632
FXUS02 KWBC 030700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST SUN NOV 3 2024
VALID 12Z WED NOV 06 2024 - 12Z SUN NOV 10 2024
..OVERVIEW
LATEST GUIDANCE MAINTAINS THE RECENT THEME OF A STRONG WESTERN
ATLANTIC UPPER RIDGE EXTENDING INTO PARTS OF THE EAST WHILE
STRONGLY DIGGING WESTERN U.S. TROUGH ENERGY LIKELY CLOSES OFF A
LOW NEAR THE FOUR CORNERS AROUND MIDWEEK, FOLLOWED BY A SLOW
EASTWARD DRIFT AND SOME ACCELERATION NORTHEASTWARD OVER THE PLAINS
BY THE WEEKEND. EXPECT THE UPPER LOW TO PRODUCE AN AREA OF
POTENTIALLY SIGNIFICANT SNOWFALL OVER PARTS OF THE CENTRAL-SOUTHERN
ROCKIES AROUND MIDWEEK AND THEN DEVELOP MODERATE TO LOCALLY HEAVY
RAIN OVER THE PLAINS LATER IN THE WEEK, WITH MOISTURE CONTINUING TO
PROGRESS DURING THE WEEKEND. AROUND THE PERIPHERY OF THE ATLANTIC
UPPER RIDGE, GUIDANCE STILL SHOWS POSSIBLE CARIBBEAN INTO GULF OF
MEXICO TROPICAL DEVELOPMENT (BEING MONITORED BY THE NATIONAL
HURRICANE CENTER) WITH A LOT OF GUIDANCE SPREAD FOR WHERE THE
SURFACE SYSTEM ITSELF MAY TRACK, AS WELL AS FOR THE PATH OF
MOISTURE TO ITS NORTH/EAST. THE NORTHWEST SHOULD SEE A WETTER TREND
BY NEXT WEEKEND WITH THE APPROACH/ARRIVAL OF A COUPLE FRONTAL
SYSTEMS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
CONSENSUS HAS HELD UP FAIRLY WELL FOR THE FOUR CORNERS UPPER LOW
AND ITS EVENTUAL EJECTION. THE ECMWF HAS GENERALLY BEEN THE MOST
CONSISTENT WITH THIS FEATURE OVER RECENT RUNS WITH THE GFS A LITTLE
MORE VARIABLE BUT USUALLY STILL REASONABLE AS PART OF A COMPROMISE
POSITION, WITH SUPPORT FROM THEIR RESPECTIVE ENSEMBLE MEANS. THE
NEW 00Z ECMWF HAS NUDGED A LITTLE SLOWER THOUGH. CMC/UKMET RUNS
HAVE BEEN MORE ERRATIC TO VARYING DEGREES, THOUGH THE 00Z CMC HAS
ADJUSTED TO THE MAJORITY CLUSTER. INTERESTINGLY, THE AVERAGE OF
MACHINE LEARNING (ML) MODELS HAS BEEN CONSISTENTLY RUNNING A FEW
DEGREES OF LONGITUDE FASTER THAN THE DYNAMICAL MODEL MAJORITY.
THERE IS STILL A LOT OF SPREAD AMONG THE DYNAMICAL AND ML MODELS
REGARDING THE COMBINATION OF POSSIBLE LEADING MOISTURE REACHING THE
SOUTHEAST/FLORIDA AND POSSIBLE CARIBBEAN INTO GULF OF MEXICO
DEVELOPMENT. THE CMC HAS TENDED TO BE ON THE FAST/EASTERN SIDE OF
THE DYNAMICAL MODEL SPREAD FOR THE POSSIBLE SYSTEM BUT SOME ML
GUIDANCE IS SOMEWHAT ON THE FASTER SIDE AS WELL WITH AN ENVELOPE
SPANNING THE CENTRAL-EASTERN GULF. THIS ML ENVELOPE OFFERS LITTLE
SUPPORT TO ECMWF RUNS THAT HAVE BEEN TRACKING THE SYSTEM INTO THE
WESTERN GULF, THOUGH THE NEW 00Z ECMWF REPRESENTS A CONTINUED
RIGHTWARD ADJUSTMENT OVER THE PAST DAY. THE MANUAL FORECAST REMAINS
CLOSE TO YESTERDAY'S WPC/NHC COORDINATED PATH FOR THE POSSIBLE
SYSTEM.
AS FOR OTHER DETAILS, ML MODELS REFLECT THE DYNAMICAL MODEL SPREAD
FOR AMPLITUDE/TIMING OF THE PACIFIC SHORTWAVE TROUGH EXPECTED TO
PROGRESS INTO WESTERN NORTH AMERICA DURING THE WEEKEND. THERE IS
ALSO SOME SPREAD FOR THE DETAILS OF EASTERN CANADA/NORTHEASTERN
U.S. TROUGHING LATE WEEK INTO THE WEEKEND AS UPSTREAM RIDGING
PROGRESSES ACROSS CANADA.
THE UPDATED FORECAST STARTS WITH AN OPERATIONAL MODEL BLEND
EMPHASIZING THE 12Z/18Z GFS AND 12Z ECMWF WITH MODEST 12Z UKMET
INPUT DURING THE FIRST HALF OF THE PERIOD, FOLLOWED BY SOME
INCLUSION OF THE 18Z GEFS/12Z ECENS MEANS. RELATIVE WEIGHT OF
12Z AND/OR 18Z GFS RUNS WAS ADJUSTED AT TIMES BASED ON COMPARISON
TO FAVORED CONSENSUS FOR FEATURES OF INTEREST.
