762  
FXUS02 KWBC 031901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT WED AUG 03 2022  
 
VALID 12Z SAT AUG 06 2022 - 12Z WED AUG 10 2022  
 
...SOUTHWEST/GREAT BASIN/ROCKIES MONSOON RESUMES A VERY ACTIVE  
PHASE LATE THIS WEEK...  
...HEAVY RAIN THREAT THIS WEEKEND FOR THE UPPER MIDWEST AND GREAT  
LAKES...  
 
   
..OVERVIEW
 
 
LATEST GUIDANCE SHOWS A FAIRLY TYPICAL SUMMERTIME PATTERN WITH THE  
MAIN BAND OF WESTERLIES ACROSS SOUTHERN CANADA AND NORTHERN TIER  
CONUS, THOUGH WITH UPPER RIDGING TO THE SOUTH TENDING TO BE  
SOMEWHAT STRONGER THAN THE CLIMATOLOGICAL MEAN. AN UPPER LOW  
SHOULD LIFT VERY SLOWLY NORTHEASTWARD OFFSHORE THE WEST COAST. THE  
MODELS AND ENSEMBLES AGREE ON THE LARGE SCALE PATTERN, BUT  
SIGNIFICANT SHORTWAVE DIFFERENCES DEVELOP WITHIN THE WESTERLIES  
FROM FAIRLY EARLY IN THE FORECAST. AS A RESULT CONFIDENCE  
DECREASES FOR SURFACE FRONT/WAVE DETAILS AND IN TURN FOR  
ASSOCIATED AREAS OF RAINFALL WHICH COULD BE HEAVY AT TIMES OVER  
PORTIONS OF THE NORTHERN HALF OF THE CENTRAL/EASTERN U.S.  
MEANWHILE THE MONSOONAL PATTERN OVER THE WEST SHOULD BECOME MORE  
PRONOUNCED AGAIN AND LIKELY REMAIN FAIRLY ACTIVE THROUGH THE  
WEEKEND AND INTO NEXT WEEK.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
COMPOSITE OF REASONABLY COMPATIBLE GUIDANCE FROM THE 06 UTC GFS  
AND 00 UTC ECMWF/UKMET/CANADIAN AND THE 13 UTC NATIONAL BLEND OF  
MODELS (NBM). THE BLEND ACTS TO MITIGATE LINGERING SMALL SCALE  
VARIANCE CONSISTENT WITH PREDICTABILITY. THE 00 UTC CANADIAN AND  
TO A LESSER DEGREE GEFS/NAEFS/ECMWF ENSEMBLES HELD CLOSED UPPER  
LOW/TROUGHING OVER THE EASTERN PACIFIC DAYS 6/7 WHILE THE 06 UTC  
GFS/ECMWF GRADUALLY ALLOWED THE SYSTEM TO WORK INTO THE PACIFIC  
NORTHWEST. EXPECT THE SYSTEM TO MAINLY HOLD OFFSHORE GIVEN  
POSITION BETWEEN TWO AMPLIFIED UPPER RIDGES. 12 UTC MODEL GUIDANCE  
HAS TRENDED OFFSHORE WITH THIS SYSTEM, BOLSTERING FORECAST  
CONFIDENCE TO ABOVE NORMAL LEVELS.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
OVER THE WEST, MAXIMUM TEMPERATURES WILL TEND TO BE SOMEWHAT BELOW  
NORMAL OVER THE GREAT BASIN/SOUTHWEST AND VICINITY DUE TO  
PERSISTENT CLOUDS AND PERIODS OF RAIN. THE NORTHWEST SHOULD TREND  
MORE ABOVE NORMAL AS SOME DEGREE OF UPPER RIDGING BUILDS,  
SPREADING INTO THE NORTHERN ROCKIES/HIGH PLAINS INTO NEXT WEEK.  
HIGHS COULD LOCALLY REACH 10-12F ABOVE NORMAL.  
 
FOR PRECIPITATION, THE MAIN THREATS FOR FLASH FLOODING WILL BE  
ASSOCIATED WITH MONSOONAL MOISTURE OVER THE SOUTHWEST/GREAT  
BASIN/ROCKIES AS WELL AS WITH FRONTS/WAVES FROM THE EAST-CENTRAL  
U.S. AS NORTHERN STREAM SHORTWAVE TROUGHS PROGRESS DONWSTREAM. THE  
COMBINED SIGNALS FOR RAINFALL AND ALREADY WET CONDITIONS OVER THE  
DESERT SOUTHWEST INTO THE CENTRAL ROCKIES/GREAT BASIN LATE INTO  
THE WEEKEND SUPPORT SEVERAL SLIGHT RISK AREAS IN THE EXPERIMENTAL  
DAYS 4-5 EXCESSIVE RAINFALL OUTLOOKS. DESPITE FRONTAL PROGRESSION,  
DEEP POOLED MOISUTRE AND INSTABILITY ALSO PROMPTED WEEKEND SLIGHT  
RISK ERO THREAT AREAS ACROSS THE UPPER MIDWEST AND GREAT LAKES IN  
A REGION WITH ENHANCED/ONGOING SHORT RANGE QPF. NBM QPF WAS  
INCREASED FOR THIS POTENTIAL.  
 
KEBEDE/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