Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
766 FXUS65 KMSO 162026 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 226 PM MDT Sun Jun 16 2024 ...Winter Storm to make backcountry travel hazardous tonight through Tuesday night... .DISCUSSION...Many of the watches have been upgraded to winter storm warnings for the incoming weather system. Snow levels and where the heaviest wrap-around precipitation will be are always a struggle to predict in these scenarios. We looked at upstream weather balloon soundings at Quillayute and Spokane, Washington to help us understand how cold the incoming trough is compared to climatology. The 9600 feet(700 millibars) temperature recorded in the Quillayute (UIL) sounding was -9.9 degrees Celsius or 14 degrees Fahrenheit. This makes it the 2nd coldest temperature (unofficially for the day) at this level...-10 degrees Celsius was recorded on June 16, 1981. The freezing level was at 4458 feet. Of course this trough will moderate a little bit in 24 hours as it swings eastward. Under the heavier precipitation band with the 700mb low, snow levels could be driven down as low as 3200 feet come Monday morning. Models continue to have a considerable spread on where this could occur. Thinking back to the May 23 snow event, there were locations at 4000 feet that saw snow and others that only saw a mixture of rain and snow with no accumulation. This could be a similar experience for folks on Monday. Nonetheless, the impacts remain the same: backcountry travel will be hazardous from north-central Idaho into western Montana. If you are going to travel in these locations, make sure you have emergency gear including a saw, extra food, clothes and water with you. The locations that experience heavy snow could see some branches broken and power outages. Models have trended a little bit more robust with another shortwave trough digging south out of Canada Tuesday morning. This will keep the snow showers going across northwest Montana, particularly in the Glacier Park region. Wednesday morning could end up being quite cold in some valley locations depending on cloud cover. Sensitive plants may need to be covered. Model ensembles agree on a warming trend for the rest of the week with periods of afternoon showers. && .AVIATION...Radar projections show showers increasing in coverage this evening and overnight, as a low pressure system in Washington circulates and moves into Idaho and western Montana. Generally, precipitation in the form of rain is expected below around 4000-5000 feet, with snow expected above 5000 feet late Sunday into Monday. However, accumulations down to many valley floors is possible under heavier precipitation, centered mainly in west- central Montana. Winter storm warnings and advisories are in effect for this very late season winter storm. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Winter Storm Warning from midnight tonight to 6 AM MDT Tuesday for Bitterroot/Sapphire Mountains...Butte/Blackfoot Region. Winter Weather Advisory from 6 AM Monday to 9 AM MDT Tuesday for West Glacier Region. Winter Weather Advisory from 3 AM to 11 AM MDT Monday for Missoula/Bitterroot Valleys. Winter Storm Warning from 3 AM Monday to 6 AM MDT Tuesday for Potomac/Seeley Lake Region. ID...Winter Storm Warning from 11 PM this evening to 5 AM PDT Tuesday for Southern Clearwater Mountains. Winter Weather Advisory from midnight tonight to 2 PM MDT Monday for Eastern Lemhi County...Western Lemhi County. && $$