textproduct: Great Falls

KEY MESSAGES

- Daily snowfall is expected in the mountains, with light snowfall possible mid week at lower elevations.

- Cold air will retreat northward today, but move back south later this week.

- Strong winds likely Monday into Tuesday.

UPDATE

/Issued 812 AM MST Sun Dec 7 2025/

Today it will be warm across most of North-central, Central, and Southwestern Montana with a round of light precipitation that will affect some areas this afternoon through this evening. Across the Hi-Line and Hill and Blaine Counties in particular the Arctic air will linger through most of the day today. For the update, temperatures across Hill and Blaine County were decreased to better reflect current observations and trends. The rest of the forecast is on track. -IG

DISCUSSION

/Issued 812 AM MST Sun Dec 7 2025/

- Meteorological Overview: Expect the weather pattern to generally change every few days over the CWA, as cold air moves north/southward this week, along with periods of snow.

As of 3 AM this morning, the warm front was now along a line from Cut Bank to Carter to Lewistown, and slowly moving northward. This warm front should move into the northern portions of Hill/Blaine counties by this evening. Some scattered light snow showers are falling along the divide, but downslope winds east of the divide are limiting how far the precip is moving off the mountains.

Thus, expect above normal temperatures over much of the CWA today, as warmer air continues to move in from the south.

On Monday, a strong area of low pressure will start to move from west to east across southern Canada. This will result in the potential for strong winds to develop along the front range of the Rockies by late Monday afternoon. The strong winds will then move eastward over the Plains Monday night, and exit the area on Tuesday morning. Overall, the timing is not great for mixing down the strong winds, however, the potential is there. Thus a high wind watch was issued for much of North Central MT. Above normal temperatures are expected once again on Monday.

On Tuesday, the strong winds will diminish in the morning, as surface winds switch around to the north. After Tue morning, the forecast models start to differ on how far/fast the cold air will move south. The GFS model is the most aggressive and likely the coldest model. Since the cold air is not going to go very far north of MT on Monday, this is a reasonable solution. As of now though, the NBM does not bring in the colder air until Wed.

For Thur/Fri...expect generally below normal temperatures across the CWA...with the potential for cold weather advisory conditions along the US/Canadian border. Additionally, periods of snow at all elevations are possible. At this time, snow amounts look light at low elevations, but with the northerly upslope, some areas could see a bit heavier snowfall than currently forecasted.

For next weekend, the forecast models would like the cold air to retreat northward once again. However, caution is urged in the temperature forecast for next weekend, as sometimes the cold air is quite slow to move out, and does not move out as quickly as the forecast models like several days out.

Note...for the mountain areas of the Rocky Mountain Front, Southwest MT and the Kings Hill area, there will be daily chances for snowfall from Monday through Friday. When the cold air moves south mid week, the snowfall could be heavy at times in the mountains.

- Forecast Confidence & Scenarios:

Winds: The main concern for the high winds is if the strong winds aloft will mix down during the overnight period Monday night into Tue morning. The NBM probability of wind gusts over 60 mph has increased to nearly 80 percent over the Plains and near 90 percent along the Rocky Mountain Front. The chance for 75 mph wind gusts along the Rocky Mountain Front is also near 80 percent in the windier locations.

Snow: Snow will be heavy at times in the mountains along the Rocky Mountain Front, Southwest MT and the Kings Hill area. At this time the heavy snow is mostly expected above pass level through Tuesday morning, with lighter snowfalls around pass level. Thus the current thinking is that a winter weather advisory might be needed for a portion of this period. For Tue afternoon into Thu, snow levels lower with the colder air moving in. Thus the potential for heavy snow will also lower. It is possible a winter storm warning might be needed later this week for some mountain ranges. By the end of the week, lighter snowfall returns to the mountain ranges.

Overall, snowfall in the mountains above pass level could average between 6 and 12 inches daily for some mountain ranges. At pass level, several days of 2 to 5 inch snowfalls are likely. Thus after several days of this type of snowfall, impacts will start to develop.

Cold: The cold air retreats today, but returns by mid week. By late in the work week, it could be cold enough along and north of the Highway 2 corridor from Browning to Harlem, that a cold weather advisory might be needed for portions of this area. Brusda

AVIATION

07/18Z TAF Period

West-northwesterly flow aloft gradually increases through the TAF period with VFR conditions prevailing beneath variable mid to high level cloud-cover. Mountain wave turbulence will increase later today and tonight with the strengthening flow across the Rockies and some instances of low level wind shear are possible later this evening and overnight before the transition to stronger surface winds develops Monday. Hoenisch

PRELIMINARY POINT TEMPS/POPS

GTF 42 35 48 41 / 10 20 10 30 CTB 36 27 42 33 / 0 10 10 40 HLN 43 32 47 39 / 20 30 20 50 BZN 40 27 45 36 / 10 20 10 30 WYS 28 21 33 26 / 60 70 60 80 DLN 40 29 44 37 / 10 20 0 30 HVR 32 25 42 30 / 0 10 0 40 LWT 40 28 43 32 / 0 20 10 30

TFX WATCHES/WARNINGS/ADVISORIES

High Wind Watch from Monday afternoon through Tuesday morning for Cascade County below 5000ft-East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Eastern Pondera and Eastern Teton-Eastern Toole and Liberty-Gates of the Mountains- Northern High Plains-Southern High Plains-Southern Rocky Mountain Front-Upper Blackfoot and MacDonald Pass.

High Wind Watch from Monday evening through Tuesday morning for Bears Paw Mountains and Southern Blaine-Big Belt, Bridger and Castle Mountains-Fergus County below 4500ft-Hill County-Judith Basin County and Judith Gap-Little Belt and Highwood Mountains- Madison River Valley-Meagher County Valleys-Northern Blaine County-Snowy and Judith Mountains-Western and Central Chouteau County.