050 FXUS65 KTFX 101527 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 927 AM MDT Wed Oct 10 2018 .UPDATE... The morning upper air sounding nicely depicts the low level easterly flow that is continuing to produce light upslope snow across most of Teton County. The last few radar scans support short-term model trends to decrease and end snowfall in this area through mid-day. Mountain passes crossing the Continental Divide remain snow covered and icy today. Areas of very light snow also persist under extensive low clouds spread across North-central Montana, including out toward the Lewistown area. Winter weather advisories were allowed to expire, except along the Southern Rocky Mountain front where the advisory is extended through noon. Snow will continue to decline in coverage and end for all but mountain areas through this evening. A secondary shortwave feature will cross southwest Montana tonight, producing another round of light snow over this area. Forecast grids were updated to better reflect observed trends through this evening. && .SYNOPSIS... A cold autumn storm system continues to influence the region today with well below average temperatures and lingering light snow over the mountains and adjacent areas. Travel over mountain passes may be difficult this morning in areas of light snow with snow and ice on road surfaces. Motorists could also encounter localized icy road surfaces this morning outside of areas that received snow overnight due to wet road surfaces with temperatures hovering around freezing. Drier conditions move into the region Thursday and Friday with temperatures warming back to near seasonal averages Friday afternoon along with increasing winds. && .AVIATION... Updated 1200Z. Low cloud ceilings will affect most terminals though much of this morning, especially across north-central MT with areas of fog and light precipitation also occurring at times this morning. Snow occurring over and near the mountains will decrease through today with some showers continuing into this evening along the Rocky Mtn Front as well SW MT. Some improvement is expected to ceilings this afternoon and evening with potential for fog development in some areas tonight as cloud-cover begins to thin. Hoenisch && .PREV DISCUSSION... /ISSUED 530 AM MDT Wed Oct 10 2018/ Today through Friday...An deep upper level trough extends south from western Canada through the western US with the embedded upper level low that brought significant snow to portions of the Northern Rockies yesterday entering WY/UT this morning. Cold and moist airmass remains in place to its NW over MT for well below average temperatures and widespread low cloud-cover. Light snow continues to decrease in coverage and intensity over western and southwest portions of MT, though easterly/upslope low level flow will keep some persistent light precipitation going along the east slopes of the Rockies through much of today while weak shortwave energy continues to rotate through SW MT later today and tonight for lingering snow showers there as well. Additional snow accumulations today will be fairly light and mainly occur this morning in the winter weather advisory area though some light snow will continue through this afternoon and evening. Impacts to travel over mountain passes should improve late this morning as precipitation decreases and road surface begin to warm. Drying begins to work into far NW portions of the forecast area late tonight then spreads across the remainder of the area on Thursday. If skies can clear enough late tonight over western portions of Glacier county, temperatures there could dip into the teens or lower by Thursday morning. Winds begin to increase along the Rocky Mtn Front late Thursday night as NW flow aloft increases under weak upper level ridging with surface low pressure developing east of the Canadian Rockies. Upper level shortwave and surface low dive SE through BC/AB Friday with gusty winds likely to develop across much of the area along with temperatures warming to near seasonal averages. Hoenisch Friday Night through Wednesday...A northeast-to-southwest oriented positively-tilted low pressure trough will deepen as it moves southeast over Montana Friday night through Saturday. The main jet/energy associated with this trough will move more so over the western and southwest Montana mountains, focusing the best chance for measurable snowfall there. This appears to be a fairly fast- moving system, so accumulations do not seem to be very heavy. The mountain snowfall forecast is in the 3 to 6 inch range, with an inch or two possible along the favored east-facing slopes of the Rockies. Of course, these amounts may need further adjustment as the event draws closer. Temperatures for most areas will struggle to get warmer than the 20s and mid 30s on Saturday as the passage of a strong Canadian cold front brings gusty northerly winds. As this system exits the area Saturday night through Monday, drier and warmer conditions are expected as a weak high pressure ridge spreads into western Montana; highs in the 40s to lower 50s are likely by Monday. However, another low pressure system will move southeast over the forecast area Monday afternoon through Monday night, but forecast models disagree on the strength of this system. Have therefore continued to broad-brush a chance of precipitation across the area. Not as much cooling is expected with this quick-moving system either. However, if the models deepen this shortwave similar to the one Friday night into Saturday, temperatures may need to be decreased and precipitation chances may need to be increased with subsequent forecasts. Drier and warming conditions return for Tuesday through Wednesday. Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 40 26 45 32 / 10 20 10 0 CTB 34 20 43 30 / 60 20 10 0 HLN 40 28 47 30 / 20 30 10 0 BZN 40 24 44 23 / 10 20 20 0 WEY 41 23 40 15 / 40 70 40 10 DLN 38 23 42 22 / 40 30 10 0 HVR 41 27 46 30 / 0 20 20 0 LWT 35 24 41 27 / 20 30 20 0 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until noon MDT today Southern Rocky Mountain Front. && $$ http://www.weather.gov/greatfalls