466  
FXUS02 KWBC 270658  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
258 AM EDT WED JUL 27 2022  
 
VALID 12Z SAT JUL 30 2022 - 12Z WED AUG 03 2022  
 
...DANGEROUS HEAT WAVE TO FOCUS OVER THE NORTHWEST/GREAT BASIN  
THROUGH THE WEEKEND, WITH ANOMALOUS HEAT MOVING INTO THE  
NORTH-CENTRAL U.S. LATE PERIOD...  
 
...HEAVY TO EXCESSIVE RAIN THREAT FROM THE CENTRAL PLAINS TO THE  
SOUTHERN MID-ATLANTIC THIS WEEKEND, WITH A LINGERING THREAT IN THE  
SOUTHWEST INTO NEXT WEEK...  
 
   
..OVERVIEW
 
 
A DANGEROUS HEAT WAVE WILL CONTINUE INTO THIS COMING WEEKEND  
ACROSS THE NORTHWEST, WITH HIGH HEAT THEN SET TO SPREAD TO THE  
NORTH-CENTRAL STATES NEXT WEEK. UPPER RIDGING AND HEAT/HUMIDITY  
WILL ALSO LINGER OVER THE SOUTHERN PLAINS AND LOWER MISSISSIPPI  
VALLEY TO THE SOUTH OF A WAVY QUASI-STATIONARY FRONT. THIS FRONT  
WILL BE A FOCUS FOR MULTI-DAY HEAVY RAIN THREATS FROM THE  
SOUTH-CENTRAL PLAINS TO THE SOUTHERN MID-ATLANTIC WITH EXCESSIVE  
RAINFALL LIKELY IN SOME PLACES. RENEWED TROUGHING WILL TAKE SHAPE  
ACROSS THE GREAT LAKES AND NORTHEAST INTO NEXT WEEK, WHILE A  
SEEMINGLY NEVER ENDING STREAM OF MONSOONAL MOISTURE CONTINUES TO  
FLOW INTO THE SOUTHWEST AND SOUTHERN ROCKIES.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
DETERMINISTIC MODELS AND ENSEMBLE MEANS REMAIN FAIRLY WELL  
CLUSTERED WITH THE LARGE-SCALE PATTERN AND EVOLUTION OF THE  
EXPANSIVE WESTERN/SOUTHERN U.S. RIDGE AND THE TROUGH DIGGING INTO  
THE NORTHEAST THIS WEEKEND. SOME MODEL DIFFERENCES REMAIN IN  
REGARDS TO THE DISTRIBUTION AND TIMING OF INDIVIDUAL ENERGIES  
WITHIN THE TROUGH, PARTICULARLY AS WEAKER SHORTWAVES MOVE THROUGH  
THE GREAT LAKES ACTING TO MAINTAIN SOME KIND OF GENERAL  
TROUGHINESS ACROSS THE REGION. MANY OF THESE DIFFERENCES ARE SMALL  
SCALE, AND WELL WITHIN THE NORMAL DEGREE OF SPREAD FOR THE MEDIUM  
RANGE. BY AROUND TUESDAY, THE GFS BECOMES FAIRLY FAST WITH ONE  
SHORTWAVE, RESULTING IN A FLATTER OVERALL LOOK COMPARED TO THE  
ECMWF, CMC, AND ENSEMBLE MEANS. OUT WEST, THERE ARE LINGERING  
QUESTIONS IN THE TIMING OF A SHORTWAVE ENTERING THE NORTHWEST,  
WHICH WOULD HAVE SOME IMPLICATIONS FOR EXCESSIVE HEAT DETAILS IN  
THAT REGION. THE GFS AND UKMET HAVE BEEN THE QUICKEST TO BRING  
THIS ENERGY ONSHORE, WHILE THE ENSEMBLE MEANS SUPPORT SOMETHING A  
LITTLE SLOWER, NOW A BIT MORE IN LINE WITH THE ECMWF, SOME RUNS OF  
THE CANADIAN AND CLIMATOLOGY. THE MODELS SUGGEST THE OVERALL  
PATTERN MAY BECOME MORE AMPLIFIED BY THE MIDDLE OF NEXT WEEK WITH  
TROUGHING OVER THE WEST AND EAST SANDWICHING A BUILDING HEAT DOME  
OVER THE FOUR CORNERS AND INTO THE PLAINS. THE WPC MEDIUM RANGE  
PRODUCT SUITE MAINLY UTILIZED A BLEND OF THE SEEMINGLY REASONABLE  
AND OVERALL COMPATIBLE GFS/ECMWF/UKMET/CANADIAN MODELS THIS  
WEEKEND, SWITCHING TO THE ENSEMBLE MEANS AND SOME DETERMINISTIC  
ECMWF AND CMC THEREAFTER TO MITIGATE GROWING SMALLER SCALE  
EMBEDDED SYSTEM VARIANCE. THIS MAINTAINS GOOD WPC PRODUCT  
CONTINUITY.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
HEAT HEADLINES WILL CONTINUE INTO THE WEEKEND FOR THE  
NORTHWEST/GREAT BASIN WITH HIGHS IN THE LOW TO MID 100S FOR THE  
COLUMBIA BASIN, AND EVEN 90S EXPECTED AS FAR WEST AS PORTLAND AND  
SEATTLE. THESE MUCH ABOVE NORMAL TEMPERATURES COMBINED WITH LITTLE  
TO NO RELIEF OVERNIGHT FROM THE HEAT, COULD CREATE A DANGEROUS  
HEAT THREAT FOR MANY ACROSS THE REGION. RECORDS FOR HIGHS/WARM  
LOWS COULD ALSO BE SET ACROSS INTERIOR PORTIONS OF THE NORTHWEST.  
THERE IS SOME FORECAST UNCERTAINTY WITH THE TIMING OF WHEN THE  
TEMPERATURES WILL MODERATE AGAIN, BUT CURRENT FORECASTS SUGGEST BY  
EARLY NEXT WEEK TEMPERATURES COULD ONCE AGAIN BOUNCE BACK CLOSER  
TO NORMAL AS THE RIDGE SHIFTS INTO THE NORTHERN PLAINS. THIS LOOKS  
TO CREATE A BUILDING HEAT DOME OVER THE CENTRAL PART OF THE NATION  
BY AROUND NEXT TUESDAY, ONCE AGAIN BRINGING ANOTHER PERIOD OF  
ABOVE NORMAL HEAT TO MUCH OF THE PLAINS STATES. EXCESSIVE HEAT  
DURING THE SHORT RANGE ACROSS THE SOUTH-CENTRAL STATES SHOULD  
FINALLY MODERATE BY THE MEDIUM RANGE, THOUGH MORE TYPICAL  
SUMMERTIME HEAT AND HUMIDITY WILL CONTINUE FROM THE SOUTHERN  
PLAINS TO THE SOUTHEAST.  
 
