529  
FXUS02 KWBC 121550  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1150 AM EDT THU JUL 12 2018  
 
VALID 12Z SUN JUL 15 2018 - 12Z THU JUL 19 2018  
   
..OVERVIEW AND WEATHER HIGHLIGHTS
 
 
TROUGHING IS FORECAST TO EASE INTO THE NORTHEAST PORTION OF THE  
LOWER 48 NEXT WEEK WHICH WILL CARRY A SURFACE FRONT OUT OF THE  
PLAINS AND THROUGH THE MID-ATLANTIC STATES. TEMPERATURES WILL BE  
NEAR TO ABOVE AVERAGE (ANOMALIES ABOUT +5 TO +15F) AHEAD OF THIS  
BOUNDARY WITH SOME ISOLATED RECORD HIGHS POSSIBLE IN AN OTHERWISE  
TYPICALLY HOT SUMMERTIME REGIME. THE COLD FRONT WILL BRING IN  
DRIER AND SLIGHTLY COOLER AIR IN ITS WAKE (ANOMALIES ABOUT -5 TO  
-10F), FIRST TO THE HIGH PLAINS LATE THIS WEEKEND THEN TO THE  
MIDWEST AND NORTHEAST LATER IN THE WEEK. PRECIPITATION WILL FOLLOW  
ALONG THE PATH OF THE FRONT WITH SCATTERED SHOWERS/STORMS OVER THE  
SOUTHEAST AND INTERIOR WEST WITH A DECREASE IN TIME OVER THE FOUR  
CORNERS REGION AS UPPER RIDGING STRENGTHENS.  
 
   
..GUIDANCE EVALUATION AND PREFERENCES
 
 
MODELS/ENSEMBLES SHOW GOOD AGREEMENT OVERALL WITH MUCH OF THE  
TIMING DIFFERENCES CONFINED TO THE HIGHER LATITUDES NORTH OF THE  
US/CANADIAN BORDER. HOWEVER, RUN-TO-RUN CONSISTENCY REMAINS A BIT  
LACKLUSTER AND CONFIDENCE IN THE DETAILS AFTER TUESDAY NEXT WEEK  
WERE AVERAGE AT BEST. PROBLEMS STEM FROM SHORT RANGE UNCERTAINTY  
OVER ALASKA THAT CARRIES INTO WESTERN CANADA EARLY IN THE PERIOD  
THAT SET THE STAGE FOR THE TROUGHING IN THE EAST TUE-THU. RECENT  
00Z/06Z GEFS ENSEMBLES AND ECMWF ENSEMBLES HAVE SOMEWHAT CONVERGED  
OVER THE MIDWEST/GREAT LAKES BY NEXT WED/THU (AT LEAST COMPARED TO  
THE 12Z RUNS FROM YESTERDAY) SO A BLEND AMONG THE DETERMINISTIC  
GFS/ECMWF AND THEIR ENSEMBLE MEANS WAS USABLE THROUGH THE PERIOD.  
THIS RESULTED IN A QUICKER FRONTAL PROGRESSION THROUGH CANADA AND  
THE EAST TUE-THU BUT OTHERWISE MAINTAINED CONTINUITY.  
 
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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