389  
FXUS02 KWBC 030659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
258 AM EDT SAT SEP 3 2022  
 
VALID 12Z TUE SEP 6 2022 - 12Z SAT SEP 10 2022  
 
***PROLONGED AND SERIOUS HEAT WAVE FOR PORTIONS OF THE WESTERN  
U.S. INTO THE MIDDLE OF NEXT WEEK***  
 
   
..GENERAL OVERVIEW
 
 
THE MAIN WEATHER HEADLINE GOING INTO NEXT WEEK WILL CONTINUE TO BE  
THE ANOMALOUS UPPER LEVEL RIDGE THAT WILL BE ANCHORED ACROSS THE  
WESTERN U.S., AND THUS A CONTINUANCE OF THE ONGOING SERIOUS HEAT  
WAVE FROM THE WEST COAST TO THE NORTHERN PLAINS INTO THE MIDDLE OF  
THE WEEK. SOME GOOD NEWS IS LIKELY ON THE WEATHER HORIZON AS A  
RELATIVELY STRONG SHORTWAVE TROUGH TRIES TO BREAK DOWN THE RIDGE  
ACROSS THE PACIFIC NORTHWEST AND SUPPRESSES THE RIDGE SOME.  
ACROSS THE EASTERN U.S., A BROAD UPPER TROUGH AND POSSIBLY WEAK  
CLOSED LOW WILL LIKELY BE IN PLACE FOR MUCH OF THE WEEK ACROSS THE  
EAST-CENTRAL U.S., AND MOISTURE FROM A TROPICAL DISTURBANCE MAY  
BEGIN APPROACHING THE SOUTHWESTERN U.S. BY THE END OF THE WEEK.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE 00Z MODEL GUIDANCE SUITE INITIALLY HAS A GOOD OVERALL SYNOPTIC  
SCALE DEPICTION OF THE OVERALL PATTERN ON TUESDAY. NOTEWORTHY  
TIMING DIFFERENCES ARE APPARENT BY THURSDAY WITH THE GFS BECOMING  
MORE PROGRESSIVE WITH THE TROUGH ACROSS THE NORTHWESTERN U.S., AND  
LOSES SUPPORT FROM ITS OWN ENSEMBLE MEAN. FORECAST CONFIDENCE IS  
WELL BELOW AVERAGE FOR THE FRIDAY THROUGH SATURDAY TIME PERIOD  
WITH POOR MODEL RUN-TO-RUN CONTINUITY OVER THE PAST 24 HOURS, AND  
FUTURE FORECASTS ARE SUBJECT TO SIGNIFICANT REVISIONS ONCE THE  
MODELS COME INTO BETTER ALIGNMENT. TELECONNECTIONS WITH THE  
GEFS/ECENS POSITIVE HEIGHT ANOMALY CENTERS FAVORED A SCENARIO  
CLOSER TO THE ECMWF FOR FRONTS/PRESSURES, AND TAKING THESE FACTORS  
INTO ACCOUNT, THE WPC FRONTS/PRESSURES FORECAST WAS PRIMARILY  
DERIVED FROM A MULTI-MODEL CONSENSUS THROUGH EARLY WEDNESDAY,  
FOLLOWED BY A GRADUAL INCREASE OF THE ENSEMBLE MEANS WHILST STILL  
KEEPING SOME OF THE ECMWF TO ACCOUNT FOR INCREASING UNCERTAINTIES  
BY THE END OF THE WEEK.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
IT WILL CONTINUE TO BE VERY HOT BY EARLY SEPTEMBER STANDARDS  
ACROSS MOST OF THE WESTERN U.S. AND EXTENDING ACROSS MUCH OF THE  
NORTHERN PLAINS AND EVEN INTO THE UPPER MIDWEST THROUGH THE MIDDLE  
OF THE WEEK. AFTERNOON HIGHS ARE EXPECTED TO BE ON THE ORDER OF  
10-20 DEGREES ABOVE AVERAGE, AND THE SAME HOLDS TRUE FOR OVERNIGHT  
LOWS, PROVIDING ONLY LIMITED RESPITE FROM THE HEAT. THIS WILL  
EQUATE TO HIGHS OF 105-115 DEGREES FOR THE LOWER ELEVATIONS OF THE  
DESERT SOUTHWEST AND EVEN THE CENTRAL VALLEY OF CALIFORNIA, AND  
WIDESPREAD 90S AND EVEN LOW 100S FOR THE INTERMOUNTAIN WEST, AND  
WELL INTO THE 90S EXTENDING NORTHEAST ACROSS MONTANA AND THE  
DAKOTAS. MULTIPLE DAILY RECORD HIGH TEMPERATURES ARE EXPECTED  
ACROSS THESE AREAS. ANOTHER FACTOR TO CONSIDER IS THE DURATION OF  
THE HEAT WAVE SINCE IT WILL BE VERY HOT DURING THE SHORT RANGE  
PERIOD AS WELL. THIS WILL INCREASE HEAT STRESS FOR THOSE WORKING  
OUTDOORS AND FOR THOSE WITHOUT AIR CONDITIONING. IT IS  
INTERESTING TO NOTE THERE WILL LIKELY BE VERY LITTLE IN THE WAY OF  
BELOW AVERAGE LOW TEMPERATURES ANYWHERE ACROSS THE CONTINENTAL  
U.S. NEXT WEEK, ALTHOUGH HIGHS MAY RUN SEVERAL DEGREES BELOW  
AVERAGE ACROSS PORTIONS OF THE SOUTH AND GULF COAST REGION OWING  
TO INCREASED CLOUDS AND RAINFALL.  
 
IN TERMS OF RAINFALL, A QUASI-STATIONARY FRONTAL BOUNDARY DRAPED  
ACROSS THE SOUTHERN TIER STATES WITH WAVES OF LOW PRESSURE ALONG  
IT, ALONG WITH A BROAD UPPER LEVEL TROUGH, WILL BE THE GENERAL  
FOCUS FOR MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS. THIS IS  
EXPECTED TO EXTEND FROM TEXAS AND DEEP SOUTH, TO THE APPALACHIANS  
AND MID-ATLANTIC/NORTHEAST. A SLIGHT RISK OF EXCESSIVE RAINFALL  
EXISTS ACROSS PORTIONS OF DEEP SOUTH TEXAS ON DAY 4 WITH THE  
POTENTIAL OF 1-2 INCHES OF RAINFALL ATOP ALREADY SATURATED SOILS  
BY THIS TIME. THE TROPICS ARE ALSO EXPECTED TO BECOME MORE ACTIVE  
BY THE END OF THE WEEK WITH A POSSIBLE DISTURBANCE MOVING INLAND  
ACROSS WESTERN MEXICO AND POTENTIALLY BRINGING A SURGE OF MOISTURE  
NORTHWARD TO NEW MEXICO AND TEXAS LATE IN THE PERIOD.  
 
HAMRICK  
 
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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