860
FXUS02 KWBC 051857
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 PM EST TUE NOV 5 2024
VALID 12Z FRI NOV 08 2024 - 12Z TUE NOV 12 2024
...WATCHING T.S. RAFAEL AS IT TRACKS INTO THE GULF OF MEXICO
TOWARD THE CENTRAL GULF COAST...
...FOUR CORNERS UPPER LOW TO BRING LINGERING ROCKIES SNOW AND
AREAS OF HEAVY RAIN AND RUNOFF ISSUES TO THE SOUTH-CENTRAL
PLAINS LATE THIS WEEK...
19Z UPDATE: THE 12Z MODEL GUIDANCE SUITE FEATURES DECENT OVERALL
AGREEMENT AMONG THE UKMET/GFS/ECMWF GUIDANCE ON FRIDAY ACROSS THE
CONTINENTAL U.S., HOWEVER THE CMC ALREADY DIFFERS WITH THE GENERAL
PATTERN NEAR THE PACIFIC NORTHWEST AND ALSO ON THE OHIO VALLEY WITH
A LEAD SHORTWAVE CROSSING THROUGH THE REGION. BY SATURDAY, THE 12Z CMC
BECOMES MUCH LESS AMPLIFIED WITH THE TROUGH CROSSING THE PACIFIC
NORTHWEST, AND IS NOT A FAVORED WPC SOLUTION, WHEREAS THE 00Z CMC
SEEMED TO FIT THE PATTERN BETTER, SO SOME OF THE 00Z RUN WAS USED
IN THE MODEL BLEND. IN TERMS OF THE TRACK FOR T.C. RAFAEL, THE GFS
REMAINS TO THE RIGHT OF THE MODEL GUIDANCE SPREAD, WHEREAS THE
ECMWF/UKMET SOLUTIONS ARE TO THE LEFT, AND THE CMC FASTER AND
WEAKER. THE ICON AND JMA ARE ALSO CLOSER TO THE ECMWF SOLUTION THAT
SUGGESTS THE STORM WILL DRIFT LEFT ACROSS THE GULF BEFORE TURNING
AGAIN TO THE NORTH. THE LATEST NHC TRACK FEATURES A POSITION
BETWEEN THE GFS AND UKMET SOLUTIONS. GIVEN INCREASING UNCERTAINTIES
BY THE LATTER HALF OF THE FORECAST PERIOD EARLY NEXT WEEK, THE
ENSEMBLE MEANS ACCOUNTED FOR UP TO HALF OF THE MODEL PREFERENCES,
AND DROPPED THE 6Z GFS GIVEN ITS STRONGER SOLUTION WITH THE TROUGH
ACROSS THE EASTERN U.S., WHICH DID NOT HAVE MUCH ENSEMBLE MEAN
SUPPORT. THE PREVIOUS DISCUSSION IS APPENDED BELOW FOR REFERENCE.
/HAMRICK
----------------
..OVERVIEW
GUIDANCE HAS MAINTAINED GOOD CONTINUITY WITH MOST ASPECTS OF THE
LARGE SCALE PATTERN EVOLUTION ALOFT. AN UPPER LOW WILL EJECT
NORTHEASTWARD FROM NEW MEXICO WHILE PERSISTENT UPPER RIDGING OVER
THE WESTERN ATLANTIC EXTENDS A RIDGE INTO PARTS OF THE EASTERN U.S.
INTO THE WEEKEND, WITH RIDGING ALSO POTENTIALLY FILLING IN OVER
THE GULF OF MEXICO AS THE MID-LEVEL REFLECTION OF RAFAEL WEAKENS.
EJECTION OF THE UPPER LOW AND ITS ASSOCIATED SURFACE SYSTEM/FRONTS
WILL PRODUCE HEAVY RAINFALL OVER PARTS OF THE PLAINS AND POSSIBLY
OVER SOME LOCATIONS FARTHER EASTWARD, WITH RAFAEL ALSO POTENTIALLY
CONTRIBUTING SOME MOISTURE AS IT REACHES THE NORTHERN GULF. AN
AMPLIFYING UPPER TROUGH PUSHING INTO THE WEST WILL BECOME THE
DOMINANT FEATURE EARLY NEXT WEEK, SPREADING RAIN AND HIGH ELEVATION
SNOW ACROSS MORE OF THE WEST BY THEN. ABOVE NORMAL TEMPERATURES
WILL PREVAIL OVER MUCH OF THE EAST INTO THE NORTHERN PLAINS, WHILE
THE SOUTHERN ROCKIES WILL BE QUITE CHILLY LATE THIS WEEK UNDER THE
UPPER LOW.
