871  
FXUS02 KWBC 060658  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
257 AM EDT SAT AUG 06 2022  
 
VALID 12Z TUE AUG 09 2022 - 12Z SAT AUG 13 2022  
 
...POTENTIALLY HEAVY RAINFALL AND FLASH FLOODING ARE POSSIBLE IN  
THE OHIO/TENNESSEE VALLEYS TUESDAY-WEDNESDAY WHILE MONSOONAL  
MOISTURE CONTINUES IN THE WEST...  
 
   
..OVERVIEW
 
 
THE OVERALL WEATHER PATTERN ACROSS THE CONTIGUOUS U.S. NEXT WEEK  
SHOULD AMPLIFY INTO A TROUGH-RIDGE-TROUGH PATTERN, AS SHORTWAVES  
COMBINE TO DEEPEN A TROUGH IN THE EAST, A SLOW-MOVING UPPER LOW  
OFF THE WEST COAST LIFTS NORTHEASTWARD INTO THE PACIFIC NORTHWEST  
AROUND WEDNESDAY-THURSDAY, AND AN UPPER HIGH NUDGES EASTWARD FROM  
THE CENTRAL ROCKIES INTO THE CENTRAL/SOUTHERN PLAINS. MOISTURE  
LIFTED AHEAD OF THE EASTERN TROUGH AND ASSOCIATED COLD FRONT WILL  
LIKELY LEAD TO AREAS OF HEAVY RAIN AND THUNDERSTORMS MAINLY ACROSS  
THE OHIO AND TENNESSEE VALLEYS TUESDAY-WEDNESDAY WITH CONVECTION  
SPREADING INTO THE EASTERN SEABOARD AS WELL. MEANWHILE, PERSISTENT  
MONSOONAL MOISTURE LOOKS TO CONTINUE ACROSS PORTIONS OF THE WEST,  
LEADING TO ADDITIONAL RAINFALL WITH A GRADUAL NORTHWARD EXPANSION  
OF THE RAIN TOWARD THE NORTHERN ROCKIES AS THE WEEK PROGRESSES.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
RECENT MODEL AND ENSEMBLE GUIDANCE AGREES REASONABLY WELL WITH THE  
OVERALL SYNOPTIC PATTERN NEXT WEEK, WHILE DIFFERENCES IN THE  
DETAILS REMAIN. THE LARGEST MODEL SPREAD PERTAINS TO THE TIMING OF  
THE UPPER LOW OFF THE WEST COAST AS IT IS FORECAST TO MOVE INTO  
THE PACIFIC NORTHWEST DURING THE LATTER HALF OF THE WEEK. IN TERMS  
OF THE 12/18Z GUIDANCE THAT COULD BE USED FOR THE WPC FORECAST,  
GOOD AGREEMENT AMONG THE GFS/ECMWF/UKMET/CMC TUESDAY DIVERGES  
SOMEWHAT BY WEDNESDAY-THURSDAY, WITH A SLOWER CMC AND FASTER ECMWF  
THAN THE GFS RUNS. THE 12Z EC ENSEMBLE MEAN IS ALSO FASTER THAN  
THE GEFS AND CMCE MEANS. HOWEVER, THE NEW 00Z ECMWF IS SLOWER AND  
ACTUALLY STALLS THE CENTER OF THE UPPER LOW OFFSHORE THE PACIFIC  
NORTHWEST THROUGH FRIDAY. THUS UNCERTAINTY CONTINUES WITH THE  
TIMING OF THIS FEATURE, AND PREFERRED A MIDDLE GROUND FORECAST  
RATHER THAN A SLOWER OR FASTER EXTREME AT THIS POINT. FARTHER  
EAST, MODELS SHOW GOOD AGREEMENT WITH THE UPPER HIGH/RIDGE, AND  
WHILE THERE ARE SOME DIFFERENCES WITH THE DETAILS OF THE EASTERN  
TROUGH, NOTHING WAS TOO EGREGIOUS FOR A MEDIUM RANGE FORECAST.  
THUS THE WPC FORECAST UTILIZED A MULTI-MODEL BLEND OF THE  
DETERMINISTIC GUIDANCE EARLY ON, WITH INCREASING PROPORTIONS OF  
THE ENSEMBLE MEANS AS THE PERIOD PROGRESSES. THE RESULTS SHOW GOOD  
CONTINUITY WITH THE PREVIOUS FORECAST PACKAGE.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
FOR THE EARLY PART OF THE MEDIUM RANGE PERIOD TUESDAY-WEDNESDAY,  
AN AXIS OF LOCALLY HEAVY RAIN AND THUNDERSTORMS AHEAD OF A COLD  
FRONT IS EXPECTED TO CONTINUE PUSHING SOUTHEASTWARD ACROSS THE  
OHIO VALLEY TO NORTHEAST INTO THE TENNESSEE VALLEY AND  
MID-ATLANTIC REGION. THE RELATIVELY SLOW PUSH OF THE FRONT COULD  
LEAD TO TRAINING STORMS THAT COULD CAUSE FLASH FLOODING. FLOODING  
CONCERNS ARE PARTICULARLY ENHANCED ACROSS PORTIONS OF  
KENTUCKY/TENNESSEE/WEST VIRGINIA ON WEDNESDAY, AS THEY HAVE  
RECEIVED ABUNDANT RAINFALL RECENTLY AND ARE SENSITIVE TO  
ADDITIONAL RAIN AMOUNTS. THE FRONT CONTINUING TO PUSH  
SOUTHEASTWARD INTO THE LATTER HALF OF THE WEEK SHOULD CLEAR  
RAINFALL OUT OF THE NORTHEASTERN QUADRANT OF THE COUNTRY, BUT  
SCATTERED CONVECTIVE ACTIVITY IS FORECAST TO CONTINUE IN THE  
SOUTHEAST. MEANWHILE, MONSOONAL MOISTURE CONTINUES TO IMPACT THE  
SOUTHWEST WITH ENHANCED RAINFALL, WITH A TREND TOWARD GRADUALLY  
LESS RAINFALL IN AREAS LIKE NEW MEXICO BUT INCREASING CHANCES FOR  
RAIN FARTHER NORTH AS THE MOISTURE PLUME EXPANDS INTO THE  
INTERMOUNTAIN WEST AND GREAT BASIN, WITH SOME LOCALLY HEAVY TOTALS  
POSSIBLE HERE AS WELL.  
 
VERY WARM TO HOT TEMPERATURES AROUND 10-15F ABOVE AVERAGE, THOUGH  
NOT QUITE TO RECORD-BREAKING LEVELS, ARE FORECAST TO SHIFT FROM  
THE NORTHWEST TUESDAY INTO THE NORTHERN AND THEN CENTRAL PLAINS AS  
THE WORKWEEK PROGRESSES WITH THE EASTWARD NUDGE OF THE UPPER HIGH.  
FARTHER EAST, SLIGHTLY BELOW NORMAL HIGHS ARE POSSIBLE IN THE OHIO  
AND TENNESSEE VALLEYS BEHIND THE COLD FRONT, WHILE TEMPERATURES  
ALONG THE EASTERN SEABOARD WILL FLIP FROM SLIGHTLY ABOVE TO  
SLIGHTLY BELOW AVERAGE. GIVEN THE RAINFALL AND CLOUDINESS OVER THE  
SOUTHWEST AND GREAT BASIN, HIGHS ARE LIKELY TO BE SEVERAL DEGREES  
BELOW NORMAL THERE THROUGH LATE WEEK.  
 
TATE/KONG  
 
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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