029
FXUS02 KWBC 101903
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
203 PM EST MON FEB 10 2025
VALID 12Z THU FEB 13 2025 - 12Z MON FEB 17 2025
...HEAVY RAIN AND FLASH FLOODING POSSIBLE FOR COASTAL CALIFORNIA AND HEAVY SNOW FROM THE SIERRA NEVADA INLAND THURSDAY-FRIDAY...
...ANOTHER ROUND OF SNOW FROM THE MIDWEST TO NORTHEAST FRIDAY-
SUNDAY WITH HEAVY RAIN LIKELY IN THE TENNESSEE VALLEY AGAIN
ESPECIALLY SATURDAY...
..OVERVIEW
THE MEDIUM RANGE PERIOD WILL FEATURE A SERIES OF SYSTEMS PRODUCING
AREAS OF SIGNIFICANT RAINFALL AND WINTER WEATHER. THE FIRST SYSTEM
SHOULD LINGER IN THE NORTHEAST ON THURSDAY WITH SNOW FOR NORTHERN
NEW ENGLAND AT THE SAME TIME A WET/SNOWY SYSTEM REACHES THE WEST
COAST, WITH HEAVIEST PRECIPITATION FOCUSED OVER CALIFORNIA.
CONTINUED PROGRESSION OF THE WEST COAST SYSTEM'S UPPER TROUGH WILL
LIKELY SUPPORT LOW PRESSURE REACHING THE EAST BY SUNDAY AND THE
CANADIAN MARITIMES BY MONDAY. THIS LOW SHOULD SPREAD WINTRY WEATHER
FROM THE UPPER MIDWEST THROUGH THE NORTHEAST, WITH HEAVY RAIN
FARTHER SOUTH OVER SOME AREAS THAT MAY BE AFFECTED BY PRIOR HEAVY
RAIN, LIKE THE TENNESSEE VALLEY. THE NEXT PACIFIC SYSTEM WILL
TRACK FARTHER NORTH THAN THE FIRST ONE, CONFINING THE RAIN AND
HIGHER ELEVATION SNOW MORE TO THE NORTHWEST FROM THE WEEKEND INTO
EARLY NEXT WEEK. PARTS OF THE PLAINS WILL SEE THE MOST PRONOUNCED
COLD ANOMALIES, ESPECIALLY ON THURSDAY AND THE WEEKEND, WHILE
GRADUALLY INCREASING PACIFIC INFLUENCE SHOULD HELP THE WEST TO
MODERATE FROM ITS COLD TEMPERATURES AS OF THURSDAY. THE SOUTHEAST
WILL TEND TO SEE ABOVE NORMAL TEMPERATURES FROM LATE WEEK THROUGH
THE WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS REASONABLY AGREEABLE FOR MOST LARGE-SCALE
SYSTEMS THROUGH THE PERIOD. A TROUGH AXIS MOVING THROUGH THE
NORTHERN TIER WILL SUPPORT A LOW PRESSURE SYSTEM WITH GOOD
AGREEMENT OVER THE LOWER GREAT LAKES REGION AT THE START OF THE
PERIOD 12Z THURSDAY QUICKLY TRACKING ACROSS THE NORTHEAST, AND A
MULTI-MODEL BLEND WORKED WELL FOR THAT. MEANWHILE, UPPER AND
SURFACE LOWS OVER THE EASTERN PACIFIC THURSDAY WILL PUSH INTO THE
WEST COAST BY FRIDAY, WITH THE REMAINING TROUGH MOVING ACROSS MUCH
OF THE LOWER 48 OVER THE WEEKEND-MONDAY. MORE MODEL DIFFERENCES
GRADUALLY ARISE INTO THE EAST, ESPECIALLY WITH THE RESULTING
SURFACE LOW. LOW PRESSURE SHOULD REDEVELOP OVER THE SOUTH-CENTRAL
PLAINS SATURDAY BUT AS IT TRACKS QUICKLY NORTHEASTWARD, THERE IS
VARIABILITY WITH ITS PLACEMENT BY SUNDAY IN THE EAST, PERHAPS MADE
MORE COMPLICATED BY THE POTENTIAL FOR A DOUBLE-BARRELLED LOW.