..GUIDANCE/PREDICTABILITY ASSESSMENT
12Z/18Z GUIDANCE PROVIDED NUMEROUS DIFFERENCES FOR SIGNIFICANT
FEATURES THROUGH THE PERIOD. SOLUTIONS CONTINUE TO SHOW REMARKABLE
DIVERGENCE FOR T.S. RAFAEL (FORECAST TO REACH HURRICANE STRENGTH
FOR A TIME PER 0300 UTC NHC ADVISORY) AFTER LATE THIS WEEK, WITH
MACHINE LEARNING (ML) GUIDANCE ALSO VARYING CONSIDERABLY BUT AS A
WHOLE NOT LEANING AS FAR WEST AS LATEST ECMWF/UKMET RUNS OR AS FAST
TO LIFT THE SYSTEM NORTHWARD AS GFS/CMC RUNS. MEANWHILE THE
18Z/00Z GFS STRAYS SOMEWHAT FAST FOR THE UPPER LOW EJECTING FROM
NEW MEXICO WHILE IT ALSO DAMPENS THE SOUTHEAST RIDGE MORE THAN
OTHER GUIDANCE (PUSHING THE COLD FRONT FARTHER EAST/SOUTHEAST
VERSUS CONSENSUS). SOME GFS RUNS ALSO SHOW CURIOUS INTERACTIONS
BETWEEN INCOMING PACIFIC ENERGY AND THE UPPER LOW AROUND THE GREAT
LAKES/SOUTHEASTERN CANADA. FINALLY, MOST ML MODELS FAVOR A FAIRLY
AMPLIFIED UPPER TROUGH (MORE THAN ECMWF RUNS) REACHING THE WEST
EARLY NEXT WEEK WITH FASTER TIMING THAN THE LATEST GFS RUNS.
CONSENSUS IS SLOWER THAN UKMET RUNS IN PARTICULAR FOR THE PRECEDING
WEAKER SHORTWAVE.
GUIDANCE COMPARISONS LED TO EMPHASIZING THE 12Z GFS/ECMWF EARLY IN
THE PERIOD WITH MINOR INPUT FROM THE 12Z UKMET, FOLLOWED BY
REMOVING THE UKMET AND TEMPERING ECMWF INPUT BY MID-PERIOD WHILE
INTRODUCING THE 18Z GEFS/12Z ECENS MEANS. THEN THE BLEND QUICKLY
SHIFTED TO MOSTLY ENSEMBLE MEANS BY NEXT MONDAY-TUESDAY AS THEY
PROVIDED THE BEST COMBINATION OF WESTERN U.S. TROUGH AMPLITUDE AND
TIMING COMPARED TO ML GUIDANCE.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER LOW EXPECTED TO EMERGE FROM NEW MEXICO AND TRACK
NORTHEASTWARD MAY BRING LINGERING POTENTIAL FOR MEANINGFUL SNOW TO
PARTS OF THE COLORADO/NEW MEXICO ROCKIES INTO FRIDAY BUT WITH LOWER
TOTALS THAN WHAT MAY OCCUR IN THE SHORTER TERM. A LITTLE SNOW COULD
EXTEND INTO THE HIGH PLAINS. IMMEDIATELY TO THE EAST, SOME HEAVY
RAINFALL SHOULD ALREADY BE IN PROGRESS OVER PARTS OF THE SOUTHERN
PLAINS AT THE START OF THE PERIOD. THIS ACTIVITY SHOULD PERSIST AND
EXPAND SOMEWHAT THROUGH FRIDAY-FRIDAY NIGHT, FAVORING MAINTENANCE
OF THE EXISTING SLIGHT RISK AREA IN THE DAY 4 EXCESSIVE RAINFALL
OUTLOOK WITH A MODEST BROADENING ON THE NORTH SIDE (YIELDING AN
AREA FROM NORTHWESTERN TEXAS INTO SOUTH- CENTRAL KANSAS) TO GIVE
SOME ACCOUNT FOR SPREAD AMONG THE SLOWER NON-GFS GUIDANCE CLUSTER.
