187  
FXUS02 KWBC 101619  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1218 PM EDT TUE JUL 10 2018  
 
VALID 12Z FRI JUL 13 2018 - 12Z TUE JUL 17 2018  
   
..OVERVIEW, GUIDANCE EVALUATION AND PREFERENCES
 
 
MODEL GUIDANCE THIS EVENING SHOWS GOOD OVERALL AGREEMENT ON THE  
EVOLUTION OF THE SYNOPTIC PATTERN THROUGH NEXT TUESDAY. FOR THE  
500 HPA HEIGHTS, PRESSURES, AND WINDS, USED A COMPROMISE OF THE  
00Z CANADIAN, 00Z UKMET, 00Z ECMWF, AND 06Z GFS INTO SUNDAY  
MORNING. THEREAFTER, STARTED BLENDING IN SOME 00Z NAEFS MEAN AND  
00Z ECMWF ENSEMBLE MEAN TO DEAL WITH THE UNCERTAINTY INHERENT AT  
LONGER RANGES. THE TEMPERATURES, DEW POINTS, CLOUDS, WEATHER, AND  
PRECIPITATION CHANCES WERE DERIVED FROM A 50/50 MIX OF  
DETERMINISTIC AND ENSEMBLE MEAN SOLUTIONS. THE PRELIMINARY DAYS  
4-7 QPF STARTS WITH A FOUR-WAY BLEND OF THE 06Z GFS, 00Z CANADIAN,  
00Z ECMWF, AND THE 12Z NATIONAL BLEND OF MODELS. SHOULD THE 12Z  
GFS PROVE USEFUL, ITS THOUGHTS COULD BE INCLUDED AS WELL.  
 
   
..WEATHER HIGHLIGHTS
 
 
ALTHOUGH THE DOMINATING SUBTROPICAL HIGH WILL BRING HEAT ACROSS A  
LARGE PORTION OF THE COUNTRY THROUGH EARLY NEXT WEEK, THERE WILL  
BE BOUTS OF COOL AIR INTRUSION FROM CANADA FOLLOWING OCCASIONAL  
FRONTAL PASSAGES ACROSS THE NORTHERN TIER. A COLD FRONT WILL  
INITIALLY BRING SHOWERS AND THUNDERSTORMS ACROSS THE NORTHERN  
PLAINS INTO THE GREAT LAKES FRIDAY BUT AS THE FRONT IS FORECAST TO  
BECOME MORE DIFFUSED WITH TIME, MORE ISOLATED COVERAGE IN THE  
NORTHEAST WILL BE THE RESULT DURING THE WEEKEND. MEANWHILE, THE  
NEXT FRONT WILL MOVE OUT OF CANADA THIS WEEKEND WITH SCATTERED  
SHOWERS AND THUNDERSTORMS ALONG/AHEAD OF ITS BOUNDARY. COOL AIR  
IN ITS WAKE WILL BREAK THE HEAT WAVE ACROSS THE NORTHERN ROCKIES  
AND IS FORECAST TO DROP TEMPERATURES MORE THAN 10 DEGREES BELOW  
NORMAL ACROSS THE NORTHERN PLAINS EARLY NEXT WEEK. AHEAD OF THE  
FRONT, TEMPERATURES WILL BE ABOUT 5-10 DEGREES ABOVE AVERAGE (80S  
AND MANY 90S), AND INITIALLY NEAR OR ABOVE 100 OVER PORTIONS OF  
THE INTERIOR PACIFIC NORTHWEST/GREAT BASIN ON FRIDAY. BUT  
TRIPLE-DIGIT HEAT IS EXPECTED TO CONTINUE IN PARTS OF INTERIOR  
CALIFORNIA.  
 
FROM THE SOUTHEASTERN U.S. WESTWARD ALONG THE GULF COAST, A  
DISSIPATING FRONT WILL KEEP A CHANCE OF SHOWERS AND THUNDERSTORMS  
IN THE VICINITY THROUGH THE WEEKEND. MONSOONAL MOISTURE WILL  
LINGER ACROSS THE FOUR CORNERS AREA WHERE LOCALLY HEAVY DOWNPOURS  
ARE POSSIBLE THROUGH EARLY NEXT WEEK. TEMPERATURES WILL GENERALLY  
BE NEAR OR BELOW AVERAGE IN THE SOUTHWEST UNDER LIMITED SOLAR  
INSOLATION AND A DAILY CHANCE OF SHOWERS/STORMS.  
 
ROTH/KONG/FRACASSO  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND AT:  
 
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTP://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTP://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTP://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTP://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  

 
 
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