textproduct: Great Falls

KEY MESSAGES

- A weak front will bring slightly cooler temperatures today, otherwise, generally milder and drier conditions prevail for much of the week.

- There may also be some patchy fog development tonight, mostly for the river valleys and higher southwest basins.

- Fast moving weather systems will bring periods of breezy to windy conditions and spotty mountain precipitation Thursday through early next week.

DISCUSSION

/Issued Issued by National Weather Service Glasgow MT/

- Meteorological Overview:

Ridging aloft will remain over the Northern Rockies for the next 24 hours, while a weak mid-level circulation moves eastward through the Great Basin. A weak frontal passage will cool todays highs by a few degrees and will bring some nighttime and early morning patchy fog development, mostly over the north-central river valleys and the higher southwest basins along the MT/ID/WY borders.

An initial trough passage will bring increased westerly winds and spotty mountain precipitation on Thursday. This will usher in an extended period of strong westerly flow aloft that will persist into early next week despite dominant ridging building for the first half of the weekend. The trend of the strongest winds aloft staying north of the Canadian border on Friday continues to gain traction, but a tightening surface pressure gradient and mountain wave activity still looks to enhance stronger winds along the Rocky Mountain Front Friday into early Saturday.

Ensembles are favoring the ridge flattening and sending a fast moving trough into the forecast area Sunday into Monday. This will bring another round of winds, strongest along the Rocky Mountain Front, and some more light precipitation along the northern divide. Temperatures look to remain above average this weekend into early next week, with only a slight cool down following any shortwave passages. - RCG

- Forecast Confidence & Scenarios:

Periods of stronger westerly winds Thursday through early next week

NBM probabilistic guidance continues to highlight Friday into Saturday for the strongest winds, with probabilities for 55 mph wind gusts running 70 to 90% along the Rocky Mountain Front and the plains along and west of highway 89 and along and west of I15 over Glacier County. The 40 to 60% chance for 75 mph wind gusts remains confined to the immediate eastern slopes of the Northern Rocky Mountain Front and will be heavily reliant on mountain wave activity. The plains east of I15 also look windy during this time as well, especially the central MT highway 87/200 corridor where 30 to 50 mph gusts will be common. The winds for Sunday into Monday have slightly lower probabilities despite stronger winds aloft, this looks to be mostly a trough timing issue. - RCG

AVIATION

04/12Z TAF Period

Ridging aloft will maintain a light wind regime and primarily VFR conditions; however, low status and patchy fog looks to bring periods of MVFR/IFR/LIFR degradations at KWYS and to a lesser degree KHVR. These conditions will be most prevalent during the 10 to 15Z period today and again on Thursday. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 49 31 54 35 / 0 0 0 0 CTB 48 29 50 34 / 0 0 0 0 HLN 48 28 48 29 / 0 0 0 0 BZN 44 27 46 28 / 0 0 0 20 WYS 50 20 41 22 / 0 0 0 20 DLN 45 25 43 24 / 0 0 0 10 HVR 44 27 51 33 / 0 0 0 0 LWT 48 30 54 31 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.