670
FXUS02 KWBC 241900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST MON FEB 24 2025
VALID 12Z THU FEB 27 2025 - 12Z MON MAR 03 2025
..OVERVIEW
REGULAR PASSAGES OF SHORTWAVES HEADING EASTWARD NEAR/ALONG THE
CANADIAN-U.S. BORDER TO THE EAST COAST OF NORTH AMERICA WILL TEND
TO PERIODICALLY REINFORCE THE BROAD TROUGHING THAT TENDS TO
MAINTAIN ITSELF ALONG THE EAST COAST OF THE U.S. MEANWHILE, A
TREND TOWARD MORE OF A SPLIT FLOW PATTERN IS INDICATED BY THE
ENSEMBLE MEANS BY NEXT WEEKEND AS AN UPPER LOW FOLLOWED BY A
DIGGING TROUGH WILL ATTEMPT TO UNDERCUT A RIDGE AXIS THAT TENDS TO
MAINTAIN ITSELF OVER THE WESTERN U.S.
..GUIDANCE/PREDICTABILITY ASSESSMENT
ENSEMBLE MEANS TODAY CONTINUE TO SHOW FAIRLY GOOD AGREEMENT ON THE
LARGE-SCALE PATTERN EVOLUTION ACROSS THE U.S. THROUGH THE MEDIUM-
RANGE PERIOD. THE DETERMINISTIC GUIDANCE FROM THE GFS HOWEVER,
DIFFERS QUITE A BIT FROM THE ECMWF AND CMC IN TERMS OF THE TRACK OF
A CLIPPER LOW PRESSURE SYSTEM THAT IS FORECAST TO REACH THE GREAT
LAKES BY DAY 4-5 (FRIDAY-SATURDAY), WITH THE GFS SHOWING A TRACK
MUCH FARTHER SOUTH THAN BOTH THE ECMWF AND CMC WHICH ARE SIMILAR TO
ONE ANOTHER. THE GEFS, ON THE OTHER HAND, SHOWS A TRACK THAT IS
FARTHER NORTH THAN THE DETERMINISTIC GFS, WHICH PLACES MORE
CONFIDENCE ON THE MORE NORTHERN TRACK ACCORDING TO THE ECMWF AND
CMC.
TOWARD THE LATTER HALF OF THE FORECAST PERIOD, THE MAIN CONCERN
WILL BE THE TIMING DIFFERENCES OF THE UPPER TROUGH/LOW FEATURES
MOVING INTO THE WESTERN U.S. ENSEMBLE MEANS SHOW RELATIVELY GOOD
AGREEMENT ON THE TIMING OF THE FIRST UPPER LOW GOING ACROSS THE
SOUTHWEST THIS WEEKEND AND REACHING INTO THE SOUTHERN PLAINS BY
NEXT MONDAY. FOR THE NEXT TROUGH DIGGING INTO THE WEST COAST BY
SUNDAY INTO MONDAY, AGREEMENT OF ENSEMBLE MEANS AMONG MODELS
APPEAR QUITE GOOD FOR A DAY 6-7 FORECAST. THE EC MEAN REMAINS THE
FASTEST WHILE THE GEFS IS LOWEST; THE CMC MEAN IS IN BETWEEN. IT
IS REASSURING TO SEE THAT THE ECMWF DETERMINISTIC SOLUTIONS HAVE
PROGRESSIVELY SLOWED DOWN FROM THE PREVIOUS FASTER FORECASTS WHILE
THE SLOW GFS SOLUTIONS HAVE PROGRESSIVELY SPED UP, WHICH LEADS TO
CONFIDENCE THAT THE MODEL SOLUTIONS ARE CONVERGING SOMEWHERE IN
BETWEEN THE FAST AND SLOW SOLUTIONS.
..WEATHER/HAZARDS HIGHLIGHTS
A COLD FRONT INTO THE EAST WILL SPREAD GENERALLY LIGHT TO MODERATE
PRECIPITATION INTO THURSDAY. SOME PRECIPITATION COULD BE SNOW IN
THE NORTHERN PART OF THE PRECIPITATION SHIELD ACROSS THE INTERIOR
NORTHEAST. A CLIPPER SYSTEM SHOULD BRING AN ADDITIONAL ROUND OF
PRECIPITATION TO THE GREAT LAKES AND NORTHEAST FRIDAY INTO
SATURDAY, WITH MODERATE SNOWFALL POSSIBLY ENHANCED BY THE LAKE
WATERS ACROSS THE UPPER GREAT LAKES FRIDAY INTO SATURDAY, WITH
MIXED PRECIPITATION JUST TO THE SOUTH. A PERIOD OF STRONG AND GUSTY
WINDS CAN ALSO BE EXPECTED ON FRIDAY ACROSS THE NORTHERN PLAINS AND
PERHAPS INTO SATURDAY NEAR THE GREAT LAKES ON THE BACK-SIDE OF THE
SYSTEM AS COLD AIR RUSHES IN BEHIND IT.
A BUILDING RIDGE SHOULD KEEP CONDITIONS QUIET AND DRY ACROSS THE
WEST THURSDAY AND FRIDAY, OTHER THAN A LITTLE LIGHT PRECIPITATION
POSSIBLE IN THE PACIFIC NORTHWEST. THE SOUTHERN STREAM UPPER LOW
MOVING ACROSS SOUTHERN CALIFORNIA FRIDAY AND INLAND NEXT WEEKEND
MAY LEAD TO LIGHT SHOWERS OVER CALIFORNIA, THE SOUTHWEST, AND INTO
THE SOUTH-CENTRAL U.S., WITH INCREASING RAIN CHANCES IN THE
SOUTHERN PLAINS BY NEXT SUNDAY AS MOISTURE INCREASES. THERE APPEARS
TO BE A BETTER SIGNAL FOR THE PRECIPITATION TO SPREAD FARTHER
EAST/NORTHEAST ACROSS THE SOUTHERN PLAINS SUNDAY INTO MONDAY. THE
NORTHERN STREAM TROUGH MOVING THROUGH THE EASTERN PACIFIC AND INTO
THE WEST NEXT WEEKEND WILL ALSO BRING PRECIPITATION BACK INTO THE
FORECAST FOR THE WEST COAST AND GREAT BASIN.
MUCH ABOVE NORMAL TEMPERATURES WILL BE WELL ESTABLISHED BY
THURSDAY ACROSS THE WEST AND INTO THE NORTHERN/CENTRAL PLAINS. THE
GREATEST ANOMALIES WILL BE ACROSS THE PLAINS WITH DAYTIME HIGHS 20
TO LOCALLY 30 DEGREES ABOVE NORMAL, WITH 60S FOR HIGHS AS FAR NORTH
AS NEBRASKA OR PERHAPS EVEN SOUTH DAKOTA AT TIMES. THE ABOVE
NORMAL TEMPERATURES WILL SPREAD SOUTH AND EAST, WITH THE WEST COAST
TRENDING COOLER BY EARLY NEXT WEEK. ACROSS THE EAST, TEMPERATURES
MAY INITIALLY BE WARM ON THURSDAY, BUT SHOULD TREND BACK TOWARDS
NORMAL (OR BELOW NORMAL) BY THE WEEKEND.
KONG/SANTORELLI
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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