141
FXUS02 KWBC 130700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST THU FEB 13 2025
VALID 12Z SUN FEB 16 2025 - 12Z THU FEB 20 2025
...STRONG STORM TO BRING HEAVY SNOW TO THE NORTHEAST ON SUNDAY WITH
LESS EXTREME RAINFALL TO THE SOUTH COMPARED TO SATURDAY...
..OVERVIEW
A DEEP UPPER TROUGH LIFTING THROUGH THE EAST ON SUNDAY WILL SUPPORT
A STRENGTHENING SURFACE LOW THAT SHOULD TRACK FROM THE UPPER OHIO
VALLEY TO THE CANADIAN MARITIMES SUNDAY INTO MONDAY. THIS STORM
WILL BRING SIGNIFICANT WINTRY PRECIPITATION AND THEN STRONG WINDS
TO NEW ENGLAND PLUS RAIN TO THE SOUTH--BUT WITH LESS EXTREME
TOTALS THAN FORECAST OVER THE TENNESSEE VALLEY/CENTRAL APPALACHIANS
ON SATURDAY. BEHIND THIS SYSTEM, ELONGATED UPPER TROUGHING WITH A
POSSIBLE EMBEDDED LOW WILL LIKELY LINGER OVER THE NORTHERN TIER
U.S. AND SOUTHERN CANADA WHILE A COUPLE SHORTWAVES/SURFACE FRONTS
TRACK INTO THE WEST. THESE FEATURES WILL BRING LOW ELEVATION RAIN
AND MOUNTAIN SNOW INTO THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA WITH SOME PRECIPITATION SPREADING FARTHER INLAND. THE
FIRST SYSTEM ARRIVING ON SUNDAY SHOULD ULTIMATELY SPREAD
PRECIPITATION OF VARYING TYPES ACROSS THE SOUTHERN TWO-THIRDS OF
THE CENTRAL-EASTERN U.S. TUESDAY ONWARD AS PLAINS LOW PRESSURE
TRACKS NEAR THE GULF COAST AND INTO THE SOUTHEAST OR FARTHER EAST
INTO THE ATLANTIC. THIS PART OF THE FORECAST CURRENTLY HAS BELOW
AVERAGE CONFIDENCE. ARCTIC HIGH PRESSURE EXPANDING SOUTH AND EAST
FROM THE NORTHERN PLAINS/SOUTHERN CANADA WILL LEAD TO WELL BELOW
NORMAL TEMPERATURES FOR MOST OF THE COUNTRY EAST OF THE ROCKIES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE MODELS CONTINUE TO SHOW GRADUAL NARROWING OF SPREAD FOR THE
SYSTEM FORECAST TO BE OVER THE UPPER OHIO VALLEY AT THE START OF
THE FORECAST EARLY SUNDAY, WITH DYNAMICAL SOLUTIONS CONTINUING TO
BE A FEW MB STRONGER THAN MACHINE LEARNING (ML) MODELS. NOTE THAT
00Z/12 AND THE 18Z/12 AIFS WERE THE MOST RECENT ML MODELS AVAILABLE
FOR REVIEW. THERE ARE STILL SOME TIMING ISSUES TO THE NORTHEAST,
WITH THE NEW 00Z UKMET STRAYING TO THE SLOW SIDE BY EARLY MONDAY.
THE SYSTEM REACHING THE NORTHWEST SUNDAY-MONDAY EXHIBITS SMALL-
SCALE DETAIL DIFFERENCES THAT WILL LIKELY TAKE INTO THE SHORTER
RANGE TO RESOLVE MORE FINELY. INTO TUESDAY GUIDANCE STILL AGREES
FAIRLY WELL WITH THE SHORTWAVE DROPPING INTO THE WEST, UNDERNEATH
ELONGATED UPPER TROUGHING ALIGNED ALONG THE CANADIAN BORDER.
