371  
FXUS02 KWBC 290638  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
238 AM EDT MON AUG 29 2022  
 
VALID 12Z THU SEP 01 2022 - 12Z MON SEP 05 2022  
   
..OVERVIEW
 
 
AT THE START OF THE MEDIUM RANGE PERIOD, THE FLOW PATTERN IS  
EXPECTED TO STILL BE FAIRLY AMPLIFIED WITH STRONG RIDGING THROUGH  
THE INTERIOR WEST WHILE TROUGHING IS FORECAST OVER THE GREAT LAKES  
AND NORTHEAST AND EASTERN PACIFIC. UNDER THE STRONG WESTERN RIDGE,  
TEMPERATURES ARE FORECAST TO BE QUITE WARM WITH DAILY HIGH RECORDS  
POSSIBLE MID TO LATE WEEK. BY LATE THIS WEEK INTO NEXT WEEKEND,  
THE FLOW IS THEN FORECAST TO BECOME MORE ZONAL AND FLATTEN OUT,  
ALLOWING SHORTWAVE ENERGY TO MOVE ACROSS THE NORTHERN CONUS.  
MEANWHILE, ACROSS THE SOUTHERN U.S., A FRONTAL BOUNDARY IS  
EXPECTED TO SETTLE ALONG THE GULF COAST AND BE THE PRIMARY FOCUS  
FOR SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS EACH DAY. SOME  
OF THE RAINFALL COULD BE LOCALLY HEAVY AND WITH SEVERAL DAYS OF  
POTENTIALLY REPEATING ROUNDS, SOME FLASH FLOODING MAY BECOME  
POSSIBLE LATE THIS WEEK INTO THIS WEEKEND FROM THE TEXAS GULF  
COAST TO THE FLORIDA PANHANDLE.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE AMPLIFIED PATTERN AT THE START OF THE PERIOD HAS VERY GOOD  
AGREEMENT AMONG THE VARIOUS DETERMINISTIC MODELS THIS CYCLE WITH  
THE STRONG RIDGE EXPECTED TO BE CENTERED OVER THE GREAT BASIN  
THROUGH THIS WEEKEND. A SHORTWAVE TROUGH EJECTING OUT OF THE  
EASTERN PACIFIC TROUGHING WILL CLIP THE PACIFIC NORTHWEST AND  
WHILE EARLIER RUNS OF THE GFS/ECMWF/UKMET/CMC HAD SOME TIMING  
ISSUES, THE LATEST GUIDANCE HAS CLUSTERED VERY WELL. BY DAY 5  
HOWEVER, THE GFS IS A BIT FLATTER WITH THE ENERGY AS IT MOVES INTO  
THE NORTHERN PLAINS WHILE THE ECMWF AND CMC DIG A SHORTWAVE INTO  
THE DAKOTAS. MEANWHILE, THE GFS IS ALSO FASTER WITH PUSHING THE  
TROUGH AXIS IN THE EASTERN PACIFIC THROUGH THE PACIFIC NORTHWEST,  
ESPECIALLY BY DAYS 6-7 WHEN THE GFS NEARLY BECOMES OUT OF PHASE  
WITH THE ECMWF/CMC SOLUTIONS, WHICH HOLDS THE EASTERN PACIFIC  
TROUGHING BACK. WHILE NOT ENTIRELY DISCOUNTING THE GFS IDEA, WILL  
LEAN MORE ON THE ENSEMBLE MEANS WHICH ARE SLOWER WITH ANY ENERGY  
MOVING INTO THE PACIFIC NORTHWEST BY DAY 7.  
 
