111  
FXUS01 KWBC 210724  
PMDSPD  
 
SHORT RANGE FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
321 AM EDT TUE AUG 21 2018  
 
VALID 12Z TUE AUG 21 2018 - 12Z THU AUG 23 2018  
 
...HEAVY RAIN AND SEVERE WEATHER EXPECTED ACROSS THE OHIO VALLEY  
AND MID-ATLANTIC TODAY...  
 
...FIRE WEATHER AND AIR QUALITY CONCERNS CONTINUE FOR PORTIONS OF  
THE WESTERN U.S...  
 
A VERY STRONG LOW PRESSURE SYSTEM WILL LIFT ACROSS THE OHIO VALLEY  
AND LOWER GREAT LAKES TODAY. FROM THIS WILL STRETCH A ROBUST COLD  
FRONT WHICH WILL DRAPE SOUTHWARD 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 PRESSURE. A SLIGHT  
RISK OF SEVERE WEATHER IS POSSIBLE FOR THE OHIO VALLEY AND  
MID-ATLANTIC AS WELL AS A SLIGHT RISK FOR FLASH FLOODING. LATER ON  
INTO WEDNESDAY, THE COLD FRONT WILL PUSH OFF THE EAST COAST--AND  
SO TOO WILL THE PRECIPITATION. SOME HEAVIER PRECIPITATION WILL  
CONTINUE TO MOVE ACROSS NEW ENGLAND AS THE COLD FRONT SWEEPS  
ACROSS THIS REGION. MEANWHILE, BEHIND THIS SYSTEM, A LARGE AREA OF  
HIGH PRESSURE WILL SET IN ACROSS THE EASTERN U.S., RESULTING IN  
MUCH DRIER WEATHER TO FINISH OUT THE WORK WEEK.  
 
FIRE WEATHER RISKS WILL CONTINUE TO BE ELEVATED ACROSS THE WEST,  
ESPECIALLY FOR PARTS OF THE GREAT BASIN TODAY. RED FLAG WARNINGS  
ARE IN EFFECT FOR A SMALL AREA OF NORTHEAST CALIFORNIA AND  
NORTHEAST NEVADA. AIR QUALITY ALSO REMAINS A CONCERN DUE TO THE  
SMOKE FROM ONGOING FIRES. AIR QUALITY ALERTS ARE IN EFFECT FOR ALL  
OF THE PACIFIC NORTHWEST, 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  
AND EXPAND ACROSS THE GREAT BASIN AND SOUTHERN/CENTRAL ROCKIES,  
RESULTING IN SCATTERED TO WIDESPREAD SHOWERS AND THUNDERSTORMS  
THROUGH THE DAY. THESE STORMS WILL THEN SHIFT EASTWARD TO  
ENCOMPASS A PORTION OF THE CENTRAL AND SOUTHERN PLAINS BY  
MID-WEEK. THE BEST SHOWER AND THUNDERSTORM POTENTIAL WILL BE IN  
THE AFTERNOON AND EARLY EVENING EACH DAY. SOME OF THESE STORMS  
COULD PRODUCE FLASH FLOODING, ESPECIALLY IN FAVORABLE TERRAIN AND  
URBAN AREAS, AS WELL AS ACROSS BURN SCAR REGIONS. FLASH FLOODING  
WILL ALSO BE A CONCERN IN THE HIGH PLAINS, WHERE ABOVE NORMAL  
RAINFALL HAS ALREADY OCCURRED OVER THE PAST WEEK.  
 
REINHART/WIX  
 
GRAPHICS AVAILABLE AT  
WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP  

 
 
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