159  
FXUS02 KWBC 100700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM 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 ALTHOUGH  
THE SPREAD HAS INCREASED SINCE YESTERDAY. THE MAIN UNCERTAINTY  
WILL BE ACROSS THE PACIFIC NORTHWEST EASTWARD INTO THE NORTHERN  
PLAINS THIS WEEKEND INTO EARLY NEXT WEEK AS A COUPLE OF SHORTWAVE  
TROUGHS ARE FORECAST TO MOVE ALONG OR JUST NORTH OF THE  
U.S.-CANADIAN BORDER. THE GFS HAS INTRODUCED A DIGGING AND HIGHER  
AMPLITUDE SHORTWAVE IN THE LAST FEW RUNS WHILE THE ECMWF KEEPS A  
LESS-AMPLIFIED POSITIVELY-TILTED TROUGH MAINLY NORTH OF THE  
BORDER. THE GEFS ON THE OTHER HAND SHOWS A LESS-AMPLIFIED MEAN  
SOLUTION COMPARABLE TO THE EC MEAN. THE ECMWF HAS ACTUALLY SHOWN  
A TENDENCY FOR INCREASING THE 500 MB HEIGHT OVER THE NORTHWESTERN  
U.S. WHILE THE GFS SHOWS THE OPPOSITE. A GENERAL COMPROMISE  
BETWEEN THE 18Z GEFS AND THE 12Z EC MEAN MIXING IN WITH THEIR  
DETERMINISTIC SOLUTIONS WAS USED TO HANDLE THIS AREA FROM DAY 5  
THROUGH DAY 7 (SUNDAY-TUESDAY), WHICH MAINTAINS GOOD CONTINUITY  
WITH THE PREVIOUS WPC PACKAGE.  
 
OTHERWISE, MODELS CONTINUE TO SHOW EXCELLENT AGREEMENT ON A  
SUBTROPICAL HIGH DOMINATING THE LOWER 48 LATER THIS WEEK INTO NEXT  
WEEK.  
   
..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 COOL AIR INTRUSION FROM CANADA FOLLOWING OCCASIONAL  
FRONTAL PASSAGES ACROSS THE NORTHERN TIER STATES. 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 INTERIOR PACIFIC  
NORTHWEST 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 100 OVER PORTIONS  
OF THE INTERIOR PACIFIC NORTHWEST/GREAT BASIN ON FRIDAY. BUT  
TRIP-DIGIT HEAT IS EXPECTED TO CONTINUE OVER 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  
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.  
 
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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