134  
FXUS02 KWBC 140654  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
253 AM EDT SUN AUG 14 2022  
 
VALID 12Z WED AUG 17 2022 - 12Z SUN AUG 21 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 THIS WEEK.  
   
..NEW ENGLAND COASTAL STORM THREAT WEDNESDAY/THURSDAY
 
 
   
..OVERVIEW
 
 
UPPER RIDGE BUILDING OVER THE WEST/NORTHWEST WILL PRODUCE AN  
EXCESSIVE HEAT PATTERN OVER THE REGION THIS WEEK. FARTHER SOUTH,  
THE PERSISTENT RIDGE AND LESS CERTAIN EMBEDDED IMPULSES WILL ALSO  
CONTINUE TO SUPPORT WIDESPREAD MONSOONAL MOISTURE STREAMING INTO  
AN UNSETTLED SOUTHWEST AND SOUTH-CENTRAL GREAT BASIN/ROCKIES. THE  
DOWNSTREAM DIGGING OF SHORTWAVES/HEIGHT FALLS TO THE LEE OF THE  
RIDGE WILL PERIODICALLY REINFORCE UPPER DIFFLUENT FLOW DOWN OVER  
THE CENTRAL U.S. BEFORE FEEDING INTO A SLOW-TO-DEPART CLOSED LOW  
OVER THE NORTHEAST. THERE IS A GROWING THREAT FOR NEW ENGLAND  
COASTAL LOW DEVELOPMENT WEDNESDAY-THURSDAY.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
COMPOSITE OF REASONABLY WELL CLUSTERED GUIDANCE FROM THE 12 UTC  
ECMWF/UKMET/CANADIAN AND THE 01 UTC NATIONAL BLEND OF MODELS (NBM)  
FOR WEDNESDAY/THURSDAY. THIS SOLUTION HAS SOLID GEFS/ECMWF  
ENSEMBLE SUPPORT FOR THIS TIME FRAME WHILE THE LAST FEW RUNS OF  
THE GFS HAVE IN PARTICULAR NOT PROVIDED RUN TO RUN CONSISTENT  
GUIDANCE FOR POTENTIAL NEW ENGLAND COASTAL SYSTEM DEVELOPMENT AND  
TRACK. THE 12 UTC ECMWF SOLUTION OVERALL STAYS BEST CLUSTERED WITH  
THE ENSEMBLE MEANS AND NBM FRIDAY INTO NEXT WEEKEND, SO USED THAT  
BLEND TO PROVIDE DETAIL CONSISTENT WITH PREDICTABILITY AMID SLOWLY  
GROWING CONUS FORECAST SPREAD. TARGETED FORECASTER DRIVEN CHANGES  
TO NBM QPF WERE TO MAINLY INCREASE THE QPF SIGNATURE OVER THE  
UPPER MIDWEST THROUGH THE PERIOD GIVEN DYNAMIC SUPPORT  
ALOFT/FRONTAL PASSAGE AND OVER THE NORTHEAST WITH THE SLOW CLOSED  
UPPER LOW AND COASTAL STORM THREAT.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
AS THE UPPER RIDGE EXPANDS OVER THE WEST/NORTHWEST THIS WEEK,  
EXPECT 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 HAVE SEEN PERSISTENT  
MONSOONAL MOISTURE OVER THE PAST COUPLE OF MONTHS, AND THIS WEEK  
WILL CONTINUE THAT PATTERN AS ANOMALOUSLY HIGH MOISTURE STREAMS  
FOCUSES INTO THE SOUTHWEST AND SOUTH-CENTRAL GREAT BASIN/ROCKIES  
IN CONJUNCTION WITH SMALL-SCALE SHORTWAVE ENERGY TO PRODUCE RAIN  
AND THUNDERSTORMS, PARTICULARLY IN THE AFTERNOON AND EVENING  
HOURS. A WPC EXPERIMENTAL MEDIUM RANGE SLIGHT RISK OF EXCESSIVE  
RAINFALL IS IN PLACE FOR THE SOUTH-CENTRAL ROCKIES/HIGH PLAINS  
THROUGH MIDWEEK AS ADDITIONALLY SUPPORTED BY DIGGING SHORTWAVE  
ENERGY/UPPER DIFFLUENCE AND TERRAIN LIFT. IN THIS PATTERN,  
CONVECTIVE ACTIVITY WILL PERSIST THROUGH LATER WEEK/NEXT WEEKEND  
THERE WHILE ALSO INCREASINGLY SPREADING DOWNSTREAM OVER THE  
SOUTHERN PLAINS.  
 
ELSEWHERE, MID-LATER WEEK CONVECTIVE CLUSTERS SHOULD BE EFFICENT  
RAINFALL PRODUCERS WITHIN THE DEEPLY MOIST PRECIPITABLE WATER  
VALUES OF THE LOWER MISSISSIPPI VALLEY/GULF COAST STATES GIVEN  
UPSTREAM HISTORY AND THUNDERSTORMS WILL ALSO SPREAD AND ORGANIZE  
ACROSS THE SOUTHEAST WITH WAVY AND SLOW MOVING FRONTAL BOUNDARIES  
IN A MOIST POOLED AIRMASS UNDERNEATH THE FAVORABLE RIGHT ENTRANCE  
REGION OF THE UPPER JET. MEANWHILE, A THREAT OF A MULTI-DAY RAIN  
AND WIND EVENT IS INCREASING FOR MUCH OF THE COASTAL NORTHEAST,  
FROM NEW JERSEY UP TO MAINE WEDNESDAY INTO THURSDAY WITH COASTAL  
CYCLOGENESIS AHEAD OF A CLOSED UPPER LOW. PERIODS OF HEAVY  
WRAP-AROUND RAINS ARE ALSO A DISTINCT POSSIBILITY OVER EASTERN NEW  
ENGLAND. THERE IS ALSO A DEVELOPING OPPORTUNITY FOR ORGANIZED  
CONVECTION FROM THE DAKOTAS/UPPER MIDWEST TO THE GREAT LAKES WITH  
THE LATE WEEK/WEEEKND DIGGING OF SHORTWAVE ENERGY AND A SLOWLY  
PROGRESSIVE LEAD FRONTAL PASSAGE.  
 
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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