916
FXUS02 KWBC 110652
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 AM EST SAT NOV 11 2023
VALID 12Z TUE NOV 14 2023 - 12Z SAT NOV 18 2023
...HEAVY RAINFALL POTENTIAL FOR THE CENTRAL GULF COAST INTO
TUESDAY...
...MOISTURE DIRECTED INTO CALIFORNIA COULD LEAD TO HEAVY RAIN AND
SNOW TUESDAY-THURSDAY...
...PATTERN OVERVIEW AND GUIDANCE EVALUATION/PREDICTABILITY
ASSESSMENT...
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF BEST CLUSTERED GUIDANCE FROM THE 18 UTC
GFS/GEFS MEAN AND 12 UTC ECMWF/ECMWF ENSEMBLE MEAN AND TO A LESSER
EXTENT THE 12 UTC CANADIAN, BUT ALSO WITH SIGNIFICANT INPUT FROM
THE 01 UTC NATIONAL BLEND OF MODELS (NBM) AND WPC CONTINUITY FOR
TUESDAY INTO WEDNESDAY. THE 12 UTC UKMET OFFERS MORE NORTHERN AND
SOUTHERN STREAM SYSTEM PHASING INTO A EASTERN PACIFIC/WEST COAST
UPPER TROUGH POSITION IN THIS PERIOD COMPARED TO THE
AFOREMENTIONED PREFERRED BLEND. THIS SEEMS A LESS LIKELY SCENARIO
GIVEN THE LATEST 00 UTC UKMET HAS SIGNIFICANTLY BACKED OFF FROM
THIS SCENARIO, TRENDING MORE TOWARD THE OTHER MODELS.
BUILDING FORECAST SPREAD INCREASES THROUGH LATER NEXT WEEK,
FURTHER LOWERING CONFIDENCE WITH SYSTEMS EMBEDDED WITHIN THE
ESTABLISHING SPLIT FLOW PATTERN OVER SOUTHERN CANADA AND THE LOWER
48. HOWEVER, RECENT RUNS OF THE ECMWF SEEM TO OFFER A BIT BETTER
RUN TO RUN CONTINUITY AND SEEM MORE IN LINE THAN THE OTHER MODELS
WITH THE 18 UTC GEFS/12 UTC ECMWF ENSEMBLE MEANS AND WPC
CONTINUITY IN BOTH MAIN FLOW STREAMS. ACCORDINGLY, BLENDED THE 12
UTC ECMWF/18 UTC GEFS MEAN WITH THE ECMWF ENSEMBLE MEAN AND NBM
THROUGH THESE LONGER TIME FRAMES, ALBEIT WITH EMPHASIS ON THE NBM
AND ECMWF ENSEMBLE MEAN WHOSE SLIGHTLY LESS PROGRESSIVE/AMPLIFIED
SOUTHERN STREAM SEEMS MORE REASONABLE GIVEN FLOW SEPARATION. THE
00 UTC ECMWF REMAINS IN LINE OVERALL FOR MUCH OF THE PERIOD AND
THE 00 UTC GFS HAS TRENDED STRONGLY TOWARD ECMWF IDEAS, BOLSTERING
FORECAST CONFIDENCE TO A DEGREE. IN CONTRAST, RECENT RUNS OF THE
CANADIAN SHOW LESS THAN STELLAR RUN TO RUN CONTINUITY.
..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, PLAN TO SHIFT
A WPC DAY 4/5 EXCESSIVE RAINFALL OUTLOOK MARGINAL RISK AREA 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. HOWEVER, LATEST PROGRESSION TRENDS AND LEAD
ENERGIES/MOISTURE SEEM SUFFICIENT TO SLOWLY SPREAD
ORGANIZED/PERIODIC MODERATE TO LOCALLY TERRAIN ENHANCING RAINS,
ESPECIALLY FOR THE CENTRAL CALIFORNIA COAST AND INLAND SPREADING
ELEVATION/MOUNTAIN SNOWS, ESPCECIALLY FOR THE SIERRA, INTO
CALIFORNIA TUESDAY/WEDNESDAY, EVENTUALLY EXPANDING 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.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page