129  
FXUS02 KWBC 161909  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
308 PM EDT TUE AUG 16 2022  
 
VALID 12Z FRI AUG 19 2022 - 12Z TUE AUG 23 2022  
 
...EXCESSIVE HEAT THREAT WILL PERSIST 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 SOUTHERN/CENTRAL PLAINS AND  
MID-LOWER MISSISSIPPI VALLEY THIS WEEKEND INTO EARLY NEXT WEEK...  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST MODEL AND ENSEMBLE SUITE ARE IN FAIRLY GOOD AGREEMENT  
WITH THE LARGE SCALE PATTERN EVOLUTION INTO NEXT WEEK WITH RIDGING  
OVER THE WESTERN HALF OF THE LOWER CONTIGUOUS STATES (PERIODS OF  
WEAKNESS) AND AN EASTERN TROUGH THAT BECOMES REINFORCED BY A DEEP  
SHORTWAVE/CLOSED LOW THAT TRACKS THROUGH THE MIDWEST. LIKE  
PREVIOUS CYCLES, THERE REMAINS SOME DIFFERENCES IN THE TIMING,  
MAGNITUDE AND LOCATIONS OF VARIOUS FEATURES THROUGH THE EXTENDED  
PERIOD. ALL IN ALL, THE CMC/UKMET/GFS/ECWMF PROVIDED A GOOD  
STARTING POINT FOR THE FORECAST AND OUT TO DAY 5. THE GFS AND  
ECWMF WERE UTILIZED MORE FOR MID AND LATER PERIODS ALONG WITH  
THEIR ENSEMBLE MEANS.  
THIS KEEPS WITH THE FORECAST CLOSE TO CONTINUITY FROM THE PRIOR  
ISSUANCE.  
   
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
 
 
MUCH OF THE INTERIOR NORTHWEST WILL CONTINUE TO HAVE OPPRESSIVE  
TEMPERATURES, WITH DAILY HIGHS RANGING FROM THE MID 90S TO 100S  
AND OVERNIGHT LOWS IN THE 50S AND 60S, INTO THE WEEKEND THUS  
MAINTAINING THE HEATWAVE. A VAST AREA OF FROM WASHINGTON/WESTERN  
IDAHO TO CENTRAL/SOUTH-CENTRAL CALIFORNIA HAVE HEAT ADVISORIES AND  
EXCESSIVE HEAT WARNINGS IN EFFECT THROUGH FRIDAY. THESE  
TEMPERATURES ARE LIKELY TO PRODUCE SOME RECORD VALUES, MOSTLY FOR  
OVERNIGHT TEMPERATURES. THE TEMPERATURES THAT HAD BEEN 10-15  
DEGREES F ABOVE NORMAL WILL BEGIN TO RELAX SOMEWHAT OVER THE  
WEEKEND AND INTO EARLY NEXT WEEK AS THE RIDGE EXPERIENCES SOME  
WEAKENING. IN CONTRAST,  
BELOW NORMAL HIGHS ARE FORECAST ACROSS PARTS OF EAST-CENTRAL U.S.  
IN THE WAKE OF A COLD FRONT. GIVEN THE CLOUD COVER AND RAINFALL  
OVER THE DESERT SOUTHWEST AND ACROSS THE SOUTHERN PORTIONS OF THE  
GREAT BASIN AND ROCKIES, DAILY TEMPERATURE READINGS NEAR OR BELOW  
NORMAL ARE EXPECTED.  
 
THE ASSIDUOUS MONSOONAL MOISTURE INTO THE SOUTHWEST, GREAT BASIN,  
AND SOUTHERN/CENTRAL ROCKIES WILL CONTINUE  
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. THE  
WPC EXPERIMENTAL MEDIUM RANGE SLIGHT RISK FOR EXCESSIVE RAINFALL  
REMAINS IN EFFECT ACROSS 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. THERE WILL LIKELY BE  
AREAS THAT HAVE PERIODS OF INTENSE RAINFALL THUS THE ELEVATED  
THREAT FOR FLOODING. 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 SOMEWHAT OVERDONE COMPARED TO MODELS AND ENSEMBLE  
MEMBERS. TO THE SOUTH, NHC ALSO INDICATES THAT THERE IS A GROWING  
MODEL/ENSEMBLE SIGNAL FOR ANOTHER TROPICAL WAVE TO REACH NORTHEAST  
MEXICO AND SOUTHERN TEXAS OVER THE WEEKEND THAT COULD MODERATELY  
FOCUS LOCAL MOISTURE AND RAINFALL POTENTIAL.  
 
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO PERSIST INTO THE WEEKEND  
ALONG A SLOW-MOVING, WAVY FRONTAL BOUNDARY OVER THE SOUTH AND  
SOUTHEAST. THERE MAY BE LOCAL AREAS THAT HAVE HEAVY DOWNPOURS  
THANKS FOR VERY MOIST AIR POOLED OVER THE REGION. 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.  
 
CAMPBELL/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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