239 FXUS65 KMSO 282047 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 247 PM MDT Fri Mar 28 2014 ...Significant Precipitation Tonight into Saturday... ...Snow accumulations above 6000 feet... .DISCUSSION...Moisture is spreading through the Pacific Northwest this afternoon and will arrive to Clearwater County in Idaho and northwest Montana by this evening and into the rest of the region by Saturday morning. Snow accumulations will mainly occur above 6000 feet with 6 to 10 inches possible, while moderate to heavy rain amounts will fall below 6000 feet. Idaho and Clearwater counties of north central Idaho are still on track to receive the highest precipitation amounts with 0.75"-1.50". Rock and mudslides are still a concern with the amount of rain expected in north central Idaho and portions of northwest Montana. Snow levels are tricky with this weather system due to its warm and moist nature. There is concern that the heavy precipitation being shown by some of the model guidance will allow for lower snow levels and accumulations through Lemhi County Idaho and into southwest Montana. Mountain pass locations above 6000 feet are expected to become snow covered by late Saturday morning, but there will also be an opportunity during the late morning and early afternoon for snow to accumulate in Butte. Winter weather advisories have been issued for the snow potential. Precipitation will decrease overnight on Saturday, but showers will return for Sunday and there is the potential for some of these to be intense snow showers especially south of I-90. A brief area of high pressure is expected Sunday night into Monday, which could reduce shower activity and possibly even bring some breaks in the clouds. The forecast gets more uncertain for the Tuesday into Wednesday time frame as forecast models begin to diverge on their solutions. Most models are showing an area of low pressure moving well south of western Montana and north central Idaho, taking all the moisture well south of the region as well. This scenario would likely result in mainly just nuisance showers. The European model continues to bring this area of low pressure further north however, placing the bulk of this moisture into southern Idaho county, Lemhi county and southwest Montana. This scenario could lead to a decent snowfall event, potentially even into the valleys. Very few changes were made to the forecast for the time being due to the uncertainty. The forecast could dry out again by Thursday into Friday due to another ridge of high pressure. && .AVIATION...A very moist weather system will begin to increase cloud cover and shower activity in north central Idaho this afternoon and western Montana tonight into Saturday. Low ceilings causing the higher terrain to be obscured will become widespread. Periods of heavy rain and high terrain snow will also cause visibility reductions. Most airfields are expected to see precipitation fall as rain, however KBTM could switch over to snow around 29/1500z which could cause low ceilings/visibility and possibly some accumulations on the runway. Precipitation will begin to let up by Saturday evening. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...WINTER WEATHER ADVISORY from 6 AM to 6 PM MDT Saturday Butte/Blackfoot Region. WINTER WEATHER ADVISORY from Midnight tonight to 6 PM MDT Saturday Bitterroot/Sapphire Mountains. WINTER WEATHER ADVISORY from 6 PM this evening to 6 PM MDT Saturday for Marias Pass IN THE West Glacier Region. ID...WINTER WEATHER ADVISORY from Midnight tonight to Midnight MDT Saturday Night ABOVE 6000 FEET FOR THE Eastern Lemhi County...Western Lemhi County. && $$ Follow us on Facebook and Twitter! https://www.facebook.com/US.NationalWeatherService.Missoula.gov https://www.twitter.com/NWSMissoula