582
FXUS02 KWBC 010643
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 AM 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. BY LATER IN THE WEEK,
LARGE SCALE TROUGHING LOOKS TO AMPLIFY OVER THE EAST AS UPPER
LEVEL RIDGING BUILDS OVER THE WEST WITH THIS GENERAL PATTERN
REMAINING MOSTLY STAGNANT INTO NEXT WEEKEND. THE PERIOD LOOKS
RATHER QUIET IN TERMS OF ANY SIGNIFICANT SENSIBLE WEATHER THREATS,
WITH HEAVY RAINS/GUSTY WINDS MOVING OFFSHORE THE MID-ATLANTIC
TUESDAY-WEDNESDAY (LIKELY IN SOME FORM THE REMNANTS OF CURRENTLY
POST-T.C. IAN). MONSOON MOISTURE INTO THE SOUTHWEST, ASSOCIATED
WITH WEAK ENERGY OVER THE REGION, WILL CONTINUE THROUGH MUCH OF
THE PERIOD AS WELL.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
BESIDES SOME LINGERING UNCERTAINTIES IN THE DETAILS OF INDIVIDUAL
SYSTEMS, THE LATEST SUITE OF GUIDANCE SHOWS ABOVE AVERAGE
AGREEMENT THROUGH MUCH OF THE PERIOD. A GENERAL BLEND OF THE
LATEST DETERMINISTIC MODELS WORKED WELL THROUGH DAY 5. BY LATER IN
THE PERIOD, THERE ARE SOME MORE NOTICEABLE DIFFERENCES WHICH ARISE
CONCERNING INDIVIDUAL SHORTWAVES RIDING DOWN THE EAST SIDE OF THE
RIDGE INTO THE LONG-WAVE TROUGHING OVER THE EAST. INCORPORATING
MODEST AMOUNTS OF THE ENSEMBLE MEANS FOR DAYS 6 AND 7 SEEMED TO
TONE DOWN THESE HARDER TO RESOLVE DIFFERENCES AND PROVIDE A
REASONABLE OVERALL PATTERN DEPICTION. THE QPF IN THE MEDIUM RANGE
WAS BASED LARGELY ON THE 01/01Z NATIONAL BLEND OF MODELS, WITH
SOME INCORPORATION OF MAINLY THE GFS AND ECMWF ACROSS THE
SOUTHWEST AND ALSO THE NORTHERN PLAINS-UPPER MIDWEST-GREAT LAKES
TO PROVIDE A BIT LARGER OF A QPF FOOTPRINT IN THESE LOCATIONS THAN
WHAT WAS DEPICTED BY THE TOO LIGHT NBM, WHICH IS A KNOWN BIAS.
OVERALL, THIS APPROACH MAINTAINED GOOD CONTINUITY WITH THE
PREVIOUS WPC FORECAST AS WELL.
..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 SOME RAINFALL AND
GUSTY WINDS ALONG THE NORTHEAST COAST, THOUGH MODELS AGREE THE
HEAVIEST RAINFALL SHOULD REMAIN OFFSHORE. ELSEWHERE, MONSOONAL
MOISTURE INTO THE SOUTHWEST WILL DRIVE SOME DIURNAL SHOWERS AND
THUNDERSTORMS INTO THURSDAY, WITH LOCALLY HEAVY RAIN IN SOME
LOCATIONS POSSIBLE. A COLD FRONT SHIFTING FROM THE NORTHERN PLAINS
TO THE UPPER MIDWEST AND GREAT LAKES SHOULD RESULT IN JUST 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 AND
TEMPERATURES OUT WEST TREND MUCH WARMER UNDERNEATH OF A BLOCKY
UPPER RIDGE. DAYTIME HIGHS OVER THE NORTHWEST COULD BE 10 TO 15
DEGREES ABOVE NORMAL INTO NEXT WEEKEND, THOUGH THE RESULTING
TEMPERATURE VALUES AREN'T LIKELY TO CREATE ANY HEAT RELATED
HAZARDS. CANADIAN HIGH PRESSURE SPILLING INTO THE NORTH-CENTRAL
U.S. AND EXPANDING EASTWARD WILL RESULT IN MUCH BELOW NORMAL
TEMPERATURES SHIFTING FROM THE NORTHERN PLAINS INTO THE UPPER
MIDWEST AND THE NORTHEAST THURSDAY-SATURDAY. DAYTIME HIGHS IN SOME
LOCATIONS COULD BE 15 TO 20 DEGREES BELOW NORMAL WITH OVERNIGHT
TEMPERATURES DROPPING INTO THE 30S (OR LOWER IN FAR NORTHERN
AREAS) FOR MANY.
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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