RECENT MODELS CLUSTER A MAIN LOW SOMEWHERE AROUND THE CENTRAL
APPALACHIANS/MID-ATLANTIC BUT SOME MODELS REMAIN WELL NORTH OF
THERE, INCLUDING THE 00Z ECMWF AND GFS. THIS LOW SHOULD STRENGTHEN
AS IT MOVES QUICKLY NORTHWARD INTO EASTERN CANADA BY MONDAY.
UPSTREAM, THE GENERAL IDEA OF TROUGHING MOVING INTO THE PACIFIC
NORTHWEST BY NEXT MONDAY IS IN GUIDANCE BUT WITH DIFFERENCES IN THE
STRENGTH AND TIMING, INCLUDING A SLIGHTLY FASTER TREND IN THE NEW
12Z GFS AND CMC.
GIVEN THE REASONABLY GOOD AGREEMENT OVERALL, THE WPC FORECAST WAS
BASED ON A BLEND OF THE 00/06Z DETERMINISTIC MODELS EARLY IN THE
PERIOD, WITH GRADUALLY INCREASING PROPORTIONS OF THE ENSEMBLE MEANS
TO 40 PERCENT BY DAY 7 TO MINIMIZE DIFFERENCES FROM INDIVIDUAL
MODELS.
..WEATHER/HAZARDS HIGHLIGHTS
THE SYSTEM TRACKING THROUGH THE NORTHEAST ON THURSDAY WILL BRING
MEANINGFUL SNOW TO NORTHERN NEW ENGLAND, WHILE THE TRAILING COLD
FRONT WILL CROSS THE SOUTHEAST. RECENT GUIDANCE RUNS HAVE BEEN
NARROWING THE SPREAD FOR THIS FRONT AND ITS ASSOCIATED AXIS OF
MOISTURE. MODELS SHOW SOME INSTABILITY WITH THIS FRONT AND
POTENTIAL FOR SOME LOCALLY HEAVY RAINFALL, MAINLY OVER PARTS OF
NORTHERN FLORIDA INTO GEORGIA. HOWEVER THIS REGION HAS DRY
ANTECEDENT CONDITIONS WITH VERY HIGH FLASH FLOOD GUIDANCE VALUES.
THUS THE DAY 4/THURSDAY EXCESSIVE RAINFALL OUTLOOK CONTINUES TO
DEPICT NO RISK AREA FOR THIS ACTIVITY. WILL CONTINUE TO MONITOR FOR
ANY TRENDS TOWARD BROADER ORGANIZED HEAVY RAINFALL ON THE HIGHER
END OF THE ENVELOPE.
WITH FAIRLY STRONG LOW PRESSURE AND ASSOCIATED FRONTAL SYSTEM
REACHING THE WEST COAST THURSDAY INTO EARLY FRIDAY, GUIDANCE HAS
MAINTAINED GOOD CONTINUITY OVER THE PAST DAY REGARDING FAVORABLE
MOISTURE ANOMALIES/ENHANCED IVT VALUES FOCUSING HEAVIEST RAINFALL
AND HIGHER ELEVATION SNOW OVER CALIFORNIA. THE INHERITED SLIGHT
RISK AREA FOR DAY 4/THURSDAY OVER A MAJORITY OF COASTAL CALIFORNIA
AND EXTENDING INTO THE SIERRA NEVADA FOOTHILLS STILL LOOKS GOOD.
EXPECT COASTAL AREAS FROM THE BAY AREA SOUTH INTO THE LOS ANGELES
METRO INCLUDING RECENT BURN SCARS TO HAVE RELATIVELY HIGHER
PROBABILITIES OF SEEING FLOODING IMPACTS, AND THIS IS CONSIDERED A
HIGH-END SLIGHT RISK. ESPECIALLY AS SHORTER TERM GUIDANCE REFINES
THE BEST FOCUS OF HEAVIEST RAINFALL AND WHAT THE RAIN RATES WILL
BE, IT IS POSSIBLE AN EVENTUAL UPGRADE TO A MODERATE RISK MAY BE
NEEDED ACROSS SOUTHERN CALIFORNIA AND IN PARTICULAR THE BURN SCAR
AREAS. THE DAY 5/FRIDAY ERO CONTINUES TO DEPICT A MARGINAL RISK
AREA ALONG THE FAR SOUTHERN COAST, WITH LINGERING MOISTURE EARLY IN
THE DAY AND THE UPPER TROUGH PASSING OVERHEAD TO PROVIDE SOME
POSSIBLE INSTABILITY OVER BURN SCAR AREAS THAT WOULD BE MOST
SENSITIVE TO ADDITIONAL SHOWERS.
