textproduct: Great Falls

KEY MESSAGES

- Colder air filters in across the region today, coldest near Havre.

- Occasional light snow at times into this weekend.

- Temperatures slowly moderate this weekend into early next week.

DISCUSSION

- Meteorological Overview:

Cyclonic northwesterly flow aloft will persist across the region through at least the weekend. Surface high pressure across northern AB/SK early this morning will slide southeastward through the day into ND and vicinity, which will help to induce a northeasterly winds across much of the plains through the day. Cooler air filters in as a result, which will result in a cold night tonight, particularly in the Havre area and vicinity.

Weak waves diving through the cyclonic flow will result in occasional periods of light snow through the rest of the week into the weekend. The first period of light snow develops tonight, though impacts look to be minimal/isolated at this point. The cold temperatures slowly moderate after Friday, given the lack of a reinforcing shot of cold air (That would keep temperatures cold), nor persistent westerly/southwesterly downslope winds developing (That would quickly warm temperatures up).

Upper level ridging looks to build in near the Pacific coast heading into next week, but struggles to make quick progress eastward. This keeps the door open for low-end probabilities for light precipitation into early next week as temperatures continue to moderate. -AM

- Forecast Confidence & Scenarios:

Cold overnight lows/wind chill tonight:

Largely light, but non-zero, winds will combine with the much cooler temperatures moving in through the day today to result in quite a chilly night across the region. Areas near Havre will be the coldest, with the Chinook, Harlem and up to the Big Flat area being the coldest. Hourly probabilistic guidance gives roughly a 50/50 probability for wind chills of -35 or less across Northern Blaine county late tonight into early Friday. The probability for wind chills that cold is lower across adjacent areas, including Hill county and southern Blaine county. -AM

AVIATION

22/06Z TAF Period

Initial concern will be for winds to shift around to be a more northerly or northeasterly direction over the plains through the morning, making inroads into Southwest Montana valleys during the day Thursday. Low-VFR or MVFR cigs will accompany these northerly winds at times, which will obscure mountains. Some light snow may develop late-day Thursday across Central Montana, but was too low of probability to include in the TAFs at this time. -AM

PRELIMINARY POINT TEMPS/POPS

GTF 19 -3 10 -1 / 10 30 10 0 CTB 13 -7 9 -3 / 10 20 0 0 HLN 24 1 12 0 / 0 20 10 0 BZN 25 1 13 -3 / 0 10 10 0 WYS 25 -3 20 -17 / 0 0 10 0 DLN 32 8 21 1 / 0 0 0 0 HVR 9 -13 1 -7 / 10 10 0 0 LWT 15 -6 5 -7 / 10 50 30 0

TFX WATCHES/WARNINGS/ADVISORIES

Cold Weather Advisory from 5 PM this afternoon to 10 AM MST Friday for Bears Paw Mountains and Southern Blaine-Hill County- Northern Blaine County.