840
FXUS02 KWBC 120724
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
223 AM EST SUN NOV 12 2023
VALID 12Z WED NOV 15 2023 - 12Z SUN NOV 19 2023
...HEAVY RAINFALL POTENTIAL FOR THE SOUTHEAST INTO
WEDNESDAY/THURSDAY...
...MOISTURE DIRECTED INTO CALIFORNIA COULD LEAD TO HEAVY RAIN AND
SNOW INTO WEDNESDAY/THURSDAY...
...PATTERN OVERVIEW AND GUIDANCE EVALUATION/PREDICTABILITY
ASSESSMENT...
THE MEDIUM RANGE PERIOD FROM MIDWEEK THROUGH NEXT WEEKEND FEATURES
AN UPPER TROUGH MOVING THROUGH THE SOUTHEAST, WITH HEAVY RAINFALL
POTENTIAL INTO THE SOUTHEAST/FLORIDA WEDNESDAY INTO THURSDAY. THIS
MAY LEAD TO A POTENTIAL WESTERN ATLANTIC LOW TO LIFT NORTHWARD OFF
THE EAST COAST HEADING INTO NEXT WEEKEND. MEANWHILE, EAST PACIFIC
TROUGHING LOOKS TO SPLIT, WITH AN AMPLIFIED NORTHERN STREAM
SHORTWAVE MOVING EASTWARD THROUGH THE FULL U.S. NORTHERN TIER,
FROM AROUND THE NORTHWEST MIDWEEK TO THE NORTHEAST BY NEXT
WEEKEND. MEANWHILE, A DUG/CLOSED SOUTHERN STREAM DEEP UPPER LOW
LOOKS TO MEANDER OFF THE CALIFORNIA COAST UNTIL ABOUT FRIDAY,
EVENTUALLY EJECTING INLAND OVER THE SOUTHWEST TO POSSIBLY THE
SOUTHERN PLAINS NEXT WEEKEND.
GUIDANCE FROM THE 18 UTC GFS/GEFS MEAN AND 12 UTC ECMWF/ECMWF
ENSEMBLE MEAN SEEMS REASONABLY WELL CLUSTERED OVERALL WITH THE
MAIN WEATHER FEATURES AND OVERALL PATTERN EVOLUTION FOR MUCH OF
THE LOWER 48 AND IN LINE WITH WPC CONTINUITY OVERALL, ALBEIT WITH
THESE MODELS SOMEWHAT LESS PROGRESSIVE WITH THE MAIN SOUTHERN
STREAM FEATURES THAN THESE ENSEMBLE MEANS. THIS SEEMS MORE
REASONABLE CONSIDERING LEAD-IN CLOSED/AMPLIFIED NATURE OF THE
SEPARATED STREAM. IN THE NORTHERN STREAM THESE MODELS HAVE TRENDED
LESS PROGRESSIVE THAN CONTINUITY AS WELL AS THE 12 UTC
CANADIAN/UKMET AND NAEFS MEAN THAT COMBINES 12 UTC GEFS/CANADIAN
ENSEMBLES. THESE TIMING DIFFERENCES SEEM MOST SENSITIVE TO THE
ULTIMATE MID-LATER WEEK UPPER RIDGE AMPLITUDE UPSTREAM FROM THE
GULF OF ALASKA INTO WESTERN CANADA THAT REMAINS LESS CERTAIN THAN
AVERAGE. ACCORDINGLY, AN OVERALL COMPOSITE BLEND OF THE GFS/GEFS,
ECMWF/ECMWF ENSEMBLES AND NAEFS SEEMED TO BEST CAPTURE FAVORABLE
GUIDANCE TRENDS IN THE SOUTHERN STREAM AND ACCOUNTS IN PART FOR
LINGERING TIMING UNCERTAINTIES IN NORTHERN STREAM FLOW, BUT WITH
EMPHASIS ON A LESS PROGRESSIVE TREND. THE LATEST 00 UTC
UKMET/CANADIAN HAVE NOW TRENDED SLOWER, BOLSTERING FORECAST
CONFIDENCE GUIDANCE/WPC PROGS HAVE TRENDED IN SUPPORT OF
DEVELOPING A BAHAMAS FRONTAL WAVE LATER THIS WEEK AS SUPPORTING
ENERGIES SHIFT OUT FROM THE GULF OF MEXICO/SOUTHEAST, BUT
SUBSEQUENT GUIDANCE SPREAD IS AMPLE. THE 12/00 UTC ECMWF RUNS HAVE
THE STRONGEST LOW AND MOST WEEKEND INTERACTION NORTHWARD TO OFF
NEW ENGLAND WHILE OTHERS ARE LESS DEFINED/MORE OFFSHORE, SENSITIVE
TO NORTHERN STREAM TIMING/AMPLITUDE VARIANCE AND ANY PHASING
POTENTIAL.
