Brooks, MT Weather

Aviation Section Updated.

Key messages

- Breezy to windy conditions decrease tonight with seasonal temperatures through Wednesday, cooling below average on Thursday.

- Snow showers affect some areas near the continental divide through Thursday, mainly near Glacier National Park.

- Next larger weather system moves into the region this weekend with rain and snow developing Saturday night through Sunday.

Discussion

- Meteorological Overview:

A baggy upper level trough remains in place across the NW US and Northern Rockies with one of multiples embedded waves lifting out into the Canadian Prairies today while another cuts east from southern ID across WY tonight. Energy dropping south along the BC coast consolidates the trough to a closed low offshore of the Pacific NW by Friday, which eventually opens and shifts inland this weekend.

Lingering afternoon light precipitation near the Hi-line associated with the energy lifting north into AB/SK will end by this evening. Gusty winds that developed today behind the departing wave will diminish for many areas this evening though breezy winds may persist through tonight along areas immediately adjacent to the Rocky Mtn Front and central MT mountains. A cooler airmass developing across AB tonight may expand as far south as areas near the international Border by early Wednesday morning, bringing some risk for lower clouds/patchy fog there. The cooler airmass slides south across the N-central MT plains later Wednesday through Thursday, cooling daytime temperatures back to below seasonal averages with less noticeable cooling reaching SW MT.

While most of the forecast area is expected to see overall dry conditions through Thursday, a steady stream of Pacific moisture embedded within the westerly flow will support orographically enhanced showers over the continental divide with more persistent periods of snow most likely for areas along the divide north of MT-200. A few isolated rain showers may track further east across north-central and SW MT, mainly in the afternoon and early evening periods today and again tomorrow as less stable conditions offset the effects of downslope drying in westerly flow.

The upper low offshore of the Pacific NW late this week splits while moving onshore this weekend in tandem with a southern stream wave and Pacific moisture streaming into CA and the Great Basin. Southerly flow developing Friday night and Saturday ahead of the trough will bring some warming as well as increasing clouds with precipitation chances increasing from south to north late Saturday. The bulk of the precipitation looks to occur later Saturday night through Sunday with the passage of the trough axis and a slow moving Pacific cold front. Snow with this system will initially be limited to higher elevations with lowering snow levels allowing for a mix or transition to snow at lower elevations Sunday. A drier period looks to follow early next week as ridging builds in behind the weekend trough. Hoenisch

- Forecast Confidence & Scenarios:

Snow levels along northern portions of the continental Divide (N of MT-200) fluctuate around 5000 ft through Thursday. Periods of snow with some minor (<1"/12hr) accumulation may occur at Marias Pass, particularly Wednesday night, but accumulations of 2" or more are primarily expected to be limited to elevations >6000 ft in Glacier NP.

Interactions between the splitting northern stream trough and southern stream moisture/energy this weekend lead to model differences and uncertainty in the more specific details of timing and precipitation amounts/type still at this time range. Snow levels may initially be above 7000 ft Saturday night but are likely to lower at least to pass levels on Sunday. Probabilities for >4" snowfall amounts this weekend are highest (50-80%) above 7000 ft in the Little Belt, Bridger, Gallatin and Madison Ranges with a 20-40% probability for 2" or higher amounts across most central and SW MT mountain passes. Hoenisch

Aviation

28/06Z TAF Period

Light rain showers will affect areas along/north of Highway 2 overnight from east of Cut Bank to Harlem. Also, expect rain/snow to affect the Rocky Mountain Front. On Wednesday, most of the precipitation will be confined to the Rocky Mountain Front. Mid and high clouds will affect much of Southwest MT through through period. Do expect some mountain ranges across the CWA to be obscured by clouds/precip through the period. Cloud cover will limit the chances of fog for most areas through the period as well. Brusda

Preliminary point temps/pops

GTF 35 52 28 39 / 0 0 0 0 CTB 30 45 24 35 / 10 0 10 0 HLN 31 49 28 46 / 10 0 0 0 BZN 30 46 27 46 / 10 0 0 0 WYS 25 37 22 42 / 30 10 0 0 DLN 29 44 27 45 / 0 0 0 0 HVR 34 48 27 40 / 30 0 10 10 LWT 32 49 28 43 / 0 0 0 0

Watches, warnings and advisories

None.