829
FXUS65 KMSO 222149
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
249 PM MST WED JAN 22 2020
DISCUSSION
THE NEXT WEATHER SYSTEM IS APPROACHING FROM THE
WEST THIS AFTERNOON AND WILL SPREAD WIDESPREAD LIGHT
PRECIPITATION INTO NORTH CENTRAL IDAHO AND WEST-CENTRAL/NORTHWEST
MONTANA THIS EVENING INTO FRIDAY MORNING. SNOW LEVELS WILL BE
GRADUALLY RISING WITH TIME. STEADY SNOWFALL WILL DEVELOP ON
PASSES, CAUSING SLICK SNOWCOVERED ROADS THROUGH THE WEDNESDAY
MORNING COMMUTE. IN PARTICULAR, LOOKOUT PASS AND LOLO PASS ARE
EXPECTED TO SEE THE MOST CONSISTENT SNOWFALL. VALLEYS IN CENTRAL
IDAHO ARE ANTICIPATED TO LARGELY SEE RAIN OR A RAIN/SNOW MIX. VALLEYS
OF WESTERN MONTANA WILL INITIALLY SEE SNOW, TRANSITIONING TO RAIN
AND PATCHES OF FREEZING RAIN TOWARDS THURSDAY MORNING. SNOW
ACCUMULATIONS IN VALLEYS WILL BE MINIMAL, AND PERHAPS THE BIGGER
IMPACT WILL BE POTENTIAL FOR ICE TO FORM ON SIDEWALKS, DRIVEWAYS
AND PARKING LOTS AS OVERNIGHT TEMPERATURES HOVER NEAR FREEZING.
FRIDAY THROUGH NEXT WEDNESDAY, A SERIES OF WEAK STORM SYSTEMS ARE
ANTICIPATED TO MOVE ACROSS THE NORTHERN ROCKIES. SIMILAR TO
RECENT WEATHER OBSERVED IN THE REGION, LIGHT SNOWFALL AT HIGH
ELEVATIONS AND A WINTRY MIX OF RAIN, SNOW, AND FREEZING RAIN AT
LOW ELEVATIONS ARE ANTICIPATED DURING THE EVENING THROUGH MORNING
PERIODS. THE LOCATIONS FAVORED FOR FREEZING RAIN WILL SHIFT AROUND
AS EACH STORM SYSTEM EVOLVES, HOWEVER VALLEYS OF NORTHWEST AND
WEST CENTRAL MONTANA, AS WELL AS PORTIONS OF LEMHI COUNTY
(INCLUSIVE OF SALMON, NORTH FORK, SHOUP), ARE THE MOST LIKELY
AREAS TO BE IMPACTED BY FREEZING RAIN. MUCH OF THE FREEZING RAIN
IMPACT WILL BE TO SIDEWALKS, DRIVEWAYS, AND PARKING LOTS. BLACK
ICE ON ROADWAYS MAY ALSO BECOME AN ISSUE, PARTICULARLY FOR LESS-
TRAVELED CORRIDORS. TEMPERATURES WILL BE GENERALLY WARMER THAN THE
SEASONAL AVERAGE THROUGHOUT THE REGION THROUGH THE MIDDLE OF NEXT
WEEK.
AFTER NEXT WEDNESDAY, A SLIGHT CHANGE IN THE UPPER LEVEL WEATHER
PATTERN APPEARS PLAUSIBLE, WARMING THE NORTHERN ROCKIES EVEN FURTHER
WITH SUBTROPICAL MOISTURE SURGES. THE PACIFIC JET STREAM IS ALSO
DEPICTED AS STRENGTHENING IN THE 7-10 DAY FORECAST PERIOD, WHICH MAY
POINT TOWARD MORE SIGNIFICANT PRECIPITATION EVENTS ACROSS THE
WESTERN US AROUND THE BEGINNING OF FEBRUARY.
AVIATION
UNSTABLE CONDITIONS THIS AFTERNOON HAVE LEAD TO THE
DEVELOPMENT OF SNOW SHOWERS ACROSS THE TERRAIN OF WESTERN MONTANA
AND CENTRAL IDAHO. THIS HAS ALSO LED TO SOME BREEZY WESTERLY
WINDS, PRIMARILY KBTM WITH GUSTS UP TO 20KTS. AN APPROACHING
WEATHER SYSTEM THIS EVENING WILL LOWER CEILINGS FROM WEST TO EAST
ACROSS CENTRAL IDAHO AND WESTERN MONTANA, CAUSING THE TERRAIN TO
BE OBSCURED. STEADY LIGHT PRECIPITATION WILL DEVELOP, MAINLY
ACROSS CENTRAL IDAHO AND WEST-CENTRAL/NORTHWEST MONTANA. KMSO AND
KGPI WILL LIKELY SEE LOWERED VISIBILITY AND CEILINGS AT TIMES
TONIGHT, STARTING AROUND 23/0300Z. PRECIPITATION IN THE VALLEYS
WILL FALL AS A MIX OF RAIN AND SNOW, WITH A PERIODS OF LIGHT
FREEZING RAIN POSSIBLE BETWEEN 23/0900Z AND 23/1400Z. THE BEST
POTENTIAL FOR FREEZING RAIN WILL BE ACROSS NORTHWEST MONTANA
VALLEYS, INCLUDING AT KGPI.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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