891 FXUS65 KMSO 031543 AAA AFDMSO Area Forecast Discussion...UPDATED National Weather Service Missoula MT 843 AM MST Sun Mar 3 2013 .UPDATE...Decreased potential for precipitation across valleys of central Idaho and for select valleys in western Montana late this morning through early afternoon. && .DISCUSSION...Depite web cam images showing Lost Trail, Lolo, and MacDonal passes all snow covered and reports of gusty winds, some locations behind the frontal passage have begun to see diminishing snow showers. While this may be the case for the remainder of the morning hours, we do still expect post-frontal convective snow showers to fill back in through the afternoon and early evening. && .AVIATION...As of 1100Z the surface cold front extends generally from just outside of KLWS, Idaho to just outside of KGPI in Montana. Gusty winds and a burst of moderate precipitation have been observed along the front with a notable wind shift from southerly to northwesterly occurring proceeding the frontal passage. The front should push through KGPI between now and 1200Z, through KMSO between 1200Z and 1300Z, through KSMN around 1400Z and then through KBTM by 1500Z. Precipitation will start as rain but quickly become mixed with snow which should result in reduced visibility and a dramatic reduction in cloud heights. Conditions will improve shortly after the front passes but remain showery and breezy throughout the day. This is when things will become particularly challenging to forecast given the highly unpredictable nature of shower development in such an unstable environment. Anticipate obscuration of terrain at all times through the next 24 hours. && .PREV DISCUSSION... /ISSUED 413 AM MST Sun Mar 3 2013/ DISCUSSION...As of 3am the surface cold front extends from just outside of Lewiston, Idaho northwest through the Flathead valley and up into southern Alberta, Canada. As expected, areas along the front have experienced gusty winds, valley rain and mountain snow. Also, the combination of winds and snow are likely creating some challenging driving conditions over Lookout Pass. All things considered, the storm system appears to be panning out as expected and feel that the current advisories remain sufficient to emphasize the ongoing and anticipated impacts throughout today. Did add mention of isolated thunderstorms along the Canadian border with one lightning strike already having occurred over the Yaak region of northwest Montana. But this is for perhaps an additional handful of strikes as the coldest part of the upper level low passes along the Canadian border. Once the cold front swings completely through western Montana this afternoon our impacts will shift to widespread snow showers present within a very unstable air mass. This will lead to many locations, valleys included, to experience rapid reductions in visibility along with roadways becoming quickly snow covered in briefly heavy snow. However, these showers will be very short-lived with conditions likely improving after 5-10 minutes. These showers will likely continue well into tonight and perhaps even into Monday morning as a second acceleration in the upper level jet swings over the region, enhancing precipitation in the "wrap around" section of the storm system. By mid-day Monday this added lift will be lost as ridging shifts the jet into central Montana and dry air begins to work its way into central Idaho and western Montana. Fog may develop by Tuesday morning, depending upon how quickly the sky clears and the existence of near surface moisture. But this should pose minimal impacts. The next storm system to impact the Northern Rockies is anticipated to be present Wednesday through Friday. Minor travel impacts will be focused over area mountain passes due to snow accumulation on roadways, particularly during each overnight and morning periods. Valleys and low elevations will experience mainly bouts of light rain, however there is a chance for a dusting on Thursday morning. Global weather models are increasing in agreement with regard to high pressure developing over the region by the end of this coming week. However, this high pressure will likely be short-lived, as storm systems continue to line up across the Pacific Ocean. There is potential for another significant system to develop over the Northern Rockies by early the following week. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...WINTER WEATHER ADVISORY until 11 AM MST this morning Bitterroot/Sapphire Mountains...Butte/Blackfoot Region... Potomac/Seeley Lake Region...West Glacier Region. WINTER WEATHER ADVISORY until 11 AM MST this morning Lower Clark Fork Region. ID...WINTER WEATHER ADVISORY until 10 AM PST this morning Northern Clearwater Mountains...Southern Clearwater Mountains. WINTER WEATHER ADVISORY until 11 AM MST this morning Eastern Lemhi County. && $$ Follow us on Facebook and Twitter! https://www.facebook.com/US.NationalWeatherService.Missoula.gov https://www.twitter.com/NWSMissoula