636
FOUS11 KWBC 091802
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
202 PM EDT MON MAR 9 2026
VALID 00Z TUE MAR 10 2026 - 00Z FRI MAR 13 2026
..PACIFIC NORTHWEST THROUGH THE NORTHERN ROCKIES... DAYS 1-3
ACTIVE WINTER WEATHER CONTINUES ACROSS THE WA CASCADES AND NORTHERN
ROCKIES THROUGH THIS WEEKEND WITH PARTICULARLY LOW SNOW LEVELS
(ESPECIALLY FOR MARCH) PERSISTING INTO WEDNESDAY.
A POWERFUL ZONAL JET SOUTH OF A GULF OF ALASKA LOW WILL CONTINUE TO
PUSH ACROSS THE WA/OR BORDER AS IT CONTINUES TO INTENSIFY TO
150KT+ THROUGH TONIGHT. A TIGHT BAROCLINIC ZONE HAS ESTABLISHED
OVER CENTRAL OR TO SOUTHERN MT WITH A MOISTURE AXIS PUSHING ACROSS
WESTERN WA WITH SHOWERY ACTIVITY THROUGH THIS EVENING UNDER A
PASSING TROUGH AXIS BEFORE TAPERING OFF UNDER BRIEF RIDGING
OVERNIGHT. THIS IS THE COLDEST PORTION OF THIS STORM, BUT PRECIP
SHOULD BE PRETTY LOCALIZED WHICH MAY LIMIT THE SNOW COVERAGE AROUND
THE GREATER SEATTLE METRO TONIGHT AS SNOW LEVELS DIP BELOW 500FT
MSL. DAY 1 SNOW PROBS FOR >8" ARE OVER 50% ABOVE ABOUT 2000FT ON
THE WA CASCADES AND AROUND 30% IN THE BITTERROOTS AND JUST SOUTH
OF GLACIER NP.
THIS INITIAL ROUND OF WINTRY PRECIPITATION PUSHES EAST LATE D1 INTO
D2, BUT IS QUICKLY FOLLOWED BY A RESURGENCE OF HEAVIER
PRECIPITATION. THIS SECONDARY SWATH OF PRECIPITATION WILL BE DRIVEN
BY AN IMPRESSIVE WESTERLY AR, WHICH WILL MOVE ONSHORE NEAR 45N
AFTER 00Z/WEDNESDAY, AND THEN MAINTAIN ELEVATED IVT INTENSITY (>250
KG/M/S) THROUGH A LONG DURATION, CONTINUING THROUGH THE END OF THE
FORECAST PERIOD. BOTH THE ECENS AND WEST-WRF ENSEMBLE PROBABILITIES
SUGGEST THE MOST SIGNIFICANT IVT WILL OCCUR 00Z/12 - 00Z/13,
DURING WHICH TIME SNOW LEVELS WILL RISE TO AS HIGH AS 4000 FT IN
WA, BUT 6000 FT IN OR, THANKS TO A SHARP COLD FRONT DEMARCATING THE
HIGHLY VARIABLE SNOW LEVELS. IN GENERAL, THOUGH, SNOW LEVELS WILL
BE QUITE LOW, AND WITH THE PROLONGED AR CONTINUING THE LATTER 2/3
OF THE FORECAST PERIOD, THIS WILL RESULT IN PERIODS OF MODERATE TO
HEAVY SNOW, ESPECIALLY ACROSS THE OLYMPICS AND CASCADES WHERE THE
ORTHOGONAL/ONSHORE FLOW WILL DRIVE PRONOUNCED UPSLOPE ENHANCEMENT
TO SNOW AMOUNTS.
WPC PROBABILITIES D2 FOR HEAVY SNOW INDICATE A HIGH RISK (>70%) FOR
AT LEAST 12 INCHES OF SNOW ACROSS THE WA CASCADES AND OLYMPICS,
WITH CONSIDERABLE IMPACTS TO PASS-LEVEL TRAVEL EXPECTED AT ALL THE
CASCADE PASSES SINCE HEAVY SNOW IS EXPECTED ABOVE 2500 FT. LOCALLY
MORE THAN 2 FEET IS EXPECTED D2 IN THE HIGHER CRESTS AND PEAKS. LIGHTER,
BUT STILL SIGNIFICANT SNOW (>4") IS LIKELY INTO THE OR CASCADES
AND NORTHERN ROCKIES.
