textproduct: Great Falls

KEY MESSAGES

- Temperatures will return to unseasonably warm levels on Wednesday and continue until a period of cooler than average temperatures begin Friday, which continue through the beginning of the following week.

- Pacific system will bring rain and mountain snow beginning Thursday night and continuing through early Saturday morning.

- Gusty winds develop Friday afternoon and continue through Friday night with the highest gusts along the Rocky Mountain Front and Central MT.

DISCUSSION

- Meteorological Overview:

Upper-level ridging will allow for mild conditions to continue through Thursday. Temperatures will be warmer than average and winds will be lighter with gusts generally remaining under 25 mph.

A weather system out of the Pacific that has been lingering over the west coast will begin to track eastward on Thursday, bringing cooler temperatures and moisture to the area. A cold front associated with this system will move through the region on Friday, resulting in the high temperatures on Friday to occur during the morning hours. Additionally, post frontal winds will develop Friday afternoon and continue through Friday night. The highest gusts are expected along the Rocky Mountain Front and Central Mountain. For southwest Montana, there is also a chance for thunderstorms due to passing of the cold front during the day on Friday. Due to snow levels not falling until the precipitation associated with this system has decreased, the bulk of snowfall is likely to be limited to the mountains. Any snowfall that does mix-in for the lowland areas will be hindered in accumulating due to recent rainfall and warm temperatures.

Looking beyond Saturday, although confidence is lower due to the how far into the future this is, upper- level troughing looks like it will remain in place over the region. Overall, temperatures will continue to be cooler with overnight freezes each night. Winds will be mild across the region with gusts generally under 25 mph. An upper-level trough has the potential to clip north Montana on Sunday and cause some light showers. With snow levels still at lower levels and daytime high temps in the upper 30s/low 40s, light showers may be snow or a snow/rain mix in the lowlands. -ESH

- Forecast Confidence & Scenarios:

High confidence for areas of mountain snowfall Thursday night through Saturday morning. 60-80% chance of 2" or more during that time frame. Main areas impacted will be the northern Rockies, Island Mountains, and SW Montana mountains.

Medium confidence for whether there will be snowfall in lowland areas on Friday night and Saturday due to an offset in snow levels falling and precipitation timing. Currently there is a <30% chance for a trace of snowfall in lowland areas. -ESH

A possible alternate scenario that would allow for more lowland snow: The low/trough phasing is slower, both delaying the progression of the troughing but also allowing deformation moisture to linger across the area while cold air drives snow levels down towards 3kft. This will introduce a window for a more persistent but light snowfall across lower elevations. That being said, warm ground temperatures and hours of rain proceeding the potential change would restrict any of this to elevated surface if any at all. -JR

AVIATION

20/18Z TAF Period

VFR conditions will prevail through the TAF period with passing scattered high-level clouds and light and variable winds. -thor

PRELIMINARY POINT TEMPS/POPS

GTF 36 71 44 72 / 0 0 0 0 CTB 30 66 38 67 / 0 0 0 0 HLN 34 66 40 69 / 0 0 0 10 BZN 33 65 37 69 / 0 0 0 0 WYS 27 60 28 61 / 0 10 10 10 DLN 35 64 37 65 / 0 0 0 10 HVR 32 68 37 71 / 0 0 0 0 LWT 34 70 44 73 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.