989
FXUS02 KWBC 040658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST TUE MAR 4 2025
VALID 12Z FRI MAR 7 2025 - 12Z TUE MAR 11 2025
..GENERAL OVERVIEW
AFTER THE DEPARTURE OF THE MAJOR EAST COAST LOW STORM SYSTEM, ANOTHER
LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE WESTERN U.S.,
WHICH WILL EJECT ACROSS THE CENTRAL PLAINS BY FRIDAY. IT WILL
LIKELY EVOLVE INTO TWO SEPARATE SHORTWAVES, WITH ONE QUICKLY
TRACKING 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, WITH A POTENTIAL CLOSED
UPPER LOW DEVELOPING ACROSS CALIFORNIA DURING THIS TIME.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE HAS COME INTO BETTER AGREEMENT
REGARDING THE EXPECTED OVERALL EVOLUTION OF THE WESTERN U.S. UPPER
TROUGH. IT APPEARS LIKELY THAT TWO SEPARATE SURFACE LOWS WILL
DEVELOP, WITH THE FIRST ONE OVER THE CENTRAL PLAINS ON FRIDAY, AND
A SECOND ONE NEAR THE GULF COAST ON SATURDAY. THERE ARE STILL SOME
MODEL DIFFERENCES THERE, SO A MULTI-MODEL MEAN IS A REASONABLE
STARTING POINT IN THE FORECAST PROCESS. BY NEXT TUESDAY WITH THE
NEXT TROUGH REACHING THE WEST COAST, THE GFS IS STRONGER WITH A
CLOSED UPPER LOW, WHEREAS THE CMC AND ECMWF FAVOR MORE OF AN OPEN
WAVE ALOFT. THE ENSEMBLE MEANS WERE GRADUALLY INCREASED TO ABOUT
40-60% BY EARLY NEXT WEEK.
..WEATHER/HAZARDS HIGHLIGHTS
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. 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. AT THIS TIME, IT DOES NOT APPEAR THAT HEAVY RAINFALL
WITH THIS EVENT WILL BE WIDESPREAD, AND GIVEN LINGERING MODEL
DIFFERENCES IN QPF PLACEMENT, THE DAY 4 AND 5 EXCESSIVE RAINFALL
OUTLOOKS DON'T DEPICT ANY RISK AREAS. IT IS POSSIBLE A MARGINAL
RISK MAY EVENTUALLY BE NEEDED FOR PORTIONS OF THE GULF COAST IN
FUTURE FORECAST UPDATES.
THE NEXT ROUND OF RAIN AND MOUNTAIN SNOW IS FORECAST TO REACH THE
WEST COAST BY SUNDAY AS A STRONG UPPER TROUGH AND COLD FRONT
APPROACHES THE COAST AND MOVES INLAND. THERE MAY BE AN ATMOSPHERIC
RIVER EVENT ACROSS PORTIONS OF CENTRAL AND SOUTHERN CALIFORNIA
GOING INTO MONDAY, ALONG WITH HEAVY SNOW FOR THE SIERRA AND
EVENTUALLY MOVING INLAND ACROSS THE HIGHER TERRAIN OF THE
INTERMOUNTAIN WEST.
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 SUNDAY AND EARLY NEXT WEEK, 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 IOWA.
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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