089  
FXUS02 KWBC 050658  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
258 AM EDT FRI AUG 05 2022  
 
VALID 12Z MON AUG 08 2022 - 12Z FRI AUG 12 2022  
 
...MONSOONAL PATTERN REMAINS ACTIVE ACROSS THE SOUTHWEST WITH  
ADDITIONAL HEAVY RAINFALL LIKELY...  
 
   
..OVERVIEW
 
 
THE OVERALL WEATHER PATTERN ACROSS THE CONTIGUOUS U.S. NEXT WEEK  
WILL BE GRADUALLY AMPLIFYING AS SHORTWAVES COMBINE TO DEEPEN A  
TROUGH IN THE EAST, WHILE AN UPPER HIGH DRIFTS FROM THE FOUR  
CORNERS TO HIGH PLAINS AND A SLOW-MOVING UPPER LOW OFF THE WEST  
COAST LIFTS NORTHWARD AND ACROSS THE PACIFIC NORTHWEST AROUND  
WEDNESDAY-THURSDAY. MOISTURE INFLOW INTO A COLD FRONT AHEAD OF THE  
EASTERN TROUGH WILL LEAD TO POTENTIALLY HEAVY RAIN AND  
THUNDERSTORMS AS THE FRONT PUSHES SOUTHEASTWARD ACROSS THE OHIO  
AND TENNESSEE VALLEYS TOWARD THE GULF COAST AND ACROSS THE EASTERN  
SEABOARD. ADDITIONALLY, PERSISTENT MONSOONAL MOISTURE LOOKS TO  
CONTINUE ACROSS PORTIONS OF THE WEST LEADING TO ADDITIONAL HEAVY  
RAINFALL, WITH EVEN SOME EXPANSION NORTHWARD ACROSS THE  
INTERMOUNTAIN WEST AS THE WEEK PROGRESSES.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
WHILE MODEL GUIDANCE IS AGREEABLE WITH THE LARGE SCALE PATTERN AND  
EVOLUTION DESCRIBED ABOVE, DIFFERENCES IN THE DETAILS REMAIN THAT  
DO HAVE IMPACTS ON THE SENSIBLE WEATHER SUCH AS FRONTAL POSITION  
AND RAINFALL PLACEMENT AND AMOUNTS. A SHORTWAVE MOVING ACROSS THE  
NORTH-CENTRAL TO NORTHEASTERN U.S. EARLY IN THE WORKWEEK SHOWS  
NOTABLE MODEL DIFFERENCES. SPECIFICALLY, THE PAST FEW GFS RUNS  
HAVE BEEN QUITE VARIABLE WITH ITS HANDLING OF THE FEATURE, AS THE  
12Z SEEMED REASONABLY CLOSE TO OTHER GUIDANCE THOUGH A BIT  
STRONGER, THE 18Z WAS WEAKER BUT FASTER THAN CONSENSUS, AND NOW  
THE 00Z INDICATES SPLIT ENERGY WITH ONE SHORTWAVE MOVING EVEN  
FASTER ACROSS THE NORTHEAST WHILE ANOTHER LINGERS OVER THE  
NORTH-CENTRAL U.S. MONDAY-TUESDAY. THE ECMWF/UKMET/CMC HAVE SHOWN  
BETTER CONSENSUS AND CONTINUITY WITH THIS FEATURE, SO THE WPC  
FORECAST LEANED MORE TOWARD THAT CLUSTER BUT DID INCLUDE A BIT OF  
THE 12Z AND 18Z GFS RUNS. OTHER THAN THAT, SLIGHT DIFFERENCES IN  
ENERGY AS THE EASTERN TROUGH DEEPENS WERE WELL WITHIN NORMAL  
MEDIUM RANGE SPREAD. MODEL GUIDANCE ALSO HAS REASONABLY GOOD  
AGREEMENT FOR THE UPPER HIGH/RIDGE GRADUALLY SHIFTING EAST THROUGH  
THE WEEK AS WELL. THERE HAS BEEN SOME MODEL VARIABILITY WITH THE  
UPPER LOW OVER THE EASTERN PACIFIC, HOWEVER--IN TERMS OF THE  
