299
FXUS02 KWBC 250657
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EST TUE FEB 25 2025
VALID 12Z FRI FEB 28 2025 - 12Z TUE MAR 04 2025
..OVERVIEW
THE MEDIUM RANGE CONTINUES TO FEATURE A RATHER PROGRESSIVE OVERALL
FLOW PATTERN. TROUGHING OVER THE EAST ON FRIDAY WILL BE REINFORCED
AGAIN THIS WEEKEND BY A SHORTWAVE THROUGH THE UPPER MIDWEST.
MEANWHILE OUT WEST, A CUTOFF UPPER LOW WILL SLIDE INTO SOUTHERN
CALIFORNIA ON FRIDAY, ACROSS THE SOUTHWEST THIS WEEKEND, AND WEAKEN
OR GET ABSORBED INTO THE LARGER SCALE FLOW EARLY NEXT WEEK OVER
THE SOUTHERN PLAINS. BEHIND THIS, ANOTHER DEEP TROUGH OR UPPER LOW
WILL MOVE INTO THE WEST COAST SUNDAY INTO MONDAY, WITH GENERAL
INDICATIONS OF A MORE AMPLIFIED PATTERN ACROSS THE WEST TO CENTRAL
U.S. NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE OVERALL
PATTERN PROGRESSION AND DOMINANT FEATURES OF THE MEDIUM RANGE
PERIOD, BUT WITH PLENTY OF UNCERTAINTY IN THE DETAILS. TWO MAIN
SOURCES OF UNCERTAINTY LIE WITH THE PAIR OF UPPER LOWS THROUGH THE
WESTERN U.S. THIS WEEKEND AND AGAIN NEXT WEEK. THE FIRST, INTO
SOUTHERN CALIFORNIA ON FRIDAY, HAS SHOWN IMPROVED CONSISTENCY IN
THE TIMING, BUT THERE IS VARIABILITY IN THE TRACK. THROUGH THE
12Z/18Z FEB 24 MODELS, THE GFS WAS NOTABLY DISPLACED NORTH OF THE
UKMET, CMC, AND ECMWF. THE EC-BASED AI MODELS WERE ALSO VARIED AND
THUS SUGGESTING THAT EITHER PLACEMENT WAS PLAUSIBLE. ALSO, TO NOTE,
THE NEW 00Z RUNS OF THE ECMWF AND CMC TONIGHT (AVAILABLE AFTER WPC
FORECAST GENERATION TIME) ALSO TRENDED SLIGHTLY NORTH. FOR THE
SECOND TROUGH EARLY NEXT WEEK, THE GUIDANCE AGREES ON ITS EXISTENCE
BUT THERE'S CONSIDERABLE UNCERTAINTY IN THE TIMING AND EVOLUTION.
THE ECMWF REMAINS ON THE FASTER SIDE, WITH THE TROUGH OVER THE
CENTRAL U.S. BY NEXT TUESDAY. THE GFS, HOWEVER, STILL HAS THE
TROUGH OVER THE WEST BY THAT TIME. THE CMC SEEMED A NICE MIDDLE
GROUND SOLUTION. ENSEMBLE MEANS GENERALLY SIDED WITH THEIR
DETERMINISTIC COUNTERPARTS, BUT WITH SLIGHTLY LESS LONGITUDINAL
SPREAD.
THE WPC BLEND FOR TONIGHT USED A MULTI-MODEL BLEND THE FIRST FEW
DAYS OF THE PERIOD, TRANSITIONING TO A NON-GFS AND HEAVILY WEIGHTED
ENSEMBLE MEAN BLEND BY DAY 7.
..WEATHER/HAZARDS HIGHLIGHTS
A CLIPPER SYSTEM SHOULD BRING A 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, 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 INTO FRIDAY. 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 AND SPREADING INLAND.
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. THE ABOVE NORMAL
TEMPERATURES WILL SPREAD SOUTH AND EAST, WITH THE WEST TRENDING
COOLER BY EARLY NEXT WEEK. ACROSS THE EAST, TEMPERATURES WILL VARY
BETWEEN NORMAL AND ABOVE NORMAL INTO SATURDAY, BUT MAY BE BELOW
NORMAL SUNDAY INTO MONDAY AS TROUGHING IS MOST ESTABLISHED.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page