043
FXUS02 KWBC 090706
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
206 AM EST SUN FEB 9 2025
VALID 12Z WED FEB 12 2025 - 12Z SUN FEB 16 2025
...ACTIVE WEATHER PATTERN ON TAP FOR THE MEDIUM RANGE PERIOD WITH
PERIODS OF HEAVY RAIN AND WINTER WEATHER ACROSS PARTS OF THE WEST
AND THE CENTRAL-EASTERN U.S....
..OVERVIEW
GUIDANCE STILL SHOWS MULTIPLE SYSTEMS PRODUCING SIGNIFICANT
WEATHER FROM THE MIDDLE OF THE WEEK THROUGH NEXT WEEKEND. FIRST, A
LINGERING WAVY FRONT INITIALLY OVER THE SOUTHERN TIER AND
DEVELOPING LOW PRESSURE LIFTING NORTHEASTWARD LATE WEDNESDAY INTO
THURSDAY WILL PRODUCE AN AREA OF HEAVY RAINFALL AND FLOODING
CONCERNS OVER PARTS OF THE SOUTHEASTERN QUADRANT OF THE LOWER 48
WITH SNOW FROM THE CENTRAL PLAINS/MIDWEST INTO THE NORTHEAST. THEN
A VIGOROUS EASTERN PACIFIC SYSTEM WILL BRING HEAVY RAIN AND
MOUNTAIN SNOW TO CALIFORNIA DURING THE LATTER HALF OF THE WEEK WITH
SOME HEAVY SNOW EXTENDING INTO THE ROCKIES. CONTINUED PROGRESSION
OF THE SYSTEM'S UPPER TROUGH WILL LIKELY SUPPORT ANOTHER AREA OF
LOW PRESSURE REACHING THE EAST BY SUNDAY, WITH ADDITIONAL HEAVY
RAIN POSSIBLE OVER SOUTH-CENTRAL AREAS AND SNOW FROM THE UPPER
MIDWEST INTO NORTHEAST. BOTH EASTERN SYSTEMS MAY HAVE A WINTRY MIX
TRANSITION ZONE BETWEEN RAIN/SNOW AREAS. THE APPROACH OF A FARTHER
NORTH PACIFIC SYSTEM SHOULD BRING SOME MOISTURE INTO THE PACIFIC
NORTHWEST NEXT WEEKEND. THE NORTHERN-CENTRAL PLAINS SHOULD SEE THE
MOST PRONOUNCED COLD ANOMALIES, WHILE GRADUALLY INCREASING PACIFIC
INFLUENCE SHOULD HELP THE WEST TO MODERATE FROM ITS COLD
TEMPERATURES AS OF MIDWEEK. THE GULF COAST AND FAR SOUTHEAST WILL
SHOULD SEE THE MOST DAYS OF ABOVE NORMAL TEMPERATURES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
AN OPERATIONAL MODEL COMPOSITE OF THE 12Z ECMWF/18Z GFS/12Z CMC/12Z
UKMET, IN ORDER FROM MORE TO LESS WEIGHT, PROVIDED A REASONABLE
STARTING POINT FOR THE EARLY-MIDDLE PART OF THE FORECAST. GUIDANCE
CLUSTERING HAS STEADILY IMPROVED FOR THE SYSTEM AFFECTING THE EAST,
WITH RECENT GFS TRENDS BRINGING IT MORE IN LINE WITH THE MAJORITY
ECMWF CLUSTER--THOUGH THE ECMWF HAS ELONGATED THE UPPER TROUGH A
BIT COMPARED TO SOME EARLIER RUNS IN A NOD TO A COMPROMISE. MACHINE
LEARNING (ML) MODELS STILL SHOW SOME SPREAD FOR UPPER TROUGH
DETAILS SO CONSENSUS MAY STILL MAKE SOME MODEST ADJUSTMENTS FOR THE
SURFACE LOW AND/OR TRAILING COLD FRONT IN FUTURE RUNS. THE FAVORED
BLEND'S DEPTH IS CONSISTENT WITH THE ML MODEL AVERAGE. THE SYSTEM
APPROACHING THE WEST COAST HAS BEEN GETTING GRADUALLY STRONGER IN
RECENT DAYS, WHILE SOME NORTH-SOUTH TRACK SPREAD PERSISTS. ML
MODELS GENERALLY FAVOR A TRACK INTO THE PACIFIC NORTHWEST, WHICH
THE MULTI-MODEL BLEND ACCOMMODATES. THERE HAS BEEN A MODEST SLOWER
TREND NOTED OVER THE PAST DAY OR SO. GREATER DIFFERENCES EXIST WITH
QPF SPECIFICS.
