823
FXUS02 KWBC 181904
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
204 PM EST TUE FEB 18 2025
VALID 12Z FRI FEB 21 2025 - 12Z TUE FEB 25 2025
...INTENSE CENTRAL TO EASTERN U.S. ARCTIC BLAST THIS WEEK TO
MODERATE BY THE WEEKEND...
..WET PACIFIC NORTHWEST PATTERN THIS WEEKEND/EARLY NEXT WEEK
..OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE CONTINUES TO OFFER A REASONABLY SIMILAR LARGER SCALE FLOW
EVOLUTION OVER THE NEXT WEEK, ALBEIT LADEN WITH NUMEROUS SMALLER
SCALE EMBEDDED SYSTEM DIFFERENCES. MODERATE PROGRESSION OF THESE
INDIVIDUAL SHORTWAVES ALOFT IN SPLIT STREAMS OVER THE LOWER 48 THIS
WEEK IS EXPECTED TO LEAD AN EVOLUTION TOWARD A LARGER SCALE MEAN
UPPER PATTERN HIGHLIGHTED BY A WESTERN RIDGE AND EASTERN TROUGH BY
THE START OF NEXT WEEK. THIS TRANSITION WILL BRING THE BEST
POTENTIAL FOR MEANINGFUL PRECIPITATION TO THE PACIFIC NORTHWEST
FROM THE WEEKEND INTO EARLY NEXT WEEK, ALONG WITH A PRONOUNCED
WARMING TREND OVER ESPECIALLY THE WESTERN-CENTRAL U.S. IN STARK
CONTRAST TO THE ONGOING ARCTIC AIRMASS THIS WEEK.
A MULTI-MODEL BLEND WITH SOME ENSEMBLE MEAN INCLUSION WORKED WELL
FOR THE START OF THE FORECAST PERIOD DESPITE THE SMALLER SCALE
DIFFERENCES. AS THE PERIOD PROGRESSED, INCREASED THE PROPORTION OF
ENSEMBLE MEANS TO OVER HALF THE BLEND BY DAYS 6-7. THIS MAINTAINED
GOOD CONTINUITY WITH THE PREVIOUS FORECAST, THOUGH A SURFACE LOW
COMING ACROSS SOUTH-CENTRAL CANADA TO THE GREAT LAKES AS A CLIPPER
SYSTEM EARLY NEXT WEEK HAS SHOWN A LITTLE MORE CLUSTERING FOR A
DEEPER LOW, DESPITE CONTINUED SPREAD.
..WEATHER/HAZARDS HIGHLIGHTS
QUITE THE IMPRESSIVE ARCTIC AIRMASS IS SETTLING OVER THE CENTRAL
AND EASTERN U.S. THIS WEEK. AN EXTREME COLD THREAT WITH WIDESPREAD
RECORD TEMPERATURES FOR MORNING LOWS/COLD DAYTIME HIGHS WILL LINGER
INTO FRIDAY OVER THE SOUTH-CENTRAL TO SOUTHERN U.S., BUT THE BROAD
AIRMASS WILL CONTINUE TO STEADILY MODERATE THROUGH THE WEEKEND
INTO NEXT WEEK. ABOVE NORMAL TEMPERATURES WILL DEVELOP OVER THE
WEST AND EVENTUALLY THE CENTRAL U.S. WHERE BY EARLY NEXT WEEK MOST
LOCATIONS WEST OF THE MISSISSIPPI RIVER WILL WARM TO ABOVE NORMAL
WITH DECENT COVERAGE OF PLUS 10-25 DEGREE ANOMALIES. BEST POTENTIAL
FOR HIGHEST ANOMALIES WILL BE OVER AND NEAR THE NORTHERN PLAINS.
TEMPERATURES OVER THE EAST SHOULD REACH NEAR NORMAL TO SLIGHTLY
WARMER INTO EARLY NEXT WEEK.
FROM SATURDAY ONWARD THE PATTERN BECOMES INCREASINGLY FAVORABLE
FOR LONGER FETCH MOISTURE FEED TO FUEL ROUNDS OF MODERATE TO HEAVY
LOWER ELEVATION RAIN AND HIGH ELEVATION/MOUNTAIN SNOW PRIMARILY
INTO THE PACIFIC NORTHWEST, BUT ALSO INLAND TO THE NORTHERN
ROCKIES. THE BEST POTENTIAL FOR HIGHEST TOTALS CURRENTLY EXISTS
OVER THE FAVORED TERRAIN AND COASTAL AREAS OF WESTERN WASHINGTON
AND NORTHWESTERN OREGON. A DAY 5/SATURDAY WPC EXCESSIVE RAINFALL
OUTLOOK (ERO) MARGINAL RISK AREA HAS BEEN EXPANDED EASTWARD TO
WESTERN FOOTHILLS OF THE CASCADES DUE TO THE INITIALLY HIGH SNOW
LEVELS AT THE START OF A MULTI-DAY PERIOD OF WET WEATHER.
FARTHER EAST, STRONGLY ORGANIZED STORM SYSTEMS GENERALLY DO NOT
LOOK LIKELY OVER THE CENTRAL TO EASTERN U.S. DESPITE MULTIPLE
UNCERTAIN IMPULSES RIDING INTO THE ERODING ARCTIC AIRMASS AND WITH
FLOW TRANSITION. ONE FEATURE TO NOTE IS EMERGING WESTERN U.S.
ENERGY THAT MAY SUPPORT PERIODIC MODERATE RAINFALL OVER THE GULF
AND POSSIBLY EXTENDING INTO THE GULF COAST STATES IN ASSOCIATION
WITH A PERSISTENT AND SLOW MOVING WAVY FRONTAL ZONE. MOST
PRECIPITATION SHOULD BE RAIN, BUT THOUGH A LITTLE WINTRY WEATHER
COULD BE POSSIBLE IN THE NORTHERN FRINGE OF THE MOISTURE SHIELD IF
IT EXTENDS FAR ENOUGH NORTH. CONFIDENCE IS LOW REGARDING HOW THE
WAVINESS MAY EVOLVE OVER THE GULF DURING THE WEEKEND, AND WHAT THE
SURFACE PATTERN MAY LOOK LIKE OFF THE EAST COAST INTO EARLY NEXT
WEEK. THE MAJORITY (THOUGH NOT ALL) OF GUIDANCE STILL SUGGESTS MOST
PRECIPITATION SHOULD STAY OFFSHORE THE MID-ATLANTIC/NEW ENGLAND
COAST. MEANWHILE, A SERIES OF WAVES MAY SPREAD LIGHT PRECIPITATION
(MOSTLY SNOW) ACROSS PARTS OF THE GREAT LAKES INTO NEW ENGLAND FROM
THE WEEKEND INTO EARLY NEXT WEEK.
SCHICHTEL/TATE
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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