456
FXUS02 KWBC 032053
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
353 PM EST SUN NOV 3 2024
VALID 12Z WED NOV 06 2024 - 12Z SUN NOV 10 2024
...WATCHING POTENTIAL TROPICAL CYCLONE EIGHTEEN AS IT TRACKS INTO
THE GULF OF MEXICO TOWARDS THE CENTRAL GULF COAST...
..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 SHOWS POTENTIAL TROPICAL CYCLONE EIGHTEEN TRACKING
INTO THE GULF OF MEXICO AROUND MID WEEK BUT STILL WITH A LOT OF
GUIDANCE SPREAD FOR THE EXACT 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
MODELS CONTINUE TO SHOW PRETTY GOOD AGREEMENT ON THE
EVOLUTION/TRACK OF THE FOUR CORNERS UPPER LOW. THE 06Z GFS WAS
QUITE A BIT FASTER THAN CONSENSUS, BUT THE 12Z RUN HAS TRENDED
SLOWER/MORE WESTWARD AND MUCH MORE IN LINE WITH CONSENSUS AND THE
WPC FORECAST BLEND. THERE REMAINS SOME QUESTION ON ITS STRENGTH AND
WHETHER IT BECOMES MORE OF AN OPEN WAVE OR A CLOSED LOW AS THE
SYSTEM TRACKS NORTHEASTWARD INTO THE UPPER MIDWEST NEXT WEEKEND.
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 PTC EIGHTEEN. THE CMC HAD TENDED TO BE ON
THE FAST/EASTERN SIDE OF THE DYNAMICAL MODEL SPREAD FOR THE
POSSIBLE SYSTEM BUT THE LATEST 12Z RUN DID COME IN MORE WESTWARD
AND CLOSER TO CONSENSUS. THE ECMWF CONTINUES TO BE MORE SUPPRESSED
AND WEST WITH THE TRACK OF EIGHTEEN INTO THE WESTERN GULF. THE
OFFICIAL NHC FORECAST TRACKS PTC EIGHTEEN TOWARDS THE CENTRAL GULF
COAST, REPRESENTING A BLEND CLOSEST TO CONSENSUS AND THE 12Z
GFS/CMC.
AS FOR OTHER DETAILS, THERE IS SOME 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 00Z ECMWF WITH MODEST 00Z UKMET AND 06Z GFS FOR THE
FIRST HALF OF THE PERIOD. ADDED MORE OF THE ENSEMBLE MEANS LATER
IN THE PERIOD TO REFLECT THE GROWING UNCERTAINTY. OVERALL, THIS
MAINTAINED GOOD AGREEMENT WITH THE PREVIOUS WPC FORECAST.
..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 PTC EIGHTEEN 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 WITH SOME GUIDANCE A LITTLE FARTHER SOUTH INTO 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 AND TRACK
OF PTC EIGHTEEN.
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-CENTRAL
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.
SANTORELLI/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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