A QUASI-STATIONARY BOUNDARY DRAPED FROM THE SOUTH-CENTRAL PLAINS  
TO THE SOUTHERN MID-ATLANTIC WILL CONTINUE TO FOCUS A THREAT FOR  
HEAVY TO EXCESSIVE RAINFALL INTO THE MEDIUM RANGE PERIOD WITH SOME  
AREAS LIKELY TO SEE REPEATED ROUNDS OF HEAVY RAINFALL INCREASING  
THE RISK FOR AT LEAST LOCALIZED FLASH FLOODING. THE DAYS 4 AND 5  
EXPERIMENTAL EROS HAVE EXPANSIVE SLIGHT RISKS DEPICTED ALONG THIS  
BOUNDARY FROM THE CENTRAL APPALACHIANS/SOUTHERN MID-ATLANTIC AND  
BACK INTO TO THE CENTRAL PLAINS. A COLD FRONT TO THE NORTH MAY  
BRING SOME LOCALLY MODERATE TO HEAVY RAINFALL TO PARTS OF THE  
UPPER MIDWEST ON SUNDAY. MEANWHILE, PERSISTENT MONSOONAL MOISTURE  
WILL CONTINUE TO SUPPORT DIURNALLY FAVORED SHOWERS/STORMS WITH  
SOME LOCALLY HEAVY TO EXCESSIVE RAINFALL OVER AN ALREADY VERY  
SOGGY FOUR CORNERS AND SOUTHERN ROCKIES REGION INTO THE MIDDLE OF  
NEXT WEEK.  
 
SANTORELLI  
 
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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