HOWEVER BY WEDNESDAY-THURSDAY THE FORECAST BECOMES RAPIDLY MORE
UNCERTAIN DUE TO THE COMBINED DIFFERENCES THAT ARISE WITH TIMING OF
THE WESTERN U.S. SHORTWAVE AND WHAT BECOMES OF THE ELONGATED
NORTHERN TROUGH. AS FOR THE LATTER, SOLUTIONS RANGE BETWEEN THE
TROUGH REMAINING OPEN OR AN UPPER LOW CLOSING OFF SOMEWHERE BETWEEN
THE NORTHERN PLAINS AND GREAT LAKES. ML GUIDANCE TENDS TO FAVOR AN
UPPER LOW POSITION A LITTLE NORTHEAST OF THE DYNAMICAL MODEL
AVERAGE. THE END RESULT IS A WIDE SPREAD FOR TIMING/STRENGTH/TRACK
OF ASSOCIATED SURFACE LOW PRESSURE. THE MOST AGREEABLE SCENARIO,
COMPRISING THE 00Z/12 ECMWF, 12Z GEFS MEAN, AND A FAIR NUMBER OF
THE ML MODELS, WAS FOR A SURFACE TRACK NEAR THE GULF COAST ON
WEDNESDAY AND THEN OFF THE SOUTHEAST COAST BY EARLY THURSDAY. AMONG
NEW GUIDANCE, THE 00Z CMC WAS CLOSEST TO THIS IDEA (AFTER BEING
SLOW IN THE PRIOR 12Z RUN). THE 00Z GFS BECOMES AN EASTERN EXTREME
DUE TO BEING SHEARED WITH THE NORTHERN TROUGH (AFTER BEING FAST BUT
CLOSER TO THE COAST IN 12Z/18Z VERSIONS). IN CONTRAST, THE NEW 00Z
ECMWF IS JUST INLAND OVER THE SOUTHEAST. NEEDLESS TO SAY,
CONFIDENCE IN THIS PART OF THE FORECAST IS BELOW AVERAGE AT THIS
TIME.
WITH THE NEXT SYSTEM REACHING THE NORTHWEST AROUND MIDWEEK, SOME
ECMWF RUNS CONTINUE TO PULL OFF MORE OF A CLOSED LOW ALOFT THAN
MOST OTHER DYNAMICAL OR ML GUIDANCE. THE 00Z/12 ECMWF AT LEAST
PROVIDED A MORE PALATABLE OPTION THAN THE 12Z RUN.
THE UPDATED FORECAST REPRESENTED THE BEST IDEAS OF GUIDANCE AND
GOOD CONTINUITY WITH GREATER EMPHASIS ON THE 18Z GFS/12Z ECMWF
RELATIVE TO THE 12Z UKMET/CMC EARLY-MID PERIOD. AS SPREAD RAPIDLY
INCREASED BY WEDNESDAY-THURSDAY, THAT PART OF THE FORECAST TRENDED
A LOT MORE TOWARD THE 12Z GEFS/ECENS MEANS WITH ONLY LINGERING
INPUT FROM THE ECMWF (MORE 00Z/12 RUN THAN 12Z) FOR THE OPERATIONAL
COMPONENT BY NEXT THURSDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THE STRENGTHENING STORM LIFTING NORTHEASTWARD FROM THE UPPER OHIO
VALLEY ON SUNDAY WILL PRODUCE SOME WARM SECTOR RAINFALL ALONG THE
EAST COAST, BUT EXPECT THE THREAT OF HEAVY RAINFALL TO DECREASE
CONSIDERABLY COMPARED TO SATURDAY AS THE LOW AND ITS TRAILING COLD
FRONT BECOME MORE PROGRESSIVE, SO THE DAY 4/SUNDAY EXCESSIVE
RAINFALL OUTLOOK DEPICTS NO RISK AREAS. THERE COULD BE SOME
LINGERING LOCALIZED ISSUES OVER THE MID-ATLANTIC AND SOUTHERN NEW
ENGLAND DEPENDING ON RAINFALL DETAILS AND EXISTING GROUND
CONDITIONS LEADING INTO SUNDAY, BUT IT WILL TAKE INTO THE SHORT
RANGE TIME FRAME TO RESOLVE THESE DETAILS.
LOCATIONS FROM NEW YORK STATE THROUGH CENTRAL AND NORTHERN NEW
ENGLAND WILL SEE THE BEST POTENTIAL FOR HEAVY SNOW ON SUNDAY, WITH
A TRANSITION ZONE OF WINTRY MIXED PRECIPITATION BETWEEN THE SNOW
AREA AND RAIN TO THE SOUTH. CONTINUE TO MONITOR FORECASTS AS THE
EXACT POSITION OF THE RAIN/SNOW LINE OR TRANSITION BAND BECOMES
BETTER RESOLVED. THERE MAY BE A PERIOD OF STRONG AND GUSTY WINDS
OVER PARTS OF THE EAST BEHIND THIS SYSTEM, ALONG WITH SOME LAKE
EFFECT SNOW.