DAYS 6-7 NEXT WEEKEND SHIFTED RAPIDLY TOWARD MORE 18Z GEFS/12Z
ECENS MEAN INPUT, BY SUNDAY REACHING 70 PERCENT, WHILE
TRANSITIONING TOWARD ONLY THE OLD 00Z/08 ECMWF FOR OPERATIONAL
MODEL DETAIL AT THAT TIME. LATEST CMC RUNS STRAY TO THE SLOW SIDE
WITH THE EMERGING WESTERN TROUGH BY SUNDAY, WHILE THE 18Z GFS
STRAYED TO THE FAST SIDE WITH EASTERN U.S. LOW PRESSURE AT THAT
TIME. THE 12Z ECMWF ALSO LEANED A BIT FAST WITH THE UPPER TROUGH BY
SUNDAY, WITH THE ENSEMBLE MEANS AND 00Z/08 ECMWF MATCHING BEST FOR
TIMING. ML MODELS SHOW A FAIR AMOUNT OF SPREAD FOR THE EASTERN U.S.
SURFACE DETAILS BY SUNDAY, WITH THE FLATTER CMC DEPICTION STILL
POTENTIALLY IN PLAY BASED ON ONE ML MODEL SOLUTION. HOWEVER MOST
OTHER ML MODELS SIDE CLOSER TO THE FAVORED ENSEMBLE MEANS AND OLD
00Z ECMWF. THE NEW 00Z ECMWF RUN SEEMS TO HAVE NUDGED A BIT IN THIS
DIRECTION. FARTHER WEST, GUIDANCE SHOWS BETTER THAN AVERAGE
AGREEMENT ON ANOTHER PACIFIC SYSTEM WHOSE FARTHER NORTH TRACK
SHOULD ULTIMATELY BRING THE EASTERN PERIPHERY OF ITS CIRCULATION
TOWARD THE PACIFIC NORTHWEST.
..WEATHER/HAZARDS HIGHLIGHTS
AN INITIAL WAVY FRONT OVER THE SOUTHERN TIER, NEARLY PARALLEL TO
UPPER FLOW, ALONG WITH ANOMALOUS MOISTURE WILL PROMOTE AN ONGOING
FOCUS FOR HEAVY RAINFALL ALONG AND NORTH OF THE BOUNDARY AS OF
EARLY WEDNESDAY. AN UPPER TROUGH EMERGING FROM THE WEST SHOULD
DEVELOP AN EMBEDDED LOW THAT TRACKS NORTHEASTWARD INTO THURSDAY.
GUIDANCE IS MAINTAINING THE SIGNAL FOR EXCESSIVE RAINFALL WITH
FLASH FLOOD POTENTIAL FROM THE LOWER MISSISSIPPI VALLEY INTO THE
SOUTHERN HALF OR SO OF THE APPALACHIANS DURING THE DAY 4 EXCESSIVE
RAINFALL OUTLOOK TIME FRAME. THE LATEST ISSUANCE WILL REFLECT
FAIRLY MINOR ADJUSTMENTS TO THE SLIGHT RISK AND SURROUNDING
MARGINAL RISK AREAS BASED ON LATEST GUIDANCE. RAINFALL FROM THE
PREVIOUS DAY WOULD MAKE THIS REGION INCREASINGLY SENSITIVE TO
ADDITIONAL RAINFALL. BY DAY 5/THURSDAY, THE COLD FRONT TRAILING
FROM DEPARTING LOW PRESSURE SHOULD REACH THE SOUTHEAST WITH THE
POSSIBILITY OF LOCALLY HEAVY RAINFALL (MOST LIKELY OVER NORTHERN
FLORIDA INTO GEORGIA). AT THIS TIME THERE IS A FAIR AMOUNT OF
SPREAD FOR SPECIFICS AND THIS REGION HAS DRY ANTECEDENT CONDITIONS
WITH HIGH FLASH FLOOD GUIDANCE VALUES. THUS DID NOT DEPICT A RISK
AREA AT THIS TIME BUT WILL CONTINUE TO MONITOR FOR ANY TRENDS
TOWARD BETTER CLUSTERING AND/OR RAIN RATES ON THE HIGHER END OF THE
ENVELOPE.
