936  
FXUS02 KWBC 030704  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
304 AM EDT WED AUG 03 2022  
 
VALID 12Z SAT AUG 06 2022 - 12Z WED AUG 10 2022  
 
...THE SOUTHWEST MONSOON RESUMES A VERY ACTIVE PHASE LATE THIS  
WEEK...  
...HEAVY RAIN LIKELY ACROSS PARTS OF THE UPPER MIDWEST ON  
SATURDAY...  
 
   
..OVERVIEW
 
 
GUIDANCE EXPECTS A FAIRLY TYPICAL SUMMERTIME PATTERN WITH THE MAIN  
BAND OF WESTERLIES ACROSS SOUTHERN CANADA AND NORTHERN TIER CONUS,  
THOUGH WITH UPPER RIDGING TO THE SOUTH TENDING TO BE SOMEWHAT  
STRONGER THAN THE CLIMATOLOGICAL MEAN. AN UPPER LOW SHOULD LIFT  
VERY SLOWLY NORTHEASTWARD OFFSHORE THE WEST COAST. THE MODELS AND  
ENSEMBLES AGREE ON THE LARGE SCALE PATTERN BUT SIGNIFICANT  
SHORTWAVE DIFFERENCES DEVELOP WITHIN THE WESTERLIES FROM FAIRLY  
EARLY IN THE FORECAST. AS A RESULT CONFIDENCE DECREASES FOR  
SURFACE FRONT/WAVE DETAILS AND IN TURN FOR ASSOCIATED AREAS OF  
RAINFALL WHICH COULD BE HEAVY AT TIMES OVER PORTIONS OF THE  
NORTHERN HALF OF THE CENTRAL/EASTERN U.S. MEANWHILE THE MONSOONAL  
PATTERN OVER THE WEST SHOULD BECOME MORE PRONOUNCED AGAIN LATE  
THIS WEEK AND LIKELY REMAIN FAIRLY ACTIVE THROUGH THE WEEKEND AND  
PERHAPS INTO NEXT WEEK.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE UPPER RIDGE ACROSS THE SOUTHERN/EASTERN PORTION OF THE LOWER  
48 WAS CAPTURED WELL BY THE DETERMINISTIC GUIDANCE AND ENSEMBLE  
MEANS THROUGHOUT THE PERIOD. THERE'S UNCERTAINTY WITH RESPECT TO  
THE UPPER TROUGH MOVING ACROSS SOUTHERN CANADA AND THE NORTHWEST  
BEGINNING ON DAY 3. THE 18Z GFS HAS CONSISTENTLY ATTEMPTED TO  
SPLIT THE UPPER FLOW ACROSS THE AFOREMENTIONED REGION WHILE THE  
12Z EC/UK HAVE A MORE UNIFORM SOLUTION. THE 12Z CMC AGREES WITH  
THE GFS WITH RESPECT TO THE SPLIT FLOW SOLUTION. THESE  
DISCREPANCIES ARE MANIFESTED IN THE QPF AS THE EC AND UK HAVE A  
STRONGER SIGNAL FOR HEAVY PRECIP ACROSS THE UPPER MIDWEST WHILE  
THE GFS HAS A WEAKER QPF FOOTPRINT. NONETHELESS, A GENERAL MODEL  
BLEND WAS UTILIZED TO SPLIT THE DIFFERENCE HERE.  
 
THE DAY 3 BLEND WAS USED ONCE AGAIN FOR DAY 4 AS A SLIGHTLY MORE  
PROGRESSIVE YET WEAKER SHORTWAVE DISPLAYED IN THE 12Z EC/UK WAS  
USED TO MITIGATE A MORE PRONOUNCED YET SLOWER SOLUTION POSED BY  
THE 18Z GFS AND 12Z CMC. THE 18Z GEFS AND 12Z ECE WERE INTRODUCED  
INTO THE BLEND BY DAY 5 TO HELP WITH SPREAD PRESENTED BY THE  
LATEST DETERMINISTIC GUIDANCE WITH RESPECT TO EMBEDDED SHORTWAVE  
IMPULSES SWINGING THROUGH THE GREAT LAKES. ENSEMBLES WERE  
PREDOMINANT IN THE BLEND BY DAYS 6 AND 7 TO ACCOUNT FOR GENERAL  
SPREAD ALONG THE EAST COAST.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
EXPECT HOT TEMPERATURES OVER NORTHERN HALF OF THE PLAINS INTO THE  
MIDWEST LATE THIS WEEK INTO THE WEEKEND, ERODING FROM THE  
NORTHWEST AS A COLD FRONT APPROACHES. SOME HIGHS MAY REACH 10-15F  
ABOVE NORMAL AND A FEW RECORD HIGHS MAY BE POSSIBLE OVER THE HIGH  
PLAINS. VERY WARM CONDITIONS SHOULD EXTEND INTO THE GREAT  
LAKES/NORTHEAST THROUGH THE WEEKEND WITH SOME GRADUAL COOLING  
EARLY NEXT WEEK. OVER THE WEST, MAXIMUM TEMPERATURES WILL TEND TO  
BE SOMEWHAT BELOW NORMAL OVER THE GREAT BASIN/SOUTHWEST AND  
VICINITY DUE TO PERSISTENT CLOUDS AND PERIODS OF RAIN. THE  
NORTHWEST SHOULD TREND MORE ABOVE NORMAL AS SOME DEGREE OF UPPER  
RIDGING BUILDS. HIGHS COULD LOCALLY REACH 10-12F ABOVE NORMAL.  
PARTS OF THE PACIFIC NORTHWEST MAY EXPERIENCE HEAT RISKS THIS  
WEEKEND AS A RESULT.  
 
FOR PRECIPITATION, THE MAIN THREATS FOR FLASH FLOODING WILL BE  
ASSOCIATED WITH MONSOONAL MOISTURE OVER THE SOUTHWEST/GREAT  
BASIN/ROCKIES AS WELL AS WITH FRONTS/WAVES OVER NORTHERN AND  
CENTRAL PARTS OF THE U.S. EAST OF THE ROCKIES. THE COMBINED  
SIGNALS FOR RAINFALL AND ALREADY WET CONDITIONS OVER THE DESERT  
SOUTHWEST INTO THE CENTRAL ROCKIES/GREAT BASIN LATE THIS WEEK INTO  
THE WEEKEND SUPPORT SOME SLIGHT RISK AREAS IN THE EXPERIMENTAL  
DAYS 4-5 EXCESSIVE RAINFALL OUTLOOKS. FARTHER EAST, ONE AREA OF  
POTENTIAL FOCUS FOR SIGNIFICANT RAINFALL WILL BE OVER THE OHIO  
VALLEY, CENTRAL APPALACHIANS AND NORTHEAST ALONG A FRONT THAT  
STALLS AND THEN RETURNS NORTH AS A WARM FRONT LATE THIS WEEK INTO  
THE WEEKEND. A TRAILING WAVY FRONT PROGRESSING EASTWARD FROM THE  
NORTHERN PLAINS MAY ALSO GENERATE SOME AREAS OF HEAVY RAINFALL  
BETWEEN THE NORTHERN HALF OF THE PLAINS AND EASTERN U.S. FROM THE  
WEEKEND INTO NEXT WEEK.  
 
KEBEDE/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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