FXUS65 KTFX 142350 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 550 PM MDT Sat Sep 14 2024 UPDATED AVIATION SECTION .SYNOPSIS... After a largely dry weekend, chances for precipitation will ramp back up Sunday evening into Monday, lasting through Wednesday in most areas. Unsettled conditions remain through the end of the week, with low-end opportunities for precipitation Thursday into the weekend. && .DISCUSSION... Through the day Sunday... Weakly southwesterly flow this afternoon will continue to become more southwesterly heading into Sunday, and eventually more southerly by late Sunday ahead of an upper level trough/closed low diving southward from the coastal Pacific Northwest toward CA. A brief period of enhanced mid level flow will combine with daytime mixing today to result in breezy southwesterly to westerly winds, mostly across the plains. Additionally, a weak shortwave clipping the Northern Rocky Mountain Front this afternoon looks to provide enough support for a few showers over terrain. Given the downsloping nature of winds today, confidence is much lower that any shower makes it onto the adjacent plains. There is a small subset of guidance that does end up tracking a few showers over the northern plains after sunset, but confidence in this being realized was a bit too low at this time to warrant mention in the forecast. As flow becomes increasingly southerly Sunday, better moisture and instability moves in from the south, initially across Southwest Montana mid-afternoon. A few showers will be possible across Southwest Montana, but the majority of precipitation, which looks to be scattered in nature, looks to hold off until the evening hours across the southwest and into Central Montana. Sunday evening through Wednesday... The upper level trough and closed low will drift eastward Sunday night into Monday before lifting northward toward the Northern Rockies Monday night into Tuesday. The disturbance lingers through Wednesday before departing northeastward Wednesday night. Another round of showers and thunderstorms develops Monday afternoon and evening, mainly across Southwest and Central Montana. Forecast soundings aren't overly impressive from a severe thunderstorm perspective, though gusty winds will remain a concern with the strongest thunderstorms that form. Additional periods of showers/thunderstorms/more widespread rain will overspread the region Monday night through Wednesday. Confidence remains high for a widespread half inch of precipitation, with chances for an inch of precipitation between Monday and Wednesday night around or greater than 50% in most areas. Any thunderstorm, more persistent showers, or heavier stratiform rain will be capable of raising concerns for flash flooding on recent burn scars through Wednesday. Snow levels still look to fall in the 7,500 ft to 8,500 ft range, with brief instances of slightly lower snow levels where precipitation is heavy. It is still a bit early to tell where snow levels will fall most, which will be dependent on the exact track of the system. As the upper level low tracks northeastward across the region, it will dig out a surface low, most likely just off to the east across eastern MT. This would result in a breezy day Wednesday, especially across the plains. The chance for a 40 mph gust continues to run at or above 50% across the plains Wednesday, with a nonzero, but generally less than 10% chance for a 58 mph gust. A scenario in which the surface low is a bit stronger and further west would result in increased confidence for stronger wind gusts. Thursday into the weekend... Ensembles are in general agreement that weak troughing will be sliding eastward across the interior west toward the central CONUS Thursday and Friday. Agreement breaks down with respect to how quickly this occurs, with quicker/further east solutions favoring a slightly more anticyclonic northwesterly flow aloft vs slower solutions favoring a more cyclonic version of northwesterly flow aloft. The main takeaway is that temperatures are likely to remain a bit below average, with at least low end chances for precipitation Thursday into the early weekend. -AM && .AVIATION... 15/00Z TAF Period VFR conditions will continue through at least 16/00Z across Southwest (KWYS, KEKS, KBZN), Central (KHLN, KGTF, KLWT), and North Central (KHVR, KCTB) Montana. A moderate westerly flow aloft will shift more southwesterly after 06Z, then more southerly after 18Z. Overall, this will keep areas of high- and mid-level cloudiness moving over the area with a persistent threat for mountain wave turbulence. There will also be a potential for some mountain top obscuration with light precipitation, especially after 18Z. Breezy westerly winds will mostly decouple at the surface after 02Z, but winds will become breezy and gusty again after 18Z, out of the east and north over North Central and Central Montana, but more southerly across Southwest Montana. -Coulston Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 47 72 46 71 / 10 10 20 20 CTB 42 66 43 69 / 10 10 30 20 HLN 49 76 49 76 / 10 10 20 40 BZN 44 82 45 77 / 0 10 20 50 WYS 28 72 36 70 / 0 10 50 70 DLN 42 75 44 72 / 0 10 40 50 HVR 47 76 49 78 / 10 0 20 30 LWT 45 77 45 72 / 0 0 20 20 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls