857
FXUS02 KWBC 041852
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
152 PM EST TUE MAR 4 2025
VALID 12Z FRI MAR 07 2025 - 12Z TUE MAR 11 2025
..GENERAL OVERVIEW
AFTER THE DEPARTURE OF THE MAJOR EAST COAST LOW STORM SYSTEM LATE
THIS WEEK, 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
APPROACH THE WEST COAST ON MONDAY WITH RAIN AND MOUNTAIN SNOW
RETURNING TO THE REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE
OVERALL LARGE SCALE PATTERN EVOLUTION DURING THE MEDIUM RANGE
PERIOD, BUT STILL SOME UNCERTAINTY IN THE DETAILS. 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 THIS WEEKEND, AS A SOUTHERN STREAM UPPER LOW BECOMES
DOMINANT. MODELS CONTINUE TO SHOW PLACEMENT, TIMING, AND STRENGTH
DIFFERENCES WITH ANY KIND OF SURFACE LOW ALONG THE GULF COAST AND
INTO THE WESTERN ATLANTIC EARLY NEXT WEEK. STILL, A MULTI-MODEL
BLEND SEEMS MOST REASONABLE AS A STARTING POINT FOR THE WPC
FORECAST TODAY THROUGH THE WEEKEND. BY MONDAY-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 (OR BRIEF CLOSING OF A LOW). GENERALLY FAVORED A BLEND OF THE
MODELS/ENSEMBLES FOR LATE PERIOD, AND THIS FIT WELL WITH PREVIOUS
WPC CONTINUITY AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
THE ASSOCIATED RAINFALL WITH A STRONG SURFACE LOW DEPARTING THE
NORTHEAST WILL BE WELL GONE BY THE START OF THE PERIOD, BUT STRONG
TO GUSTY WINDS IN ITS WAKE COULD CONTINUE INTO FRIDAY. RAIN AND
MOUNTAIN SNOW WILL BE ONGOING ACROSS SOUTHERN CALIFORNIA, AND THE
SOUTHWEST/FOUR CORNERS REGION THROUGH FRIDAY. MODERATE TO HEAVY
SNOWS ARE POSSIBLE FOR THE HIGHEST TERRAIN OF UTAH, ARIZONA, AND
THE SOUTHERN ROCKIES WITH SOME GUSTY WINDS AS WELL. STRONG WINDS
AND LOW RELATIVE HUMIDITY BEHIND A DRY LINE, WILL INCREASE THE FIRE
WEATHER THREAT AS WELL.
INTO THE 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. THIS LOOKS TO SET UP A PARTICULARLY WINDY
PATTERN FOR PARTS OF THE WEST AS WELL.
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.
SANTORELLI/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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