257  
FXUS01 KWBC 192017  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
416 PM EDT SUN AUG 19 2018  
 
VALID 00Z MON AUG 20 2018 - 00Z WED AUG 22 2018  
 
...HEAVY RAINFALL AND STRONG THUNDERSTORMS EXPECTED TO IMPACT  
PARTS OF THE PLAINS, MIDWEST AND MISSISSIPPI VALLEY THROUGH  
TONIGHT, SHIFTING EASTWARD THROUGH THE WORK WEEK...  
 
...AIR QUALITY WILL REMAIN A CONCERN ACROSS PORTIONS OF THE  
WESTERN U.S. AND THE UPPER MIDWEST...  
 
A STRENGTHENING LOW PRESSURE SYSTEM IS CURRENTLY LOCATED ACROSS  
THE CENTRAL PLAINS, WITH A COLD FRONT EXTENDING SOUTH INTO THE  
SOUTHERN PLAINS, AND A WARM FRONT EXTENDING EASTWARD INTO THE  
LOWER/MID MISSISSIPPI VALLEY AND OHIO VALLEY. THIS SYSTEM WILL  
CONTINUE TO PUSH EASTWARD AS IT STRENGTHENS DURING THE FIRST PART  
OF THE WORK WEEK. A STRONG INFLUX OF WARM AND MOIST AIR FROM THE  
GULF OF MEXICO IS AIDING IN HEAVY RAIN PRODUCTION AND STRONG TO  
SEVERE STORMS NEAR THIS SYSTEM. MEANWHILE, ANOTHER COLD FRONT  
ORIGINATING FROM CANADA WILL CONTINUE TO QUICKLY DIVE SOUTHWARD,  
BRINGING WITH IT A MUCH COOLER AIRMASS. THESE TWO SYSTEMS ARE  
CURRENTLY IN FAIRLY CLOSE PROXIMITY TO ONE ANOTHER, AND WILL  
CONTINUE TO INTERACT WITH ONE ANOTHER IN THE COMING DAYS,  
EXASPERATING THE STORM AND HEAVY RAIN POTENTIAL. THE WEATHER  
PREDICTION CENTER HAS ISSUED A SLIGHT RISK FOR EXCESSIVE RAINFALL  
THROUGH TONIGHT ACROSS A LARGE NORTH-TO-SOUTH ORIENTED REGION  
STRETCHING FROM THE NORTHERN PLAINS AND UPPER MIDWEST SOUTHWARD  
INTO THE LOWER MISSISSIPPI VALLEY. THIS SLIGHT RISK REGION WILL  
SHIFT EASTWARD WITH THE LOW PRESSURE AND FRONTAL SYSTEMS FOR  
MONDAY AND TUESDAY. ON MONDAY IT WILL ENCOMPASS PORTIONS OF THE  
MID/NORTHERN MISSISSIPPI, OHIO, AND WESTERN TENNESSEE VALLEYS. ON  
TUESDAY THE SLIGHT RISK REGION WILL ENCOMPASS AN AREA FROM THE  
LOWER GREAT LAKES TO THE CENTRAL APPALACHIANS. MEANWHILE, A FLASH  
FLOOD WATCH IS CURRENTLY IN EFFECT THROUGH MONDAY MORNING FOR  
EASTERN NEBRASKA AND SOUTHWEST IOWA. PREEMPTIVE FLASH FLOOD  
WATCHES ARE ALSO IN EFFECT ACROSS PORTIONS OF SOUTHEAST WISCONSIN  
AND SOUTHERN LOUISIANA. THE STORM PREDICTION CENTER ALSO HAS A  
SLIGHT RISK FOR SEVERE STORMS THROUGH TONIGHT FOR AN AREA  
INCLUDING NORTHWEST ARKANSAS AND SOUTHWEST MISSOURI. THIS SLIGHT  
RISK AREA WILL ALSO SHIFT EASTWARD OVER THE NEXT COUPLE OF DAYS,  
ENCOMPASSING MANY OF THE SAME AREAS AS WAS OUTLINED BY THE WEATHER  
PREDICTION CENTERS RISK FOR EXCESSIVE RAINFALL.  
 
FIRE WEATHER REMAINS A CONCERN ACROSS THE WESTERN U.S. THE  
COMBINATION OF HIGH WINDS AND LOW HUMIDITIES MAY CONTRIBUTE TO  
IGNITING WILDFIRES AS WE HEAD INTO THE WORK WEEK. SEVERAL FIRE  
WEATHER WATCHES ARE CURRENTLY IN EFFECT, INCLUDING PORTIONS OF  
UTAH, WASHINGTON, AND MONTANA. DUE TO THE SMOKE POLLUTION FROM  
ONGOING WILDFIRES, AIR QUALITY ALERTS REMAIN IN PLACE FOR LARGE  
PORTIONS OF OREGON, WASHINGTON, IDAHO, AND ALL OF MONTANA.  
 
WIX  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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