746  
FXUS02 KWBC 151832  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
231 PM EDT MON AUG 15 2022  
 
VALID 12Z THU AUG 18 2022 - 12Z MON AUG 22 2022  
 
...EXCESSIVE HEAT THREAT FROM INTERIOR CALIFORNIA THROUGH THE  
NORTHWEST/NORTH-CENTRAL INTERMOUNTAIN WEST THIS WEEK...  
 
...MONSOONAL HEAVY RAIN THREAT CONTINUES FOR THE SOUTHWEST AND  
SOUTH-CENTRAL GREAT BASIN/ROCKIES....  
   
..NEW ENGLAND COASTAL STORM THREAT INTO THURSDAY
 
 
   
..SOUTH/SOUTHEAST HEAVY RAIN THREAT THROUGH THIS WEEKEND
 
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
FOR THE MOST PART, THE LATEST SUITE OF MODELS AND ENSEMBLES REMAIN  
IN AGREEMENT ON THE LARGER SCALE PATTERN WHICH FEATURES TROUGHING  
OVER THE EAST REINFORCED BY A DEEP SHORTWAVE/CLOSED LOW THROUGH  
THE MIDWEST LATE THIS WEEK, AND AMPLIFIED RIDGING OVER MUCH OF THE  
WEST AND CENTRAL U.S.. THERE ARE SOME CONTINUED SMALL SCALE  
DIFFERENCES INCLUDING TIMING OF VARIOUS FEATURES, PARTICULARLY  
LATE PERIOD. THE ECMWF IS FASTER WITH THE SHORTWAVE ACROSS THE  
MIDWEST THIS WEEKEND, WHILE THE CMC IS QUICKER TO CUT THE ENERGY  
OFF FROM THE MAIN TROUGH AND HANG IT BACK INTO THE MID-UPPER  
MISSISSIPPI VALLEY EARLY NEXT WEEK. OUT WEST, THE CMC IS NOTABLY  
FASTER WITH THE NEXT TROUGH INTO THE WEST COAST AROUND  
SUNDAY-MONDAY. FOR BOTH SYSTEMS, THE GFS AND ECMWF SEEM BETTER  
ALIGNED WITH THE ENSEMBLE MEANS. ACCORDINGLY, THE WPC FORECAST  
USED A COMPOSITE BLEND OF THE DETERMINISTIC GUIDANCE DAYS 3-5,  
WITH A BLEND OF THE ENSEMBLE MEANS WITH GFS/ECMWF DAYS 6-7. THIS  
MAINTAINS GOOD CONTINUITY WITH THE PREVIOUS WPC FORECAST AS WELL.  
THE WPC QPF WAS BASED HEAVILY ON THE 13 UTC NATIONAL BLEND OF  
MODELS WHICH SEEMED REASONABLE ACROSS ALL AREAS THROUGH THE  
PERIOD, AMIDST FAIRLY GOOD FORECAST SPREAD. SOME TARGETED EDITS  
WERE MADE ACROSS HIGHER IMPACTED REGIONS, INCLUDING THE SOUTHWEST  
AND SOUTHERN TIER.  
   
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
 
 
AMPLIFIED UPPER RIDGING OVER THE WEST/NORTHWEST THIS WEEK WILL  
SUPPORT A HEAT WAVE WITH DAYTIME/OVERNIGHT TEMPERATURE 10-20F  
ABOVE NORMAL. THESE TEMPERATURES ARE LIKELY TO PRODUCE SOME RECORD  
DAYTIME AND OVERNIGHT VALUES. MEANWHILE, BELOW NORMAL HIGHS ARE  
EXPECTED IN THE EAST-CENTRAL U.S. BEHIND A MAIN FRONT. GIVEN  
RAINFALL AND CLOUDINESS OVER THE SOUTHWEST AND SOUTH-CENTRAL GREAT  
BASIN/ROCKIES, MAXIMUM TEMPERATURES THERE SHOULD ALSO TEND TO BE  
BELOW NORMAL.  
 
MEANWHILE, A LARGE SWATH OF THE WEST HAS SEEN PERSISTENT MONSOONAL  
MOISTURE OVER THE PAST COUPLE OF MONTHS, AND THIS WEEK WILL  
CONTINUE THAT PATTERN AS ANOMALOUSLY HIGH MOISTURE FEEDS INTO THE  
SOUTHWEST AND SOUTH-CENTRAL GREAT BASIN/ROCKIES IN CONJUNCTION  
WITH SMALL-SCALE SHORTWAVE ENERGY TO PRODUCE MAILY DIURNALLY  
DRIVEN RAIN AND THUNDERSTORMS. A WPC EXPERIMENTAL MEDIUM RANGE  
SLIGHT RISK OF EXCESSIVE RAINFALL WAS MAINTAINED FOR SOUTHERN  
ARIZONA FOR THURSDAY, AND EXPANDED INTO CENTRAL/EASTERN ARIZONA  
AND WESTERN NEW MEXICO ON FRIDAY GIVEN ENHANCED QPF/ARI AND AN  
OVERALL PERSISTENT FAVORABLE PATTERN.  
 
CONVECTIVE ACTIVITY WILL PERSIST THROUGH LATER THIS WEEK/WEEKEND  
NEAR A SLOW MOVING AND WAVY FRONT ACROSS THE SOUTH/SOUTHEAST  
WITHIN A VERY MOIST ENVIRONMENT. THE HIGHEST THREAT OF HEAVY RAIN  
MAY BE OVER THE LOWER MISSISSIPPI VALLEY WHERE WPC HAS AN  
EXPERIMENTAL MEDIUM RANGE SLIGHT RISK OF EXCESSIVE RAINFALL ON  
THURSDAY/THURSDAY NIGHT. ORGANIZED RAINS WILL ALSO SLOWLY LIFT TO  
THE MID-ATLANTIC THIS WEEKEND AS THE FRONT BEGINS TO LIFT SLOWLY  
NORTH AS A WARM FRONT. TO THE NORTH, THERE IS A LINGERING THREAT  
FOR COOLED WRAP-AROUND RAINS/ENHANCED WINDS OVER ESPECIALLY  
NORTHERN NEW ENGLAND THURSDAY WITH COASTAL CYCLOGENESIS AHEAD OF A  
CLOSED UPPER LOW. THE DEEPENED COASTAL LOW THEN DEPARTS FOR THE  
CANADIAN MARITIMES WITH EJECTION OF THE CLOSED UPPER SYSTEM.  
 
EXPECT SOME DEGREE OF ORGANIZED CONVECTION TO SPREAD ACROSS THE  
MIDWEST WITH LATE WEEK/WEEKEND DIGGING OF SHORTWAVE ENERGY AND A  
SLOWLY PROGRESSIVE LEAD LOW/FRONTAL PASSAGE. ELSEWHERE, MODELS  
CONTINUE TO SHOW AN INCREASING HEAVY RAINFALL SIGNAL ACROSS THE  
SOUTH-CENTRAL PLAINS TO THE MID-MISSISSIPPI VALLEY OVER THE  
WEEKEND. THIS SEEMS REASONABLE AS MOISTURE AND INSTABILITY POOL  
WITH RETURN FLOW INTO A SLOW MOVING FRONT IN FAVORABLE UPPER  
DIFFLUENT FLOW ALOFT.  
 
SANTORELLI/SCHICHTEL  
 
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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