931  
FXUS02 KWBC 302005  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
404 PM EDT FRI SEP 30 2022  
 
VALID 12Z MON OCT 03 2022 - 12Z FRI OCT 07 2022  
   
..OVERVIEW
 
 
A WAVY PATTERN SHOULD BE IN PLACE BY THE START OF THE MEDIUM RANGE  
PERIOD ON MONDAY, WITH A TROUGH/UPPER LOW OVER THE EAST (WHICH  
INCLUDES THE EXTRATROPICAL REFLECTION OF IAN) AND A SLOW MOVING  
NORTHERN ROCKIES INTO HIGH PLAINS UPPER LOW. THE LATTER IS  
SANDWICHED BETWEEN RIDGES OVER THE WEST COAST AND CENTRAL-SOUTHERN  
PLAINS INTO THE MIDWEST. TROUGHING LOOKS TO BE MAINTAINED OVER THE  
EAST EVEN AS THE REMNANTS OF IAN MOVE OFFSHORE TUES-WED, BUT UPPER  
LEVEL RIDGING BUILDING OVER THE WEST WHICH SHOULD ACT TO  
ACCELERATE THE SECOND SHORTWAVE TOWARDS THE UPPER MIDWEST AND  
FURTHER AMPLIFY TROUGHING OVER THE EAST LATE NEXT WEEK. SENSIBLE  
WEATHER THREATS HOWEVER DURING THE MEDIUM RANGE PERIOD LOOK TO  
MAINLY SURROUND THE REMNANTS OF IAN AS THEY MOVE THROUGH THE  
MID-ATLANTIC NEXT MONDAY-TUESDAY WITH SOME LOCALLY HEAVY RAINFALL  
AND GUSTY WINDS LINGERING ALONG MAINLY COASTAL REGIONS FROM THE  
OUTER BANKS, NC TO SOUTHERN NEW ENGLAND.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
GUIDANCE HAS TRENDED MORE PROGRESSIVE WITH IAN'S REMNANT TROPICAL  
MOISTURE EARLY NEXT WEEK. ELSEWHERE, THE HIGH FREQUENCY PATTERN  
ACROSS THE LOWER 48 IS CAPTURED WELL BY A GENERAL MODEL BLEND. A  
DETERMINISTIC BLEND CONSISTING OF THE 00Z EC/UKMET/CMC AND 06Z GFS  
WERE USED TO DEPICT THE WAVY PATTERN ON DAY 3 AND AMPLIFYING RIDGE  
IN THE WEST ON DAY 4. THE 00Z ECE AND 06 GEFS WERE INTRODUCED ON  
DAY 5 TO ACCOUNT FOR UNCERTAINTY, PARTICULARLY IN THE 00Z EC,  
REGARDING THE ORIENTATION OF A TROUGH IN THE SOUTHERN  
PLAINS/SOUTHWEST. THIS TROUGH UNCERTAINTY IN THE EC CONTINUES INTO  
DAY 6 BEFORE RIDGING DISCREPANCIES PRESENTED BY THE EC AND CMC  
ARISE OVER THE EASTERN PACIFIC/WEST COAST ON DAY 7. THE ENSEMBLE  
MEANS NEGOTIATE THE AMPLIFIED WESTERN RIDGE AND EASTERN TROUGH  
AXES REASONABLY WELL ON DAY 7, WHICH IS WHY THEY MAKE UP A  
MAJORITY OF THE BLEND.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE POTENTIALLY SLOW MOVING EASTERN U.S. UPPER LOW AND ASSOCIATED  
LOW PRESSURE (WHETHER INITIALLY FROM IAN OR EVENTUAL REDEVELOPMENT  
JUST OFF THE EAST COAST) MAY CONTINUE TO PRODUCE LOCALLY HEAVY  
RAINFALL OVER PARTS OF THE MID-ATLANTIC INTO EARLY NEXT WEEK.  
BRISK TO STRONG WINDS, AIDED BY HIGH PRESSURE TO THE NORTH, SHOULD  
BE MOST NOTICEABLE OVER COASTAL AREAS. LINGERING GUIDANCE  
DIFFERENCES FOR SPECIFICS AT THE SURFACE AND ALOFT DIRECTLY  
RELATED TO THE EXTRATROPICAL TRANSITION OF IAN THIS WEEKEND  
CONTINUE TO OFFER A LOWER CONFIDENCE FORECAST IN RAINFALL COVERAGE  
AND AMOUNTS, SO ADJUSTMENTS TO THE CURRENT FORECAST IS LIKELY IN  
THE DAYS TO COME.  
 
THE REMAINDER OF THE CONUS LOOKS TO BE FAIRLY QUIET IN TERMS OF  
ANY LARGER SCALE PRECIPITATION FOCUS AREAS NEXT WEEK. THE UPPER  
LOW EMERGING FROM THE NORTHERN ROCKIES SHOULD PRODUCE AREAS OF  
PRECIPITATION FROM THE SOUTHWEST/FOUR CORNER REGION INTO THE HIGH  
PLAINS AND SUFFICIENT MOISTURE COULD SUPPORT SOME AREAS OF LOCALLY  
MODERATE TO HEAVY RAINFALL EARLY NEXT WEEK. HIGHEST ELEVATIONS OF  
THE COLORADO/SOUTHERN ROCKIES UNDER THE UPPER LOW MAY SEE SOME  
SNOW AS WELL. THIS PRECIPITATION SHOULD BECOME LIGHTER/MORE  
SCATTERED BY THE MIDDLE OF NEXT WEEK AND ONWARD AS THE UPPER  
FEATURE OPENS UP AND MOVES EASTWARD.  
 
MUCH OF THE EAST WILL SEE BELOW NORMAL HIGHS DURING THE FIRST HALF  
OF NEXT WEEK. PARTS OF THE MID-ATLANTIC INTO SOUTHEAST MAY BE  
10-15F BELOW NORMAL INTO EARLY NEXT WEEK WITH THE CLOUDS/RAIN  
ORIGINALLY ASSOCIATED WITH IAN, WHILE COOL HIGH PRESSURE PREVAILS  
OVER NEW ENGLAND. OUT WEST, PERSISTENT UPPER RIDGING WILL KEEP  
MUCH OF THE REGION WARMER THAN AVERAGE WITH SOME LOCATIONS IN THE  
NORTHWEST POTENTIALLY SEEING HIGHS 10-15F ABOVE NORMAL FOR MOST OF  
THE PERIOD. MODESTLY ABOVE NORMAL TEMPERATURES OVER THE PLAINS  
WILL EVENTUALLY SHIFT MORE OVER SOUTHERN AREAS WHILE LOCATIONS  
OVER THE NORTHERN TIER AND INTO THE MIDWEST/GREAT LAKES SHOULD  
TREND COLDER AS CANADIAN HIGH PRESSURE SETTLES OVER THE REGION.  
 
KEBEDE/SANTORELLI  
 
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  
 
HAZARDS:  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE SOUTHERN APPALACHIANS,  
THE MID-ATLANTIC, AND THE CENTRAL  
APPALACHIANS.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHEAST.  
- FLOODING LIKELY ACROSS PORTIONS OF THE SOUTHEAST.  
- HIGH WINDS ACROSS PORTIONS OF THE MID-ATLANTIC AND THE  
NORTHEAST, MON, OCT 3.  
 
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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