612  
FXUS02 KWBC 160538  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
137 AM EDT TUE AUG 16 2022  
 
VALID 12Z FRI AUG 19 2022 - 12Z TUE AUG 23 2022  
 
...EXCESSIVE HEAT THREAT FROM INTERIOR CALIFORNIA TO THE NORTHWEST  
THROUGH THE WEEKEND...  
...MONSOONAL HEAVY RAIN THREAT FOR THE SOUTHWEST AND SOUTH-CENTRAL  
GREAT BASIN/ROCKIES INTO THE WEEKEND MAY RELAX EARLY NEXT WEEK...  
...EXCESSIVE RAINFALL THREAT FOR THE SOUTH-CENTRAL PLAINS AND  
MID-LOWER MISSISSIPPI VALLEY THIS WEEKEND INTO EARLY NEXT WEEK...  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODELS AND ENSEMBLES REMAIN IN AGREEMENT ON THE LARGER SCALE UPPER  
PATTERN OVER THE NEXT WEEK AS HIGHLIGHTED BY TROUGHING OVER THE  
EAST REINFORCED BY A DEEP SHORTWAVE/CLOSED LOW THROUGH THE  
MIDWEST, AND RIDGING WITH WEAKNESSES FROM PARTS OF THE WEST TO THE  
CENTRAL U.S.. THERE ARE SOME CONTINUED SMALL SCALE DIFFERENCES  
INCLUDING TIMING/AMPLITUDE OF VARIOUS FEATURES, PARTICULARLY LATE  
PERIOD. A COMPOSITE MODEL BLEND SEEMS TO DECENTLY MITIGATE THESE  
DIFFERENCES CONSISTENT WITH PREDICTABILITY THROUGH THE WEEKEND. AT  
LONGER TIME FRAMES, THE GFS AND ECMWF OVERALL CONTINUE TO SEEM  
BETTER ALIGNED WITH THE ENSEMBLE MEANS. ACCORDINGLY, THE WPC  
PRODUCT SUITE WAS PRIMARILY DERIVED FROM A COMPOSITE BLEND OF THE  
GFS/ECMWF/UKMET/CANADIAN 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.  
   
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
 
 
UPPER RIDGING OVER THE INTERIOR NORTHWEST WILL EXTEND THE HEATWAVE  
INTO THE WEEKEND WITH DAYTIME/OVERNIGHT TEMPERATURES 10-15F ABOVE  
NORMAL. THESE TEMPERATURES ARE LIKELY TO PRODUCE SOME RECORD  
VALUES, MOSTLY FOR OVERNIGHT TEMPERATURES. 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 TO PRODUCE MAINLY  
DIURNALLY DRIVEN RAIN AND THUNDERSTORMS. THIS IS IN CONJUNCTION  
WITH EMBEDDED UPPER VORTS AND THE LATER WEEK/WEEKEND LARGER SCALE  
INFLUX OF PACIFIC UPPER TROUGH ENERGY WHOSE SUBSEQUENT EASTWARD  
TRACK ACROSS THE REGION NOW HAS MORE AMPLE GUIDANCE SUPPORT. WPC  
EXPERIMENTAL MEDIUM RANGE SLIGHT RISKS OF EXCESSIVE RAINFALL ARE  
ISSUED FOR PORTIONS OF ARIZONA AND NEW MEXICO FRIDAY AND SATURDAY  
GIVEN ENHANCED QPF/ARI AND AN OVERALL PERSISTENT FAVORABLE PATTERN  
THAT MAY ENTRAIN DEEPER MOISTURE FROM A NORTHERN MEXICO FEATURE  
WITH TROPICAL CONNECTION. EVEN SO, THE WIDESPREAD NBM  
VOLUMETRIC/AREAL COVERAGE OF HEAVY RAINFALL SEEMS A BIT OVERDONE  
OVERALL COMPARED TO MODELS AND ENSEMBLE MEMBERS. THERE IS A  
GROWING GUIDANCE SIGNAL THAT THE MONSOONAL PATTERN MAY RELAX EARLY  
NEXT WEEK.  
 
DOWNSTREAM, A HEAVY RAINFALL/FLASH FLOODING SIGNAL THEN EMERGES  
FROM THE SOUTH-CENTRAL PLAINS TO THE MID-LOWER MISSISSIPPI VALLEY  
THIS WEEKEND INTO EARLY NEXT WEEK. THE THREAT SEEMS REASONABLE AS  
MOISTURE AND INSTABILITY POOL WITH RETURN FLOW INTO A SLOW MOVING  
FRONT IN FAVORABLE UPPER DIFFLUENT FLOW ALOFT, AND ESPECIALLY WITH  
UPPER TROUGH ENERGIES EJECTING OUT FROM THE WEST. EVEN SO, THE  
WIDESPREAD NBM VOLUMETRIC/AREAL COVERAGE OF HEAVY RAINFALL SEEMS  
SOMEHWAT OVERDONE COMPARED TO MODELS AND ENSEMBLE MEMBERS.  
 
ELSEWHERE, CONVECTIVE ACTIVITY WILL PERSIST MAINLY THROUGH LATER  
THIS WEEK/WEEKEND NEAR A SLOW MOVING AND WAVY FRONT THAT WILL  
PERSIST ACROSS THE SOUTH/SOUTHEAST. POOLED HIGH PRECIPITABLE WATER  
VALUES SUPPORT RUNOFF ISSUES WITH HEAVY LOCAL DOWNPOURS. ORGANIZED  
RAINS WILL ALSO SLOWLY LIFT TO THE MID-ATLANTIC BY THE WEEKEND  
WITH THE WAVY FRONT SLATED TO LIFT SLOWLY NORTHWARD.  
 
FARTHER NORTH, CONVECTION WILL GRADUALLY SPREAD ACROSS THE MIDWEST  
WITH LATER WEEK TO EARLY NEXT WEEK DIGGING OF SHORTWAVE ENERGY TO  
FORM A CLOSED LOW AND WITH A SLOW TO PROGRESS FRONT. SLOW CELL  
MOTIONS AND INSTABILITY NEAR THE CLOSED FEATURE MAY PRODUCE RUNOFF  
ISSUES. LOCAL NBM QPF HAS SEEMED TOO LIGHT WITH THIS SYSTEM OVER  
THE PAST FEW DAYS, BUT CONTINUES TO GRADUALLY TREND WETTER.  
 
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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