191  
FXUS02 KWBC 031901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT SAT SEP 03 2022  
 
VALID 12Z TUE SEP 06 2022 - 12Z SAT SEP 10 2022  
 
...PROLONGED HEAT WAVE ACROSS MUCH OF THE WEST WILL LAST THROUGH  
THE MIDDLE OF NEXT WEEK...  
 
   
..OVERVIEW
 
 
A STRONG UPPER LEVEL HIGH WILL BE ANCHORED OVER THE CENTRAL GREAT  
BASIN THROUGH MUCH OF NEXT WEEK, PROMOTING CONTINUED EXCESSIVE  
HEAT ACROSS MUCH OF THE WEST AND INTO THE NORTHERN PLAINS THAT  
COULD BE RECORD BREAKING. THE HEAT WAVE IS EXPECTED TO GRADUALLY  
RECEDE ESPECIALLY ACROSS THE NORTHWEST DURING THE LATTER HALF OF  
NEXT WEEK AS AN ENERGETIC TROUGH COMES IN AND SUPPRESSES THE  
RIDGE/HIGH. MEANWHILE A BROAD UPPER TROUGH WITH EMBEDDED ENERGY  
AND A WEAK CLOSED LOW AT TIMES WILL PERSIST ACROSS THE EAST, ALONG  
WITH A COUPLE OF FRONTAL BOUNDARIES THAT COULD ENHANCE CHANCES FOR  
RAIN AND THUNDERSTORMS, PARTICULARLY IN THE MID-ATLANTIC ON  
TUESDAY AND SPREADING FROM SOUTHERN TEXAS ACROSS THE GULF COAST  
AND SOUTHEAST THROUGH THE WEEK. ADDITIONAL MOISTURE MAY APPROACH  
THE SOUTHWESTERN U.S. BY THE END OF NEXT WEEK STREAMING IN FROM  
TROPICAL SYSTEM THAT IS LIKELY TO FORM TO THE SOUTH IN THE EASTERN  
PACIFIC AND TRACK NEAR BAJA CALIFORNIA.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
GOOD MODEL AGREEMENT IS PRESENT AT THE BEGINNING OF THE PERIOD  
TUESDAY WITH THE 594+DM UPPER HIGH AT 500MB AND THE HIGH REMAINING  
CENTERED AROUND THE CENTRAL GREAT BASIN THROUGH AT LEAST  
WEDNESDAY, WITH MORE GUIDANCE THAN NOT NOW SHOWING IT PERSISTING  
THERE INTO THURSDAY. THE DETAILS OF ITS SUPPRESSION GO AWRY BY  
THURSDAY-SATURDAY AS IT DEPENDS ON THE FLOW FARTHER NORTH,  
SPECIFICALLY A SHORTWAVE TROUGH COMING INTO THE NORTHWEST PROBABLY  
THURSDAY, SLOWER THAN A DAY OR SO AGO. GFS RUNS AND MANY GEFS  
MEMBERS INDICATE THIS SHORTWAVE AS WEAKER AND FASTER THAN OTHER  
GUIDANCE, AS THEY SPLIT OFF SOME OF THE ENERGY AND HAVE IT SPIN IN  
THE PACIFIC SEPARATE FROM THE MAIN JET. THE 00Z ECMWF AND CMC  
APPEARED CLUSTERED WELL AND WERE WELL ALIGNED WITH THE EC MEAN  
WITH ITS TIMING, WHILE THE UKMET WAS ON THE SLOWER AND STRONGER  
SIDE. THUS THE MIDDLE GROUND ECMWF/CMC/EC MEAN WAS FAVORED FOR THE  
TIMING OF THIS SHORTWAVE, AND FOR SHOWING SOME QPF ACROSS THE  
NORTHWESTERN U.S. ASSOCIATED WITH THIS TROUGH WHILE GFS-BASED  
SOLUTIONS WERE DRY THERE. BUT THIS REMAINS A QUITE UNCERTAIN  
FEATURE GIVEN THE MODEL DISAGREEMENTS AND THE ENERGY'S ORIGINS  
NEAR/OVER SIBERIA. THE INCOMING 12Z MODELS SHOW ADDITIONAL  
DIVERGENCE IN SOLUTIONS AS THE CMC IS SLOWER THAN ITS PREVIOUS RUN  
WHILE THE ECMWF IS FASTER. SO ADDITIONAL FORECAST ADJUSTMENTS ARE  
LIKELY WITH TIME. THIS PARTICULAR FORECAST ENDED UP SLIGHTLY  
FASTER WITH THE ASSOCIATED COLD FRONT SATURDAY IN THE  
NORTH-CENTRAL U.S. COMPARED TO THE PREVIOUS WPC FORECAST.  
 