..WEATHER/HAZARDS HIGHLIGHTS
THE SLOW AND STEADY PROGRESSION OF A LEADING/AMPLIFIED SOUTHERN
STREAM UPPER TROUGH AND ASSOCIATED WAVY SURFACE FRONT HAS
INCREASINGLY SHOWN A SIGNAL SUPPORTIVE OF LOWER LATITUDE/GULF OF
MEXICO AND EASTERLY FETCH ATLANTIC MOISTURE INFLOW TO FUEL
PROTRACTED RAINFALL POTENTIAL THROUGH THE SOUTHEAST/FLORIDA INTO
WEDNESDAY/THURSDAY. THIS SOAKER MAY LEAD TO SOME COASTAL/LOCAL AND
URBAN RUNOFF ISSUES GIVEN POTENTIAL FOR SEVERAL INCHES OF FRONTAL
OVERRUNNING RAINS AND A THREAT FOR SOME HEAVIER LOCAL
REPEAT/TRAINING DURATION AMOUNTS. ACCORDINGLY, WPC DAY 4/5
EXCESSIVE RAINFALL OUTLOOK MARGINAL RISK AREAS CONTINUE ACROSS
THESE AREAS.
MEANWHILE UPSTREAM IN THE ACTIVE SOUTHERN STREAM BRANCH OF FLOW,
RECENT GUIDANCE INDICATES THAT AMPLE UPPER TROUGH/CLOSED LOW
DEVELOPMENT OVER THE EASTERN PACIFIC BY EARLY NEXT WEEK MAY PROVE
SLOW TO WORK UNTIL LATE WEEK/NEXT WEEKEND INTO THE WEST
COAST/CALIFORNIA IN SEPARATED FLOW. THERE HAS BEEN SOME RECENT
TRENDS AWAY FROM WIDESPREAD IMPACTFUL RAINFALL AMOUNTS, BUT IT'S
LIKELY THAT MOISTURE SHOULD SLOWLY SPREAD ORGANIZED AND
PERIODICALLY MODERATE TO LOCALLY TERRAIN ENHANCED RAINS INTO THE
CENTRAL TO SOUTH-CENTRAL CALIFORNIA COAST, AND INLAND MOUNTAIN
SNOWS FOR THE SIERRAS WEDNESDAY AND THURSDAY. RAINFALL AMOUNTS
HAVE INCREASED A BIT WITH THIS CYCLE AND FORECAST SPREAD DECREASES
NOW DO SEEM JUST ENOUGH TO ADD WPC EXCESSIVE RAINFALL OUTLOOK
MARGINAL RISK AREAS TO HIGHLIGHT FOR COASTAL TERRAIN AREAS FOR
BOTH THE DAY 4/5 EROS. THIS ACTIVITY SHOULD LESSEN BUT SPREAD
BROADLY INLAND OVER THE SOUTHWEST INTO NEXT WEEKEND AND BEFORE
MODEST OVERSPREADING OF THE SOUTH-CENTRAL GREAT BASIN/ROCKIES TO
INCLUDE SOME MOUNTAIN SNOWS. LATER WEEKEND INTO EARLY NEXT WEEK
POTENTIAL SYSTEM GENESIS OVER THE SOUTHERN PLAINS MAY THEN LEAD TO
AN EMERGING RAINFALL SHIELD WITH ADDED GULF OF MEXICO MOISTURE
INFLOW.
UPPER TROUGH AND SURFACE SYSTEM ENERGIES ARE EXPECTED TO WORK
ACROSS THE PACIFIC NORTHWEST/NORTHWEST THROUGH THE NORTHERN
ROCKIES AGAIN BY MIDWEEK AND THEN AGAIN NEXT WEEKEND TO SUPPORT
MODEST TO TERRAIN ENHANCED MODERATE RAINS/SNOWS ACROSS THE REGION.
DOWNSTREAM LATER WEEK NORTHERN STREAM ENERGY PROGRESSION ACROSS
THE NORTH-CENTRAL U.S. WILL HAVE LIMITED MOISTURE TO TAP, BUT
DYNAMICS AND THE POTENTIAL FOR AN UPTICK IN MOISTURE MAY SUPPORT
MORE WIDESPREAD AND ENHANCED PRECIPITATION FROM THE EASTERN GREAT
LAKES STATES THROUGH THE NORTHEAST NEXT WEEKEND, ESPECIALLY IN
SOME GUIDANCE FOR EASTERN NEW ENGLAND IF ABLE TO TAP ANY SOUTHERN
STREAM/COASTAL LOW MOISTURE.
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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