Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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710 FXUS65 KTFX 172112 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 312 PM MDT Mon Jun 17 2024 .SYNOPSIS... Cool and wet conditions continue through tonight and early tomorrow morning as a cold spring weather system moves through the area. After widespread showers on Tuesday, we will continue to have a few isolated to scattered afternoon showers and thunderstorms during the afternoons each day through the end of the week. && .DISCUSSION... Key Points: -Rain and mountain snow continue through Tuesday morning with precipitation becoming showery during the day Tuesday -Showers and thunderstorms will develop most afternoons Wednesday through Friday as temperatures gradually warm Through Thursday Ongoing widespread rain and mountain snowfall continue across North Central and Southwestern Montana through the evening and overnight tonight as an anomalously cold weather system continues to work its way through the area. So far, most areas have seen a general .1-.2 inches of rainfall, though areas along a line from the Bears Paw Mountains to Great Falls to the Bob Marshall Wilderness Complex have seen amounts come in a bit higher, with up to .75 inches of precipitation in the past 24 hours, with some of that falling as snow above 6000 feet or so. Where snow has fallen, it appears that accumulations have generally been limited to grassy and elevated surfaces, and even there accumulations have generally been around an inch or two early this morning before daytime heating began to melt the snow faster than it fell after sunrise. We will have to watch for some accumulations after sunset again tonight, but this will come as the main area of precipitation begins to move off to the northeast, so any additional accumulations of snow will generally be a coating of up to 6 inches on the highest peaks. In the wake of this system tomorrow, upper level troughing and cold air aloft will linger across North Central and Southwestern Montana, which will help to spur the development of scattered to widespread showers and maybe a thunderstorm or two across the area. These showers and storms should bring a bit of additional moisture to many of us, with most areas seeing up to 0.1 inches of additional rainfall tomorrow. Temperatures will moderate a bit Wednesday and Thursday as our upper level flow becomes zonal/westerly, though we will have a few showers and thunderstorms develop each afternoon. Ludwig Thursday through Friday...ensemble clusters favor southwesterly flow aloft over the Northern Rockies as shortwave troughing moves from over the Eastern Pacific/Western Seaboard and towards the Northern and Central Rockies. This southwesterly flow regime will help to maintain scattered to numerous showers and storms, particularly over Central and North Central Montana, each day. Additionally, temperatures will moderate to near normal. Saturday through next Monday...quasi southwest to zonal flow is favored within the multi-model ensemble mean during the period, which is expected to translate to well above normal temperatures and isolated showers/storms each day across the Northern Rockies. - Moldan && .AVIATION... 17/18Z TAF Period Note: The NWS Great Falls Weather Forecast Office manages the following TAFs: KCTB, KHVR, KGTF, KLWT, KHLN, KBZN, KEKS and KWYS. Rain/snow continues throughout this TAF period, causing MVFR/IFR/LIFR conditions at our airfields. Mountain obscuration should be expected. Periods of winds with gusts to 20KT are included in the KGTF, KLWT and KEKS TAFs, with the winds at all other airfields remaining, mostly, light. Having said this, some gusty winds to 35KT are forecast through the north-south oriented mountain valleys/passes of far southwest Montana. These winds decrease after 18/02Z. There is a 30% to 40% chance for thunderstorms to develop across southwest Montana, this afternoon and evening, with a 20% to 25% chance for thunderstorm activity to occur across north central and central Montana. A PROB30 for thunderstorm is included in the KBZN TAF; however, confidence was too low to include thunderstorm for the TAFs of any other airfields. - Fogleman Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 39 58 37 67 / 80 80 40 30 CTB 35 53 32 65 / 40 80 30 30 HLN 42 64 40 72 / 90 70 40 20 BZN 36 59 33 69 / 90 60 30 20 WYS 28 52 24 63 / 90 60 20 10 DLN 34 56 32 65 / 80 30 20 10 HVR 42 61 40 69 / 80 70 40 30 LWT 34 54 34 65 / 100 80 40 40 && .TFX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until noon MDT Tuesday for East Glacier Park Region-Southern Rocky Mountain Front. Winter Weather Advisory until 6 AM MDT Tuesday for Big Belt, Bridger and Castle Mountains-Elkhorn and Boulder Mountains- Gallatin and Madison County Mountains and Centennial Mountains- Little Belt and Highwood Mountains-Northwest Beaverhead County- Snowy and Judith Mountains. && $$ http://www.weather.gov/greatfalls