280  
FXUS02 KWBC 302002  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
401 PM EDT TUE AUG 30 2022  
 
VALID 12Z FRI SEP 02 2022 - 12Z TUE SEP 06 2022  
 
...PROLONGED AND DANGEROUS HEAT WAVE FOR PORTIONS OF THE WESTERN  
U.S. THROUGH THE HOLIDAY WEEKEND...  
 
...HEAVY RAIN THREAT FROM SOUTHERN/SOUTHEAST TEXAS THROUGH THE  
CENTRAL GULF COAST STATES...  
 
   
..OVERVIEW
 
 
IT REMAINS THE CASE THAT ANOMALOUSLY STRONG UPPER RIDGING TO BE  
ONGOING AT THE START OF THE MEDIUM RANGE PERIOD OVER MUCH OF THE  
WEST AND PERSIST THROUGH EARLY NEXT WEEK. THIS WILL SUPPORT VERY  
WARM TO HOT TEMPERATURES IN THAT REGION, WITH POTENTIALLY RECORD  
BREAKING AND DANGEROUS HIGH TEMPERATURES. THE OTHER FOCUS FOR  
SIGNIFICANT WEATHER WILL BE FOUND FROM SOUTHERN/SOUTHEAST TEXAS  
THROUGH THE GULF COAST/SOUTH WHERE INTERACTIONS WITH A STALLING  
FRONTAL BOUNDARY AND DEEPER GULF MOISTURE COULD SPELL A MULTI-DAY  
HEAVY RAINFALL PERIOD LEADING TO SOME FLASH FLOODING. SOME OF THAT  
MOISTURE AND POTENTIAL HEAVY RAIN MAY LIFT NORTHWARD THROUGH THE  
LOWER MISSISSIPPI VALLEY BY LATE IN THE WEEKEND. MEANWHILE,  
SHORTWAVE TROUGHING WILL WORK THROUGH THE MIDWEST/GREAT LAKES AND  
NORTHEAST THIS WEEKEND INTO EARLY NEXT WEEK, BRINGING ANOTHER COLD  
FRONT WITH THUNDERSTORMS.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
COMPOSITE OF REAOSNABLY WELL CLUSTERED MASS FIELD GUIDANCE FROM  
THE 06 UTC GFS AND 00 UTC ECMWF/UKMET/CANADIAN ALONG WITH WPC  
CONTINNUITY AND THE 13 UTC NATIONAL BLEND OF MODELS (NBM) DAYS 3-5  
(FRIDAY-SUNDAY). THE MAIN MODEL QPF FOCUS WAS MORE VARIED OVER  
TEXAS AND THE SOUTH, BUT FAVORABLE SUPPORT AND PROTRACTED THREAT  
POTENTIAL EXISTS ON A ELONGATED AXIS ACROSS THE BROAD REGION GIVEN  
DEEP MOISTURE POOLED NEAR A STALLED AND WAVY FRONT. LATER, A BLEND  
OF THE ECMWF/ECMWF ENSEMBLES SEEMS TO HAVE A BETTER IDEA INTO DAY  
6/7 (LABOR DAY/NEXT TUESDAY). SOMEWHAT ON THE MORE AMPLIFIED SIDE  
OF THE ENVELOPE WITH THE SOUTHWARD DIGGING OF AMPLE SHORTWAVE  
TROUGH ENERGIES THROUGH THE MIDWEST TO THE LEE OF THE AMPLIFIED  
UPPER RIDGE OVER THE WEST. ACCORDINGLY, THE 06/12 UTC GFS SEEM TOO  
WARM OVER THE REGION FOR THIS PERIOD AND OVERALL WPC QPF/POPS WERE  
CREATED AS PER A TARGETTED CHANGE TO THE NBM TO SHOW MUCH MORE  
AREAL COVERAGE AND SOME EMBEDDED CONVECTIVE MAXES FROM THE MIDWEST  
INTO THE EAST.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
AN ANOMALOUSLY STRONG UPPER RIDGE FOR EARLY SEPTEMBER POSITIONED  
OVER THE WESTERN U.S. WILL SUPPORT MUCH ABOVE NORMAL TEMPERATURES  
FRIDAY THROUGH EARLY NEXT WEEK, WITH THE GREATEST DEPARTURES FROM  
NORMAL EXPECTED FROM CALIFORNIA THROUGH THE PACIFIC NORTHWEST,  
GREAT BASIN, AND THE NORTHERN ROCKIES. DAYTIME HIGHS BETWEEN  
10-20F ABOVE NORMAL AND NIGHTTIME LOWS BETWEEN 15-20F ABOVE NORMAL  
ARE LIKELY. THE HOLIDAY WEEKEND LOOKS PARTICULARLY HOT WITH HIGHS  
FROM THE DESERT SOUTHWEST THROUGH THE CALIFORNIA CENTRAL VALLEY  
WELL ABOVE 100 WITH SOME READINGS GREATER THAN 110 WHILE MID TO  
UPPER 90S LIKELY FOR PORTIONS OF THE NORTHERN ROCKIES. WIDESPREAD  
DAILY RECORDS ARE POSSIBLE EACH DAY AND FOR PORTIONS OF DESERT  
SOUTHWEST THROUGH CALIFORNIA, A POTENTIALLY DANGEROUS AND RECORD  
BREAKING HEAT WAVE IS POSSIBLE.  
 
