274  
FXUS02 KWBC 042005  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
405 PM EDT THU AUG 04 2022  
 
VALID 12Z SUN AUG 07 2022 - 12Z THU AUG 11 2022  
 
...MONSOONAL PATTERN REMAINS ACTIVE ACROSS THE SOUTHWEST WITH  
ADDITIONAL HEAVY RAINFALL LIKELY...  
 
   
..OVERVIEW
 
 
GUIDANCE AGREES ON AN EVENTUAL AMPLIFYING TREND TO THE UPPER  
PATTERN NEXT WEEK. GENERAL UPPER RIDGING OVER MUCH OF THE  
CENTRAL/SOUTHERN LOWER 48 SUNDAY-MONDAY SHOULD BUILD MORE STRONGLY  
OVER PARTS OF THE ROCKIES/PLAINS BY MID-LATE WEEK. THIS EVOLUTION  
COMBINED WITH RIDGING DOWNSTREAM FROM A MEAN TROUGH OVER ALASKA  
SHOULD SUPPORT GRADUAL TROUGH AMPLIFICATION OVER EASTERN NORTH  
AMERICA. AN UPPER LOW OFF THE WEST COAST WILL LIKELY LIFT  
NORTHWARD AND MAY BRUSH THE PACIFIC NORTHWEST AROUND  
WEDNESDAY-THURSDAY. THE MOST PROMINENT AREAS OF POTENTIALLY  
SIGNIFICANT RAINFALL WILL BE WITHIN THE PERSISTENT MONSOONAL  
MOISTURE SHIELD OVER THE WEST AND ALONG/AHEAD OF A COLD FRONT  
PUSHING SOUTHEASTWARD FROM THE UPPER GREAT LAKES/CENTRAL PLAINS TO  
THE EAST COAST/MID-SOUTH. THE PATTERN TRANSITION WILL LEAD TO A  
COOLER TREND FROM INITIAL HEAT OVER THE EASTERN HALF OF THE  
COUNTRY, ALONG WITH A SHIFT OF VERY WARM TO HOT WEATHER FROM THE  
NORTHWEST INTO THE NORTHERN HALF OF THE PLAINS.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
AS HAS BEEN THE CASE LATELY, THERE ARE SOME DETAIL DIFFERENCES  
WITHIN THE MORE AGREEABLE LARGE SCALE EVOLUTION. THE MOST  
SIGNIFICANT ONE APPEARS TO BE WITH THE SHORTWAVE CROSSING THE  
NORTHERN TIER EARLY IN THE WEEK, AFFECTING THE STRENGTH/TRACK OF  
AN ASSOCIATED FRONTAL WAVE AS WELL AS THE CORRESPONDING RAINFALL  
PATTERN. RECENT GFS RUNS HAVE BEEN DEEPER THAN OTHER MODELS AND  
HAVE EVEN DEPICTED AN EMBEDDED CLOSED LOW AT SOME VALID TIMES.  
THIS RESULTS IN A DEEPER/NORTHWARD SURFACE WAVE IN THE GFS. THE  
NEW 12Z RUN IS STILL ON THE DEEP SIDE ALOFT BUT HAS PARTIALLY  
TRENDED TOWARD THE REMAINING GUIDANCE. AFTER TUESDAY THERE IS  
FAIRLY TYPICAL SPREAD WITH ENERGY THAT REACHES THE EAST, AS WELL  
AS FOR AN UPSTREAM SOUTHERN CANADA SYSTEM THAT ULTIMATELY FEEDS  
INTO THE DEVELOPING EASTERN NORTH AMERICA MEAN TROUGH. FARTHER  
WEST THE GFS/GEFS END UP A BIT EAST OF THE ECMWF/CMC AND THEIR  
MEANS WITH THE ROCKIES-PLAINS UPPER RIDGE BY NEXT THURSDAY BUT ALL  
OF THESE SOLUTIONS ARE WITHIN TYPICAL GUIDANCE ERROR RANGES THAT  
FAR OUT IN TIME. FINALLY, A COMPROMISE TIMING LOOKS GOOD FOR THE  
EASTERN PACIFIC UPPER LOW THAT SHOULD EJECT NORTHEASTWARD BY  
MID-LATE WEEK. 12Z/06Z GFS RUNS TRENDED FASTER TOWARD THE 00Z  
ECMWF BUT THE NEW 12Z UKMET IS SLOWER THROUGH THE END OF ITS RUN  
EARLY WEDNESDAY. BASED ON THE CURRENT GUIDANCE ARRAY, THE UPDATED  
FORECAST STARTED WITH A 00Z/06Z OPERATIONAL MODEL COMPOSITE FOR  
THE FIRST HALF OF THE PERIOD. THIS INCLUDED SLIGHTLY LESS THAN  
TYPICAL GFS INPUT DUE TO QUESTION MARKS FOR ITS NORTHERN TIER  
EVOLUTION. THE BLEND TRANSITIONED TO A MODEL/ENSEMBLE MEAN MIX  
LATER IN THE PERIOD TO YIELD AN INTERMEDIATE SOLUTION, BALANCING  
THE GOOD PATTERN AGREEMENT BUT SOME DECREASE IN CONFIDENCE FOR  
SPECIFICS.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE SOUTHWEST AND FOUR CORNERS REGION WILL BE ONE AREA OF FOCUS  
FOR EPISODES OF POTENTIALLY HEAVY RAINFALL AND FLASH FLOODING WITH  
PERSISTENCE OF MONSOONAL MOISTURE. THE BEST POSSIBILITY OF  
ENHANCED RAINFALL OVER COLORADO/NEW MEXICO MAY BE AROUND  
SUNDAY-MONDAY FOLLOWED BY A LIGHTER RAINFALL TREND/SOUTHWARD  
SUPPRESSION OF MOISTURE. THE SOUTHWEST SHOULD SEE PERIODS OF RAIN  
DURING MOST OF THE PERIOD WHILE THE LARGE SCALE PATTERN EVOLUTION  
MAY PROMOTE A NORTHWARD EXPANSION OF MOISTURE/RAINFALL INTO THE  
GREAT BASIN BY MIDWEEK WITH SOME LOCALLY HEAVY TOTALS POSSIBLE  
HERE AS WELL. SOME SLIGHT RISK AREAS ARE DEPICTED IN THE  
EXPERIMENTAL DAYS 4-5 EXCESSIVE RAINFALL OUTLOOKS GIVEN GUIDANCE  
SIGNALS FOR HEAVY RAINFALL POTENTIAL AND ALREADY WET GROUND  
CONDITIONS. MEANWHILE, EXPECT A FAIRLY BROAD AREA OF RAINFALL TO  
PUSH STEADILY SOUTH AND EAST FROM THE UPPER GREAT LAKES/MIDWEST  
WITH TIME AS A SUPPORTING COLD FRONT PUSHES INTO THE EAST. IT IS  
LIKELY THAT SOME LOCATIONS WILL SEE A PERIOD OF HEAVY RAINFALL  
WITH THIS FRONT. INSTABILITY AND DEEP MOISTURE SUPPORTED  
MAINTENANCE OF THE SLIGHT RISK AREA FOR EXCESSIVE RAINFALL OVER  
PARTS OF THE UPPER GREAT LAKES/MIDWEST, THOUGH SOME LINGERING  
UNCERTAINTY EXISTS FOR SPECIFICS.  
 
