Marine Weather and Tide Forecast for Big Sky, MT

DISCUSSION

- Meteorological Overview:

Increasing moisture ahead of the front has begun precipitation just to the east of the Continental Divide. The cold front pushing east across the state later today will continue to bring showers/mountain snow through the overnight hours Sunday. Cooler temperatures settle in behind the front, with temperatures cooling back towards normal for the week. A broad, upper level trough sets up along the Northwest U.S for most of the week. This will bring daily chances for lower elevation rain and mountian snow.
The best chances for widespread, precipitation will be Sunday night through early Tuesday morning where there is better forcing from the trough aloft. Weak instability in place Sunday and Monday will allow for a few isolated thunderstorms in the afternoon/evening. However, vertical profile soundings don't support for robust thunderstorms outside of the typical sub-severe gusty winds. Snow levels will generally stay between 6,000-7,000ft Sunday, but will fall Monday and Tuesday morning, which can allow light snow to mix in across lower elevations.

- Forecast Confidence & Scenarios:

Forcing along the front today doesn't look robust, so moisture amounts will generally stay below 0.1" except for some areas in Southwest MT, where they have better chances for 0.1"-0.25" of moisture. For Sunday night through early Tuesday morning, there's a 40-80% chance for 0.1" of moisture across lower elevations and a 30-50% for 0.25" of moisture east of the Havre to Monida line.
Through the week, precipitation remains on the lighter side unless you get a good shower or thunderstorm.

Most of the snow will be above pass level in the Glacier Park region and the Gallatin and Madison County Mountains. They have a 60-90% chance for 6" or more. Down to Pass level, there's a 50% chance for 4" at King's Hill Pass and a 40-60% chance for 2" of snow along Marias, Chief Joseph, and Raynolds Pass. The most impactful time period for snow on passes will be overnight Sunday/Monday morning with lower snow levels and temperatures below freezing.
Warming temperatures during the morning will likely turn snow covered roads to slush, and melt off Monday afternoon. -Wilson

AVIATION
19/18Z TAF Period

VFR CIGS early this afternoon will lower to primarily MVFR/low- VFR through the late afternoon and evening hours as a Pacific cold front sweeps east across the Northern Rockies. Scattered to numerous rain showers will accompany the front as it moves east across Southwest through North Central Montana, with the most persistent showers expected along and southeast of a KEKS, to KBZN, to KLWT line from between 03z to 12z Sunday. Periods of IFR CIGS are possible beneath this more persistent shower activity given favorable orographic upslope flow here. Mountains will be obscured from from northwest to southeast beyond 19/21z to 20/03z. - Moldan

Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information.

PRELIMINARY POINT TEMPS/POPS
GTF 37 59 36 54 / 60 40 40 70 CTB 33 54 31 50 / 20 50 20 60 HLN 37 59 36 50 / 40 50 60 80 BZN 33 56 31 46 / 80 30 90 90 WYS 27 49 25 45 / 60 60 80 90 DLN 31 57 32 48 / 70 20 60 60 HVR 35 60 34 56 / 60 60 60 70 LWT 36 55 34 50 / 50 50 90 80

TFX WATCHES/WARNINGS/ADVISORIES
None.