545
FXUS02 KWBC 080700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST SAT FEB 8 2025
VALID 12Z TUE FEB 11 2025 - 12Z SAT FEB 15 2025
...HEAVY RAIN AND POTENTIAL FLOODING CONCERNS DEVELOPING IN THE
SOUTHEASTERN QUADRANT OF THE LOWER 48 THROUGH WEDNESDAY...
...ROUNDS OF SNOW AND ICE ARE POSSIBLE STRETCHING FROM THE
CENTRAL PLAINS TO MID-ATLANTIC/NORTHEAST NEXT WEEK...
..OVERVIEW
MODELS AND ENSEMBLES SHOW A VERY ACTIVE PATTERN DURING THE
TUESDAY-SATURDAY PERIOD. SHORTWAVE ENERGY EMERGING FROM THE
WEST/PLAINS AND ASSOCIATED FRONTAL WAVES WILL LIKELY FOCUS AN AXIS
OF HEAVY RAINFALL AND FLOODING CONCERNS OVER PARTS OF THE
SOUTHEASTERN QUARTER OF THE LOWER 48 EARLY-MID WEEK WITH SNOW
FARTHER NORTH FROM THE CENTRAL PLAINS INTO THE NORTHEAST TUESDAY
INTO THURSDAY. A WINTRY MIX WILL BE POSSIBLE BETWEEN THE RAIN/SNOW
AREAS. THEN DURING THE LATTER HALF OF THE WEEK A PACIFIC SYSTEM
SHOULD BRING AREAS OF SIGNIFICANT RAIN AND MOUNTAIN SNOW TO PARTS
OF THE WEST. THIS SYSTEM MAY REACH FAR ENOUGH EAST TO DEVELOP
PRECIPITATION OVER THE CENTRAL/EASTERN U.S. ONCE AGAIN BY NEXT
SATURDAY. EXPECT WELL BELOW NORMAL TEMPERATURES TO PERSIST OVER THE
NORTHWEST AND INTO THE NORTHERN-CENTRAL PLAINS TUESDAY-THURSDAY.
THE WEST SHOULD SEE SOME MODERATION LATE WEEK INTO THE WEEKEND AS
THE REGION SEES GREATER INFLUENCE FROM PACIFIC FLOW. THE
CENTRAL/SOUTHERN PLAINS WILL BRIEFLY TREND WARMER LATE IN THE WEEK
BUT EXPECT THE COLD AIR STILL OVER THE NORTHERN PLAINS TO PUSH
SOUTHWARD AGAIN ON SATURDAY. THE GREATEST NUMBER OF DAYS WITH ABOVE
NORMAL TEMPERATURES WILL LIKELY BE OVER THE GULF COAST AND FAR
SOUTHEAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE UPDATED FORECAST STARTED WITH A 12Z OPERATIONAL MODEL COMPOSITE
CONSISTING OF 40 PERCENT ECMWF AND LESSER WEIGHTS OF THE
GFS/CMC/UKMET FOR ABOUT THE FIRST HALF OF THE PERIOD AND THEN
TRANSITIONED TO 40 PERCENT ENSEMBLE MEANS (18Z GEFS AND 12Z
ECENS/CMCENS) AND THE REST EVENLY SPLIT AMONG THE GFS/ECMWF/CMC BY
DAY 7 SATURDAY.
THE BEST CLUSTERING OF DYNAMICAL AND MACHINE LEARNING (ML) GUIDANCE
CONTINUES TO BE SOMEWHAT FASTER THAN THE GFS/GEFS MEAN (AND
ESPECIALLY THE 18Z GFS) FOR SHORTWAVE ENERGY INITIALLY DROPPING
INTO THE NORTHWEST AND THEN EJECTING EASTWARD, LEADING TO LOW
PRESSURE REACHING THE EAST BY THURSDAY AND CONTINUING ON TOWARD THE
CANADIAN MARITIMES BY FRIDAY. HOWEVER THERE WERE A COUPLE 12Z ML
MODELS THAT HAD HEDGED A BIT SLOWER THAN THE ECMWF/CMC CLUSTER,
WITH SOME GUIDANCE ALSO HINTING AT POTENTIAL FOR A LITTLE MORE
NORTHERN STREAM SHORTWAVE INFLUENCE. THIS SUPPORTED AT LEAST A
MINIMAL INCLUSION OF THE 12Z GFS WHICH WAS CLOSER TO THE OTHER
GUIDANCE THAN THE 18Z RUN. THE NEW 00Z ECMWF/UKMET ALSO SHOW SOME
NUDGES, IN PARTICULAR TOWARD SLOWER PROGRESSION OF THE SOUTHERN
PART OF THE TRAILING COLD FRONT.