AS THE SURFACE SYSTEM CONTINUES EASTWARD INTO SATURDAY, THERE IS
INCREASING SPREAD FOR WHERE HEAVY RAINFALL COULD FOCUS DEPENDING ON
FRONTAL PROGRESSION AND DETAILS OF A POTENTIAL AXIS OF MOISTURE
ANOMALIES EXTENDING NORTHWARD FROM THE GULF OF MEXICO (SUGGESTING
A CONNECTION WITH SOME OF RAFAEL'S MOISTURE). THE DAY 5 ERO
INTRODUCES A MARGINAL RISK AREA FROM FAR EASTERN TEXAS INTO
SOUTHERN KENTUCKY WHERE THE BEST POTENTIAL FOR MOISTURE/FRONTAL
INTERACTION EXISTS AMONG THE NON-GFS ENVELOPE, BETWEEN THE SLOWER
ECMWF/UKMET AND FASTER CMC. THE 0300 UTC NATIONAL HURRICANE CENTER
TRACK FOR RAFAEL WOULD LIKELY KEEP MOST OF THE ENHANCED RAINFALL
DIRECTLY AROUND THE SYSTEM NEAR OR JUST SOUTH OF THE CENTRAL GULF
COAST DURING THE DAYS 4-5 ERO PERIOD. EXPECT RAINFALL OF VARYING
INTENSITY TO CONTINUE SPREADING EASTWARD/NORTHEASTWARD ACROSS THE
EASTERN U.S. THROUGH SUNDAY.
THE FORECAST CONTINUES TO SHOW THE NORTHWEST TRENDING WETTER WITH
HIGH ELEVATION SNOW FROM FRIDAY ONWARD DUE TO A SUCCESSION OF
SYSTEMS. THE LEADING ONE WILL BRING MODERATE AMOUNTS OF
PRECIPITATION TO THE PACIFIC NORTHWEST AND FAR NORTHERN ROCKIES
DURING FRIDAY-SATURDAY. THE NEXT SYSTEM SHOULD BE STRONGER AND MORE
AMPLIFIED, BRINGING HIGHER TOTALS ALONG WITH EXPANDING
SOUTHEASTWARD COVERAGE INTO CALIFORNIA AND THE INTERMOUNTAIN
WEST/ROCKIES BY THE START OF NEXT WEEK. THERE IS STILL A FAIR
AMOUNT OF GUIDANCE SPREAD FOR THE EXACT TIMING AND AMPLITUDE OF THE
UPPER TROUGH, TEMPERING CONFIDENCE FOR SOME ASPECTS OF
PRECIPITATION MAGNITUDE AND COVERAGE AT THIS TIME.
THE FOUR CORNERS STATES AND SOUTHERN HIGH PLAINS WILL SEE
ANOMALOUSLY CHILLY TEMPERATURES CONTINUE INTO FRIDAY WITH SOME
HIGHS 15-25F BELOW NORMAL AS THE UPPER LOW DRIFTS ACROSS THE
REGION. THE WEEKEND WILL BRING A NOTICEABLE MODERATING TREND AS
THE UPPER LOW DEPARTS, THOUGH PARTS OF 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 DURING THE
WEEKEND AND GENERALLY INTO MONDAY. THE AMPLIFYING UPPER TROUGH
FORECAST TO REACH THE WEST BY NEXT TUESDAY SHOULD BRING FAIRLY
BROAD COVERAGE OF BELOW NORMAL READINGS, WITH ANOMALIES DETERMINED
BY THE TROUGH'S TIMING AND DEPTH. MEANWHILE, ASIDE FROM NORTHERN
NEW ENGLAND STAYING CLOSE TO NORMAL FRIDAY-SUNDAY, THE EASTERN
U.S. PLUS THE UPPER MIDWEST/FAR NORTHERN PLAINS SHOULD SEE ABOVE
NORMAL TEMPERATURES THROUGH THE PERIOD. THE WARMEST ANOMALIES OF
PLUS 15-20F OR GREATER SHOULD BE FOR MORNING LOWS OVER THE
SOUTHEAST FRIDAY-SATURDAY (WHEN SOME DAILY RECORDS FOR WARM MOWS
ARE POSSIBLE) AND THEN SPREADING NORTH-NORTHEAST AHEAD OF A FRONT
BY SUNDAY-MONDAY. HIGHS WILL TEND TO BE 5-15F ABOVE NORMAL. THE
SOUTHERN PLAINS MAY SEE SOME OF THIS WARMTH EARLY NEXT WEEK AS
WELL.
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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