A RESIDUAL FRONTAL BOUNDARY DRAPED ACROSS THE GULF COAST  
INTERACTING WITH FAVORABLE GULF MOISTURE TRANSPORT AND A WEAK  
UPPER LEVEL DISTURBANCE WILL HELP FOCUS WIDESPREAD SHOWERS AND  
THUNDERSTORMS THROUGH THE WEEKEND INTO EARLY NEXT WEEK. FOR  
FRIDAY, THE BEST FOCUS LOOKS TO BE OVER THE FLORIDA PANHANDLE THEN  
THE MOISTURE/DISTURBANCE MOVES WESTWARD TOWARD THE TEXAS GULF  
COAST BY THIS WEEKEND INTO EARLY NEXT WEEK. SOME OF THIS ENERGY  
MAY GET DRAWN NORTHWARD ACROSS THE LOWER MISSISSIPPI VALLEY,  
BRINGING THE THREAT FOR HEAVY RAINFALL NORTHWARD ACROSS PORTIONS  
OF MISSISSIPPI AND ALABAMA THROUGH THE HOLIDAY WEEKEND. OVER THE  
ENTIRE PERIOD, THE GREATEST THREAT FOR MULTI-DAY TOTALS REACHING  
SEVERAL INCHES LOOKS TO BE ACROSS THE TEXAS GULF COAST AND THE  
CENTRAL GULF COAST WITH SLIGHTLY LESS CONFIDENCE FURTHER  
INLAND/NORTH ACROSS THE LOWER MISSISSIPPI VALLEY. A SLIGHT RISK IN  
THE DAY 5 (12Z SAT - 12Z SUN) EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK WAS INTRODUCED GIVEN THE POTENTIAL FOR BOTH INTENSE RAIN  
RATES AND LONGER DURATION HEAVY RAIN THAT COULD LEAD TO FLASH  
FLOODING. SOME OF THESE AREAS HAVE SEEN RECENT HEAVY RAINFALL WITH  
THE LATEST SOIL MOISTURE ANOMALIES WELL ABOVE 90 PERCENT,  
PARTICULARLY ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY.  
THERE DOES REMAIN SOME MEANINGFUL MODEL DIFFERENCES, SO OVERALL  
CONFIDENCE IN SPECIFIC DETAILS AND LOCATIONS OF HEAVY RAIN/FLASH  
FLOODING IS A BIT LOWER NOW, BUT THE ENVIRONMENTAL INGREDIENTS DO  
SUPPORT THE POTENTIAL SOMEWHERE IN THE REGION.  
 
ELSEWHERE, THE COMBINATION OF A WEAKENING WARM FRONT CROSSING THE  
PLAINS AND COLD FRONT PUSHING INTO THE NORTHERN TIER LATE THIS  
WEEK MAY PRODUCE SHOWERS/THUNDERSTORMS OF VARYING INTENSITY FROM  
THE UPPER GREAT LAKES SOUTHWESTWARD WITH SOME THREAT OF LOCALIZED  
HEAVY RAINFALL ACROSS THE UPPER PENINSULA OF MICHIGAN ON FRIDAY  
WHERE SLIGHTLY HIGHER MOISTURE POOLS AHEAD OF THE ADVANCING FRONT.  
AFTER STARTING METEOROLOGICAL FALL WITH A DRIER AIRMASS, THERE  
REMAINS UNCERTAINTY IN THE FORECAST FOR THE EAST COAST BY LATE IN  
THE WEEKEND AND LABOR DAY AS MODEL GUIDANCE HAS TRENDED WETTER  
OVER THE LAST COUPLE OF CYCLES. DEEPER MOISTURE BEING PULLED  
NORTHWARD INTO THE REGION FROM THE GULF BY LABOR DAY INTERACTING  
WITH FAVORABLE UPPER LEVEL DYNAMICS COULD BRING GREATER CHANCES OF  
SHOWERS AND THUNDERSTORMS.  
 
SCHICHTEL/TAYLOR  
 
HAZARDS:  
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST AND THE LOWER  
MISSISSIPPI VALLEY, SAT-SUN, SEP 3-SEP 4.  
- HEAVY RAIN ACROSS PORTIONS OF SOUTHERN TEXAS, SAT-TUE, SEP 3-SEP  
6.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE LOWER  
MISSISSIPPI VALLEY.  
- FLOODING LIKELY ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE PACIFIC NORTHWEST AND THE  
NORTHERN ROCKIES, FRI, SEP 2.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE PACIFIC NORTHWEST, THE  
NORTHERN ROCKIES, THE GREAT BASIN, CALIFORNIA, AND THE SOUTHWEST,  
FRI-TUE, SEP 2-SEP 6.  
 
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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