AT LEAST THROUGH THE 12Z/18Z CYCLE, GUIDANCE WAS SHOWING BETTER
CLUSTERING FOR THE PACIFIC SYSTEM TRACKING TOWARD THE WEST COAST
AFTER MIDWEEK, WITH CONSENSUS TRENDING STRONGER OVER THE PAST
COUPLE DAYS ALONG WITH THE SURFACE LOW TRACK CLUSTERING IN THE
CENTRAL-NORTHERN PART OF THE PRIOR ENVELOPE. THE NEW 00Z ECMWF/ICON
ADD A LITTLE DOUBT THOUGH, WITH A SOUTHWARD ADJUSTMENT. THE ECMWF
ALSO TRENDED NOTICEABLY SLOWER. AS THIS SYSTEM CONTINUES EASTWARD,
THERE IS BETTER THAN AVERAGE AGREEMENT IN CONCEPT BUT WITH TYPICAL
DIFFERENCES IN TIMING/STRENGTH OF THE UPPER TROUGH AND ASSOCIATED
CENTRAL U.S. SURFACE PRESSURE BY NEXT SATURDAY. ML MODELS SUGGEST
SOME SKEPTICISM OF THE STRONG 12Z ECMWF AND NEW 00Z GFS FOR THE
PLAINS SURFACE LOW. CONSENSUS IS ALSO DECENT FOR A NORTH PACIFIC
SYSTEM WHOSE LEADING WARM FRONT MAY APPROACH THE NORTHWEST BY NEXT
SATURDAY.
..WEATHER/HAZARDS HIGHLIGHTS
RAPID PROGRESSION OF A LEADING WAVE AND THE APPROACH OF A STRONGER
SHORTWAVE FROM THE WEST WILL MAINTAIN A WAVY FRONTAL BOUNDARY OVER
THE SOUTH DURING TUESDAY-WEDNESDAY, ESSENTIALLY PARALLEL TO
SOUTHWESTERLY FLOW ALOFT, AND INTERACTING WITH ANOMALOUS MOISTURE.
GUIDANCE HAS BEEN SIGNALING THE POTENTIAL FOR EXCESSIVE RAINFALL
WITH FLASH FLOOD POTENTIAL DURING THIS TIME FRAME IN RECENT DAYS
AND CONTINUES TO REFINE THE EXPECTED AXIS OF HEAVIEST RAINFALL IN
SUCCESSIVE RUNS. THE NEW DAY 4 EXCESSIVE RAINFALL OUTLOOK VALID ON
TUESDAY HAS EXPANDED THE SLIGHT RISK AREA BACK TO THE NORTHERN PART
OF THE TEXAS/LOUISIANA BORDER PER LATEST GUIDANCE, WHILE HOLDING
THE EASTERN EXTENT OF THE FAIRLY CONSISTENT OVER FAR SOUTHEASTERN
TENNESSEE AND NORTHWESTERN GEORGIA. THE FAVORED AREA FOR HEAVY
RAINFALL ON DAY 5 WEDNESDAY COMES CLOSE TO OVERLAPPING THIS REGION,
SHIFTING ONLY A FRACTION EAST/NORTHEAST, WITH A SLIGHT RISK AGAIN
INDICATED. RAINFALL FROM THE PREVIOUS DAY WOULD MAKE THIS REGION
INCREASINGLY SENSITIVE TO ADDITIONAL RAINFALL. EASTERN U.S. LOW
PRESSURE TRACKING NORTHEASTWARD ON THURSDAY SHOULD DRAG A COLD
FRONT THROUGH THE SOUTHEAST, WITH ASSOCIATED RAIN TRENDING LESS
INTENSE.
THE NORTHERN SIDE OF THE PRECIPITATION SHIELD MAY CONTAIN ROUNDS
OF POTENTIALLY DISRUPTIVE WINTRY PRECIPITATION NEXT WEEK. THE
FAVORED BAND FOR WINTER WEATHER SHOULD EXTEND FROM THE CENTRAL
PLAINS THROUGH THE MIDDLE MISSISSIPPI VALLEY, OHIO VALLEY, CENTRAL
APPALACHIANS, AND MID-ATLANTIC/NORTHEAST WHERE MOISTURE
OVERRUNNING SOUTHERN TIER FRONTS WILL INTERACT WITH COLD AIR.