..WEATHER/HAZARDS HIGHLIGHTS
GUIDANCE CONTINUES TO HAVE DIFFICULTY IN RESOLVING THE DETAILS OF
MOISTURE AND SHORTWAVE ENERGY ROUNDING THE WESTERN ATLANTIC DEEP-
LAYER RIDGE AND POTENTIALLY BRINGING AREAS OF SIGNIFICANT RAINFALL
TO THE SOUTHEAST/FLORIDA, WITH POSSIBLE CARIBBEAN INTO GULF OF
MEXICO TROPICAL DEVELOPMENT PROVIDING ANOTHER POTENTIAL RAINFALL
INFLUENCE. OVER THE COURSE OF THE DAYS 4/5 EXCESSIVE RAINFALL
OUTLOOK PERIOD (WEDNESDAY THROUGH THURSDAY NIGHT) THERE IS A FAIR
CLUSTERING OF DYNAMICAL/ML GUIDANCE SUGGESTING AN AREA OF ENHANCED
FOCUS OVER OR NEAR GEORGIA/SOUTH CAROLINA WHILE GFS/GEFS RUNS PLACE
MORE EMPHASIS OVER PARTS OF FLORIDA. THESE SOLUTIONS ALL LIE
WITHIN A GENERAL AREA OF ANOMALOUS MOISTURE AND SOME INSTABILITY,
SUPPORTING A BROAD MARGINAL RISK AREA IN BOTH ERO DAYS AS THE BEST
REPRESENTATION OF THE SITUATION AT THIS TIME. RAINFALL DETAILS
CONTINUE TO BE UNCERTAIN BEYOND EARLY FRIDAY, AGAIN DEPENDING ON
THE ULTIMATE EVOLUTION OF POSSIBLE TROPICAL DEVELOPMENT.
THE CURRENT FORECAST PATH OF THE UPPER LOW TRACKING THROUGH THE
FOUR CORNERS REGION WOULD BRING THE BEST POTENTIAL FOR SIGNIFICANT
SNOWFALL TO PORTIONS OF THE COLORADO AND NEW MEXICO ROCKIES IN THE
WEDNESDAY-THURSDAY TIME FRAME. GRADUAL IMPROVEMENT IN GUIDANCE
CLUSTERING FOR UPPER LOW SPECIFICS OVER THE PAST DAY HAS RAISED THE
PROBABILITIES FOR SOME OF THIS SNOW TO EXTEND INTO THE HIGH PLAINS.
JUST TO THE EAST, THIS SYSTEM SHOULD PRODUCE SOME AREAS OF LOCALLY
HEAVY RAINFALL OVER THE SOUTHERN/CENTRAL PLAINS THURSDAY-FRIDAY.
THE MARGINAL RISK AREA DEPICTED OVER THE SOUTHERN PLAINS IN THE
DAY 5 ERO REPRESENTS THE MOST AGREEABLE REGION OF FOCUS IN THE
GUIDANCE DURING THE FIRST PART OF THIS EVENT. EXPECT THE
PRECIPITATION SHIELD TO PROGRESS EASTWARD/NORTHEASTWARD INTO THE
WEEKEND, GENERALLY WITH LIGHTER AMOUNTS BUT WITH UNCERTAINTY OVER
HOW MUCH INTERACTION THERE COULD BE WITH GULF MOISTURE AND THE
POSSIBLE SURFACE SYSTEM. THUS POTENTIAL STILL EXISTS FOR SOME AREAS
OF HEAVIER RAIN INTO THE WEEKEND.
THE NORTHWEST SHOULD BE DRY AROUND MIDWEEK AND THEN SEE INCREASING
RAIN/HIGH ELEVATION SNOW BY LATE WEEK AND THE WEEKEND, AS A LEADING
DYING FRONT APPROACHES FRIDAY AND THEN STRONGER SYSTEMS
APPROACH/ARRIVE DURING THE WEEKEND.
FOR THE MOST PART, EASTERN U.S. TEMPERATURES SHOULD BE ABOVE
NORMAL THROUGH THE PERIOD DUE TO PERSISTENT UPPER RIDGING OVER THE
WESTERN ATLANTIC AND EXTENDING INTO PARTS OF THE EAST. WEDNESDAY
INTO EARLY THURSDAY SHOULD BE PARTICULARLY WARM WITH BROAD COVERAGE
OF PLUS 15-25F ANOMALIES, CHALLENGING DAILY RECORDS FOR HIGHS/WARM
LOWS. BY LATE WEEK INTO THE WEEKEND EXPECT HIGHS TO MODERATE
SOMEWHAT (5-15F ABOVE NORMAL) WHILE SOME AREAS OVER THE SOUTHERN
HALF OR SO OF THE EAST COULD STILL SEE MORNING LOWS 15-20F ABOVE
NORMAL. CANADIAN FLOW COULD BRING TEMPERATURES CLOSER TO NORMAL
OVER NEW ENGLAND. MEANWHILE, AS THE FOUR CORNERS UPPER LOW FORMS
AND THEN EVENTUALLY EJECTS INTO THE PLAINS, MUCH OF THE WEST WILL
SEE WELL BELOW NORMAL HIGHS ON WEDNESDAY FOLLOWED BY PERSISTENCE OF
VERY CHILLY HIGHS OVER/NEAR THE CENTRAL-SOUTHERN ROCKIES THROUGH
FRIDAY (SOME LOCATIONS POSSIBLY 20-30F BELOW NORMAL FOR A DAY OR
TWO) WHILE THE INTERIOR WEST MODERATES. THEN THE UPPER LOW'S
DEPARTURE SHOULD SUPPORT A WARMER TREND OVER THE CENTRAL-SOUTHERN
ROCKIES DURING THE WEEKEND.
RAUSCH
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.PHPSCHICHTEL/HAMRICK
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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