IN THE WEST, A PACIFIC SYSTEM WILL LIKELY CONTINUE TO PRODUCE RAIN
AND MOUNTAIN SNOW OVER THE PACIFIC NORTHWEST INTO SUNDAY.
PRECIPITATION AMOUNTS/RATES ARE STILL FORECAST TO STAY BELOW THE
CRITERIA FOR AN EXCESSIVE RAINFALL OUTLOOK AREA, BUT LIGHT TO
MODERATE PRECIPITATION WILL STILL BE POSSIBLE. PRECIPITATION WILL
PUSH EAST/SOUTHEAST THROUGH THE ROCKIES EARLY NEXT WEEK WHILE
TAPERING OFF IN THE PACIFIC NORTHWEST. ANOTHER SYSTEM SHOULD BRING
PRECIPITATION BACK TO THE NORTHWEST TUESDAY INTO WEDNESDAY WITH
ANOTHER ROUND OF LIGHT TO MODERATE TOTALS.
AS THE UPPER TROUGH CROSSING THE WEST EARLY NEXT WEEK HEADS INTO
THE CENTRAL U.S. BY WEDNESDAY AND FLOW TO THE NORTH POTENTIALLY
INTERACTS, EXPECT PRECIPITATION TO DEVELOP FROM THE
CENTRAL/SOUTHERN PLAINS EASTWARD. WINTRY WEATHER WILL BE POSSIBLE
IN THE NORTHERN PART OF THE PRECIPITATION SHIELD WITH RAIN OVER THE
SOUTH. CURRENTLY THE RELATIVELY GREATER POTENTIAL FOR WINTRY
WEATHER EXTENDS FROM THE CENTRAL PLAINS TO THE MID-ATLANTIC, WITH
LATEST PROBABILITIES FOR 0.25 INCH OF LIQUID IN THE FORM OF SHOW
REACHING 30-50 PERCENT OR SO OVER PARTS OF MISSOURI AND KANSAS
DURING TUESDAY-TUESDAY NIGHT. PROBABILITIES BECOME MORE DIFFUSE
FARTHER EASTWARD DURING THE NEXT DAY AS GUIDANCE SPREAD RAPIDLY
INCREASES WITHIN A BROAD RANGE BETWEEN A PROGRESSIVE SYSTEM WITH
LIGHT AMOUNTS OR A SLOWER/WESTWARD SYSTEM PRODUCING HEAVIER SNOW
AND OTHER WINTRY PRECIPITATION TYPES.
WELL BELOW NORMAL TEMPERATURES WILL LIKELY PREVAIL THROUGH THE
PERIOD OVER MUCH OF THE CENTRAL U.S., WITH SURGES REACHING INTO THE
SOUTHERN PLAINS ON SUNDAY AND AGAIN NEXT WEDNESDAY-THURSDAY. RECENT
COLDER TRENDS IN GUIDANCE SUGGEST SOME LOCATIONS COULD BE AT LEAST
30 DEGREES BELOW NORMAL (ESPECIALLY FOR HIGHS) WITH AN INCREASING
SIGNAL FOR SOME DAILY RECORD LOWS/COLD HIGHS BY AROUND MIDWEEK. THE
EAST WILL ALSO SEE SIGNIFICANTLY COLDER TEMPERATURES AFTER A VERY
BRIEF EPISODE OF WARMTH ALONG THE EAST COAST AHEAD OF THE SUNDAY
SYSTEM'S COLD FRONT. COLDEST ANOMALIES OF 10-25 DEGREES BELOW
AVERAGE OVER THE EAST SHOULD EXTEND OVER THE GREAT LAKES/OHIO
VALLEY INTO THE MID-ATLANTIC/SOUTHERN NEW ENGLAND. EXPECT
TEMPERATURES IN THE WEST TO REMAIN FAIRLY CLOSE TO NORMAL, WITH THE
NORTHWEST TENDING TO BE SLIGHTLY BELOW AND SOUTHERN AREAS A LITTLE
ABOVE.
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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