397  
FXUS01 KWBC 280750  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
350 AM EDT TUE AUG 28 2018  
 
VALID 12Z TUE AUG 28 2018 - 12Z THU AUG 30 2018  
 
...A SLIGHT RISK OF SEVERE THUNDERSTORMS AND EXCESSIVE RAINFALL  
FROM THE MIDDLE MISSISSIPPI VALLEY TO THE UPPER GREAT LAKES  
TODAY...  
 
...EXCESSIVE HEAT EXPECTED TO CONTINUE ACROSS MUCH OF THE SOUTHERN  
AND EASTERN U.S....  
 
...AN AIR QUALITY ALERT DUE TO WILDFIRES REMAINS IN EFFECT ACROSS  
SOUTHERN OREGON...  
 
A COLD FRONT IS CURRENTLY STRETCHING FROM CANADA, ACROSS THE UPPER  
GREAT LAKES REGION, AND SOUTHEASTWARD INTO THE CENTRAL GREAT  
BASIN. SEVERAL AREAS OF LOW PRESSURE ARE EMBEDDED WITHIN THE  
STRUCTURE, ENHANCING THE INSTABILITY AND LIFT IN THESE LOCATIONS.  
STRONG SOUTHERLY FLOW IS PULLING WARM AND MOIST AIR INLAND FROM  
THE GULF OF MEXICO TOWARDS THE FRONTAL BOUNDARY, WHILE COLDER  
CANADIAN AIR CONTINUES TO FILL IN BEHIND. THE CLASH OF THESE TWO  
AIR MASSES IS LEADING TO SHOWERS AND THUNDERSTORMS ALONG AND JUST  
AHEAD OF THE FRONTAL BOUNDARY, ENHANCED BY ANY EMBEDDED LOW  
PRESSURE CIRCULATIONS. THE STORM PREDICTION CENTER HAS ISSUED A  
SLIGHT RISK FOR SEVERE THUNDERSTORMS STRETCHING FROM THE MIDDLE  
MISSISSIPPI VALLEY NORTHEAST INTO THE UPPER GREAT LAKES TODAY. THE  
WEATHER PREDICTION CENTER HAS ALSO ISSUED A SLIGHT RISK FOR  
EXCESSIVE RAINFALL FOR THE SAME REGION, AS WELL AS A MODERATE RISK  
OF EXCESSIVE RAINFALL FOR SOUTHERN WISCONSIN AND FAR NORTHERN  
ILLINOIS, WHERE A FLASH FLOOD WATCH AS WELL AS MULTIPLE ADVISORIES  
AND WARNINGS ARE ONGOING. THE RISK OF SEVERE STORMS AND EXCESSIVE  
RAINFALL WILL SLOWLY SHIFT EASTWARD WITH THE MOVEMENT OF THE COLD  
FRONT IN THE COMING DAYS.  
 
MEANWHILE, FOR LOCATIONS SOUTH AND EAST OF THE COLD FRONT, THE  
STRONG PULL OF WARM AND HUMID AIR IS LEADING TO SUPPRESSING HEAT.  
THIS HEAT IS EXPECTED TO PERSIST THROUGH THE COMING DAYS, WITH A  
STRONG UPPER LEVEL RIDGE IN PLACE, MAKING IT HARD FOR THE COLD  
FRONT TO MAKE MUCH EASTWARD PROGRESSION. MANY LOCATIONS COULD SEE  
HIGH TEMPERATURES IN THE MID AND UPPER 90S TODAY WITH HEAT INDEXES  
IN THE TRIPLE DIGITS. HEAT ADVISORIES ARE IN EFFECT FOR PORTIONS  
OF THE MID MISSISSIPPI VALLEY, INCLUDING ALL OF CENTRAL ILLINOIS,  
LOWER MICHIGAN, AS WELL AS ACROSS MUCH OF THE NORTHEAST AND  
NORTHERN MID-ATLANTIC. AN EXCESSIVE HEAT WARNING IS ALSO IN PLACE  
TODAY ACROSS THE ST. LOUIS METROPOLITAN AREA.  
 
ELSEWHERE, A MUCH COLDER CANADIAN AIRMASS IS SHIFTING SOUTHWARD  
AND ACROSS THE NORTHWESTERN U.S.. THE COMBINATION OF COOLER AIR  
AND LIGHT WINDS IS SUPPRESSING THE ONGOING FIRE CONCERNS, AND  
HELPING TO ALLEVIATING THE EXCESSIVE SMOKE IN THE AIR. ONLY ONE  
AIR QUALITY ALERT REMAINS IN PLACE FOR TODAY ACROSS SOUTHERN  
OREGON, WHERE AN ONGOING WILDFIRE CONTINUES TO BURN. MEANWHILE,  
HEAVY, WET SNOW WAS IMPACTING THE NORTHERN ROCKIES OVERNIGHT, BUT  
SHOULD CLEAR OUT THROUGHOUT THE MORNING.  
 
WIX  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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