604
FXUS02 KWBC 041840
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
140 PM EST MON NOV 4 2024
VALID 12Z THU NOV 07 2024 - 12Z MON NOV 11 2024
...WATCHING POTENTIAL TROPICAL CYCLONE EIGHTEEN AS IT TRACKS INTO
THE GULF OF MEXICO TOWARD THE CENTRAL GULF COAST...
...FOUR CORNERS UPPER LOW TO BRING SIGNIFICANT ROCKIES SNOW AND
AREAS OF HEAVY RAIN AND RUNOFF ISSUES TO THE SOUTH-CENTRAL PLAINS...
..OVERVIEW
LATEST MODELS AND ENSEMBLES CONTINUE TO AGREE FAIRLY WELL OVERALL WITH
THE LARGE SCALE PATTERN EVOLUTION, WITH NORTHEASTWARD EJECTION OF
A FOUR CORNERS UPPER LOW WHILE UPPER RIDGING PREVAILS OVER PORTIONS
OF THE WESTERN ATLANTIC, GULF OF MEXICO, AND EASTERN U.S. THE
UPPER LEVEL REFLECTION OF POTENTIAL TROPICAL CYCLONE EIGHTEEN,
FORECAST TO REACH THE GULF BY THE START OF THE PERIOD EARLY
THURSDAY, SHOULD BECOME EMBEDDED WITHIN THE LARGER SCALE RIDGE.
MEANWHILE THE WEST COAST WILL SEE STEADILY DECREASING HEIGHTS ALOFT
AS A SEQUENCE OF SHORTWAVES DAMPEN INITIAL RIDGING, WITH THE
STRONGEST ONE LIKELY TO REACH THE COAST AROUND NEXT MONDAY. THE
FOUR CORNERS UPPER LOW WILL PRODUCE SIGNIFICANT SNOW OVER THE
SOUTHERN HALF OF THE ROCKIES AND INTO THE SOUTHERN HIGH PLAINS AS
WELL AS AREAS OF HEAVY RAIN OVER THE SOUTH-CENTRAL PLAINS, WHILE
THE UNCERTAIN TRACK OF PTC EIGHTEEN KEEPS CONFIDENCE LOWER FOR HOW
MUCH OF ITS MOISTURE MAY REACH INTO THE SOUTH. TRENDS ALOFT NEAR
THE WEST COAST WILL INCREASE PRECIPITATION COVERAGE AND INTENSITY
OVER THE PACIFIC NORTHWEST INTO NORTHERN CALIFORNIA BY THE WEEKEND
INTO EARLY NEXT WEEK. THE FOUR CORNERS STATES WILL SEE CHILLY
TEMPERATURES LATE THIS WEEK WHILE MUCH OF THE EAST SHOULD SEE
PERSISTENTLY ABOVE NORMAL TEMPERATURES THROUGH THE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST WPC FORECAST PACKAGE CONSIDERED THE DETAIL OF THE
MODELS, BUT GIVEN LOCAL TIMING AND FOCUS DIFFERENCES THAT SEEM
DIFFICULT TO RESOLVE OVER THE LOWER 48 AND ESPECIALLY WITH TROPICAL
SYSTEMS, INSTEAD USED A COMPOSITE BLEND OF THE MORE COMPATIBLE AND
RUN TO RUN CONSISTENT GEFS/ECMWF/CANADIAN ENSEMBLE MEANS THROUGHOUT
MEDIUM RANGE TIME SCALES. THIS LENDS TO THE BEST PREDICTABLE
FORECAST SYSTEMS/COMPONENTS THAT ALONG WITH APPLICATION OF WPC MANUAL
ADJUSTMENTS STILL SUPPORTS ONGOING THREAT MESSAGING.
DYNAMICAL AND MODEL GUIDANCE STILL OFFER VERY DIVERSE TRACKS FOR
PTC EIGHTEEN. RECENT ECMWF/UKMET RUNS CONTINUE TO BE FAIRLY FAR ON
THE FAR WESTERN SIDE OF THE ENVELOPE, TRACKING SURFACE REFLECTION
INTO THE WESTERN GULF. MACHINE LEARNING (ML) MODELS FAVOR A TRACK
OVER THE EAST-CENTRAL GULF TO THE GULF COAST. THIS IS CLOSER BUT
SLIGHTLY WEST OF THE TRACK OF RECENT RUNS OF THE GFS/CANADIAN, BUT
MOST IN LINE WITH LATEST GUIDANCE FROM THE NHC AND A COMPOSITE OF
THE ENSEMBLE MEANS. YET ANOTHER POTENTIAL TROPICAL SYSTEM OFFERS A
WEAKER DEPICTION MOVING WESTWARD TO THE EASTERN GULF IN A WEEK THAT
WILL ALSO CONTINUE TO BE MONITORED FOR SIGNS OF DEVELOPMEMT.
