921 FXUS65 KTFX 061155 CCA AFDTFX Area Forecast Discussion...CORRECTED AVIATION DISCUSSION National Weather Service Great Falls MT 555 AM MDT Wed Oct 6 2021 ...UPDATED AVIATION SECTION... .SYNOPSIS... Dry, warm, and breezy weather will persist for one more day across the region, but a change in the weather pattern is on the way. The passage of a cold front today will gradually usher in cooler temperatures and more unsettled weather through Friday. A few thunderstorms are also possible in the southwest. The weekend should be mostly dry with near normal temperatures, but cooler and wetter than normal conditions early next week could bring at least a mix of rain and snow, even to lower elevations. && .DISCUSSION... Today through Tonight... One more day of dry and breezy conditions is on tap for today for North Central and Southwest Montana. A southwest flow aloft ahead of an approaching Pacific low pressure trough will keep skies partly to mostly cloudy today with areas of smoke and haze. This will help limit daytime heating and keep highs only about 10 to 15 degrees above normal (about 10 degrees cooler than yesterday). The leading edge of a Pacific cold front will also move across the area today, which will help shift the gusty southwest winds more westerly from west to east. Gusts up to 25 mph will occur at times for much of the area, but ridge tops and areas on the Rocky Mountain Front may see gusts up to 40 mph at times; overall, though, winds should decrease overnight as the shift more so to out of the northwest. A disturbance in the southwest flow will bring scattered showers first to Southwest Montana later this afternoon, which will spread northeast over much of the remainder of the area. A few thunderstorms may move over Southwest Montana through the evening as well, with the main threats being isolated lightning strikes, erratic wind gusts, and brief periods of heavy rain showers. Cannot rule out localized debris flows and flash flooding from these showers, but mainly in steep terrain and in burn scar areas. Overnight temperatures should also cool back closer to normal. Thursday through Sunday... The low pressure trough will move across the Pacific Northwest into the Northern Rockies during this period, keeping the area under moist southwest flow aloft. Energy in this flow will continue to bring periods of rain showers to the area, but mainly along and southeast of a line from Missoula to Havre. These areas will mostly receive between 0.10 and 0.20 inches at lower elevations, but up to 0.50 inches of precipitation is possible in the mountains. A few afternoon and evening thunderstorms will also remain possible over Southwest Montana. Precipitation in the higher mountain peaks will also mix with or change over to snow at times, but accumulations there should only be a few inches. The associated initial push of colder air will help cool temperatures to near or slightly below normal. This trough will exit the area into Saturday and bring a weak high pressure ridge into Montana on Sunday, which should help dry out the area and keep temperatures near to slightly above normal for the weekend. Monday through next Wednesday... Another deep Pacific trough is forecast to set up over the western United States during this period, bringing even cooler weather to the area. Highs in the 30s in the mountains and in the 40s at lower elevations will be common, possibly lowering snow levels down to the plains and valley floors at times. Periods of precipitation are also expected, but just how much precipitation, including snow, will fall is still a bit uncertain, but this pattern change should be a welcome respite to our drought-stricken state. -Coulston && .AVIATION... 555 AM MDT Wed Oct 6 2021 (06/12Z TAF period) VFR conditions with periods of minor visibility reductions in smoke will mostly persist over north central and southwest Montana through much of the next 24 hours. A southwest flow aloft will keep areas of mid and high level cloudiness over the area. A disturbance in the flow may bring some light showers to portions of southwest and central Montana through 16Z (mainly KWYS KBZN KEKS KHLN KGTF KLWT). Winds aloft may be translated down to the surface over central Montana (KHLN KGTF KLWT) with these showers, potentially causing low level wind shear and periods of gusts up to 35 kt at times through 16Z. A frontal boundary moving west to east across the area between 18Z and 00Z will shift winds from southwesterly to more westerly with gusts mostly up to 25 kt, but stronger gusts up to 40 kt will be possible closer to the Rocky Mountain Front. Another disturbance will then bring a chance of showers and thunderstorms with erratic wind gusts and periods of brief heavy rain to the area south of KGTF between 22Z and 03Z; some showers may cause some mountain obscuration. Another disturbance will bring more widespread showers to southwest Montana after 06Z, possibly with periods of mountain obscuring MVFR conditions. -Coulston Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .FIRE WEATHER... Dry and breezy conditions will linger across North Central and Southwest Montana for one more day. The southwest flow aloft will continue to move clouds and smoke over the area today, which should help limit daytime heating and keep temperatures about 10 degrees cooler than yesterday. Afternoon humidity will be on the dry side again, but the cooler temperatures will keep the minimum values this afternoon around 20 percent for only a few hours. A Pacific cold front will also move east across the area today, causing gusty southwest winds to shift more westerly. This may cause locally elevated fire weather conditions, but it should not be significant enough to warrant any fire weather highlights. The main push of cold air behind the front will not move into the area until tonight through Thursday, which will help bring moderate overnight recovery and values above 30 percent for Thursday. Weak disturbances in the southwest flow aloft will also bring scattered showers and thunderstorms to much of the area at times from late this afternoon through the day on Friday. The main focus for thunderstorm activity will remain over the southern portions of zones 117 and 118. The main threats from any storms will be lightning, erratic wind gusts, and brief heavy rain. The overall cooler and wetter pattern will then continue into next week with gradually lowering snow levels. && .PRELIMINARY POINT TEMPS/POPS... GTF 78 41 59 37 / 10 50 30 20 CTB 71 36 57 29 / 0 10 10 10 HLN 78 44 62 40 / 20 50 50 40 BZN 77 43 61 39 / 20 50 80 60 WYS 62 35 51 35 / 30 60 90 70 DLN 72 41 59 37 / 30 40 60 40 HVR 80 41 59 37 / 10 20 30 20 LWT 78 40 57 38 / 10 30 50 50 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls