025  
FXUS02 KWBC 091600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1159 AM EDT MON JUL 09 2018  
 
VALID 12Z THU JUL 12 2018 - 12Z MON JUL 16 2018  
   
..OVERVIEW
 
 
UPPER RIDGING WILL CONTINUE TO DOMINATE THE LOWER 48 LATER THIS  
WEEK INTO NEXT WEEK. CURRENT TROPICAL STORM CHRIS WILL LIFT  
NORTHEASTWARD AWAY FROM NEW ENGLAND INTO SOUTHEASTERN CANADA  
THURSDAY/FRIDAY WITH A TRAILING UPPER TROUGH HELPING TO KEEP IT  
OFFSHORE. ANOTHER SHORTWAVE WILL DIG THROUGH SOUTHWESTERN CANADA  
FRI/SAT AND THEN HEAD EASTWARD ACROSS THE CANADIAN PRAIRIES SUNDAY  
BEFORE LIFTING TOWARD HUDSON BAY NEXT MONDAY AS THE 594 DM UPPER  
HIGH OVER THE MIDDLE MISSISSIPPI VALLEY MEANDERS IN PLACE. THIS  
WILL ALLOW A FRONTAL BOUNDARY TO DIP INTO THE NORTHERN ROCKIES AND  
HIGH PLAINS/UPPER MIDWEST THIS WEEKEND BUT SLOW AS IT SINKS  
SOUTHEASTWARD INTO THE MIDWEST.  
   
..GUIDANCE EVALUATION AND PREFERENCES
 
 
LATEST 00Z/06Z GUIDANCE OFFERED A GOOD STARTING POINT AND A  
BLENDED SOLUTION WAS IMPLORED TO START. THE 00Z UKMET REMAINED A  
BIT SLOWER WITH CHRIS OFF THE EAST COAST AND DEEPER WITH THE  
TRAILING UPPER TROUGH BUT OTHERWISE WAS CLOSE TO THE DETERMINISTIC  
CONSENSUS FOR THE REST OF THE CONUS/SOUTHERN CANADA. BY SUN/MON  
NEXT WEEK, THE GFS RUNS WERE STRONGER WITH THE TROUGH OVER  
NORTHEASTERN MONTANA INTO NORTH DAKOTA THAN THE ENSEMBLES (EVEN  
DEEPER THAN THE DEEPEST ENSEMBLE MEMBER FROM THE 90-MEMBER  
GEFS/ECMWF/CANADIAN ENSEMBLES) BUT THE 00Z ECMWF/CANADIAN MAY HAVE  
BEEN TOO FAR NORTHEAST PER THE ENSEMBLE CONSENSUS. A BLEND TOWARD  
THE ENSEMBLES WAS USED FOR DAYS 6-7 (SUN/MON) GIVEN UNCERTAINTY IN  
THE UPPER TROUGH AND SFC FRONT STRENGTH/SPEED.  
 
   
..WEATHER HIGHLIGHTS
 
 
A COLD FRONT WILL BRING SHOWERS/STORMS TO THE NORTHERN PLAINS INTO  
THE GREAT LAKES THU/FRI BUT MORE ISOLATED COVERAGE SAT/SUN IN THE  
NORTHEAST WITH DECREASING UPPER SUPPORT. THE NEXT FRONT WILL MOVE  
OUT OF CANADA THIS WEEKEND WITH SCATTERED SHOWERS AND  
THUNDERSTORMS ALONG/AHEAD OF ITS BOUNDARY AND COOLER AIR IN ITS  
WAKE. TEMPERATURES WILL BE BELOW AVERAGE ON SUNDAY OVER MONTANA  
THEN SOUTHEASTWARD TO MINNESOTA/NEBRASKA ON MONDAY. AHEAD OF THE  
FRONT, TEMPERATURES WILL BE ABOUT 5-10 DEGREES ABOVE AVERAGE (80S  
AND MANY 90S). TEMPERATURES INITIALLY NEAR 100 OVER PORTIONS OF  
THE INTERIOR PACIFIC NORTHWEST/GREAT BASIN WILL COOL A BIT THIS  
WEEKEND.  
 
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  
WILL BE POSSIBLE THROUGH EARLY NEXT WEEK. TEMPERATURES WILL  
GENERALLY BE NEAR TO BELOW AVERAGE IN THE SOUTHWEST UNDER LIMITED  
SOLAR INSOLATION AND A DAILY CHANCE OF SHOWERS/STORMS.  
 
FRACASSO/KONG  
 
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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