184 FXUS65 KTFX 240217 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 817 PM MDT Wed Oct 23 2019 .UPDATE... Weak energy in the somewhat unstable northerly flow aloft has kept scattered snow showers along the Rocky Mountain Front and south into the mountains of Central Montana north and northeast of Helena. These showers and their associated cloudiness have been slow to dissipate after sunset. However, forecast models indicate that the energy should weaken through midnight, allowing the clouds and showers to dissipate. Regardless, additional snow accumulation will be minor, but roads will remain icy overnight. Otherwise, the decreasing cloudiness and low level moisture from the showers will allow patchy fog to form, mainly in the wind- protected valleys of Southwest Montana. A light southwest wind will likely prevent fog from forming along the east slopes of the Rockies, but there will be less wind over the eastern TFX plains area (including the Havre and Lewistown areas), so patchy fog will be possible there, especially in the river valleys. Temperatures have been trending similar to those previously forecast, so have kept the overnight lows as is. Coulston && .SYNOPSIS... Areas of snow will gradually end this evening. Dry conditions return for Thursday, with slightly warmer temperatures. Friday sees continued warming and the potential of widespread strong winds. Another cold front could then bring more cold and snow this weekend. && .AVIATION... Updated 545 PM MDT Wed Oct 23 2019 (24/00Z TAF Period) VFR conditions are expected through the period, except where mentioned otherwise. Scattered light snow showers south of a KCTB- KLWT line will continue to decrease through 03Z, but periods of MVFR conditions will be possible with the showers. Otherwise, the mid level cloudiness will decrease overnight and high cloudiness will move into the forecast area from the northwest. Patchy fog may cause periods of MVFR/IFR visibilities in some Southwest Montana valleys between 08Z and 17Z, especially at KWYS. Mid and high level cloudiness will continue to increase through the day on Thursday, and breezy westerly winds will develop over the plains. Coulston && .PREV DISCUSSION... /ISSUED 545 PM MDT Wed Oct 23 2019/ A subtle shortwave disturbance embedded in the persistent northerly flow aloft helped maintain areas of snow across central Montana on Wednesday. Current radar trends show that these areas of snow are becoming less widespread. Precipitation will continue to dissipate and end by later this evening. Watch for icing on bridges tonight as snowmelt runoff could ice up as temperatures drop back below freezing. Drier air at the surface and aloft is moving into the region as high pressure strengthens over the region. Thus fog development, if any, will be limited mainly to the higher southwest valleys. Furthermore, southwest winds begin to pick up early Thursday morning as pressure falls along the lee of the Northern Rockies. The combination of drier air and increasing winds should inhibit fog formation except for isolated lower protected valleys. Temperatures trend warmer on Thursday as surface winds shift to westerly and the upper ridge leans further over the Northern Rockies. A noticeable breeze develops for most of North-central Montana Thursday, with gusts nearing 20 to 30 mph by afternoon. Dry, mild and breezy conditions continue Thursday night into Friday under a strengthening westerly flow aloft. PN Friday through Saturday night... A high wind event is increasingly likely for Fri and Fri evening, and it could be as strong, or perhaps even a bit stronger, than the Tuesday high wind event. These winds will be courtesy of a tightening pressure gradient along and east of the Divide as high pressure building into the Great Basin and Idaho contrasts with a strong low pressure system passing by north of the border. At the same time, models showing fairly widespread 60kt winds at and below 700mb, with some localized 70kt+ winds at 700mb over the Rocky Mountain Front and immediately adjacent High Plains, lending confidence to the expected high wind potential. At this time, the temporal and spatial extent of the High Wind Watch appears good, but will need to monitor the southern tier of counties for inclusion, especially Gallatin. Winds will quickly diminish and shift NW-N'ly Fri night into Sat AM as the front attached to the low over Canada dives south into north- central Montana. This front will be accompanied by some moisture and a shortwave trough that looks to form the leading edge of a broader trough that will be digging into the western US over the weekend. As of now, the snow setup appears to be eerily similar to today's snow event, with a fairly quick hit (12 hrs or less) of snow on the plains, but much longer duration of snow along the Rocky Mtn Front and into the central and southwest mountains. It may be a bit colder than today's event, so a bit more snow may be possible on the Plains. Currently, we have 3 inches or less for lower elevations, with 5 to 10 inches for much of the Divide and Front north of Lincoln, and 4 to 8 inches in the Little Belts. -Kredensor Sunday through next Wednesday... Northwesterly flow looks to persist early next week, keeping temperatures well below normal, with highs forecast in the 20s and 30s for Sun thru Tue. Another round of precipitation is possible across the region Monday into Tuesday as some models have an upper- level disturbance crossing the region, but model agreement does begin to breakdown somewhat in this time frame. Thus POPs were kept to chance at best for now. Ridging looks to start to build in by mid- week, reflected by some moderating temps, as highs generally rise into the 40s. -Kredensor && .PRELIMINARY POINT TEMPS/POPS... GTF 25 51 39 65 / 10 0 0 0 CTB 24 50 36 61 / 0 0 0 10 HLN 24 52 33 65 / 20 0 0 0 BZN 19 50 26 61 / 20 0 0 0 WEY 6 37 13 44 / 20 0 0 0 DLN 21 48 28 57 / 10 0 0 0 HVR 24 52 36 68 / 10 0 0 10 LWT 22 48 35 64 / 10 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Watch from Friday morning through Friday evening Blaine...Broadwater...Cascade...Central and Southern Lewis and Clark...Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...Fergus...Hill...Jefferson...Judith Basin...Liberty... Meagher...Northern Rocky Mountain Front...Southern Rocky Mountain Front...Toole. && $$ http://www.weather.gov/greatfalls