MEANWHILE IN THE EAST, THERE IS GENERAL MODEL AGREEMENT FOR UPPER  
TROUGHING WITH AN AXIS IN THE EAST-CENTRAL U.S. AND POTENTIALLY  
SOME OCCASIONAL RIDGING FOR FLORIDA/THE CAROLINA COAST. THE  
DETAILS OF EMBEDDED ENERGY IN THE TROUGH ARE LESS CERTAIN, BUT  
MODELS HAVE COME INTO BETTER AGREEMENT WITH AN UPPER LOW CLOSING  
OFF IN THE LOWER MISSISSIPPI VALLEY/SOUTHEAST ON THURSDAY AND  
LINGERING INTO THE END OF THE WEEK.  
 
THUS THE WPC FORECAST USED A MULTI-MODEL DETERMINISTIC BLEND EARLY  
IN THE PERIOD, TRANSITIONING TOWARD A BLEND FAVORING THE ECMWF/EC  
MEAN/CMC ALONG WITH A BIT OF THE GEFS MEAN FOR THE AFOREMENTIONED  
REASONS. THIS LED TO REASONABLE CONTINUITY WITH THE PREVIOUS  
FORECAST ESPECIALLY CONSIDERING THE BELOW AVERAGE MODEL CONFIDENCE  
BY THE END OF THE PERIOD.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
CONSIDERABLY HOT TEMPERATURES PARTICULARLY BY SEPTEMBER STANDARDS  
ARE FORECAST TO CONTINUE INTO THE WORKWEEK FROM CALIFORNIA THROUGH  
THE GREAT BASIN INTO CENTRAL/NORTHERN PORTIONS OF THE ROCKIES AND  
HIGH PLAINS. HIGH AND LOW TEMPERATURES OF 10-25F ABOVE AVERAGE  
WILL BE WIDESPREAD THROUGH AT LEAST WEDNESDAY, AS ACTUAL  
TEMPERATURES OF 110+ ARE FORECAST FOR THE DESERT SOUTHWEST AND  
CALIFORNIA'S CENTRAL VALLEY, WHILE WIDESPREAD 90S AND SOME 100S  
ARE EXPECTED ACROSS THE INTERMOUNTAIN WEST INTO THE NORTHERN HALF  
OF THE PLAINS. MULTIPLE DAILY RECORDS WILL BE SET, WITH SOME  
SEPTEMBER MONTHLY RECORDS POSSIBLE AS WELL. THE MAGNITUDE AND  
DURATION OF THE DANGEROUS HEAT WILL BOTH BE CONTRIBUTORS TO  
POTENTIAL SAFETY CONCERNS FOR SENSITIVE GROUPS SUCH AS THE  
ELDERLY, THOSE WORKING OUTSIDE, AND THOSE WITHOUT AIR  
CONDITIONING. TEMPERATURES ARE EXPECTED TO MODERATE NEARER TO  
NORMAL IN THE NORTHWEST BY THURSDAY, BUT MAY REMAIN MUCH ABOVE  
NORMAL FOR CALIFORNIA STRETCHING INTO THE NORTHERN PLAINS,  
GRADUALLY MODERATING ON FRIDAY AND SATURDAY. MEANWHILE, SLIGHTLY  
BELOW NORMAL HIGHS AND AROUND NORMAL LOWS ARE EXPECTED FOR  
PORTIONS OF TEXAS INTO THE SOUTHEAST GIVEN THE CLOUDY AND SHOWERY  
FORECAST. PARTS OF THE NORTHEAST COULD SEE HIGHS THAT ARE BELOW  
NORMAL BY A FEW DEGREES ON TUESDAY, BEFORE GRADUALLY WARMING TO  
ABOVE NORMAL THROUGH THE WEEK.  
 
A MEANDERING FRONTAL BOUNDARY IS LIKELY TO STAY DRAPED ALONG THE  
GULF COAST INTO SOUTHERN TEXAS THROUGH THE WEEK, WHICH COMBINED  
WITH GULF MOISTURE WILL PRODUCE CONTINUED SHOWERS AND  
THUNDERSTORMS, ALONG WITH SOME POTENTIAL FOR FLOODING ISSUES GIVEN  
THE RECENT WET PATTERN. THE RECENT FORECAST/MODELS SHOW A TREND  
TOWARD THE RAINFALL FOCUS SPREADING INTO THE CENTRAL/EASTERN GULF  
COAST THROUGH THE LATTER PART OF THE WEEK (WITH REDUCED AMOUNTS IN  
TEXAS AS THE FRONT PUSHES SOUTH), WHILE SHOWERS AND THUNDERSTORMS  
COULD ALSO INCREASE IN COVERAGE ACROSS THE SOUTHEAST AND SOUTHERN  
APPALACHIANS. BY THE END OF THE PERIOD, A SURGE OF INCREASED  
MOISTURE MAY ARRIVE IN THE SOUTHWEST IN CONJUNCTION WITH A  
TROPICAL SYSTEM TO THE SOUTH THAT HAS GOOD LIKELIHOOD OF FORMING  
PER THE NATIONAL HURRICANE CENTER.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page