Scientific Forecaster Discussion
000 FXUS65 KMSO 221040 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 340 AM MST Wed Nov 22 2017 .DISCUSSION...The next wave of moderate precipitation will continue to move through Idaho and western Montana this morning. Rain will become less common in the valleys by the afternoon, but remain in the mountains. Rain showers will be around for the beginning of Thanksgiving day, but the main story remains the damaging wind threat. The strong wind scenario that model guidance are depicting has been very consistent, so strong winds in the terrain of 50 mph and higher should be planned for. Areas that we are concerned with experiencing strong winds include the Flathead Valley south to Missoula, through the Bitterroot Valley, and the valleys of southwestern Montana, so the High Wind Watch has not been changed. There is still a chance that a few locations in Lincoln County may see gusts near 50 mph, but confidence is not as high. The winds in the forecast have been increased in the latest update since confidence continues to increase. One aspect of this Thursday weather pattern that is interesting is that the upper jet will be parallel to the cold front which is usually a good set up for precipitation, so moderate to even heavy rain may accompany the strong winds. Showers may organize into a line along the front, and high resolution model guidance are already showing indications of a strong line of showers during the evening. Features like this are notorious strong wind producers. Snow levels will lower behind the cold front Thursday night so snow is likely to return to the high terrain and there may even be some snow at lower elevations. The next impactful weather system looks to arrive to north-central Idaho and western Montana on Sunday. Precipitation is forecast to start as rain during Sunday and change to snow at most elevations for Monday morning. This weather system is much colder than what has been occurring recently, so travel impacts from snow and/or ice are of concern. Snow chances will linger through Tuesday. && .AVIATION...Visibilities and ceilings have been quite variable at valley locations overnight with nearly saturated surface conditions due to a strong plume of moisture moving through the region. These variable conditions will last through much of the morning with a mix of fog, rain, and low ceilings. Precipitation will taper off and mixing will increase at low elevations so improvements are expected by this afternoon, though a stratus deck may remain. The higher terrain has been and will continue to be obscured with moisture via moist southwesterly flow today. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...High Wind Watch from Thursday afternoon through late Thursday night Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...Flathead/Mission Valleys...Missoula/Bitterroot Valleys...Potomac/Seeley Lake Region...West Glacier Region.