233  
FXUS02 KWBC 170606  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
204 AM EDT WED AUG 17 2022  
 
VALID 12Z SAT AUG 20 2022 - 12Z WED AUG 24 2022  
 
...EXCESSIVE HEAT THREAT TO PERSIST FOR INTERIOR PORTIONS OF  
CALIFORNIA/NORTHWEST U.S. INTO THE WEEKEND...  
...SIGNIFICANT MONSOONAL EXCESSIVE RAINFALL THREAT FOR THE  
SOUTHWEST AND SOUTH-CENTRAL GREAT BASIN/ROCKIES INTO THE WEEKEND  
MAY RELAX EARLY NEXT WEEK AS HAZARD FOCUS SHIFTS TO THE SOUTHERN  
PLAINS THEN LOWER MISSISSIPPI/TENNESSEE VALLEYS...  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL AND ENSEMBLE SOLUTIONS SEEM REASONABLY WELL CLUSTERED  
THROUGH MEDIUM RANGE TIME SCALES WITH THE MID-LARGER SCALE PATTERN  
EVOLUTION INTO NEXT WEEK WITH MEAN RIDGING WITH AMPLE WEAKNESSES  
OVER THE WESTERN HALF OF THE LOWER 48 AND AN EASTERN U.S. TROUGH  
THAT BECOMES REINFORCED BY A DEEP SHORTWAVE/CLOSED LOW THAT TRACKS  
THROUGH THE MIDWEST. THERE REMAIN SOME DIFFERENCES IN THE TIMING  
AND MAGNITUDE OF SMALLER SCALE FEATURES. A COMPOSITE  
GFS/ECMWF/UKMET/CANADIAN AND GEFS/ECMWF ENSEMBLES ALONG WITH THE  
NATIONAL BLEND OF MODELS SEEMS TO DECENTLY MITIGATE THESE  
DIFFERENCES CONSISTENT WITH PREDICTABILITY TO MAINTAIN GOOD WPC  
PRODUCT CONTINUITY.  
   
..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,  
MAINTAINING THE HEATWAVE. A VAST AREA OF FROM WASHINGTON/WESTERN  
IDAHO TO CENTRAL/SOUTH-CENTRAL CALIFORNIA ALREADY HAVE HEAT  
ADVISORIES AND EXCESSIVE HEAT WARNINGS IN EFFECT THROUGH FRIDAY.  
THESE TEMPERATURES ARE LIKELY TO PRODUCE SOME RECORD VALUES,  
MOSTLY FOR OVERNIGHT TEMPERATURES. TEMPERATURES SHOULD BEGIN TO  
RELAX SOMEWHAT THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK AS THE  
RIDGE WEAKENS. IN CONTRAST, BELOW NORMAL HIGHS ARE FORECAST ACROSS  
PARTS OF EAST-CENTRAL U.S. IN THE WAKE OF A WAVY 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 ONGOING MONSOONAL PATTERN WILL CONTINUE THROUGH THE WEEKEND AS  
ANOMALOUSLY HIGH MOISTURE FEEDS INTO THE SOUTHWEST AND  
SOUTH-CENTRAL GREAT BASIN/ROCKIES TO PRODUCE MAINLY DIURNALLY  
DRIVEN HEAVY RAINS AND THUNDERSTORMS. THIS IS IN CONJUNCTION WITH  
EMBEDDED UPPER VORTS AND THE LATER WEEK/WEEKEND LARGER SCALE  
INFLUX OF PACIFIC UPPER TROUGH ENERGY ACROSS THE REGION. A WPC  
EXPERIMENTAL MEDIUM RANGE SLIGHT RISK FOR EXCESSIVE RAINFALL  
SHIFTS EASTWARD ACROSS ARIZONA AND NEW MEXICO AS FUELED BY  
ENHANCED QPF/ARI AND A 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. THE MONSOONAL PATTERN MAY  
RELAX EARLY NEXT WEEK.  
MEANWHILE, NHC ALSO INDICATES THAT ANOTHER TROPICAL WAVE MAY REACH  
NORTHEAST MEXICO AND SOUTHERN TEXAS OVER THE WEEKEND THAT COULD  
FOCUS LOCAL MOISTURE AND RAINFALL POTENTIAL.  
 
LATER, THE MAIN HEAVY RAINFALL/FLASH FLOODING THREAT SHOULD EMERGE  
DOWNSTREAM TO FOCUS ACROSS THE SOUTHERN PLAINS AND THE LOWER  
MISSISSIPPI/TENNESSEE VALLEYS LATER THROUGH EARLY-MID NEXT WEEK.  
THE THREAT SEEMS FORMIDABLE AS MOISTURE AND INSTABILITY POOL WITH  
RETURN FLOW INTO SLOW MOVING/WAVY FRONTS IN FAVORABLE UPPER FLOW  
AS UPPER TROUGH ENERGIES EJECT OUT FROM THE WEST. WPC QPF HAS  
TRENDED SIGNIFICANTLY UPWARDS FROM CONTINUITY GIVEN A STRONG  
GUIDANCE SIGNAL FOR REPEAT/TRAINING OF CELLS AND A ERO SLIGHT RISK  
AREA WAS ISSUED. WHILE MANY LOCATIONS MAY EXPERIENCE HIGH EVENT  
TOTALS, WPC QPF VOLUMETRIC/AREAL COVERAGE WAS TARGETED TO BE  
SOMEWHAT LOWER THAN THE EVEN WETTER 01 UTC NBM TO BE MORE  
CONSISTENT WITH MODELS/ENSEMBLES AND TO LIMIT THE WPC CONTINUITY  
CHANGE.  
 
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 OVER THE WEEKEND WITH  
THE WAVY FRONT SLATED TO LIFT SLOWLY NORTHWARD.  
 
FARTHER NORTH, CONVECTION WILL GRADUALLY SPREAD ACROSS THE MIDWEST  
THIS WEEKEND/EARLY NEXT WEEK AS DIGGING SHORTWAVE ENERGY FORMS A  
CLOSED LOW. SLOW CELL MOTIONS AND INSTABILITY NEAR THE CLOSED  
FEATURE OFFER POTENTIAL FOR LOCAL DOWNPOURS WITH RUNOFF ISSUES.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page