50+ PERCENT PROBABILITIES FOR A QUARTER INCH OF LIQUID EQUIVALENT
SNOW/SLEET REMAIN IN PLACE FROM THE CENTRAL APPALACHIANS INTO
PARTS OF THE MID-ATLANTIC FOR TUESDAY TO WEDNESDAY MORNING (70-90
PERCENT OVER PARTS OF WEST VIRGINIA AND VIRGINIA), INCLUDING SOME
OF THE LARGER I-95 METROPOLITAN AREAS--ALBEIT WITH A VERY SLIGHT
SOUTHWARD NUDGE FROM PRIOR ISSUANCE BASED ON TRENDS FROM SOME
INCOMING 00Z MODELS. MEANWHILE SLEET AND FREEZING RAIN ARE
POSSIBLE BETWEEN THE CHANCES FOR HEAVY RAIN TO THE SOUTH AND SNOW
TO THE NORTH. STAY TUNED FOR REFINEMENTS TO THE FORECAST AS THE
PLACEMENT, AMOUNT, AND TYPE OF PRECIPITATION REMAINS UNCERTAIN AT
ANY INDIVIDUAL LOCATION. THE NEXT WAVE, REACHING THE EAST ON
THURSDAY, SHOULD PRODUCE A SOMEWHAT FARTHER NORTHWARD BAND OF SNOW,
FROM THE MIDWEST INTO THE NORTHERN MID-ATLANTIC AND NORTHEAST.
AFTER A FAIRLY DRY PERIOD EARLY IN THE WEEK, EXPECT A PACIFIC
SYSTEM TO SPREAD POTENTIALLY SIGNIFICANT RAIN AND MOUNTAIN SNOW
INTO THE WEST AFTER MIDWEEK. FOR THE DAY 5 ERO PERIOD WEDNESDAY-
WEDNESDAY NIGHT, MODELS VARY BETWEEN HEAVY AND MINIMAL
PRECIPITATION REACHING CALIFORNIA. STARTING OUT WITH A MARGINAL
RISK AREA ALONG THE NORTHERN HALF TO TWO-THIRDS OF THE CALIFORNIA
COAST PROVIDES A REASONABLE INTERMEDIATE REFLECTION OF THE GUIDANCE
ENVELOPE AT THIS TIME, WITH CONFIDENCE LOWER THAN AVERAGE. AFTER
EARLY THURSDAY EXPECT MOISTURE TO CONTINUE THROUGH THE WEST, WITH
THIS SYSTEM LIKELY EMERGING INTO THE PLAINS NEXT SATURDAY AND
DEVELOPING ANOTHER AREA OF VARIOUS PRECIPITATION TYPES OVER THE
CENTRAL/EASTERN U.S.
NORTHWESTERN AND NORTH-CENTRAL PARTS OF THE LOWER 48 WILL SEE
COLDER THAN AVERAGE TEMPERATURES NEXT WEEK. THE COLD WILL BE
ESPECIALLY PRONOUNCED ACROSS MONTANA AND NORTH DAKOTA EARLY IN THE
WEEK, WITH LOWS FORECAST TO BE IN THE -10S AND -20S, ALONG WITH
SOME BELOW ZERO HIGHS. COLDER THAN AVERAGE TEMPERATURES WILL SPREAD
SOUTH BEHIND A COLD FRONT NEXT WEEK, DISPLACING UNSEASONABLE
WARMTH ACROSS THE SOUTHERN TIER DURING THE WEEKEND. WARMER THAN
AVERAGE TEMPERATURES SHOULD BE LIMITED TO FLORIDA AND THE ADJACENT
SOUTHEAST BY MIDWEEK. INTRODUCTION OF PACIFIC FLOW SHOULD PROMOTE A
MODERATING TREND OVER THE WESTERN-CENTRAL U.S. BY NEXT FRIDAY (BUT
REMAINING QUITE COLD OVER THE NORTHERN PLAINS). LOW PRESSURE
EMERGING OVER THE PLAINS BY NEXT SATURDAY WILL HELP TO PULL DOWN
THE LINGERING NORTHERN PLAINS COLD AIR BACK DOWN INTO THE CENTRAL
PLAINS. AT THE SAME TIME, PARTS OF THE EAST SHOULD BEGIN TO TREND
SOMEWHAT WARMER.
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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