872  
FXUS02 KWBC 141901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM 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 SUPPORT 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. TO FOCUS PERIODS OF HEAVY RAIN/THUNDERSTORMS MOST  
LIKELY DOWN THE LOWER MISSISSIPPI VALLEY NEAR AND SOUTH OF A WAVY  
FRONT. ACROSS NEW ENGLAND, THERE CONTINUES TO BE A THREAT OF  
COASTAL CYCLOGENESIS WEDNESDAY-THURSDAY WHERE MODEL UNCERTAINTY  
REMAINS HIGH.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL ENSEMBLE MEANS REMAIN QUITE AGREEABLE WITH ONE ANOTHER ON  
PREDICTING THE RELATIVELY AMPLIFIED UPPER AIR PATTERN ACROSS THE  
MAINLAND U.S. THROUGH NEXT WEEKEND. A SLOW-TO-DEPART CLOSED LOW  
OVER THE NORTHEAST MIDWEEK CONTINUES TO BE A FEATURE WHERE MODELS  
INDICATE THE GREATEST AMOUNT SPREAD AND RUN-TO-RUN VARIABILITY.  
THERE CONTINUES TO BE THE POTENTIAL FOR THE CLOSED LOW TO INTERACT  
WITH ATLANTIC MOISTURE PASSING OVER THE GULF STREAM TO TRIGGER  
COASTAL CYCLOGENESIS. RAINFALL AMOUNTS ARE HIGHLY SENSITIVE TO  
THE INTENSITY AND TRACK OF THE CYCLONE AS WELL. ACROSS THE  
MID-SOUTH, MODELS ARE IN RELATIVELY GOOD AGREEMENT ON THE  
PLACEMENT OF AN AREA OF ENHANCED RAINFALL AHEAD OF A LOW PRESSURE  
WAVE AND A STATIONARY FRONT. SOME NORTH-SOUTH MODEL DIFFERENCES  
WERE NOTED REGARDING THE PLACEMENT OF THE RAINFALL AXIS FROM THE  
DEEP SOUTH TO THE EAST COAST LATE THIS WEEK. FOR THE MONSOONAL  
RAINS OVER THE WEST, MODELS HAVE GENERALLY BEEN INDICATING A SLOW  
DECREASING TREND ON THE QPF THROUGH THE END OF THE WEEK. FINALLY,  
UNCERTAINTY IN THE AMPLITUDE OF THE NEXT SHORTWAVE DIPPING INTO  
THE NORTHERN PLAINS CONTINUES TO RESULT IN SOME MODEL SPREAD  
REGARDING THE ASSOCIATED TIMING AND PLACEMENT QPFS LATER THIS WEEK.  
 
THE WPC MEDIUM-RANGE FORECASTS WERE COMPOSED BASED ON A CONSENSUS  
OF 40% FROM THE 06Z GFS/GEFS, 40% FROM THE 00Z EC/EC MEAN, AND 20%  
FROM THE 00Z CMC/CMC MEAN, TOGETHER WITH THE 13Z NBM,  
TRANSITIONING TO MOSTLY A CONSENSUS OF THE ENSEMBLE MEANS BY DAY 7.  
   
..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 FEEDS 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 NEAR AND SOUTH OF A  
SLOWLY PROGRESSIVE COLD FRONT ACROSS THE DEEP SOUTH TO THE  
SOUTHEAST, WITH THE HIGHEST THREAT OF HEAVY RAIN DOWN THE LOWER  
MISSISSIPPI VALLEY. THE ENHANCED RAINFALL IS FORECAST TO SLOWLY  
WORK ITS WAY ACROSS THE EAST COAST BY NEXT WEEKEND WITH A COASTAL  
WAVY FRONT.  
 
ELSEWHERE, MID-LATER WEEK CONVECTIVE CLUSTERS SHOULD BE EFFICIENT  
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/WEEKEND DIGGING OF SHORTWAVE ENERGY AND A SLOWLY  
PROGRESSIVE LEAD FRONTAL PASSAGE.  
 
KONG/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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