAINFALL IN THE LAST WEEK, ELEVATING THE CHANCES OF  
LOCALIZED FLASH FLOODING. ADDITIONALLY, THERE IS A SLIGHT RISK OF  
SEVERE WEATHER IN A SMALL AREA OF SOUTHEAST COLORADO AND THE  
OKLAHOMA PANHANDLE.  
 
WIX  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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