060  
FXUS01 KWBC 270808  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
407 AM EDT MON AUG 27 2018  
 
VALID 12Z MON AUG 27 2018 - 12Z WED AUG 29 2018  
 
...STRONG THUNDERSTORMS AND HEAVY RAINFALL WILL IMPACT THE UPPER  
MISSISSIPPI VALLEY AND UPPER GREAT LAKES TODAY...  
 
...EXCESSIVE HEAT IS EXPECTED ACROSS THE SOUTHERN/CENTRAL PLAINS  
AND THE ENTIRE EASTERN THIRD OF THE U.S. OVER THE COMING DAYS...  
   
..ONGOING FIRE WEATHER CONCERNS ACROSS THE WEST
 
 
...ACCUMULATING WET SNOW FORECAST ACROSS THE NORTHERN ROCKIES  
TODAY AND TONIGHT...  
 
AN UPPER LEVEL TROUGH IS EXPECTED ACROSS THE NORTHWESTERN U.S. AND  
THE DAKOTAS THROUGH TUESDAY, WHILE AN UPPER LEVEL RIDGE CONTINUES  
TO BUILD ACROSS THE EASTERN THIRD OF THE NATION. MEANWHILE AT THE  
SURFACE, A ACTIVE FRONTAL ZONE IS CURRENTLY IN PLACE, DRAPING FROM  
THE INTERMOUNTAIN WEST NORTHEAST INTO THE NORTHERN PLAINS AND  
UPPER MISSISSIPPI VALLEY. A STRONG SURGE OF WARM, MOIST AIR IS  
BEING PULLED NORTHWARD FROM THE GULF OF MEXICO TOWARDS THE FRONTAL  
BOUNDARY, RESULTING IN SHOWERS AND THUNDERSTORMS ALONG AND JUST  
AHEAD OF THE BOUNDARY. THE BEST SHOWER AND THUNDERSTORM ACTIVITY  
WILL BE FOUND NEAR THE CENTERS OF LOW PRESSURE EMBEDDED WITHIN THE  
NORTHERN PORTION OF THE BOUNDARY. THE STORM PREDICTION CENTER HAS  
OUTLINED A LARGE AREA ENCOMPASSING MUCH OF THE UPPER MISSISSIPPI  
VALLEY AND UPPER GREAT LAKES REGION AS BEING IN A SLIGHT RISK OF  
SEVERE STORMS THROUGH TODAY. THE WEATHER PREDICTION CENTER HAS  
ALSO OUTLINED MUCH OF THE SAME REGION AS BEING IN A SLIGHT RISK  
FOR EXCESSIVE RAINFALL TODAY AS WELL. THE RISK OF EXCESSIVE  
RAINFALL AND SEVERE STORMS WILL SHIFT SLIGHTLY FARTHER SOUTHEAST  
FOR TUESDAY, STRETCHING FROM THE MID MISSISSIPPI VALLEY NORTHEAST  
INTO THE UPPER GREAT LAKES.  
 
WHILE A COOLER AIRMASS IS IN PLACE BEHIND THE FRONTAL BOUNDARY,  
THE STRONG RIDGE IN PLACE ACROSS THE EASTERN AND SOUTHEASTERN U.S.  
WILL MAKE IT HARD FOR THE FRONT TO MOVE EAST QUICKLY. AS A RESULT,  
MUCH OF THE SOUTHERN AND EASTERN U.S. WILL CONTINUE TO SEE HOT AND  
HUMID SOUTHERLY FLOW FOR MUCH OF THE WEEK. ABOVE NORMAL  
TEMPERATURES ARE EXPECTED IN MANY LOCATIONS. HEAT ADVISORIES HAVE  
BEEN POSTED ACROSS MUCH OF ILLINOIS AND ALONG THE MID AND LOWER  
MISSISSIPPI RIVER, AS WELL AS ACROSS PORTIONS OF THE NORTHEAST AND  
NORTHERN MID-ATLANTIC. SPECIAL WEATHER STATEMENTS FOR HEAT ARE  
ALSO IN EFFECT ACROSS PORTIONS OF THE OHIO VALLEY. HEAT INDICES  
WILL EXCEED 100 DEGREES FOR MANY LOCATIONS TODAY AND TUESDAY, AND  
SOME HIGH TEMPERATURE RECORDS MAY BE BROKEN AS WELL.  
 
ACROSS THE WESTERN U.S., FIRE WEATHER CONCERNS PERSIST. A RED FLAG  
WARNING IS IN EFFECT THROUGH THIS EVENING ACROSS THE WESTERN  
CENTRAL PLAINS DUE TO WINDY CONDITIONS AND LOW HUMIDITY. AIR  
QUALITY ALSO CONTINUES TO BE COMPROMISED BY SMOKE FROM ONGOING  
WILD FIRES. AIR QUALITY ALERTS ARE ONGOING ACROSS CENTRAL  
CALIFORNIA, SOUTHWEST OREGON, NORTHERN WASHINGTON, SOUTHERN AND  
NORTHERN IDAHO, AND NORTHWEST MONTANA. AS MENTIONED ABOVE, MUCH  
COLDER AIR IS PUSHING IN BEHIND THE FRONTAL BOUNDARY. THIS COLD  
AIR WILL MAKE IT INTO THE NORTHERN ROCKIES AND NORTHERN PLAINS  
TODAY. IN FACT, THERE IS ENOUGH COLD AIR FLOWING ACROSS THE  
NORTHERN ROCKIES THAT ACCUMULATING WET SNOW IS EXPECTED. WINTER  
WEATHER ADVISORIES ARE IN EFFECT WITH 4 TO 8 INCHES FORECAST  
THROUGH TUESDAY MORNING.  
 
WIX  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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