539  
FXUS02 KWBC 030429  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1229 AM EDT FRI AUG 03 2018  
 
VALID 12Z MON AUG 06 2018 - 12Z FRI AUG 10 2018  
   
..OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
PATTERN NEXT WEEK WILL FEATURE A STRONG UPPER HIGH OVER THE  
SOUTHWEST AND RESURGENT TROUGHING IN THE EASTERN HALF OF THE LOWER  
48. AN UPPER LOW WELL OFF THE PACIFIC NORTHWEST COAST WILL ONLY  
SLOWLY MOVE TOWARD BRITISH COLUMBIA BY THE END OF NEXT WEEK. THE  
MODELS/ENSEMBLES WERE IN GOOD AGREEMENT OVERALL WITH SOME EXPECTED  
TIMING/AMPLITUDE DIFFERENCES. THE UNCERTAINTY MOSTLY STEMMED FROM  
ALASKA IN A SWIFT ZONAL FLOW. THOUGH THE 12Z ECMWF WAS SLOWER THAN  
THE GFS/UKMET/CANADIAN IN THE HIGH LATITUDES, THE LINGERING  
UNCERTAINTY WITH THE UPPER LOW PLACEMENT WELL WEST OF WASHINGTON  
COUPLED WITH UNCERTAIN INITIAL CONDITIONS OVER THE NORTH PACIFIC  
SUGGESTS THAT A BLENDED SOLUTION SHOULD SUFFICE. THE DETERMINISTIC  
MODELS HAVE LED THE WAY FOR THE ENSEMBLES OVER THE PAST FEW RUNS  
AND OPTED TO WEIGHT THEM IN THE MAJORITY THROUGH THE PERIOD.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
WITH THE UPPER LOW LINGERING OFFSHORE, RIDGING WILL SUPPORT WELL  
ABOVE AVERAGE TEMPERATURES IN THE WEST AND ESPECIALLY THE INTERIOR  
WEST. RECORD HIGHS (INCLUDING WARM OVERNIGHT MINIMUMS) ARE AGAIN  
LIKELY FOR SOME AREAS WEST OF THE DIVIDE. THE EAST WILL SEE ONE  
DAY OF WELL ABOVE AVERAGE TEMPERATURES ON MONDAY (SOME RECORD  
HIGHS POSSIBLE AROUND NYC) BEFORE HEIGHTS LOWER FOR THE REST OF  
THE WEEK AND THE FRONT PUSHES EASTWARD, RAISING THE CHANCE FOR  
PRECIPITATION.  
 
PRECIPITATION WILL FOCUS ALONG/AHEAD OF THE FRONT THAT WILL PUSH  
OUT OF THE HIGH PLAINS/GREAT LAKES EARLY IN THE WEEK AND THEN INTO  
THE SOUTHEAST FROM WED-FRI. WARM/HUMID AIRMASS WILL SUPPORT  
SCATTERED CONVECTION WITH LOCALLY HEAVY RAINFALL.  
 
FRACASSO  
 
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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