240  
FXUS02 KWBC 260551  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
150 AM EDT SUN AUG 26 2018  
 
VALID 12Z WED AUG 29 2018 - 12Z SUN SEP 02 2018  
   
..WEATHER PATTERN HIGHLIGHTS AND HAZARDS
 
 
A SERIES OF SHORTWAVE TROUGHS WILL DIG OVER THE NORTHEAST PACIFIC  
TO SPLIT OFF THE WEST COAST, WITH ENERGETIC FLOW AND MODEST  
PRECIPITATION POTENTIAL WORKING INTO THE PACIFIC NORTHWEST/WEST  
BEFORE PROGRESSING EAST-NORTHEASTWARD OVER SOUTHERN CANADA/U.S.  
NORTHERN TIER. WAVY FRONTAL SYSTEMS UNDERNEATH WILL POOL DEEPENED  
MOISTURE AND INSTABILITY TO FUEL PERIODS OF HEAVY  
CONVECTION/COMPLEXES, WITH A MAIN MEDIUM RANGE FOCUS FROM THE  
EASTERN PLAINS/MISSISSIPPI VALLEY TO THE MIDWEST/MID-SOUTH AND  
NORTHEAST/MID-ATLANTIC.  
 
EXPECT A THREAT FOR LOCALLY EXCESSIVE, BUT LESS ORGANIZED  
THUNDERSTORMS/HEAVY DOWNPOURS INTO A HOT SECTOR SPRAWLING THE  
SOUTHERN/EASTERN U.S. TO ALIGN WITH MESO-BOUNDARIES AND LOCAL  
CONVERGENCE EFFECTS. THIS POTENT LATE SUMMER HOT SECTOR UNDER  
RIDGING ALOFT WILL OFFER SPOTTY RECORD MAXIMUM TEMPERATURES OVER  
THE NORTHEAST/MID-ATLANTIC WEDNESDAY WITH NUMEROUS RECORD HIGH  
MINIMUM TEMPERATURES MAINLY WEDNESDAY INTO THURSDAY WITH POOLING  
DEEP MOISTURE AHEAD OF A SUBSEQUENTLY MODERATING EASTERN U.S.  
FRONTAL PUSH. OTHERWISE, THE HOT SECTOR OVER THE U.S. SOUTHERN  
TIER GENERALLY HOLDS FIRM FOR THE COMING WEEK.  
 
   
..GUIDANCE AND UNCERTAINTY ASSESSMENT
 
 
THE LARGER SCALE FLOW PATTERN IS REASONABLY WELL DEPICTED IN  
GUIDANCE SO WHILE OVERALL WEATHER THREATS SEEM DOCUMENTED,  
DETERMINISTIC EFFORTS TO DETAIL MUCH LESS PREDICTABLE EMBEDDED  
FEATURES AND LOCAL FOCUS FOR CONVECTION ARE INCREASINGLY SUFFERING  
FROM RUN TO RUN VARIANCE AND FLIP-FLOPPING. ACCORDINGLY, THE WPC  
MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM A COMPOSITE  
BLEND OF ENSEMBLES, THE NATIONAL BLEND OF MODELS AND WPC  
CONTINUITY, WITH LESS THAN NORMAL DETERMINITSIC MODEL INPUT AMID  
GROWN UNCERTAINTY.  
 
SCHICHTEL  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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