DURING D3, THERE IS LITTLE ADJUSTMENT TO THE FOOTPRINT OF HEAVY
SNOW AS THE WESTERLY AR CONTINUES WITH LITTLE LATITUDINAL
FLUCTUATION. THE BIGGEST DIFFERENCE WILL BE ACROSS OR WHERE SNOW
LEVELS CLIMBING TO AS HIGH AS 6000 FT SHUTS DOWN THE PASS-LEVEL
CONCERNS IN THE OR CASCADES. HOWEVER, HEAVY SNOW CONTINUES ABOVE
3000 FT (OR LOWER IN THE NORTHERN WA CASCADES AND NORTHERN ROCKIES)
WHERE WPC PROBABILITIES REMAIN ABOVE 70% FOR AN ADDITIONAL 12+
INCHES OF SNOWFALL, AND COMPOUNDING PASS-LEVEL IMPACTS AT LOCATIONS
SUCH AS SNOQUALMIE AND STEVENS PASSES LEADING TO EXTREMELY
DANGEROUS TRAVEL. ADDITIONALLY, THIS SNOW WILL HAVE A GENERALLY LOW
SLR, SO THE COMBINATION OF HEAVY RATES AND THE HEAVY-WET NATURE OF
THE SNOW, OVER A PROLONGED PERIOD OF TIME, COULD RESULT IN
WIDESPREAD MAJOR IMPACTS ACROSS THE CASCADES AS REFLECTED BY THE
RECENT WSSI-P.
..NORTHERN PLAINS THROUGH THE NORTHERN GREAT LAKES
DAYS 1-2..
NORTHERN AND SOUTHERN STREAM SHORTWAVES WILL CROSS THE COUNTRY
FROM THE WEST, REACHING THE PLAINS BY WEDNESDAY MORNING. ALTHOUGH
THESE FEATURES WILL REMAIN SEPARATE, DOWNSTREAM MOISTURE ADVECTION
WILL STEADILY INTENSIFY, WITH IMPRESSIVE IVT EXCEEDING 500 KG/M/S
SURGING NORTHWARD FROM THE GULF SUGGESTING AN ATMOSPHERIC RIVER
(AR), WHICH IS ALSO MODELED BY THE RECENT PSL ARDT TOOL BY LATE
TUESDAY NIGHT. THIS WILL SURGE IMPRESSIVE MOISTURE (PWS REACHING +4
SIGMA INTO THE GREAT LAKES), INTO WHICH A DEVELOPING LOW PRESSURE,
AIDED BY BROAD SYNOPTIC ASCENT, WILL DEVELOP TO EXPAND
PRECIPITATION ACROSS THE AREA. AS THE LOW DEVELOPS AND MOISTURE
EXPANDS, MID-LEVEL ISENTROPIC ASCENT/WAA WILL LEAD TO A NARROW
CORRIDOR OF FGEN BETWEEN 700-600MB, RESULTING IN A STRIPE OF
MODERATE TO HEAVY SNOW FROM SOUTH DAKOTA THROUGH MINNESOTA AND INTO
THE U.P. OF MICHIGAN. SNOWFALL RATES OF 1"/HR OR MORE ARE POSSIBLE
WITHIN THIS EXPANDING BAND OF SNOW, AND WHILE THIS SHOULD
ACCUMULATE EFFICIENTLY, THE DURATION OF HEAVY SNOW IS EXPECTED TO
BE LIMITED, REDUCING THE POTENTIAL FOR WIDESPREAD SIGNIFICANT
ACCUMULATIONS. STILL, WPC PROBABILITIES ARE MODERATE (30-70%
CHANCE) FOR AT LEAST 4 INCHES OF SNOWFALL FROM FAR NORTHERN WI
THROUGH THE U.P. OF MI, WITH MORE THAN 2 INCHES LIKELY ANYWHERE
ALONG THIS BAND FROM EASTERN SD THROUGH THE GREAT LAKES.
