124  
FXUS02 KWBC 280559  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
158 AM EDT THU JUL 28 2022  
 
VALID 12Z SUN JUL 31 2022 - 12Z THU AUG 04 2022  
 
...DANGEROUS HEAT WAVE PERSISTS INTO SUNDAY OVER THE  
NORTHWEST/GREAT BASIN BEFORE ANOMALOUS HEAT SHIFTS EAST NEXT  
WEEK...  
 
...HEAVY TO EXCESSIVE RAIN THREAT FOR PARTS OF THE TENNESSEE  
VALLEY AND SOUTHERN MID-ATLANTIC THROUGH MONDAY, WITH MONSOONAL  
FLOODING CONCERNS ACROSS THE SOUTHWEST...  
 
   
..OVERVIEW
 
 
UPPER LEVEL RIDGING SANDWICHED BETWEEN A TROUGH OVER THE EAST  
PACIFIC AND RENEWED TROUGHING OVER THE GREAT LAKES/NORTHEAST  
SHOULD SHIFT SLOWLY EASTWARD WITH TIME. A DANGEROUS HEAT WAVE WILL  
CONTINUE INTO SUNDAY ACROSS THE NORTHWEST BEFORE THE HEAT  
HEADLINES THEN SHIFT EAST INTO THE NORTH-CENTRAL STATES ON  
MONDAY-WEDNESDAY AND EVENTUALLY THE NORTHEAST BY NEXT THURSDAY.  
UPPER RIDGING AND HEAT/HUMIDITY WILL ALSO LINGER OVER THE SOUTHERN  
PLAINS AND LOWER MISSISSIPPI VALLEY. EXCESSIVE RAIN THREATS FROM  
THE SHORT RANGE WILL PERSIST THROUGH MONDAY ACROSS THE TENNESSEE  
VALLEY AND SOUTHERN MID-ATLANTIC ALONG A WARM FROM BEFORE IT LIFTS  
NORTH AHEAD OF A COLD FRONT THROUGH THE NORTHERN TIER STATES.  
MEANWHILE, A SEEMINGLY NEVER ENDING STREAM OF MONSOONAL MOISTURE  
WILL CONTINUE TO FLOW INTO THE SOUTHWEST AND SOUTHERN ROCKIES NEXT  
WEEK, WITH SOME AT LEAST LOCALIZED FLOODING CONCERNS.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST MODELS ARE WELL CLUSTERED WITH THE LARGE SCALE OVERALL  
PATTERN, BUT OFFER INCREASING UNCERTAINTIES IN THE DETAILS OF  
SYSTEMS. THE GREATEST UNCERTAINTY REMAINS OUT WEST REGARDING A  
SHORTWAVE OFF THE COAST, WHICH SHOULD SHIFT INLAND BRINGING A  
RELIEF TO THE HEAT WAVE ACROSS THE NORTHWEST. THE GFS REMAINS THE  
QUICKEST MODEL TO BRING THE ENERGY INLAND, WHILE THE REMAINDER OF  
THE DETERMINISTIC MODELS TEND TO LINGER IT OFFSHORE AN EXTRA DAY  
OR SO AS IT WAITS FOR THE NEXT SHORTWAVE TO DROP INTO THE REGION  
AROUND TUESDAY. THE ECMWF HAS ALSO BEEN SOMEWHAT CONSISTENT IN  
KEEPING A CUT OFF COMPACT CLOSED LOW OFF THE NORTHERN CALIFORNIA  
COAST WELL INTO NEXT WEEK, WHICH DOES NOT HAVE MUCH SUPPORT FROM  
THE OTHER MODELS OR ENSEMBLES AT THIS TIME. AFTER DAY 5, THE  
ENSEMBLE MEANS SEEM BETTER EQUIPPED TO HANDLE THE UNCERTAINTIES IN  
TIMING OF INDIVIDUAL SHORTWAVES AND FLOW DETAILS, AND THUS THE WPC  
FORECAST FOR THE SECOND HALF OF THE PERIOD LEANED MORE ON THE  
MEANS. THE GFS WAS NOT USED FOR DAYS 3-4 BECAUSE OF HOW IT HANDLES  
THE FIRST NORTHWEST U.S. SHORTWAVE, BUT IT WAS INCORPORATED SOME  
(WITH THE ECMWF) TO HELP BRING A LITTLE EXTRA DEFINITION TO THE  
PATTERN DAYS 5-7. THIS APPROACH FITS WELL WITH THE PREVIOUS WPC  
FORECAST AS WELL.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE HEAT WAVE IN THE NORTHWEST/GREAT BASIN CONTINUES THROUGH  
SUNDAY BEFORE RELIEF COMES IN THE FORM OF AN UPPER TROUGH AROUND  
MONDAY. HOWEVER, THIS SHIFTS THE ANOMALOUS HEAT EAST ACROSS THE  
NORTHERN AND CENTRAL PLAINS THROUGH THE FIRST HALF OF NEXT WEEK  
WHERE DAYTIME HIGHS COULD ONCE AGAIN APPROACH OR EXCEED 100F.  
TEMPERATURES SHOULD ALSO BE ON THE RISE FROM THE OHIO VALLEY INTO  
THE NORTHEAST AS HEIGHTS BEGIN TO BUILD LATER IN THE PERIOD.  
MEANWHILE, MOSTLY TYPICAL OR SLIGHTLY ABOVE NORMAL HEAT AND  
HUMIDITY CONTINUES FOR THE SOUTHERN PLAINS AND SOUTHEAST THROUGH  
THE NEXT WEEK.  
 
A QUASI-STATIONARY BOUNDARY IN THE SHORT RANGE CAUSING DAYS OF  
HEAVY RAINFALL, SHOULD BEGIN LIFTING NORTH AS A WARM FRONT BY THE  
START OF THE MEDIUM RANGE PERIOD. HOWEVER, HEAVY TO EXCESSIVE  
RAINFALL SEEMS LIKELY TO CONTINUE ACROSS PARTS OF THE TENNESSEE  
VALLEY AND INTO THE SOUTHERN MID-ATLANTIC WITH SLIGHT RISKS  
PRESENT ON THE EXPERIMENTAL DAYS 4 AND 5 ERO. THERE IS POTENTIAL  
FOR AN UPGRADE TO THE FLASH FLOOD RISK ESPECIALLY FOR PARTS OF THE  
TENNESSEE VALLEY, OVER AREAS THAT MAY RECEIVE REPEATED DAYS OF  
RAINFALL IN THE SHORT RANGE. ELSEWHERE, PERSISTENT MONSOONAL  
MOISTURE WILL CONTINUE TO SUPPORT DIURNALLY FAVORED SHOWERS/STORMS  
WITH LOCALLY HEAVY TO EXCESSIVE RAINFALL OVER AN ALREADY VERY  
SOGGY SOUTHWEST NEXT WEEK. A PROGRESSIVE COLD FRONT THROUGH THE  
GREAT LAKES ON SUNDAY MAY BRING SOME MODERATE TO LOCALLY HEAVY  
SHOWERS AS WELL.  
 
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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