176  
FXUS02 KWBC 220613  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
213 AM EDT WED AUG 22 2018  
 
VALID 12Z SAT AUG 25 2018 - 12Z WED AUG 29 2018  
 
...DUE TO TECHNICAL DIFFICULTIES, SOME WPC PRODUCTS MAY NOT BE  
AVAILABLE OR UPDATED. WE APOLOGIZE FOR ANY INCONVENIENCE THIS MAY  
HAVE CAUSED...  
 
   
..PATTERN OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES
 
 
MODELS CONTINUE TO FAVOR DEVELOPMENT OF STRONG UPPER RIDGING  
ACROSS THE NORTH CENTRAL/NORTHEAST PACIFIC, WHICH FAVORS  
DOWNSTREAM TROUGHING ACROSS THE WESTERN U.S. AND EXPANSION OF  
UPPER RIDGING EASTWARD FROM THE LOWER/MID-MISSISSIPPI VALLEY TO  
THE EASTERN SEABOARD. DUE TO LIMITED MODEL AVAILABILITY, A BLEND  
OF THE 12Z GUIDANCE WAS USED TO GENERATE MEDIUM RANGE FORECAST  
PRODUCTS. THE ECMWF AND CMC SOLUTIONS WERE FAVORED OVER THE 12Z  
GFS GIVEN THEIR SLOWER/MORE AMPLIFIED SOLUTIONS WITH UPPER  
TROUGH/SHORTWAVE ENERGY ACROSS THE WESTERN U.S. THROUGHOUT THE  
PERIOD.  
 
   
..WEATHER HIGHLIGHTS AND HAZARDS
 
 
A WEAKENING STATIONARY FRONTAL BOUNDARY ALONG THE SOUTHEAST U.S.  
COAST THROUGH MUCH OF THE MEDIUM RANGE PERIOD WILL RESULT IN  
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WITH LOCALLY HEAVY  
RAINFALL POSSIBLE. AREAS OF POTENTIALLY HEAVY CONVECTION WILL ALSO  
BE POSSIBLE FROM THE NORTHERN PLAINS TO THE GREAT LAKES AND NEW  
ENGLAND A COUPLE WAVES OF LOW PRESSURE TRAVERSE A FRONTAL  
BOUNDARY. SCATTERED AFTERNOON/EVENING SHOWERS AND STORMS ARE ALSO  
EXPECTED TO PERSIST ACROSS THE FOUR CORNERS REGION, WITH MONSOONAL  
MOISTURE REMAINING IN PLACE. SHOWERS WILL SPREAD INTO MUCH OF THE  
PACIFIC NORTHWEST AS WELL AS UPPER TROUGHING AMPLIFIES OVERHEAD.  
 
AS THE UPPER RIDGE EXPANDS OVERHEAD, A WARMING TREND WILL FOLLOW  
AS HIGH TEMPERATURES 5 TO 10 DEG F ABOVE AVERAGE ARE FORECAST TO  
EXPAND EASTWARD FROM THE CENTRAL U.S. TOWARD THE EASTERN U.S.  
DURING THE WEEKEND. HEIGHT FALLS ACROSS THE NORTHWEST WILL LEAD TO  
A COOLING TREND WITH TEMPERATURES FALLING TO MORE THAN 10 DEG  
BELOW AVERAGE IN THE INTERIOR BY SUNDAY INTO MONDAY.  
 
RYAN  
 
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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