textproduct: Great Falls

KEY MESSAGES

- Unseasonably cool and windy today with locally strong winds across portions of central and north-central Montana.

- Some higher elevation wet snow is expected today and tonight with accumulation mainly above 6000 feet.

- After drier and warmer conditions Thursday and Friday another cool and showery period is expected early this weekend.

DISCUSSION

- Meteorological Overview:

An unseasonably potent upper level trough continues to slide east across the Northern Rockies and MT today. Daytime temperatures will be around 15 degrees below seasonal averages with windy conditions making it feel colder. Showers initially will be more widespread along northern portions of the Continental Divide including the Glacier NP vicinity this morning with scattered to numerous showers across much of the area this afternoon as the airmass destabilizes beneath cold/cyclonic northwesterly mid level flow around the trough. An area of more organized precipitation is likely to slide south across north-central MT later this afternoon/evening and eventually through eastern portions of central and southwest MT later this evening/overnight as an area of moisture rotates around the backside of the trough. Precipitation tonight will favor areas near the central MT mountains and Gallatin/Bridger ranges enhanced by orographic/upslope moist northwest flow. Windy condtions are expected across most of the area today as unseasonably strong (35- 45kt mid level northwesterly flow continues through this evening.

A drier period follows Thursday into Friday with temperatures trending back towards seasonal levels. Another weather disturbance tracks southeast from WEstern Canada across the region Friday night through Saturday brinign another round of showery and cooler conditions to start the weekend. Most longer range model ensembles support an simplifying ridge early next week centered along the Pacific NW/BC coast which flattens by the middle of next week. This should provide warmer temperatures and initially dry conditions early next week. Hoenisch

- Forecast Confidence & Scenarios:

Snow levels were generally around 6500 ft early this morning and may fall to as low as 5500 ft for a period later this morning around Glacier NP. The best chance for minor snow accumulation below 6000 ft in Glacier NP is this morning while areas above 6000 ft have a 60- 80% probability of snow accumulation today in excess of 2 inches with isolated peaks above 7500 ft seeing higher amounts. Timing of precipitation later today across the mountains of central MT and eastern portions of southwest MT will coincide with snow levels closer to 6500 ft. There is 50-60% probability for snow accumulation of 2 inches or more over Kings Hill (~7000ft) this evening. Primarily impacts from any mountain snow today/tonight will mainly to those recreating at the highest elevations in these mountain ranges.

Hi-resolution models continue to show emebedded areas of stronger mid- level wind (45-50kt) moving across central MT this morning and again this evening. This will support periods with gusts exceeding 50 mph along the Rocky Mountain Front this morning and gusts exceeding 45 mph across much of central MT later this morning and likely again this evening across eastern portions of north-central MT(Fergus/JB counties). The risk for localized gusts in excess of 50 mph across central MT is greatest (30-60%) across the higher terrain near the continental divide and Big Belts as well as immediately downwind of these areas and the central MT mountain/island ranges. With expected isolated coverage of stronger wind gusts the High Wind Watch will be cancelled, though those traveling in high-profile vehicles or with lightweight trailers should exercise caution. Hoenisch

AVIATION

10/06Z TAF Period

Light showers are diminishing over the eastern portions of the CWA, while light rain/snow showers continue along the Rocky Mountain Front. Expect gusty surface winds to develop overnight over much of the CWA and then continue thru the day on Wed. Showers/isolated thunderstorms will also redevelop on Wed afternoon over North Central MT, and move southward into Central MT by Wed evening. Mountains/passes will be obscured at times across the CWA through the period. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 60 46 72 44 / 50 70 0 0 CTB 55 42 67 41 / 80 50 0 0 HLN 59 44 72 44 / 10 30 0 0 BZN 57 38 70 39 / 40 30 0 0 WYS 51 25 63 29 / 50 10 0 0 DLN 56 33 71 38 / 30 10 0 0 HVR 60 44 71 43 / 80 80 20 10 LWT 58 39 66 40 / 20 90 10 0

TFX WATCHES/WARNINGS/ADVISORIES

None.