12Z/18Z MODEL CYCLE, THE UKMET WAS A LITTLE SLOWER THAN OTHER  
MODELS AND THE ENSEMBLE MEANS. THE 00Z GFS AND CMC TRENDED  
SLIGHTLY SLOWER BUT THE 00Z ECMWF ACTUALLY TRENDED FASTER/FARTHER  
EAST WITH THE TIMING AND TRACK OF THE UPPER LOW NEARING THE  
PACIFIC NORTHWEST AROUND WEDNESDAY, SO THERE IS STILL CONTINUED  
SPREAD. THUS THE WPC FORECAST WAS BASED ON A BLEND FAVORING THE  
12Z ECMWF/CMC WITH LESSER COMPONENTS OF THE GFS/UKMET EARLY IN THE  
PERIOD, WITH INTRODUCTION AND INCREASING PROPORTIONS OF THE  
ENSEMBLE MEANS BY THE LATTER PART OF THE WEEK AMID INCREASING  
UNCERTAINTY WITH THE DETAILS ESPECIALLY IN THE WEST.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
AS THE MEDIUM RANGE PERIOD BEGINS MONDAY, RAIN AND THUNDERSTORMS  
ARE EXPECTED TO STRETCH FROM THE MID-MISSISSIPPI VALLEY ACROSS  
PORTIONS OF THE OHIO VALLEY AND GREAT LAKES REGION TO NORTHERN NEW  
ENGLAND ALONG AND AHEAD OF A COLD FRONT. RAIN AND STORMS WILL  
SHIFT SOUTHEAST EACH DAY AS THE FRONT PROGRESSES, SLIDING ACROSS  
THE EASTERN SEABOARD AND LOWER OHIO/TENNESSEE VALLEYS  
TUESDAY-WEDNESDAY AND LINGERING IN THE SOUTHEAST THURSDAY-FRIDAY.  
SOME HEAVY RAIN RATES AND AMOUNTS COULD LEAD TO POTENTIAL FOR  
FLASH FLOODING IN THESE AREAS, ESPECIALLY OVER SENSITIVE LOCATIONS  
THAT HAVE RECEIVED ABUNDANT RAINFALL RECENTLY, THOUGH SOME  
WAFFLING IN MODEL GUIDANCE LOWERS CONFIDENCE IN THE DETAILS.  
MEANWHILE, MONSOONAL MOISTURE CONTINUES TO IMPACT THE SOUTHWEST  
WITH ENHANCED RAINFALL. ANOTHER WET DAY IS LIKELY ON MONDAY, WITH  
SOME INDICATIONS OF A FOCUS NEAR THE COLORADO/NEW MEXICO BORDER  
(WHERE CONDITIONS ARE ALREADY QUITE WET) THAT HAS PROMPTED A  
SLIGHT RISK ISSUANCE IN THE EXPERIMENTAL DAY 4 ERO. WHILE RAIN  
AMOUNTS MAY GRADUALLY LESSEN IN THIS AREA AS THE WEEK PROGRESSES,  
THE MOISTURE PLUME IS LIKELY TO EXPAND FARTHER NORTH 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 MONDAY INTO THE NORTHERN AND THEN CENTRAL PLAINS AS  
THE WORKWEEK PROGRESSES AND THE UPPER RIDGE AXIS MOVES EAST.  
FARTHER EAST, SLIGHTLY ABOVE AVERAGE HIGHS IN THE  
NORTHEAST/MID-ATLANTIC EARLY IN THE WORKWEEK WILL MODERATE TO  
RIGHT AROUND NORMAL BEHIND THE COLD FRONT, WHILE SOME BELOW NORMAL  
HIGHS ARE POSSIBLE IN THE OHIO AND TENNESSEE VALLEYS. GIVEN THE  
RAINFALL AND CLOUDINESS OVER THE SOUTHWEST AND GREAT BASIN, HIGHS  
ARE LIKELY TO BE SEVERAL DEGREES BELOW NORMAL THERE.  
 
TATE  
 
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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