107
FXUS02 KWBC 011850
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 PM EDT SAT OCT 01 2022
VALID 12Z TUE OCT 04 2022 - 12Z SAT OCT 08 2022
..OVERVIEW
A WAVY PATTERN SHOULD BE IN PLACE BY THE START OF THE MEDIUM RANGE
PERIOD ON TUESDAY, WITH A COMPACT UPPER LOW OVER THE EAST AND
SHORTWAVE MOVING THROUGH THE HIGH PLAINS. AS THE WEEK PROGRESSES,
ENERGY DIVING SOUTHWARD ACROSS CANADA COMBINING WITH THE LATTER
SHORTWAVE WILL AMPLIFY UPPER TROUGHING ACROSS THE EAST WHILE
RIDGING BUILDS ACROSS THE WEST, WITH THIS PATTERN REMAINING
GENERALLY STAGNANT INTO NEXT WEEKEND. RELATIVELY QUIET WEATHER
CONDITIONS ARE EXPECTED ACROSS THE CONUS AFTER LINGERING
SHOWERS/GUSTY WINDS (RELATED TO WHAT WILL BE LEFT OF IAN) MOVE
OFFSHORE THE MID-ATLANTIC/NORTHEAST TUESDAY-WEDNESDAY. MONSOONAL
MOISTURE AND WEAK ENERGY OVER THE SOUTHWEST COULD LEAD TO SHOWERS
AND STORMS THERE AND PERHAPS EXTENDING INTO PORTIONS OF THE
PLAINS. THE LARGE-SCALE TROUGH SHOULD PUSH A POTENT COLD FRONT
ACROSS THE CENTRAL AND EASTERN U.S., WITH POTENTIAL FOR SOME RAIN
PARTICULARLY IN THE UPPER GREAT LAKES AND A SURFACE HIGH BEHIND
THE FRONT COOLING TEMPERATURES CONSIDERABLY.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS QUITE AGREEABLE WITH THE SYNOPTIC PATTERN
THROUGH THE MEDIUM RANGE PERIOD, THOUGH THEY SHOW SOME SMALLER
SCALE DIFFERENCES. AS THE PERIOD BEGINS TUESDAY, ENERGY ASSOCIATED
WITH IAN IN THE FORM OF AN UPPER LOW AND A SURFACE LOW PRESSURE
SYSTEM HAVE FAIRLY GOOD AGREEMENT, WITH THE 00Z UKMET AS A SLIGHT
EXCEPTION AS IT DISPLACED THE FEATURES NORTHEAST OF CONSENSUS, AND
THE CMC HELD MORE QPF ONSHORE THAN OTHER GUIDANCE. THUS THE EARLY
PART OF THE WPC FRONTS/PRESSURES FORECAST WAS BASED MAINLY ON THE
00Z ECMWF AND 00Z/06Z GFS, ALONG WITH LESSER AMOUNTS OF THE 00Z
CMC, AND THIS BLEND WORKED WELL FOR THE NORTH-CENTRAL U.S.
SHORTWAVE AS WELL.
WHILE MODELS AGREE ON TROUGHING AMPLIFYING IN THE EAST DURING THE
LATTER HALF OF NEXT WEEK, THERE ARE SOME MINOR DETAIL DIFFERENCES
WITH ROUNDS OF ENERGY DIVING SOUTHWARD THROUGH THE EAST SIDE OF
THE RIDGE/WEST SIDE OF THE TROUGH, LEADING TO SOME VARIABILITY IN
WHETHER OR NOT MODELS SHOW A CLOSED LOW OR TWO WITHIN THE TROUGH
BY LATE NEXT WEEK. THE WPC FORECAST WAS ABLE TO MAINTAIN A
MAJORITY OF DETERMINISTIC MODELS EVEN LATER IN THE FORECAST, BUT
THE EC AND GEFS ENSEMBLE MEANS WERE ALSO INCORPORATED BY DAYS 6-7
TO TONE DOWN SOME OF THE DIFFERENCES. THIS MAINTAINED GOOD
CONTINUITY FROM THE PREVIOUS FORECAST. IN TERMS OF THE
PRECIPITATION FORECAST, THE QPF WAS BASED ON THE 12Z NATIONAL
BLEND OF MODELS BUT WITH A WIDER FOOTPRINT FOR LIGHT AMOUNTS ADDED
ACROSS THE SOUTHWEST AND THE NORTH-CENTRAL TO NORTHEASTERN U.S. AS
THE NBM TYPICALLY UNDERFORECASTS THESE LOW AMOUNTS.
..WEATHER/HAZARDS HIGHLIGHTS
THE POTENTIALLY SLOW-MOVING EASTERN U.S. UPPER LOW AND ASSOCIATED
SURFACE LOW PRESSURE SYSTEM THAT ARE RELATED TO IAN'S REMNANTS MAY
CONTINUE TO PRODUCE SOME RAINFALL AND GUSTY WINDS ALONG THE
MID-ATLANTIC AND NORTHEAST COAST TUESDAY-WEDNESDAY, THOUGH MODELS
AGREE THE HEAVIEST RAINFALL SHOULD REMAIN OFFSHORE. ELSEWHERE,
MONSOONAL MOISTURE COMING INTO THE SOUTHWEST, PERHAPS ENHANCED ON
TUESDAY BY WHAT IS CURRENTLY HURRICANE ORLENE, WILL DRIVE SOME
DIURNAL SHOWERS AND THUNDERSTORMS THERE. LOCALLY HEAVY RAIN IS
POSSIBLE IN SOME LOCATIONS, AND SOME RAIN CHANCES COULD LAST
THROUGH LATE WEEK ACROSS THE FOUR CORNERS STATES. MEANWHILE, A
COLD FRONT SHIFTING FROM THE NORTHERN PLAINS TO THE UPPER MIDWEST
AND GREAT LAKES SHOULD RESULT IN SOME WIDESPREAD SHOWERS THROUGH
THE REGION AS THE FRONT MOVES THROUGH.
INITIALLY BELOW NORMAL TEMPERATURES ALONG THE EAST COAST SHOULD
TREND BACK TOWARDS NORMAL BY THE MIDDLE OF NEXT WEEK, WHILE
TEMPERATURES OUT WEST TREND MUCH WARMER UNDERNEATH A BLOCKY UPPER
RIDGE. DAYTIME HIGHS OVER THE NORTHWEST COULD BE 10 TO 15 DEGREES
ABOVE NORMAL INTO NEXT WEEKEND, THOUGH THE RESULTING TEMPERATURES
PEAKING IN THE 70S AND 80S (90S FOR PARTS OF CALIFORNIA) ARE
UNLIKELY TO CREATE ANY HEAT RELATED HAZARDS. CANADIAN HIGH
PRESSURE SPILLING INTO THE NORTH-CENTRAL U.S. AND EXPANDING
EASTWARD BEHIND THE COLD FRONT WILL RESULT IN MUCH BELOW NORMAL
TEMPERATURES SHIFTING FROM THE NORTHERN PLAINS INTO THE MIDWEST
AND THE NORTHEAST THURSDAY-SATURDAY. DAYTIME HIGHS IN SOME
LOCATIONS COULD BE 15 TO 20 DEGREES BELOW AVERAGE WITH OVERNIGHT
TEMPERATURES DROPPING INTO THE 30S FOR MANY, AND EVEN 20S FOR FAR
NORTHERN AREAS OF NORTH DAKOTA/MINNESOTA PARTICULARLY FRIDAY
MORNING.
TATE/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
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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