622  
FXUS02 KWBC 081753  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
152 PM EDT THU SEP 08 2022  
 
VALID 12Z SUN SEP 11 2022 - 12Z THU SEP 15 2022  
   
..GENERAL OVERVIEW
 
 
A PATTERN CHANGE WILL BE UNDERWAY ACROSS MUCH OF THE ROCKIES AND  
THE CENTRAL/NORTHERN PLAINS INTO THE MIDWEST AS A STRONG COLD  
FRONT HERALDS A CHANGE TO MUCH COOLER TEMPERATURES FOR THE  
WEEKEND, COMPARED TO THE ANOMALOUS WARM WEATHER PRESENTLY. THE  
UPPER TROUGH THAT IS ACCOMPANYING THIS FRONT IS FORECAST TO EVOLVE  
INTO A SLOW MOVING CLOSED UPPER LOW ACROSS THE OHIO VALLEY AND  
GREAT LAKES REGION BY EARLY MONDAY, WITH A RIDGE AXIS NEAR THE  
EAST COAST SLOWING ITS EASTWARD PROGRESSION, AND MOISTURE AHEAD OF  
THIS FEATURE MAY BRING LOCALLY HEAVY RAINFALL TO THE PORTIONS OF  
THE SOUTHEAST AND MID-ATLANTIC LATE THIS WEEKEND INTO EARLY NEXT  
WEEK. MOISTURE ASSOCIATED WITH WHAT WILL EVENTUALLY BE THE  
REMNANTS OF HURRICANE KAY IS EXPECTED TO ADVECT INLAND ACROSS  
CALIFORNIA AND THE GREAT BASIN, ALBEIT WITH LIGHTER RAINFALL BY  
THIS TIME. THERE WILL LIKELY BE ANOTHER TROUGH APPROACHING THE  
PACIFIC NORTHWEST BY THE MIDDLE OF THE WEEK.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
OVERALL, THE MODEL GUIDANCE WAS IN REASONABLY GOOD AGREEMENT AND  
SHOWED DECENT CONSISTENCY AND CONTINUITY FROM THE PREVIOUS  
FORECAST CYCLE. THE TWO AREAS OF MOST MODEL CONCERN WERE THE  
DEVELOPING CLOSED MID/UPPER LOW OVER THE OHIO VALLEY AND IT'S  
LONGITUDINAL POSITION. THE CMC REMAINS A SLOWER/WEST SOLUTION  
COMPARED TO THE CONSENSUS WHILE THE GFS MAY BE SLIGHTLY AHEAD OF  
THE CONSENSUS BUT WELL WITHIN TOLERABLE RANGE. THERE ARE MORE  
SENSIBLE WEATHER DIFFERENCES/POTENTIAL IMPACTS THOUGH, AS A SURGE  
OF MOISTURE LIFTING OUT AHEAD OF IT MAY RESULT IN A HEAVY RAINFALL  
EVENT SOMEWHERE OVER THE SOUTHEAST TO MID-ATLANTIC (AND  
POTENTIALLY NORTHEAST) LATER IN THE PERIOD. THE OTHER AREA OF  
CONCERN WAS THE DEVELOPING LONGWAVE TROUGH OVER THE WESTERN U.S.  
THAT ADVANCES LATER THIS WEEKEND INTO NEXT WEEK, HELPING TO BREAK  
DOWN THE STRONG/ANOMALOUS UPPER RIDGE THAT HAS BEEN IN PLACE OVER  
THE WEST. THE TYPICAL MODEL BIASES WERE SEEN HERE, SO OVERALL  
USING A MULTI-MODEL CONSENSUS/BLEND WAS FAVORED AND THIS LED TO  
GOOD CONTINUITY FROM OVERNIGHT AND ADJUSTS WELL TO THE LATEST  
MODEL TRENDS. OVERALL, THE BLEND INCORPORATED THE 13Z NBM WITH  
INCLUSION OF THE 00Z/06Z GFS, 00Z ECMWF, 00Z CMC, AND 00Z UKMET  
FOR PRESSURES/FRONTS AND MAINLY A COMBINATION OF THE 13Z NBM AND A  
MULTI-MODEL ENSEMBLE BIAS CORRECTED BLEND FOR QPF DAYS 4-7.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE FIRST STRONG COLD FRONT OF SEPTEMBER IS FORECAST TO BRING  
QUITE A CHANGE TO THE PLAINS AND THEN THE MIDWEST AND GREAT LAKES  
REGION FOR THE WEEKEND. HIGHS ARE EXPECTED TO BE ONLY IN THE 60S  
ACROSS MOST OF THE UPPER MIDWEST ON SUNDAY, WHICH IS ROUGHLY 5-15  
DEGREES BELOW NORMAL FOR THIS TIME OF YEAR. SIGNIFICANT ABATEMENT  
OF THE HEAT IS ALSO EXPECTED ACROSS CALIFORNIA AND DESERT  
SOUTHWEST, WITH MUCH OF THIS COOL DOWN ATTRIBUTABLE TO CLOUDS AND  
RAINFALL ASSOCIATED WITH A WEAKENING TROPICAL STORM KAY BY THAT  
TIME. THERE WILL BE WARMER CONDITIONS FOR THE PACIFIC NORTHWEST  
FOR SUNDAY AND MONDAY, BUT NOT TO THE SAME MAGNITUDE AS THIS PAST  
WEEK. ACROSS THE EASTERN U.S., READINGS SHOULD GENERALLY BE  
WITHIN 5 DEGREES OF CLIMATOLOGICAL AVERAGES FOR HIGHS, WHILE  
OVERNIGHT LOWS NEAR THE EAST COAST SHOULD BE ABOUT 5-10 DEGREES  
ABOVE NORMAL MOST NIGHTS, OWING TO HIGHER HUMIDITY AND MORE CLOUD  
COVER.  
 
MOISTURE FROM THE FUTURE REMNANTS OF HURRICANE KAY WILL LIKELY BE  
IN PLACE ACROSS THE INTERMOUNTAIN WEST ON SUNDAY, ALTHOUGH THE  
MOST IMPACTFUL RAIN SHOULD BE OVER BY THAT TIME. FARTHER TO THE  
EAST, A COLD FRONT THAT WILL BE IN THE PROCESS OF BECOMING  
OCCLUDED IS EXPECTED TO PRODUCE MODERATE TO LOCALLY HEAVY RAIN  
FROM IOWA TO SOUTHERN WISCONSIN AND NORTHWESTERN ILLINOIS, AND A  
SLIGHT RISK OF EXCESSIVE RAINFALL IS NOW IN EFFECT FOR THESE AREAS  
ON THE DAY 4 EXPERIMENTAL OUTLOOK. ACROSS PORTIONS OF THE  
SOUTHEAST INTO THE MID-ATLANTIC, THERE IS AN INCREASING SIGNAL FOR  
A HEAVY RAINFALL EVENT. FAVORABLE FORCING FOR ASCENT PROVIDED BY  
AMPLE UPPER DIVERGENCE AHEAD OF THE MID/UPPER LEVEL LOW, PLENTY OF  
MOISTURE BEING LIFTED NORTHWARD OUT OF THE GULF, AND THE  
EXPECTATION FOR SUFFICIENT INSTABILITY IN PLACE COULD PRODUCE  
MODERATE TO HEAVY RAINFALL. AS A RESULT, A SLIGHT RISK WAS  
INTRODUCED IN THE DAY 4 EXPERIMENTAL ERO (12Z SUN-12Z MON) FOR  
PORTIONS OF THE CAROLINAS INTO THE MID-ATLANTIC REGION.  
 
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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