VERY WARM TO HOT TEMPERATURES OVER THE NORTHWEST FROM SUNDAY INTO  
THE EARLY PART OF NEXT WORK WEEK WILL SHIFT OVER INTO AN  
INCREASING PORTION OF THE NORTHERN HALF OF THE PLAINS BY  
TUESDAY-THURSDAY. HIGH TEMPERATURES MAY REACH UP TO 10-15F OR SO  
ABOVE NORMAL AT SOME AREAS. THESE VALUES SHOULD BE BELOW DAILY  
RECORDS EXCEPT PERHAPS FOR A FEW ISOLATED LOCATIONS. MEANWHILE  
VERY WARM TO HOT WEATHER INITIALLY FROM THE MIDWEST THROUGH  
NORTHEAST/MID-ATLANTIC WILL TREND COOLER OVER THE COURSE OF THE  
WEEK AS COOL TEMPERATURES OVER THE NORTHERN PLAINS ON SUNDAY  
(HIGHS UP TO 10F OR SO BELOW NORMAL) SPREAD SOUTHEASTWARD WITH  
TIME. THIS TREND SHOULD YIELD NEAR TO SLIGHTLY BELOW NORMAL HIGHS  
OVER MUCH OF THE EAST BY NEXT THURSDAY. THE MONSOONAL  
MOISTURE/RAINFALL OVER THE SOUTHWEST AND VICINITY WILL TEND TO  
KEEP HIGHS SEVERAL DEGREES BELOW NORMAL ON MOST DAYS.  
 
RAUSCH  
 
HAZARDS:  
- HEAVY RAIN ACROSS PORTIONS OF THE GREAT LAKES, MIDWEST, AND OHIO  
VALLEY, SUN-MON, AUG 7-AUG 8.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN  
APPALACHIANS, OHIO VALLEY, AND TENNESSEE VALLEY, TUE-WED, AUG  
9-AUG 10.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL HIGH PLAINS AND  
CENTRAL AND SOUTHERN ROCKIES, SUN-MON, AUG 7-AUG 8.  
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHWEST, SUN-THU, AUG 7-AUG  
11.  
- HEAVY RAIN ACROSS PORTIONS OF THE GREAT BASIN, TUE-THU, AUG  
9-AUG 11.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI  
VALLEY AND THE OHIO VALLEY.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE OHIO  
VALLEY AND THE NORTHERN PLAINS.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE CENTRAL PLAINS AND THE  
MIDDLE MISSISSIPPI VALLEY, SUN, AUG 7.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE SOUTHERN PLAINS AND THE  
LOWER MISSISSIPPI VALLEY, SUN-TUE, AUG 7-AUG 9.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE NORTHEAST, SUN-MON, AUG  
7-AUG 8.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE PACIFIC NORTHWEST AND THE  
NORTHERN GREAT BASIN, MON-TUE, AUG 8-AUG 9.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE NORTHERN HIGH PLAINS,  
TUE-THU, AUG 9-AUG 11.  
 
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