GUIDANCE STILL DIFFERS ON SOME OF THE DETAILS OF MOISTURE ARRIVING
INTO CALIFORNIA AROUND WEDNESDAY-WEDNESDAY NIGHT AHEAD OF A
VIGOROUS EASTERN PACIFIC SYSTEM. VARIOUS MODEL SOLUTIONS FALL
WITHIN THE ESTABLISHED MARGINAL RISK AREA ON THE DAY 4 ERO SO THAT
AREA REMAINS UNCHANGED. THERE IS SOMEWHAT BETTER AGREEMENT FOR
HEAVIEST ACTIVITY ON DAY 5/THURSDAY WITH FAVORABLE MOISTURE
ANOMALIES/ENHANCED IVT VALUES, FAVORING INTRODUCTION OF A SLIGHT
RISK AREA OVER A MAJORITY OF COASTAL CALIFORNIA AND EXTENDING INTO
FAVORED TERRAIN OF THE SIERRA NEVADA. THIS AREA REFLECTS THE BEST
OVERLAP OF HEAVIEST FORECAST RAINFALL AND CURRENT SENSITIVITIES
FROM EITHER WET ANTECEDENT CONDITIONS OR BURN SCARS.
CONTINUED PROGRESSION OF THIS SYSTEM WILL SPREAD AREAS OF HEAVY
SNOW FARTHER INLAND TO THE ROCKIES, AND THEN BY NEXT WEEKEND
SUPPORT ANOTHER EASTERN U.S. SYSTEM THAT MAY GENERATE ADDITIONAL
HEAVY RAINFALL OVER OR NEAR SOME AREAS EXPECTED TO SEE SIGNIFICANT
TOTALS FROM THE PREVIOUS EVENT.
BOTH SYSTEMS AFFECTING THE EAST MAY PRODUCE AREAS OF POTENTIALLY
DISRUPTIVE WINTRY PRECIPITATION. PROBABILITIES OF 0.25 INCH IN THE
FORM OF SNOW SUGGEST THE BEST POTENTIAL FOR SIGNIFICANT
ACCUMULATIONS WILL EXTEND FROM THE CENTRAL PLAINS THROUGH THE
MIDWEST AND THEN PARTS OF THE GREAT LAKES AND NORTHEAST/NORTHERN
MID-ATLANTIC. AT THIS TIME THE AXIS OF NEXT WEEKEND'S POTENTIAL
EVENT LOOKS TO BE A LITTLE NORTHWARD OF THE ONE THIS WEDNESDAY INTO
THURSDAY. A TRANSITION ZONE OF FREEZING RAIN AND/OR SLEET MAY EXIST
BETWEEN THE SNOW AREA AND RAIN TO THE SOUTH. CONTINUE TO MONITOR
FORECASTS AS GUIDANCE REFINES IMPORTANT DETAILS.
ANOTHER PACIFIC SYSTEM COMING INTO THE PICTURE BY THE WEEKEND MAY
SPREAD SOME PRECIPITATION INTO THE PACIFIC NORTHWEST. EXPECT
MODERATE AMOUNTS OVERALL BUT SOME LOCALIZED ENHANCEMENT WILL BE
POSSIBLE.
THE NORTHERN AND CENTRAL PLAINS WILL SEE THE MOST PERSISTENT BELOW
NORMAL TEMPERATURES FROM WEDNESDAY THROUGH THE WEEKEND, WITH MOST
DAYS 15-30F BELOW NORMAL ASIDE FROM THE CENTRAL PLAINS MODERATING
BRIEFLY ON FRIDAY. COLD AIR WILL EXTEND INTO THE WEST, AND IN
PARTICULAR THE NORTHWEST, THOUGH WITH A GRADUAL TREND TOWARD LESS
EXTREME ANOMALIES HEADING INTO THE WEEKEND AS PACIFIC FLOW GAINS
INFLUENCE. A FEW LOCATIONS IN THE NORTHWEST COULD SEE DAILY
RECORDS FOR LOWS/COLD HIGHS ON WEDNESDAY. ANOMALOUS WARMTH SHOULD
BE CONFINED MOSTLY TO THE GULF COAST AND FAR SOUTHEAST. PARTS OF
FLORIDA COULD SEE RECORD HIGHS ON ONE OR MORE DAYS, WHILE READINGS
COULD GET CLOSE TO RECORDS ON WEDNESDAY FARTHER WEST. SYSTEMS
TRACKING THROUGH THE EAST WILL BRIEFLY BRING SOME OF THIS WARMTH
NORTHWARD ON THURSDAY AND AGAIN 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.PHP
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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