071
FXUS02 KWBC 081812
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
211 PM EDT SUN OCT 08 2023
VALID 12Z WED OCT 11 2023 - 12Z SUN OCT 15 2023
...EXCESSIVE RAIN THREATS FOR THE MIDWEST TO NORTHEAST AND CENTRAL
GULF COAST/SOUTHEAST/NORTHERN FLORIDA MID TO LATE WEEK...
..OVERVIEW
A CLOSED UPPER LOW WILL SHIFT SLOWLY EASTWARD ACROSS EASTERN
CANADA MID-LATER WEEK TO END GREAT LAKE EFFECT RAINS AND SHIFT
UNSETTLED CONDITIONS UNDER/AROUND THIS AMPLIFIED FEATURE AWAY FROM
THE NORTHEAST. FAR UPSTREAM, DYNAMIC UPPER TROUGH ENERGIES WILL
WORK ONSHORE AND DIVE SOUTHEASTWARD THROUGH THE WEST. EARLY WEEK
RAINS WILL EASE OVER THE PACIFIC NORTHWEST WITH SYSTEM/FRONTAL
PROGRESSIONS TO FAVOR ENHANCED MOUNTAIN SNOWS FROM THE CASCADES TO
ESPECIALLY THE NORTHERN ROCKIES WITH CLOSED TROUGH/LOW DEVELOPMENT
AND PASSAGE. THIS POTENT UPPER SYSTEM WILL STEADILY TRACK FROM THE
PLAINS TO THE NORTHEAST FRIDAY INTO NEXT WEEKEND. THIS WILL FOSTER
ENHANCED PRECIPITATION CHANCES TO SPREAD IN EARNEST FROM THE
CENTRAL U.S./MIDWEST THROUGH THE NORTHEAST AS INFLOW MOISTURE
INCREASES AHEAD OF DEEP CYCLOGENESIS. TO THE SOUTH, A FRONTAL
BOUNDARY ENHANCED WITH TROPICAL MOISTURE WILL LIFT THROUGH THE
GULF OF MEXICO TO INCREASE HEAVY PRECIPITATION CHANCES ACROSS THE
CENTRAL GULF COAST AND FLORIDA/SOUTHEAST BY MID TO LATER THIS WEEK
BEFORE LIFTING OFF THE EAST COAST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE GUIDANCE AGREEMENT CONTINUES TO BE ABOVE
AVERAGE THROUGH THE MEDIUM RANGE PERIOD, AND THE WPC BLEND
UTILIZED A DETERMINISTIC MODEL BLEND FOR DAYS 3-5. BY DAYS 6 AND
7, THERE ARE SOME TIMING DIFFERENCES WITH THE DEEP UPPER LOW
THROUGH THE MIDWEST/GREAT LAKES, AND SOME LINGERING RUN TO RUN
DISCONTINUITIES. THE CMC IS A LITTLE SLOWER/DISPLACED TO THE
NORTHWEST OF THE BETTER CONSENSUS. ALSO SOME TIMING DIFFERENCES
WITH THE NEXT TROUGH ENTERING THE WEST LATE IN THE PERIOD.
INCORPORATION OF THE ENSEMBLE MEANS SEEMED TO MITIGATE THESE
DIFFERENCES AND THE WPC BLEND LATE PERIOD USED A 50/50 OPERATIONAL
(ECMWF AND GFS) AND ENSEMBLE MEAN BLEND. THIS MAINTAINED GOOD
CONTINUITY WITH THE PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
DYNAMIC UPPER TROUGH/HEIGHT FALLS AND SURFACE SYSTEM PASSAGE
ACROSS THE WEST INTO MID-LATER WEEK WILL FAVOR A SWATH OF AUTUMN
MOUNTAIN SNOWS FROM THE CASCADES THROUGH THE INTERMOUNTAIN WEST
AND ESPECIALLY THE NORTHERN ROCKIES. DOWNSTREAM, PRECIPITATION
CHANCES WILL EXPAND EAST THROUGHOUT THE WEEK AS A FRONTAL SYSTEM
MOVES ACROSS THE NATION, REACHING THE CENTRAL U.S. BY MIDWEEK.
DEEP CYCLOGENESIS AND WRAPPING ANOMALOUS MOISTURE INTO A LEADING
WARM FRONT LIFTING THROUGH THE EAST-CENTRAL U.S. WILL SHIFT FOCUS
FOR EMERGING HEAVY RAINS FROM THE CENTRAL PLAINS THROUGH THE
MIDWEST INTO WEDNESDAY. THE WPC DAY 4/WEDNESDAY EXCESSIVE RAINFALL
OUTLOOK (ERO) SHOWS A MARGINAL RISK OVER THE MID-MS VALLEY GIVEN
RISK FOR TRAINING AND GROWING MODEL AND ENSEMBLE SIGNALS. GUIDANCE
SUGGESTS THIS HEAVY RAINFALL AREA WILL LIKELY EXPAND ACROSS THE
MIDWEST WITH CONTINUED SYSTEM DEVELOPMENT AND TRACK/INFLOW THAT IS
COVERED AT THIS POINT BY A MARGINAL DAY 5/THURSDAY ERO RISK AREA.
MEANWHILE, A SEPARATE WARM FRONT LIFTING THROUGH THE GULF OF
MEXICO AND THE FLORIDA PENINSULA BRINGS A THREAT FOR HEAVY
RAINFALL FROM THE CENTRAL GULF COAST TO THE SOUTHEAST
WEDNESDAY/THURSDAY. THIS MAY BE AIDED BY AN AREA OF LOW PRESSURE
IN THE GULF OF MEXICO AND POSSIBLE REMNANT TROPICAL MOISTURE TO BE
MONITORED. AN ERO MARGINAL RISK AREA CONTINUES FOR DAY 4/WEDNESDAY
FROM THE CENTRAL GULF COAST TO THE FLORIDA PENINSULA. A DAY
5/THURSDAY ERO MARGINAL RISK AREA WAS ALSO INCLUDED DOWNSTREAM TO
SPAN PARTS OF THE SOUTHEAST. THESE TWO MAIN SYSTEMS MAY
INCREASINGLY INTERACT TO SOME DEGREE TO SPREAD ENHANCED RAINFALL
AND RUNOFF ISSUES POSSIBLE ACROSS THE EAST/NORTHEAST FRIDAY INTO
SATURDAY, WITH WIDESPREAD ENHANCED BACKSIDE WINDS AND POST-FRONTAL
FALLING AUTUMN TEMPERATURES.
SANTORELLI/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 FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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