..WEATHER/HAZARDS HIGHLIGHTS
OVER THE SOUTHEAST/NORTHERN FLORIDA AS OF THURSDAY, GUIDANCE
CONTINUES TO OFFER SOME SIGNAL OF LINGERING HEAVY RAINFALL
POTENTIAL FROM ANOMALOUS MOISTURE AND SHORTWAVE ENERGY ROUNDING
THE WESTERN ATLANTIC DEEP-LAYER RIDGE, TO THE NORTH OF POTENTIAL
TROPICAL CYCLONE EIGHTEEN THAT SHOULD REACH THE SOUTHERN GULF OF
MEXICO. CLUSTERING FOR SPECIFICS REMAINS FAIRLY POOR, FAVORING
MAINTENANCE OF A SLIGHTLY SMALLER VERSION OF THE EXISTING MARGINAL
RISK AREA IN THE DAY 4 EXCESSIVE RAINFALL OUTLOOK. BY FRIDAY THE
GUIDANCE SIGNAL BECOMES MORE DIFFUSE OVER THE SOUTHEAST, WHILE MOST
RAINFALL DIRECTLY ASSOCIATED WITH PTC EIGHTEEN SHOULD STILL BE
OVER THE GULF, FAVORING NO AREA IN THE DAY 5 OUTLOOK. AFTER EARLY
SATURDAY, EXPECT SOME INCREASED RAINFALL ALONG/INLAND FROM THE
CENTRAL GULF COAST BASED ON THE 15 UTC NHC ADVISORY TRACK FOR PTC
EIGHTEEN, WITH SOME POTENTIAL INTERACTION WITH A FRONT APPROACHING
FROM THE WEST/NORTH AS DEEPER MOISTURE WORKS INLAND IN ADVANCE.
THE UPPER LOW FORECAST TO TRACK ACROSS ARIZONA/NEW MEXICO AND THEN
DEPART TO THE NORTHEAST WOULD BRING THE BEST POTENTIAL FOR
SIGNIFICANT SNOWFALL TO PORTIONS OF THE COLORADO AND NEW MEXICO
ROCKIES INTO LATE THIS WEEK, WITH SOME OF THIS SNOW LIKELY
EXTENDING A LITTLE EASTWARD 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 DAY
4 ERO MADE ONLY MINOR ADJUSTMENTS WITH A SOUTHWARD SHIFT GIVEN
LATEST GUIDANCE TO THE EXISTING MARGINAL RISK AREA DEPICTED OVER
THE SOUTHERN-CENTRAL PLAINS WHILE THE NEW DAY 5 OUTLOOK EXPANDS
THE MARGINAL RISK AREA. THE COMBINATION OF GUIDANCE TOTALS AND DAMP
SOILS FROM OBSERVED/SHORT-TERM RAINFALL SUGGESTED POTENTIAL FOR AN
EMBEDDED SLIGHT RISK AREA THAT WAS INTRODUCED. CONTINUED
PROGRESSION OF THE UPPER LOW AND SURFACE SYSTEM/FRONTS WILL SPREAD
RAINFALL OF VARYING INTENSITY INTO THE EAST BY THE WEEKEND.
AFOREMENTIONED MOISTURE FROM PTC EIGHTEEN MAY PROVIDE SOME
ENHANCEMENT DEPENDING ON THE SYSTEM'S TRACK, BUT DID TREND TOWWARD
A SLOWER EASTWARD TRANSLATION GIVEN LEADING HIGH PRESSURE DUG IN.
THE NORTHWEST WILL SEE A STEADILY WETTER PATTERN WITH HIGH
ELEVATION SNOW FROM FRIDAY ONWARD DUE TO A SUCCESSION OF SYSTEMS,
WITH THE ONE ARRIVING BY MONDAY TO BRING THE HIGHEST TOTALS ALONG
WITH FARTHER SOUTHWARD EXTENT INTO NORTHERN CALIFORNIA.
THE FOUR CORNERS STATES AND NEARBY AREAS WILL BE THE FOCUS FOR
BELOW NORMAL TEMPERATURES LATE THIS WEEK AS THE UPPER LOW DRIFTS
ACROSS THE REGION. SOME LOCATIONS MAY SEE HIGHS AT LEAST 20-25F
BELOW NORMAL ON THURSDAY AND ONLY A FEW DEGREES WARMER ON FRIDAY.
THE WEEKEND WILL BRING A NOTICEABLE MODERATING TREND AS THE UPPER
LOW DEPARTS, THOUGH THE SOUTHERN ROCKIES MAY NOT QUITE RECOVER
BACK TO NORMAL BY EARLY NEXT WEEK. THE REMAINDER OF THE WEST SHOULD
TREND TO NEAR NORMAL READINGS BY THE WEEKEND INTO EARLY NEXT WEEK.
EXCEPT FOR NORTHERN NEW ENGLAND LIKELY STAYING CLOSE TO NORMAL
MOST DAYS, THE EASTERN U.S. SHOULD SEE ABOVE NORMAL TEMPERATURES
THROUGH THE PERIOD DUE TO THE PERSISTENT MEAN RIDGE ALOFT OVER THE
WESTERN ATLANTIC AND PARTS OF THE GULF, PLUS EXTENDING INTO THE
EAST THROUGH EARLY SUNDAY. THURSDAY MORNING SHOULD BE PARTICULARLY
WARM WITH LOWS 20-25F ABOVE AVERAGE FROM PARTS OF THE MID-ATLANTIC
INTO THE SOUTHEAST. OTHERWISE, WITH DAY-TO-DAY VARIABILITY EXPECT
SOME COVERAGE ON MOST DAYS OF PLUS 15-20F ANOMALIES FOR MORNING
LOWS AND PLUS 10-15F ANOMALIES FOR DAYTIME HIGHS. ABOVE NORMAL
TEMPERATURES SHOULD EXTEND ACROSS THE UPPER MIDWEST AND NORTHERN
PLAINS AS WELL.
RAUSCH/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.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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