339  
FXUS02 KWBC 070700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 AM EDT SAT JUL 07 2018  
 
VALID 12Z TUE JUL 10 2018 - 12Z SAT JUL 14 2018  
   
..PATTERN OVERVIEW/GUIDANCE EVALUATION/PREFERENCES
 
 
A PERSISTENT MID/UPPER-LEVEL RIDGE ACROSS THE WESTERN/CENTRAL U.S.  
WILL REMAIN FIXED OVER THE REGION WHILE FLATTENING IN TIME IN  
RESPONSE TO AMPLIFICATION ALONG THE INTERNATIONAL BORDER WITH  
CANADA. WHILE 500-MB ANOMALIES SHOULD WEAKEN FROM THE EXPECTED 2  
TO 2.5 SIGMA VALUES EARLY IN THE WEEK, THE ANTICYCLONE WILL LIKELY  
SET UP ACROSS FOUR CORNERS INTO THE SOUTHERN PLAINS BY DAY 6/7,  
JULY 13/14. TO THE NORTH OF THIS POSITIVE HEIGHT ANOMALY, AN  
ACTIVE PATTERN IS ANTICIPATED AS A PAIR OF AMPLIFIED SYSTEMS TRACK  
FROM THE PACIFIC NORTHWEST/SOUTHERN BRITISH COLUMBIA TOWARD HUDSON  
BAY. EACH WILL LIKELY BE FAIRLY IMPRESSIVE IN NATURE WITH  
ATTENDANT DEEP SURFACE CYCLONES TRACKING THROUGH CENTRAL CANADA.  
ULTIMATELY THIS WILL HAVE THE INFLUENCE OF FLATTENING THE NORTHERN  
EXTENT OF THE PREVAILING RIDGE ACROSS THE WESTERN/CENTRAL STATES.  
MEANWHILE, WHAT IS EXPECTED TO BECOME TROPICAL STORM THREE SHOULD  
GRADUALLY MIGRATE NORTHEASTWARD AWAY FROM THE GULF STREAM AFTER  
STALLING DURING THE SHORT RANGE PERIOD. THE PARENT ELONGATED UPPER  
TROUGH WHICH HELPS STEER THIS TROPICAL CYCLONE OUT TO SEA WHICH  
LINGER OVER THE EASTERN U.S. THROUGH THURSDAY BEFORE MOVING  
OFFSHORE.  
 
OVERALL GUIDANCE HAS BEEN STRUGGLING WITH THE HANDLING OF THE  
TROPICAL CYCLONE WITH A FEW RANDOM SOLUTIONS TAKING THE SYSTEM  
TOWARD THE EASTERN SEABOARD. HOWEVER, THE 00Z GUIDANCE HAS SHIFTED  
EASTWARD WHICH MORE CLOSELY MIMICS THE FORECAST FROM THE NATIONAL  
HURRICANE CENTER. CONSIDERING THE REMAINDER OF THE COUNTRY, MODELS  
HAVE BOUNCED AROUND A BIT WITH THE TIMING OF THE LEAD SYSTEM  
TRACKING ACROSS CENTRAL CANADA MID-WEEK ALTHOUGH THEY AGREE ON THE  
EVOLUTION OF A RATHER DEFINED SURFACE LOW. IN ITS WAKE, THE  
GUIDANCE HAS TRENDED DEEPER WITH THE TRAILING UPPER TROUGH WHICH  
ACCELERATES INTO BRITISH COLUMBIA/ALBERTA BY FRIDAY WITH SOME  
SOUTHWARD EXTENSION INTO THE NORTHWESTERN U.S. AT THIS POINT, THE  
ENSEMBLE MEANS SUFFICIENTLY SMOOTH OUT THE PATTERN BUT ARE IN  
AGREEMENT IN MAINTAINING THE TIGHTEST HEIGHT GRADIENT ALONG THE  
INTERNATIONAL BORDER WITH CANADA. IN TERMS OF PREFERENCES,  
GENERALLY FOLLOWED A COMBINATION OF THE 18Z GFS/GEFS MEAN, 12Z  
ECMWF/ECMWF ENSEMBLE MEAN, AND 12Z NAEFS MEAN WITH DECREASING  
OPERATIONAL INFLUENCES DEEPER INTO THE FORECAST PERIOD.  
 
   
..WEATHER THREATS/HIGHLIGHTS
 
 
WHILE A VAST MAJORITY OF THE COUNTRY CAN EXPECT ABOVE AVERAGE  
TEMPERATURES NEXT WEEK, THE EXCEPTION WILL BE THE DESERT SOUTHWEST  
EASTWARD INTO THE SOUTHERN PLAINS. AN ACTIVE MONSOONAL FLOW REGIME  
SHOULD MAINTAIN ENHANCED CLOUD COVER AND WIDESPREAD  
SHOWERS/THUNDERSTORMS ACROSS THE FOUR CORNERS. THIS SHOULD KEEP  
NUMBERS SEVERAL DEGREES BELOW CLIMATOLOGY FOR MUCH OF THE PERIOD.  
MEANWHILE, THE MOST PRONOUNCED WARMTH WILL LIKELY FOCUS OVER THE  
PACIFIC NORTHWEST STARTING WEDNESDAY WITH WIDESPREAD 90S EXPECTED  
INLAND WITH COOLER READINGS CLOSER TO THE COAST. IN TERMS OF  
PRECIPITATION, THE MOST ORGANIZED AREA OF CONVECTION WILL BE VIA  
THE ACTIVE MONSOONAL FLOW WHILE DIURNALLY FORCED ACTIVITY IS  
EXPECTED ACROSS THE SOUTHERN U.S. TO THE NORTH, SOME FRONTAL  
PRECIPITATION IS POSSIBLE OVER THE NORTH-CENTRAL STATES IN  
RESPONSE TO WARM ADVECTION AHEAD OF THE NEXT POTENT SHORTWAVE.  
 
RUBIN-OSTER  
 
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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