452  
FXUS02 KWBC 150658  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
257 AM EDT FRI JUL 15 2022  
 
VALID 12Z MON JUL 18 2022 - 12Z FRI JUL 22 2022  
 
...HEAT THREAT TO PERSIST OVER MUCH OF THE WESTERN AND CENTRAL  
U.S....  
   
..OVERVIEW
 
 
A STRONG UPPER RIDGE CENTERED OVER THE FOUR CORNERS REGION DURING  
THE PERIOD WILL SUPPORT A BROAD AREA OF HOT TEMPERATURES OVER A  
MAJORITY OF THE WESTERN/CENTRAL U.S., WITH THE GREATEST ANOMALIES  
AND POTENTIAL FOR SCATTERED DAILY RECORD HIGHS LIKELY TO BE OVER  
OR NEAR THE PLAINS. FLOW AROUND THIS RIDGE SHOULD CONTINUE TO  
FEED INTO A LONG-TERM MEAN TROUGH OVER THE NORTHEASTERN QUADRANT  
OF THE LOWER 48, WITH SURFACE SYSTEMS/FRONTS GENERATING EPISODES  
OF SHOWERS/THUNDERSTORMS OF VARYING INTENSITY. MONSOONAL MOISTURE  
UNDER THE UPPER RIDGE WILL OFFER DAILY CHANCES FOR RAIN/STORMS AS  
WELL. WEAK TROUGHING WILL TEND TO PREVAIL OFF THE WEST COAST.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LARGE SCALE MEAN PATTERN ANCHORED BY THE FOUR CORNERS RIDGE  
HAS GOOD AGREEMENT/CONSISTENCY AND PREDICTABILITY, BUT THE  
FORECAST OF SOME SPECIFICS AROUND AND DOWNSTREAM FROM THE RIDGE IS  
MORE UNCERTAIN. ALREADY IN THE FIRST HALF OF THE PERIOD,  
SIGNIFICANT DIFFERENCES DEVELOP FOR THE COMBINATION OF A TROUGH  
CROSSING THE SOUTHERN HALF OF EASTERN CANADA AND EJECTING EASTERN  
U.S. SHORTWAVE ENERGY. THE MOST PROMINENT DIFFERENCE INVOLVES THE  
LATEST GEFS MEANS NOT EVEN DEPICTING THE SOUTHEASTERN CANADA  
TROUGH SEEN IN OTHER GUIDANCE BY DAYS 4-5 TUESDAY-WEDNESDAY.  
MEANWHILE, ENSEMBLES SHOW A VERY WIDE SPREAD FOR THE COMPACT UPPER  
LOW/CORRESPONDING TROUGH EXPECTED TO TRACK ALONG THE U.S. CANADIAN  
BORDER AND EVENTUALLY REACH SOUTHEASTERN CANADA. OPERATIONAL RUNS  
THROUGH 12Z/18Z SHOWED BETTER AGREEMENT IN PRINCIPLE, WITH THE  
MAIN DIFFERENCE BEING THAT 12Z AND ESPECIALLY 18Z RUNS OF THE GFS  
WERE A LITTLE FASTER THAN THE 12Z ECMWF/UKMET/CMC DURING THE FIRST  
HALF OF THE PERIOD. IT IS NOT SURPRISING TO SEE THE NEW 00Z RUNS  
OFFER SOME ADDITIONAL ADJUSTMENTS/SPREAD GIVEN THE ENSEMBLE  
DIVERSITY. SLIGHTLY FASTER TREND IN THE UKMET/CMC AND GFS  
CONTINUITY LEAVE THE 12Z ECMWF A BIT ON THE SLOW SIDE EARLY IN THE  
WEEK (00Z ECMWF IS A TAD FASTER MONDAY-TUESDAY) WHILE THE UKMET  
STRAYS SOUTH OF THE OTHER GUIDANCE BY WEDNESDAY. ADDITIONAL  
DIFFERENCES ARISE WITH A NORTHEASTERN PACIFIC TROUGH THAT  
PROGRESSES ACROSS THE WESTERN AND CENTRAL PARTS OF SOUTHERN  
CANADA, WITH SOME INFLUENCE ON THE NORTHERN TIER U.S. THE 12Z GFS  
WAS THE MOST EXTREME WITH THIS TROUGH'S AMPLITUDE. FINALLY,  
GUIDANCE OFFERS A VARIETY OF IDEAS FOR HOW UPPER LOW/TROUGH ENERGY  
COULD EJECT FROM THE MID-LATITUDES OF THE EASTERN PACIFIC. AT THE  
VERY LEAST CONSENSUS SUGGESTS THAT THE 12Z ECMWF IS LIKELY TOO  
QUICK. THE NEW 00Z ECMWF IS SIMILAR BUT OTHER MODELS STILL HOLD  
IT BACK.  
 