THE OTHER AREA OF MODEL DIFFERENCES IS ACROSS THE GULF COAST WITH  
RESPECT TO THE STATIONARY/RESIDUAL BOUNDARY THAT INTERACTS WITH  
GULF MOISTURE. THE FOCUS FOR WIDESPREAD SHOWERS AND THUNDERSTORMS  
WILL LIKELY BE FOUND INITIALLY OVER THE FLORIDA PANHANDLE AND  
SOUTHERN PLAINS LATER THIS WEEK THEN SHIFT TOWARD THE TEXAS GULF  
COAST THIS WEEKEND INTO EARLY NEXT WEEK AS A STRONG FETCH OF  
MOISTURE TRANSPORT IMPINGES ON THAT BOUNDARY. WITH ANOMALOUSLY  
HIGH PWS FORECAST (NEAR 90TH PERCENTILE AND 2 SIGMA ABOVE NORMAL),  
FORECAST MODELS SHOW POTENTIAL FOR SEVERAL INCHES OVER THE PERIOD  
BUT THE CONVECTIVE/MESOSCALE NATURE EXPECTED LIMITS CONFIDENCE AND  
DETAILS AT THIS TIME.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE START OF METEOROLOGICAL FALL WILL FEEL VERY FALL-LIKE FOR THE  
EASTERN U.S., IN THE WAKE OF THE MID-WEEK FRONTAL PASSAGE.  
CANADIAN HIGH PRESSURE BUILDING IN ITS WAKE WILL PROVIDE  
SEASONABLE TEMPERATURES, LESS HUMIDITY, AND DRY CONDITIONS.  
MORNING LOWS MAY DIP INTO THE 40S AND 50S ACROSS THE GREAT LAKES  
AND INTERIOR NORTHEAST THURSDAY AND FRIDAY MORNINGS. THE FRONTAL  
BOUNDARY IS THEN EXPECTED TO SETTLE ALONG THE GULF COAST AND ITS  
INTERACTION WITH AMPLE INSTABILITY AND MOISTURE WILL BE ENOUGH OF  
A LIFT/FOCUS FOR SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS  
ACROSS THE FLORIDA PANHANDLE THURSDAY INTO THE WEEKEND. MEANWHILE,  
A WEAKNESS IN THE UPPER RIDGE OVER TEXAS AND ITS INTERACTION WITH  
THE TAIL OF THE FRONTAL BOUNDARY WILL PROVIDE FOCUS FOR MORE  
THUNDERSTORMS AND BENEFICIAL RAINFALL OVER TEXAS. SOME OF THIS  
RAINFALL COULD BE LOCALLY HEAVY WITH INTENSE RAIN RATES. BY THIS  
WEEKEND, A SURGE OF GULF MOISTURE INTERACTING WITH THE FRONT IN  
THE AREA WILL BRING GREATER CHANCES OF WIDESPREAD PRECIPITATION TO  
THE TEXAS GULF COAST EASTWARD TO THE FLORIDA PANHANDLE. SOME OF  
THIS RAINFALL MAY BE HEAVY AND WITH REPEATING DAYS OF RAINFALL,  
SOME CONCERN FOR FLASH FLOODING MAY DEVELOP BY LATE IN THE WEEKEND  
INTO EARLY NEXT WEEK. OVER THE PERIOD, RAINFALL TOTALS COULD BE  
SEVERAL INCHES, PARTICULARLY ALONG THE TEXAS GULF COAST.  
 
MEANWHILE, THE REST OF THE COUNTRY LOOKS TO BE MAINLY DRY ASIDE  
FROM LIGHT RAIN CHANCES ACROSS CENTRAL PARTS OF THE ROCKIES/PLAINS  
AND A FRONTAL PASSAGE CLIPPING THE NORTHWEST. HOWEVER, THE MAIN  
STORY FOR THE WEST TO NORTHERN PLAINS WILL BE THE WARMTH. HIGHS  
LATER THIS WEEK INTO THE WEEKEND ARE EXPECTED TO BE 10-20F ABOVE  
NORMAL FOR EARLY SEPTEMBER WITH THE POTENTIAL FOR DAILY RECORD  
HIGHS FOR PORTIONS OF THE INTERIOR WEST. SOME LOCATIONS COULD EVEN  
FLIRT WITH MONTHLY TEMPERATURE RECORDS. THOSE WARM TEMPERATURES  
ARE THEN EXPECTED TO SPREAD EASTWARD TO THE NORTHEAST BY SUNDAY  
INTO MONDAY WITH HIGHS AS MUCH AS 10F ABOVE NORMAL.  
 
TATE/TAYLOR  
 
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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