786  
FXUS02 KWBC 281600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1159 AM EDT TUE AUG 28 2018  
 
VALID 12Z FRI AUG 31 2018 - 12Z TUE SEP 04 2018  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE CONTINUES TO BE IN GOOD AGREEMENT WITH THE OVERALL  
SYNOPTIC PATTERN ACROSS THE U.S. THROUGH THE MEDIUM RANGE PERIOD.  
THE UPPER RIDGE WILL REMAIN THE DOMINANT FEATURE ACROSS THE  
CENTRAL U.S., SOUTHEAST AND EAST COAST. MEANWHILE, MODEL GUIDANCE  
CONTINUES TO SHOW AN AMPLIFIED TROUGH OVER THE PACIFIC NORTHWEST  
AND NORTHERN ROCKIES. THIS TROUGH WILL SLIDE EASTWARD TOWARD THE  
U.S. NORTHERN TIER LATER IN THE MEDIUM RANGE PERIOD. MEANWHILE,  
PACIFIC ENERGY WILL MOVE INLAND ACROSS CALIFORNIA--EITHER IN  
SEPARATE OR BROADER SOUTHERN STREAM FLOW BY LATE THIS WEEKEND AND  
INTO EARLY NEXT WEEK. MODEL GUIDANCE STILL NEEDS TO RESOLVE THE  
EVOLUTION OF THIS ENERGY--ALTHOUGH THE 00Z NAEFS/00Z ECMWF AND THE  
06Z GEFS SHOW A TROUGH OVER THE WEST COAST BY DAY 5 BUT DETAILS  
ARE SLIGHTLY DIFFERENT. THE 00Z NAEFS/00Z ECMWF ARE ALSO IN  
AGREEMENT IN DAY 6/7 A TROUGH OVER THE WEST COAST SLIDING OVER THE  
INTERMOUNTAIN WEST/NORTHERN PLAINS. WPC USED A BLEND OF THE 00Z  
CMC/ECMWF AND 06Z GFS IN THE BEGINNING OF THE MEDIUM RANGE PERIOD  
AND INCREASED THE USE OF THE 00Z NAEFS/00Z ECENS LATER IN THE  
PERIOD TO ACCOUNT FOR THE ABOVE AVERAGE FORECAST SPREAD ESPECIALLY  
FROM THE FLOW EVOLUTIONS UPSTREAM OVER THE PACIFIC.  
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
WITH MULTIPLE FRONTS MOVING INTO THE NORTHERN PLAINS AND UPPER  
MIDEWST, DEEPE  
 
REINHART/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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