THE UPDATED FORECAST BASED ON GUIDANCE THROUGH THE 12Z/18Z CYCLES  
EMPHASIZED THE OPERATIONAL RUNS FOR ABOUT THE FIRST HALF OF THE  
PERIOD, WITH GFS INPUT TILTED TOWARD THE 12Z RUN FOR ITS BETTER  
CLUSTERING WITH THE NORTHERN TIER UPPER LOW EARLY IN THE WEEK.  
GENERAL AGREEMENT ON THE MEAN PATTERN BUT INCREASING DETAIL  
UNCERTAINTIES LED TO A TRANSITION TOWARD NEARLY HALF TOTAL INPUT  
FROM THE ENSEMBLE MEANS BY LATE IN THE PERIOD. GFS INPUT REVERTED  
BACK EXCLUSIVELY TO THE 18Z RUN FOR ITS INCOMING NORTHEASTERN  
PACIFIC TROUGH WHILE ENSEMBLE MEAN INPUT WAS SPLIT AMONG THE  
ECENS/CMCENS/GEFS TO DOWNPLAY THE LESS DESIRABLE GEFS EVOLUTION  
OVER EASTERN CANADA AND VICINITY.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
EXPECT THE HIGHEST TEMPERATURE ANOMALIES TO BE OVER PARTS OF THE  
PLAINS WHERE SOME LOCATIONS SHOULD SEE ONE OR MORE DAYS WITH HIGHS  
OF 10-15F OR SO ABOVE NORMAL. SOME DAILY RECORDS WILL BE POSSIBLE  
FOR BOTH DAYTIME HIGHS AND WARM LOWS. MONSOONAL MOISTURE AND  
ASSOCIATED DIURNALLY FAVORED SHOWERS/STORMS WITH LOCALLY HEAVY  
RAINFALL MAY KEEP PARTS OF THE FOUR CORNERS/GREAT BASIN REGION  
CLOSER TO NORMAL FOR HIGHS WHILE OTHER PARTS OF THE WEST SHOULD BE  
SOMEWHAT WARMER THAN NORMAL. EXCEPTIONS WILL BE OVER THE FAR  
NORTHERN ROCKIES UNDER THE INITIAL UPPER LOW/TROUGH AS WELL AS  
ALONG THE IMMEDIATE WEST COAST. A LEADING WAVE/FRONTAL SYSTEM MAY  
GENERATE SHOWERS AND THUNDERSTORMS OVER PARTS OF THE EAST EARLY IN  
THE WEEK. A TRAILING STRONGER SYSTEM FORECAST TO TRACK ACROSS THE  
NORTHERN TIER/GREAT LAKES AND INTO SOUTHEASTERN CANADA MAY PRODUCE  
ANOTHER EPISODE OF RAIN/STORMS FROM THE FAR NORTHERN TIER INTO  
PORTIONS OF THE EAST. IN BOTH CASES SOME AREAS OF HEAVY RAINFALL  
ARE POSSIBLE BUT GUIDANCE SIGNALS ARE NOT YET AGREEABLE ENOUGH TO  
PROVIDE GREAT CONFIDENCE IN RESOLVING COVERAGE/LOCATION/MAGNITUDE.  
A TRAILING FRONT REACHING THE NORTHERN TIER BY LATE IN THE WEEK  
COULD PRODUCE ADDITIONAL RAINFALL THAT IS CURRENTLY EXPECTED TO BE  
SOMEWHAT LIGHTER AND MORE SCATTERED THAN WITH THE TWO LEADING  
FEATURES. EXCEPT FOR A COOL START TO THE WEEK OVER THE CENTRAL  
APPALACHIANS, THE NORTHERN TWO-THIRDS OF THE EAST WILL TEND TO SEE  
ABOVE NORMAL TEMPERATURES DUE TO BEING IN THE WARM SECTOR OF  
INDIVIDUAL SYSTEMS ON MOST DAYS. PERSISTENT MOISTURE WILL ALLOW  
FOR MULTIPLE EPISODES OF SHOWERS/THUNDERSTORMS OVER THE  
SOUTHEAST/FLORIDA AND CENTRAL GULF COAST REGION. TEMPERATURES  
SHOULD BE NEAR NORMAL OVER THOSE AREAS.  
 
RAUSCH  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES ARE  
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/#PAGE=ERO  
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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