CONTINUED PROGRESSION OF THIS SYSTEM WILL SPREAD AREAS OF RAIN AND
HEAVY MOUNTAIN SNOW FARTHER INLAND, EASTWARD TO THE ROCKIES. THE
UPPER TROUGH WILL LIKELY SUPPORT SURFACE LOW DEVELOPMENT OVER THE
EASTERN HALF OF THE COUNTRY DURING THE WEEKEND. SOUTH-CENTRAL AREAS
THAT WILL ALREADY BE SENSITIVE DUE TO PRIOR HEAVY RAINFALL CAN
EXPECT ANOTHER EPISODE OF HEAVY RAIN, PARTICULARLY SATURDAY IN THE
TENNESSEE VALLEY. MEANWHILE AREAS FROM THE MIDWEST INTO THE
NORTHEAST WILL SEE THE BEST POTENTIAL FOR SIGNIFICANT SNOW FRIDAY-
SUNDAY. A TRANSITION ZONE OF WINTRY MIX MAY SEPARATE THE RAIN/SNOW
AREAS. THERE MAY BE A PERIOD OF GUSTY WINDS OVER PARTS OF THE EAST
BEHIND THIS SYSTEM.
A FARTHER NORTHWARD TRACK OF THE NEXT PACIFIC SYSTEM WILL FAVOR THE
NORTHWEST FOR THE NEXT ROUND OF RAIN AND HIGHER ELEVATION SNOW FROM
THE WEEKEND INTO EARLY NEXT WEEK. AMOUNTS SHOULD START OUT ON THE
LIGHT TO MODERATE SIDE ON SATURDAY BUT MAY TREND SOMEWHAT HEAVIER
ON SUNDAY. EXPECT MOISTURE TO SPREAD FARTHER EASTWARD/SOUTHEASTWARD
INTO THE ROCKIES BY MONDAY.
PARTS OF THE CENTRAL U.S. WILL SEE WELL BELOW NORMAL TEMPERATURES
FOR MOST OF THE PERIOD, WITH SOME CENTRAL-SOUTHERN PLAINS
LOCATIONS 20-30F BELOW NORMAL FOR HIGHS ON THURSDAY FOLLOWED BY
ANOTHER COLD SURGE BRINGING SIMILAR ANOMALIES INTO THE FAR NORTHERN
PLAINS ON FRIDAY AND EXTENDING FARTHER SOUTHWARD DURING THE
WEEKEND. PROGRESSION OF AN UPPER TROUGH INTO THE EAST WILL SPREAD A
MODIFIED FORM OF THIS COLD AIR EASTWARD BY NEXT MONDAY WITH MOST
OF THE NORTHEASTERN QUADRANT OF THE LOWER 48 SEEING HIGHS 10-20F
BELOW NORMAL. COLD AIR WILL ALSO EXTEND INTO THE NORTHWEST THROUGH
LATE WEEK BUT THE WEST AS A WHOLE WILL GRADUALLY TREND WARMER AS
PACIFIC FLOW GAINS INFLUENCE. THE FOUR CORNERS STATES AND VICINITY
MAY ACHIEVE ABOVE NORMAL HIGHS BY THE START OF NEXT WEEK. SYSTEMS
FORECAST TO REACH THE EAST AROUND THURSDAY AND SUNDAY SHOULD PULL
SOME ABOVE NORMAL TEMPERATURES NORTHWARD FROM THE GULF
COAST/SOUTHEAST. A FEW LOCATIONS OVER THE FLORIDA PENINSULA COULD
CHALLENGE RECORD HIGHS ON ONE OR MORE DAYS. EVEN THE SOUTHEAST
COULD COOL TO A BIT BELOW NORMAL BY NEXT MONDAY BEHIND A COLD
FRONT.
TATE/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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