683  
FXUS02 KWBC 080659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
258 AM EDT THU SEP 8 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. 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
 
 
THE 00Z MODEL GUIDANCE SUITE INITIALLY HAS A GOOD OVERALL SYNOPTIC  
SCALE DEPICTION OF THE MAIN PATTERN THROUGH ABOUT EARLY TUESDAY,  
WITH THE TYPICAL MESOSCALE MODEL DIFFERENCES. AS THE UPPER LOW  
BUILDS IN ACROSS THE MIDWEST BY MONDAY, THE GFS IS INITIALLY  
FASTER WITH ITS EASTWARD PROGRESSION EARLY ON, AND THEN THE 00Z  
ECMWF BECOMES FASTER LATER IN THE WEEK COMPARED TO ITS EARLIER  
RUNS AND THE GFS/CMC. BY NEXT THURSDAY, THE GFS AND ECMWF BECOME  
MORE OUT OF PHASE ACROSS SOUTH-CENTRAL CANADA WITH A TROUGH  
CROSSING THE HUDSON BAY REGION. IN TERMS OF QPF, THE NBM ALONG  
WITH ABOUT 15% OF THE OPERATIONAL 12Z ECMWF WAS USED AS A  
BASELINE. THE WPC FRONTS/PRESSURES FORECAST UTILIZED A  
MULTI-MODEL DETERMINISTIC BLEND THROUGH TUESDAY, GRADUALLY  
INCREASING USE OF THE ECMWF AND GEFS MEANS TO ABOUT HALF BY THE  
END OF THE PERIOD AS INDIVIDUAL MODEL DIFFERENCES INCREASE.  
 
   
..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. THE OVERALL UPPER TROUGH  
ANCHORED BY THIS UPPER LOW AND THE LEADING SURFACE SYSTEM MAY  
INTERACT WITH THE MOISTURE INITIALLY OVER THE SOUTH TO SPREAD A  
BROADER SHIELD OF RAINFALL OVER THE EASTERN U.S. INTO EARLY NEXT  
WEEK.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page