textproduct: Great Falls

KEY MESSAGES

-Generally milder and drier conditions prevail for much of the workweek, but a weak front will bring slightly cooler temperatures on Wednesday.

-Patchy fog development will increase over the next couple of nights over the plains and southwest valleys.

-Passing weather systems will bring periods of breezy to windy conditions heading into the weekend and early next week.

DISCUSSION

/Issued Issued by National Weather Service Glasgow MT/

- Meteorological Overview:

Ridging aloft looks to bring general mild and dry conditions for much of the upcoming workweek; however, there will be a weak frontal passage that brings a cooler low level easterly flow tonight into Wednesday. The effects of this will be mostly felt over the plains where there looks to be some nighttime and early morning patchy fog development and a slight cooldown. There will also be some patchy fog over some of the southwest valleys during this time, especially the colder high valleys along the MT/ID/WY borders. Otherwise, temperatures will mostly run a few degrees above average for most locations and there will be localized breeziness.

Strong westerly flow aloft becomes established over the Northern Rockies during the second half of the week. The first of a series of fast moving zonal shortwaves will bring an initial round of breezy to windy conditions Thursday into Friday. This will be followed by additional systems parading through the forecast area during the weekend. Ensembles are having some difficulty resolving the timing and strength of each system, but they do agree that the Rocky Mountain Front and plains will be the recipients of the strongest winds. With ridging generally remaining the most influential weather feature, despite the elevated westerly flow and shortwave passages, temperatures look to remain above average and precipitation will generally be spotty and confined to mountain areas. - RCG

- Forecast Confidence & Scenarios:

Periods of stronger westerly winds Thursday through early next week

Ensemble guidance is having trouble resolving the individual shortwaves moving through the aforementioned elevated westerly flow aloft. Theres even some variation in precisely where the strongest H500/H700 flow will be. Some of the newer deterministic guidance places the strongest mid-level flow north of the Canadian border. With that being said, the NBM probabilistic guidance is eyeing Friday into Saturday for the strongest winds, with probabilities for 55 mph wind gusts running above 70% along the Rocky Mountain Front and the plains west of I15. Moreover, the 60% chance for 75 mph wind gusts along the immediate eastern slopes of the Northern Rocky Mountain Front look reasonable given the expectation for mountain wave activity. Of course this will be contingent on the timing/phasing of strongest westerly flow aloft. Plains areas also look pretty windy during this time, especially the central MT highway 87/200 corridor where 30 to 50 mph gusts will be common. There will be additional periods of stronger winds later in the weekend and into next week as the progressive westerly flow continues. - RCG

AVIATION

3/12Z TAF Period

General VFR conditions prevail for much of the TAF period, but there will be a few exceptions. MVFR stratus will continue over KWYS through around 03/18Z and there is around a 20% chance that IFR fog can develop early this morning. A weak front will bring cooler north/easterly flow over the plains tonight into Wednesday morning, with patchy MVFR/IFR stratus and or fog developing along the Hi-Line (KCTB, KHVR) after 04/06Z. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 56 29 48 31 / 0 0 0 0 CTB 49 27 48 28 / 0 0 0 0 HLN 48 27 48 27 / 0 0 0 0 BZN 46 26 43 26 / 0 0 0 0 WYS 45 19 50 19 / 0 0 0 0 DLN 45 25 45 25 / 0 0 0 0 HVR 49 28 43 27 / 0 0 0 0 LWT 53 30 46 29 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.