SOUTH OF THIS HEAVY SNOW BAND, AN AXIS OF SIGNIFICANT FREEZING RAIN
IS LIKELY AS THE ACCOMPANYING WAA PUSHES A WARM NOSE >0C NORTHWARD
THROUGH EASTERN WISCONSIN AND THE L.P. OF MICHIGAN. AS THIS OCCURS,
SURFACE TEMPERATURES WILL REMAIN BELOW FREEZING THANKS TO WEAK E/NE
WINDS FLOWING OUT OF A SURFACE HIGH PRESSURE TO THE NORTHEAST TO
KEEP WET-BULB TEMPERATURES BELOW FREEZING. THE DURATION OF FREEZING
RAIN IN A NARROW CORRIDOR COULD BE SIGNIFICANT, ESPECIALLY FROM
NEAR THE DOOR PENINSULA OF WI THROUGH THE NORTHERN L.P. OF MI, BUT
TEMPERATURES RIGHT AROUND 0C WILL SOMEWHAT LIMIT ACCRETION
EFFICIENCY. STILL, WPC PROBABILITIES INDICATE A HIGH CHANCE OF AT
LEAST 0.01" OF ICE FROM CENTRAL WI THROUGH MUCH OF THE L.P. OF MI,
WITH LOCALLY MORE THAN 0.25" POSSIBLE EAST OF TRAVERSE CITY AND
TOWARDS THE TIP OF THE MITT. ANY FREEZING RAIN ACCRETIONS ABOVE
0.25" COULD RESULT IN LOCAL INFRASTRUCTURE IMPACTS, AND THE
WEDNESDAY MORNING COMMUTE WILL LIKELY BE TREACHEROUS IN THESE
AREAS.
..NORTHERN NEW ENGLAND & EASTERN GREAT LAKES
DAYS 2-3...
POTENT NORTHERN STREAM SHORTWAVE LIFTING STEADILY EASTWARD FROM THE
CENTRAL PLAINS WILL CROSS INTO THE GREAT LAKES/OHIO VALLEY THURSDAY
WHILE AMPLIFYING. DOWNSTREAM OF THIS TROUGH AMPLIFICATION, A
MERIDIONALLY ARCING JET STREAK WILL FAVORABLY INFLUENCE ASCENT
THROUGH THE RRQ TO HELP STRENGTHEN A SURFACE LOW TRACKING FROM
LOWER MICHIGAN INTO ONTARIO, AND THEN EVENTUALLY MOVING OVER
NORTHERN MAINE THURSDAY MORNING. DOWNSTREAM OF THIS SYSTEM,
MOISTURE ADVECTION WILL INTENSIFY FROM THE GULF, DRIVEN BY POTENT
850MB WAA, WHICH WILL ADDITIONALLY SURGE THE SURFACE WARM FRONT
NORTHWARD. THE COMBINATION OF THE DEEP LAYER ASCENT WITH THE
RESULTING FGEN (AS A RESULT OF THE WAA) WILL CREATE HEAVY
PRECIPITATION ALONG THE INTERNATIONAL BORDER WITH CANADA AND THEN
INTO NORTHERN MAINE. PRECIPITATION WILL LIKELY START AS SNOW ACROSS
NORTHERN MAINE, BUT EVERYWHERE ELSE, AND THEN LATER IN THE PERIOD
ACROSS NORTHERN MAINE, A MIX OF SLEET AND FREEZING RAIN, EVENTUALLY
BECOMING RAIN, IS EXPECTED, AS THE WARM NOSE SURGES NORTHWARD. THE
GUIDANCE HAS TRENDED SLIGHTLY WARMER THE PAST FEW RUNS, BUT HEAVY
SNOW RATES EXCEEDING 1"/HR ARE LIKELY IN NORTHERN MAINE,
CONTRIBUTING TO A HIGH RISK (>70% CHANCE) FOR AT LEAST 4 INCHES OF
SNOW, WITH LOCALLY 6-8 INCHES POSSIBLE. ELSEWHERE, ICE WILL LIKELY
BE THE PRIMARY HAZARD, WITH WPC PROBABILITIES INDICATING A MODERATE
RISK (30-70% CHANCE) OF AT LEAST 0.1 INCHES OF ICE IN THE NORTHERN
ADIRONDACKS, NORTHERN NEW HAMPSHIRE, AND PARTS OF NORTH-CENTRAL
MAINE.
AS THIS LOW PULLS AWAY, STRONG CAA IN ITS WAKE MAY RESULT IN
PERIODS OF MODERATE TO HEAVY LAKE EFFECT SNOW (LES) ACROSS UPSTATE
NEW YORK. REGIONAL SOUNDINGS INDICATE A MODEST ENVIRONMENT FOR
HEAVY RATES, BUT WHERE THE FLOW IS MOST UNIFORM ACROSS THE LAKES,
WPC PROBABILITIES INDICATE A MODERATE RISK (30-70%) FOR AT LEAST 2
INCHES OF SNOWFALL ALONG THE CHAUTAUQUA RIDGE AND INTO THE TUG HILL
PLATEAU, WITH LOCAL AMOUNTS ABOVE 4 INCHES POSSIBLE.
WEISS
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