856
FOUS11 KWBC 031808
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 PM EDT FRI OCT 3 2025
VALID 00Z SAT OCT 04 2025 - 00Z TUE OCT 07 2025
..NORTHERN ROCKIES
DAYS 2-3...
DYNAMIC LONGWAVE PATTERN WILL TRANSPIRE ACROSS THE WESTERN CONUS
AS WE MOVE INTO THE WEEKEND WITH A DEEP CLOSED UPPER-LOW OVER THE
GREAT BASIN PIVOTING NORTHEAST INTO THE NORTHERN ROCKIES BEFORE
OPENING UP INTO A RELATIVELY STRONG NEGATIVELY-TILTED SHORTWAVE
TROUGH BEFORE EXITING. STRONG HEIGHT-FALLS OCCURRING OVER THE BASIN
THROUGH THE NORTHERN ROCKIES WILL ALLOW FOR FREEZING LEVELS TO
PLUMMET OVER THE COURSE OF FRIDAY NIGHT INTO SATURDAY, CONTINUING
FURTHER INTO EARLY SUNDAY MORNING. COMBINATION OF FALLING HEIGHTS
AND STRONG UPPER-LEVEL ASCENT ACROSS THE REGION MIXING WITH
ELEVATED PWATS WILL GENERATE A TRANSITION FROM RAIN TO SNOW ACROSS
PORTIONS OF THE TETONS OVER INTO THE ABSAROKA/BEARTOOTH RANGES OF
MT/WY, FOLLOWED BY THE BIG HORN MOUNTAINS A BIT DOWNSTREAM. SNOW
LEVELS WILL TUMBLE TO AROUND 7000FT MSL BY SUNDAY MORNING ACROSS
THE TERRAIN WITH A REASONABLE PRECIP DISTRIBUTION CONTRIBUTING TO
PERIODS OF MODERATE TO LOCALLY HEAVY SNOW WITHIN THE TERRAIN AND
ADJACENT FOOTHILLS.
AS THAT NEGATIVELY-TILTED SHORTWAVE TRACKS INTO THE PLAINS SUNDAY
MORNING, A SECOND SHORTWAVE ROUNDING THE BACK OF THE LONGWAVE
TROUGH WILL DIVE SOUTHEASTWARD OUT OF ALBERTA THROUGH MUCH OF
MT FROM SATURDAY NIGHT THROUGH MUCH OF THE DAY ON SUNDAY. THIS
SHORTWAVE WILL RESULT IN A PERIOD OF HEAVY SNOW ACROSS MUCH OF
GLACIER NP LATE SATURDAY NIGHT THROUGH SUNDAY MORNING. THIS
SECONDARY FORCING WILL KEEP THE SNOW THAT BEGAN WITH THE FIRST
SHORTWAVE SATURDAY ONGOING THROUGH SUNDAY. THE SNOW WILL END FROM
NORTH TO SOUTH SUNDAY AND SUNDAY NIGHT. WPC PROBABILITIES FOR MORE
THAN 6 INCHES OF SNOW REMAIN BETWEEN 50-90% FOR THE BEARTOOTH,
ABSAROKA, AND BIG HORN RANGES.
THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.
WEGMAN/KLEEBAUER
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