625
FXUS02 KWBC 111901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SAT NOV 11 2023
VALID 12Z TUE NOV 14 2023 - 12Z SAT NOV 18 2023
...HEAVY RAINFALL POTENTIAL FOR THE CENTRAL GULF COAST AND PARTS
OF THE SOUTHEAST INTO THURSDAY...
...MOISTURE DIRECTED INTO CALIFORNIA COULD LEAD TO HEAVY RAIN AND
SNOW TUESDAY-THURSDAY...
...PATTERN OVERVIEW AND GUIDANCE EVALUATION/PREDICTABILITY
ASSESSMENT...
THE MEDIUM RANGE PERIOD (TUESDAY-SATURDAY) FEATURES SHORTWAVE
ENERGY EXITING THE NORTHEAST AND ADDITIONAL TROUGHING MOVING
THROUGH THE DEEP SOUTH, WITH EARLY-MID WEEK HEAVY RAINFALL
POTENTIAL ALONG THE GULF COAST AND INTO PARTS OF THE
SOUTHEAST/FLORIDA. MEANWHILE, EAST PACIFIC TROUGHING LOOKS TO
SPLIT, WITH AN AMPLIFIED NORTHERN STREAM SHORTWAVE MOVING QUICKLY
EASTWARD THROUGH THE NORTHERN TIER, REACHING THE GREAT
LAKES/NORTHEAST BY FRIDAY-SATURDAY. A SOUTHERN STREAM DEEP UPPER
LOW LOOKS TO MEANDER OFF THE CALIFORNIA COAST UNTIL ABOUT FRIDAY,
EVENTUALLY EJECTING INLAND BY NEXT WEEKEND.
MODELS SHOW GOOD ENOUGH AGREEMENT TUESDAY-THURSDAY FOR A PURELY
DETERMINISTIC MODEL BLEND AS A STARTING POINT FOR THE WPC MEDIUM
RANGE FORECAST. AFTER THIS, THERE REMAINS PLENTY OF
TIMING/STRENGTH DIFFERENCES WITH THE NORTHERN STREAM SHORTWAVE
INTO THE GREAT LAKES LATE NEXT WEEK, AND ALSO PLACEMENT OF THE
UPPER LOW OFF THE CALIFORNIA COAST AND TIMING OF ITS EVENTUALLY
MOVE INLAND. THIS NECESSITATED A SHIFT TOWARDS THE ENSEMBLE MEANS
FOR TODAYS WPC FORECAST BLEND. THESE DIFFERENCES HOWEVER HAVE
BIGGER IMPLICATIONS FOR RESULTING QPF ACROSS CALIFORNIA, WITH THE
LATEST NATIONAL BLEND OF MODELS CONTINUING TO APPEAR WELL OVERDONE
WITH QPF, WITH NOT MUCH SUPPORT FOR THESE HIGHER AMOUNTS FROM THE
BETTER CONSENSUS OF MODELS. THE WPC QPF FORECAST SIDED MORE
CLOSELY WITH THE ENSEMBLE MEANS AND THE GFS/ECMWF/CMC, WHICH
RESULTS IN A SLIGHT REDUCTION IN AMOUNTS COMPARED TO PRIOR SHIFT
CONTINUITY, AND NOTICEABLY LOWER THAN THE NBM.
..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 SOME EASTERN PACIFIC AND
ENHANCED GULF OF MEXICO MOISTURE INFLOW TO FUEL PROTRACTED
RAINFALL POTENTIAL FROM THE CENTRAL GULF COAST STATES TUESDAY
THROUGH THE SOUTHEAST/FL WITH ADDED ATLANTIC INFLOW THROUGH
WEDNESDAY, EXITING THURSDAY. THE 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 LATER NEXT WEEK INTO THE WEST COAST/CALIFORNIA
IN SEPARATED FLOW. THERE HAS BEEN A NOTICEABLY TREND AWAY FROM ANY
WIDESPREAD IMPACTFUL RAINFALL AMOUNTS, BUT EVEN STILL, IT'S LIKELY
THAT MOISTURE SHOULD SLOWLY SPREAD ORGANIZED AND PERIODICALLY
MODERATE TO LOCALLY TERRAIN ENHANCED RAINS INTO THE CENTRAL
CALIFORNIA COAST, AND INLAND MOUNTAIN SNOWS FOR THE SIERRAS
TUESDAY/WEDNESDAY. CONSIDERED A MARGINAL RISK ON THE DAY 5 ERO FOR
THE COASTLINE, BUT AFTER COORDINATION WITH MONTEREY AND LOS
ANGELES/OXNARD FORECAST OFFICES, OPTED TO HOLD OFF ON ANY
INTRODUCTION OF A RISK GIVEN DRY ANTECEDENT CONDITIONS AND STILL
PLENTY OF UNCERTAINTY IN THE FORECAST. THIS ACTIVITY SHOULD
EVENTUALLY EXPAND INLAND OVER THE SOUTHWEST LATER NEXT WEEK.
IN THE NORTHERN STREAM, LEAD/AMPLIFIED UPPER TROUGHING IS SLATED
TO INCREASINGLY SHIFT FROM THE NORTHEAST TO THE NORTHERN ATLANTIC
TUESDAY ONWARD AS PRIMARILY A MARITIME LOW DEVELOPER WITH AN
INCREASING OFFSHORE WEATHER FOCUS. HIGH PRESSURE WILL LINGER OVER
MUCH OF THE EAST IN THE WAKE OF THIS SYSTEM. WELL UPSTREAM, UPPER
TROUGH AND SURFACE SYSTEM ENERGIES ARE EXPECTED TO WORK ACROSS THE
PACIFIC NORTHWEST/NORTHWEST THROUGH THE NORTHERN ROCKIES EARLY-MID
NEXT WEEK THEN AGAIN LATE WEEK TO SUPPORT MODEST TO TERRAIN
ENHANCED MODERATE RAINS/SNOWS ACROSS THE REGION.
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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