205
FXUS02 KWBC 031901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 PM EST MON MAR 3 2025
VALID 12Z THU MAR 06 2025 - 12Z MON MAR 10 2025
..GENERAL OVERVIEW
THE BACK-SIDE OF A DEEP LOW PRESSURE SYSTEM WILL TAKE ITS TIME
EXITING NEW ENGLAND AND THE EAST COAST LATE THIS WEEK DUE TO ITS
EXPANSIVE SIZE. ANOTHER LOW PRESSURE SYSTEM DEVELOPING OVER THE
WESTERN U.S. IS FORECAST TO EJECT INTO THE CENTRAL PLAINS BY
FRIDAY. IT WILL LIKELY EVOLVE INTO TWO SEPARATE SHORTWAVES--ONE
HEADS QUICKLY TOWARD THE OHIO VALLEY FOLLOWED BY A SOUTHERN STREAM
WAVE IN ITS WAKE TO TRACK GENERALLY NEAR OR JUST NORTH OF THE GULF
COAST WITH UNCERTAIN DOWNSTREAM DEVELOPMENT ALONG THE EAST COAST
EARLY NEXT WEEK. MEANWHILE, A PACIFIC COLD FRONT WILL LIKELY
APPROACH THE WEST COAST SUNDAY NIGHT INTO MONDAY WITH RAIN AND
MOUNTAIN SNOW RETURNING TO THE REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MUCH OF THE UNCERTAINTY IN THE MEDIUM-RANGE PERIOD CONTINUES TO BE
RELATED TO HOW ENERGY ASSOCIATED WITH AN AMPLIFIED WESTERN U.S.
UPPER TROUGH WILL EVENTUALLY EJECT INTO THE MID-SECTION OF THE
COUNTRY LATE THIS WEEK AND WHETHER TWO SUBSEQUENT SHORTWAVE
TROUGHS INTERACT WITH THE NORTHERN JET STREAM. THE LATEST MODEL
GUIDANCE SUITE CONTINUES TO SUPPORT THE IDEA THAT TWO SHORTWAVES
WILL DEVELOP OVER THE CENTRAL PLAINS FOLLOWING THE EJECTION OF THE
WESTERN U.S. LOW PRESSURE SYSTEM LATE THIS WEEK. MODELS HAVE
TRENDED NOTICEABLY FASTER FOR THE FIRST WAVE TO TRACK ACROSS THE
OHIO VALLEY FRIDAY NIGHT AND THEN QUICKLY OFF THE SOUTHERN NEW
ENGLAND COAST SATURDAY MORNING. THIS WILL BE QUICKLY FOLLOWED BY A
SECOND SHORTWAVE TO TRACK QUICKLY EASTWARD CLOSER TO THE GULF COAST
DURING THE WEEKEND. LATEST GFS OPENS THE POSSIBILITY FOR THIS
SECOND WAVE TO INTERACT WITH THE NORTHERN STREAM ENERGY AND RESULT
IN SIGNIFICANT CYCLOGENESIS OVER THE MID-ATLANTIC REGION LATE THIS
WEEKEND INTO MONDAY. THIS SCENARIO IS NOT CURRENTLY SUPPORTED BY
THE ECMWF AND THE EC-AIFS BUT IS SUGGESTED BY THE GRAPHCAST GFS.
THIS SITUATION WILL NEED TO BE MONITORED IN SUBSEQUENT WPC FORECAST
UPDATES.
MEANWHILE, A TROUGH IS FORECAST TO APPROACH THE WEST COAST LATE
THIS WEEKEND INTO EARLY NEXT WEEK. THE LATEST COUPLE OF RUNS FROM
THE GFS AND GEFS HAVE SPED UP THE FORWARD MOTION OF THIS TROUGH.
THE LATEST ECMWF FROM THE 12Z RUN HAS ALSO SPED UP THE TROUGH FROM
PREVIOUS RUNS. THE WPC MEDIUM-RANGE FORECASTS WERE BASED ON
CONSENSUS OF THE 06Z GFS/GEFS, 00Z EC/EC MEAN, AND 00Z CMC/CMC
MEAN BUT LEANING SLIGHTLY MORE TOWARD THE EC MEAN FOR DAYS 6 AND 7.
..WEATHER/HAZARDS HIGHLIGHTS
AN AMPLIFIED UPPER-LEVEL TROUGH IS FORECAST TO REACH THE NORTHEAST
U.S. BY THURSDAY AFTERNOON, ALONG WITH A STRONG SURFACE LOW THAT
WILL TRACK ACROSS QUEBEC, WITH SECONDARY SURFACE CYCLOGENESIS NEAR
NOVA SCOTIA THURSDAY NIGHT. MOST OF THE SIGNIFICANT RAINFALL SHOULD
ALREADY BE OFF THE COAST BY THIS TIME, WITH SOME LINGERING SHOWERS
OVER MAINE AND SNOW ACROSS THE HIGHER TERRAIN OF NEW ENGLAND AND
UPSTATE NEW YORK.
THE LARGE UPPER TROUGH OVER THE WESTERN U.S. LATE IN THE WEEK, IN
COMBINATION WITH EMBEDDED SHORTWAVE ENERGY, WILL RESULT IN NUMEROUS
SNOW SHOWERS ACROSS THE INTERMOUNTAIN WEST AND CENTRAL/NORTHERN
ROCKIES, WITH HEAVY SNOW LIKELY FOR THE SOUTHERN SIERRA, THE
WASATCH RANGE, AND THE HIGHER TERRAIN OF WYOMING AND WESTERN
COLORADO. MAINLY MODERATE HEAVY RAIN IS EXPECTED FOR SOUTHERN
CALIFORNIA AND THE PENINSULAR AND TRANSVERSE MOUNTAIN RANGES, AND
GIVEN RECENT BURN SCAR SENSITIVITIES FOR PORTIONS OF THIS REGION, A
MARGINAL RISK REMAINS VALID FOR THE NEW DAY 4 PERIOD THURSDAY. THE
OVERALL QPF SIGNAL IS NOT AS IMPRESSIVE GOING INTO FRIDAY (DAY 5)
ACROSS THE ROCKIES AND THE CENTRAL PLAINS, AND THEREFORE NO RISK
AREAS ARE NECESSARY FOR THE DAY 5 PERIOD. LOOKING AHEAD TO NEXT
WEEKEND, SHOWERS AND SOME THUNDERSTORMS ARE EXPECTED TO DEVELOP
NEAR THE GULF COAST AS THE SURFACE LOW EVOLVES WITH UNCERTAIN
DOWNSTREAM CYCLOGENESIS NEAR THE MID-ATLANTIC. THE NEXT ROUND OF
RAIN AND MOUNTAIN SNOW IS FORECAST TO REACH THE WEST COAST BY
SUNDAY.
COOLER THAN AVERAGE READINGS ARE LIKELY FROM THE INTERMOUNTAIN
WEST TO THE WESTERN HIGH PLAINS IN CONJUNCTION WITH THE UPPER
TROUGH SITUATED ACROSS THE SOUTHERN ROCKIES FOR THE END OF THE
WEEK. LOOKING AHEAD TO NEXT SUNDAY/MONDAY, THERE WILL LIKELY BE A
WARMING TREND ACROSS THE NORTH-CENTRAL U.S., WITH DAYTIME HIGHS
POTENTIALLY 10-20+ DEGREES ABOVE EARLY MARCH AVERAGES, WITH HIGHS
POTENTIALLY REACHING WELL INTO THE 60S FROM THE DAKOTAS INTO
PORTIONS OF THE UPPER MIDWEST.
KONG/HAMRICK
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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