textproduct: Great Falls

KEY MESSAGES

- Periods of light snow will continue along the Rocky Mountain Front through Sunday evening.

- Warmer temperatures and generally dry conditions will continue across most of the region through Monday.

- More seasonable temperatures and an active pattern is expected starting next Tuesday.

DISCUSSION

- Meteorological Overview:

Westerly to southwesterly flow will allow for continuing periods of snowfall along the Continental Divide through Sunday with generally light accumulations expected at pass level and heavier amounts expected to remain confined to the peaks.

Well above normal temperatures will continue through Monday with generally drier conditions across much of the region before an upper level trough moves over the western CONUS on Tuesday. This will bring more seasonable temperatures and a series of weather systems that will last through at least Thursday bringing daily chances for precipitation across the region.

- Forecast Confidence & Scenarios:

Snow Saturday/Sunday:

Snow totals along the Continental Divide have not changed much compared to previous forecast packages with most of the impactful snow expected above pass level. The latest HREF run has Marias Pass sitting at around a 60% chance of greater than 4 inches and 30% chance at greater than 6 inches over the course of 36 hours. When looking at snowfall rates, there is no period where moderate to heavy snow is expected along Marias Pass so, in general, snowfall accumulations are expected to occur slowly through Sunday evening which is expected to produce only typical winter driving conditions. Thus when considering snowfall rates and total accumulation amounts, and the fact that the most impactful snow will occur well above pass level, the decision was made to forego issuing a Winter Weather Advisory at this time. That being said, folks traveling in the area should be prepared for changing road conditions and adjust travel plans accordingly.

Tuesday and Beyond:

A great deal of uncertainty still remains as to how next week will play out but increasingly it is looking like Tuesday will carry the best chances for widespread lower elevation snow. Snow totals up to 3 inches are possible across the lower elevations with locally higher amounts possible. As expected the mountains will carry the higher amounts with these weather systems. But there is a constant shifting with every model run as to which higher elevation locations will receive the heavier amounts so for now it is too early to pin point exactly which areas will receive significant or impactful snowfall. But there is increasing confidence that there will be a shift towards more seasonable temperatures and a more active pattern next week. -thor

AVIATION

14/00Z TAF Period

Moist, southwesterly flow aloft will maintain mountain obscuration along the Continental Divide and across Southwest Montana throughout the duration of the 1400/1500 TAF period; with scattered to broken mid-level clouds over the terminals of Southwest through North Central Montana. Winds will become strong and gusty over the plains of Central and North Central Montana on Saturday, especially at the KCTB and KGTF terminals beyond 18z. Mountain wave turbulence will remain possible in lee of the Continental Divide over the plains through much of Saturday. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 51 34 54 33 / 0 0 0 10 CTB 46 27 49 25 / 0 0 10 0 HLN 47 26 50 30 / 0 0 10 20 BZN 46 23 49 30 / 0 0 0 10 WYS 36 16 36 18 / 10 0 10 10 DLN 46 25 49 30 / 0 0 0 0 HVR 51 28 54 28 / 0 0 0 10 LWT 43 26 47 29 / 0 0 0 20

TFX WATCHES/WARNINGS/ADVISORIES

None.