Helena Valley Southeast, MT Weather

Key Messages

- Patchy to areas of dense fog will bring localized sharp visibility reductions across short distances and isolated slippery spots from frost deposition again tonight in Monday morning.

- Pacific weather systems will bring periods of light snow this week, most widespread over the higher terrain along the Continental Divide and southwest Montana Monday night into Tuesday.

- Temperatures will generally remain below average heading into the latter part of October.

Discussion

/Issued 237 PM MDT Sun Oct 25 2026/

- Meteorological Overview:

Low level easterly flow looks to bring another round low stratus and patchy/areas of dense fog again tonight. Areas along the Continental Divide, the southwest valleys, and the plains east/northeast of the Rocky Mountain Front/Big Belts will see the greatest coverage and overall visibility impacts. The general flow aloft will shift southwesterly in advance of a closed low moving onto the Pacific NW coast. This will bring variable cloudiness and a slight warm up on Monday before the low heads into the Northern Rockies and sends a wave of mostly mountain light snow moving in southwest to northeast fashion Monday night into Tuesday. Accumulations in the 1 to 4 inch range will generally favor the higher terrain along the Continental Divide and the southwest mountains.

Ensembles then highlight another closed low moving southeast out of the gulf of AK before slowing down and remaining near or just off the Pacific NW coast for much of the week. This will bring a southwesterly flow aloft again and send a series of weak shortwaves and periods of spotty light rain and snow into the Northern Rockies for much of the remaining week. This system is progged to move towards the Great Basin/SW conus by early next week. Similar to many systems so far this fall, splitting and shearing will make for a challenging forecast. A further north track while maintaining strength would favor more snow and colder temperatures heading into early next week. Roughly half of the ensembles favor this. - RCG

- Forecast Confidence & Scenarios:

...Dense fog increasing tonight into Monday morning...

Aviation

25/18Z TAF Period

Update: Low clouds continue linger across portions of Southwest MT including KBZN through the rest of the day, though there may be a few breaks from LIFR ceiling to IFR ceilings through the early evening. Confidence is increasing for another round of lower clouds and fog in Southwest MT tonight into Monday morning. Up in North-Central MT, MVFR clouds continue through the afternoon before lifting. There is a slight chance for low stratus and fog in North-Central MT Monday morning, though confidence isn't high enough to include in this TAF cycle. -Wilson

Preliminary Point Temps

GTF 18 43 30 50 / 0 0 40 40 CTB 19 43 25 50 / 0 0 30 40 HLN 22 48 32 50 / 0 0 80 30 BZN 19 52 28 47 / 0 0 90 60 WYS 17 49 18 38 / 0 10 100 70 DLN 22 52 30 46 / 0 0 90 20 HVR 23 52 28 49 / 0 0 40 70 LWT 22 50 29 45 / 0 0 60 70