034
FXUS02 KWBC 171849
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
249 PM EDT MON MAR 17 2025
VALID 12Z THU MAR 20 2025 - 12Z MON MAR 24 2025
..SNOWSTORM ON THURSDAY IN THE MIDWEST/GREAT LAKES
..OVERVIEW
THE GUIDANCE AGREES ON A FLOW PATTERN THAT HAS SOME AMPLITUDE BUT
REMAINS PROGRESSIVE. THIS PATTERN FAVORS MULTI-DAY UNSETTLED AND
WET WEATHER FOR THE WEST/NORTHWEST THIS WEEK, WITH AN ENHANCED
MOISTURE/RAIN FOCUS INTO THE PACIFIC NORTHWEST AND TERRAIN ENHANCED
HEAVY SNOW POTENTIAL INLAND ACROSS THE NORTHWEST TO THE ROCKIES.
EXPECT LESS DEFINED RAINY PERIODS FOR THE CENTRAL TO EASTERN U.S.
MAY BECOME BETTER ORGANIZED LATER PERIOD CONTINGENT ON EMERGING
RETURN INFLOW WITH EXPECTED UPPER FLOW AMPLIFICATION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES SHOW GOOD AGREEMENT, ALBEIT WITH UNCERTAINTY
IN DETAILS AS IS TYPICALLY THE CASE. THE WPC FORECAST BLEND WAS
COMPRISED OF EVEN PARTS OF THE GFS/ECMWF/CMC/UKMET EARLY ON, BEFORE
INCLUDING THE NAEFS/ECMWF ENSEMBLE MEANS THIS WEEKEND INTO EARLY
NEXT WEEK FOR THE PRESSURES, WINDS, FRONTS, QPF, AND POPS WHICH
SHOULD ACCOUNT REASONABLY FOR ANY LINGERING UNCERTAINTY. THE
REMAINDER OF THE GRIDS WERE MORE STRONGLY TIED TO THE 13Z NBM
OUTPUT.
..WEATHER/HAZARDS HIGHLIGHTS
A SERIES OF PACIFIC LOW PRESSURE/FRONTAL SYSTEMS WILL MOVE INTO
THE WEST/NORTHWEST AND TRIGGER REPEATING ROUNDS OF PRECIPITATION
THROUGH THE WEEKEND. MODERATELY HEAVY RAIN AND MOUNTAIN SNOW ARE
LIKELY IN THE PACIFIC NORTHWEST WHERE MODERATE MOISTURE WILL BE
CHANNELED ONSHORE. THE WPC DAY 5/FRIDAY EXCESSIVE RAINFALL OUTLOOK
MAINTAINS A MARGINAL RISK AREA FOR PORTIONS OF THE COASTAL RANGES
OF NORTHWEST OR AND WA GIVEN COMPOUNDING EFFECTS OF MULTIPLE DAYS
OF PRECIPITATION WHICH MAY LEAD TO LOCAL RUNOFF ISSUES. THERE WILL
ALSO BE PERIODIC HEAVY SNOW THREATS INLAND AS ENHANCED BY TERRAIN
ACROSS THE NORTHWEST TO THE NORTH- CENTRAL ROCKIES. THESE PACIFIC
SYSTEMS ARE FORECAST TO MOVE EAST ACROSS THE CENTRAL AND EASTERN
U.S. FRIDAY THROUGH THE WEEKEND AND MAY PRODUCE MAINLY MODEST
PRECIPITATION CHANCES THIS WEEK, BUT ACTIVITY MAY INTENSIFY INTO
NEXT WEEK GIVEN POTENTIAL SYSTEM ORGANIZATION WITH EXPECTED UPPER
FLOW AMPLIFICATION, PARTICULARLY ACROSS PORTIONS OF THE MIDWEST AND
SOUTHEAST.
A BIG WEATHER STORY SURROUNDS A LATE SEASON WINTER STORM EXPECTED
TO PRODUCE BLIZZARD CONDITIONS FOR PARTS OF THE NORTH-CENTRAL U.S.
INTO MIDWEEK. A LOW PRESSURE SYSTEM WILL TRACK FROM THE CENTRAL
PLAINS TO THE UPPER MIDWEST AND REACH THE GREAT LAKES BY THURSDAY.
THE STORM WILL HAVE A WRAP-AROUND HEAVY SNOW THREAT ON THE NORTHERN
SIDE OF THE LOW TRACK, AND THE TIGHT PRESSURE GRADIENT AROUND THE
SYSTEM WILL LIKELY PRODUCE STRONG GUSTY WINDS THAT COULD CREATE
BLIZZARD CONDITIONS. THIS WINDY SYSTEM FORMS A NEW CENTER NEAR
CHESAPEAKE BAY WHICH MOVES JUST OFFSHORE THE NEW ENGLAND COAST LATE
THURSDAY INTO FRIDAY, AND SOME WINTRY WEATHER CAN BE EXPECTED IN
NORTHERN/INTERIOR NEW ENGLAND AND THE HIGHER TERRAIN OF THE
CENTRAL APPALACHIANS. SHOWERS AND THUNDERSTORMS WITH A
TRAILING/WAVY COLD FRONT OF THIS SYSTEM WILL WORK ACROSS AND SWEEP
OFFSHORE THE EAST COAST THURSDAY.
ROTH/SCHICHTEL
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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