242  
FXUS02 KWBC 191903  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT MON SEP 19 2022  
 
VALID 12Z THU SEP 22 2022 - 12Z MON SEP 26 2022  
 
...HEAVY RAINFALL THREAT LINGERS FOR THE FOUR CORNERS/ROCKIES INTO  
THURSDAY...  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
LATEST MODEL AND ENSEMBLE SOLUTIONS SEEM PRETTY WELL CLUSTERED  
THROUGH MEDIUM RANGE TIME SCALES OVER THE LOWER 48, BOLSTERING  
FORECAST CONFIDENCE DESPITE SOME LINGERING LOCAL EMBEDDED SYSTEM  
TIMING/STRENGTH DIFFERENCES. THE WPC MEDIUM RANGE PRODUCT SUITE  
WAS PRIMARILY DERIVED FROM A COMPOSITE OF THE 06 UTC GFS/GEFS, 00  
UTC ECMWF/EC MEAN, AND THE 00Z CMC/CMC MEAN. THE RESULTS AGREE  
WITH THE 13 UTC NATIONAL BLEND OF MODELS (NBM) WELL EXCEPT FROM  
DAY 5 ONWARD WHEN THE MODEL BLEND PROVIDED A LARGER QPF FOOTPRINT  
THAN THE NBM. GIVEN THE RELATIVELY GOOD MODEL AGREEMENT OUT TO  
DAY 7, MORE OF THE DETERMINISTIC SOLUTIONS WERE INCORPORATED INTO  
THE BLEND FOR DAYS 6 AND 7. GUIDANCE DIFFERENCES SEEM WELL  
MITIGATED BY THIS BLENDING PROCESS CONSISTENT WITH PREDICTABILITY.  
WPC PRODUCT CONTINUITY IS WELL MAINTAINED IN THIS MANNER AND  
NEWER 12 UTC ECMWF GENERALLY REMAINS IN LINE.  
   
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
 
 
ON THURSDAY, ENHANCED RAINFALL SHOULD BE EXITING NEW ENGLAND AS A  
COLD FRONT MOVES STEADILY INTO EASTERN CANADA. MEANWHILE, AN  
AMPLIFIED UPPER TROUGH/LOW AND FRONTAL SYSTEM SLOWING LIFTING  
THROUGH THE NORTH-CENTRAL GREAT BASIN/ROCKIES THURSDAY INTO FRIDAY  
WILL FAVOR COOLER TEMPERATURES THAT MAY LEAD TO SOME SNOW FOR HIGH  
ELEVATIONS IN NORTHWESTERN WYOMING THURSDAY NIGHT. MAXIMUM DAILY  
TEMPERATURES ARE FORECAST TO TEMPORARILY DIP 10 TO 15 DEGREES F  
BELOW AVERAGE. MEANWHILE, ANOMALOUS MOISTURE CARRIED ACROSS THE  
FOUR CORNERS REGION ASSOCIATED WITH THE SOUTHERN JET STREAM IS  
FORECAST TO EXTEND INTO THE BEGINNING OF THE MEDIUM-RANGE PERIOD  
ON THURSDAY BEFORE WANING BY FRIDAY. MODERATE TO LOCALLY HEAVIER  
RAINFALL/THUNDERSTORMS APPEAR TO BE FOCUSED FROM THE FOUR CORNERS  
TO AREAS IMMEDIATELY TO THE EAST, WHERE A SLIGHT RISK OF EXCESSIVE  
RAINFALL IS INDICATED ON THE DAY 4 EXPERIMENTAL WPC EXCESSIVE  
RAINFALL OUTLOOK. FARTHER NORTH, AN AREA OF ENHANCED RAINFALL  
CLOSER TO THE SURFACE LOW CENTER WILL WORK ACROSS THE NORTHERN  
GREAT BASIN/ROCKIES INTO THE NORTHERN HIGH PLAINS ON THURSDAY WITH  
SOME HEAVY RAIN POSSIBLE. BY FRIDAY, THE MAIN ACTIVITIES SHOULD  
MOVE ACROSS THE NORTHERN PLAINS INTO THE UPPER MIDWEST. BY LATE  
NEXT WEEK INTO THE WEEKEND, THE SYSTEM SHOULD CONTINUE TO WORK ITS  
WAY EAST ACROSS THE GREAT LAKES REACHING THE NORTHEAST BY MONDAY.  
BEST CHANCE OF SHOWERS AND SOME THUNDERSTORMS WILL BE AHEAD OF  
THIS SYSTEM AS WELL AS WHAT APPEARS TO BE A WELL-DEFINED COLD  
FRONT TRAILING ACROSS THE APPALACHIANS AND THROUGH THE SOUTH. A  
SURGE OF COOL CANADIAN AIR SHOULD USHER IN FALL-LIKE WEATHER  
THROUGH THE NORTHERN TIER THROUGH THE WEEKEND AND THEN TOWARD THE  
EAST COAST BY NEXT MONDAY.  
 
AN ERODING LEAD UPPER RIDGE OVER THE SOUTH WILL SUPPORT LINGERING  
10-15F WARMER THAN AVERAGE TEMPERATURES INTO THURSDAY. THIS WILL  
BE IN ADVANCE OF THE AFOREMENTIONED COLD FRONT. HEAT WILL QUICKLY  
GET SUPPRESSED WITH THIS FRONTAL PASSAGE AS QUITE COOLED CANADIAN  
POST-FRONTAL HIGH PRESSURE SETTLES INTO THE CENTRAL TO EASTERN  
U.S. THE LINGERING FRONT MAY FOCUS SOME SHOWERS ACROSS FLORIDA  
THROUGH THE WEEKEND.  
 
KONG/SCHICHTEL  
 
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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