895
FOUS11 KWBC 100714
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
314 AM EDT SAT OCT 10 2026
VALID 12Z SAT OCT 10 2026 - 12Z TUE OCT 13 2026
..NORTHERN ROCKIES
DAYS 1-3...
A MID-LEVEL LOW SINKING SOUTHWARD FROM BRITISH COLUMBIA INTO WA
WILL COMBINE WITH A PACIFIC SHORTWAVE AND SINK SOUTHWARD INTO OR
AND NORCAL SUNDAY NIGHT INTO MONDAY. AT THE SAME TIME, BROAD SW
FLOW WILL TRANSPORT MOISTURE FROM THE THE SUBTROPICS OFF CA
INCLUDING MOISTURE ASSOCIATED WITH TROPICAL STORM RACHEL. THOSE
REMNANTS WILL MOVE INTO THE NORTHERN ROCKIES LATE SUNDAY INTO
MONDAY. AT THE SURFACE, LOW PRESSURE IN THE NORTHERN PLAINS WILL
CONTINUE EASTWARD, ALLOWING COLDER AIR TO RUSH SOUTHWARD INTO
MONTANA TODAY. THIS WILL SET UP A MODEST TO LOCALLY HEAVY SNOW
EVENT FOR THE TERRAIN WITH SOME SNOW INTO THE VALLEY LOCATIONS AS
SNOW LEVELS CRASH.
BANDED PRECIPITATION WILL EXPAND THIS MORNING AND CHANGE FROM RAIN
TO SNOW AS SNOW LEVELS CRASH FROM 6000-7000 FEET THIS MORNING TO
3000-4000 FEET BY THIS AFTERNOON OVER WESTERN/NORTHWESTERN MT. SNOW
BANDS ARE EXPECTED TO INCREASE IN COVERAGE AND INTENSITY TONIGHT,
SOME OF WHICH MAY BE HEAVY AT TIMES. THIS WILL AID IN COOLING THE
COLUMN FURTHER AND BRINGING SNOW TO THE VALLEY FLOORS LATER
TODAY/THIS EVENING. THE 00Z HREF/REFS INDICATE OROGRAPHICALLY-
FORCED SNOW RATES NEAR 1"/HR ESPECIALLY VERY EARLY SUNDAY. FOR DAY
1, WPC PROBABILITIES OF AT LEAST 6 INCHES OF SNOW ARE >50% ALONG
THE EASTERN SLOPES OF THE LEWIS AND FLATHEAD RANGES AND >70% FOR
THE BIG/LITTLE BELTS, BIG SNOWY MTNS, AND THE ANACONDA RANGE.
THE COLD AIR SHIFTS SOUTH THROUGH THE REST OF WESTERN MONTANA
THROUGH SUNDAY MORNING WITH ADDITIONAL SNOW BANDS DEVELOPING DOWN
TO THE WYOMING BORDER. THIS WILL BE A HEAVY/WET SNOW AND THE WSSI
SHOWS SOME MODERATE IMPACTS FROM SNOW LOAD OVER THE SOUTHERN MT
RANGES SUNDAY INTO MONDAY.
AS THE REMNANT MOISTURE OF RACHEL IS PULLED NORTH-NORTHEASTWARD
SUNDAY, A JET STREAK WILL PASS THROUGH THE REGION AND HELP
INVIGORATE ADDITIONAL SNOW OVER WESTERN MT. ONCE AGAIN, 00Z REFS
PROBS INCREASE OVER SOUTHERN MT SUNDAY AFTERNOON. WPC PROBABILITIES
FOR AT LEAST 6 INCHES OF SNOW DAY 2 ARE >50% FOR MOST OF THE WEST-
CENTRAL AND SOUTHWESTERN MONTANA RANGES INCLUDING THE CRAZY, RED
LODGE PORTION OF THE NORTHERN ABSAROKAS, AND GALLATIN.
OVER WY, SNOW LEVELS WILL REMAIN HIGH IN THE DEEPER/MILDER
MOISTURE PLUME (AROUND 10,000FT), SO ONLY THE HIGHEST ABSAROKAS AND
THE WIND RIVER RANGE WILL SEE SNOW. HOWEVER, FAVORABLE FLOW AND
PLENTY OF MOISTURE WILL MAXIMIZE SNOWFALL IN THE HIGH TERRAIN WHERE
1-2 FT OF SNOW IS EXPECTED.
SNOWFALL WINDS DOWN OVER MONTANA EARLY MONDAY AND GRADUALLY OVER
WY INTO THE EVENING AND OVERNIGHT.
..SIERRA NEVADA/GREAT BASIN/UINTAS
DAYS 2-3...
AS THE WESTERN TROUGH DROPS DOWN THE NORTHERN CA/NV BORDER ON
MONDAY, SNOW LEVELS ON THE SIERRA NEVADA DROP TO AROUND 7000FT WITH
GENERALLY LIGHT PRECIP. PROBABILITIES OF AT LEAST 8 INCHES OF SNOW
ARE AROUND 50% ON THE HIGH SIERRA PEAKS. OVERNIGHT SUNDAY INTO
MONDAY, SNOW LEVELS WILL START TO LOWER JUST A BIT OVER THE GREAT
BASIN AND UINTAS (8000 TO 10,000FT, RESPECTIVELY). A FEW INCHES OF
SNOW IS EXPECTED ON THE HIGHEST PEAKS WITH PERHAPS >6" OVER THE
UNITAS ABOVE 11,000FT.
THE PROBABILITY OF SIGNIFICANT ICE ACROSS THE CONUS DAYS 1-3 IS
LESS THAN TEN PERCENT.
FRACASSO
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