textproduct: Great Falls

KEY MESSAGES

- It will be windy tonight into tomorrow morning across North- central Montana with the strongest winds in locations near the mountains.

- Wednesday through Friday it will gradually cool down each day to have well-below seasonal average temperatures on Thursday and Friday.

- It will be mostly dry through the entire forecast period and will begin to warm back up Sunday through early next week.

DISCUSSION

- Meteorological Overview:

This afternoon there is northerly flow aloft this will keep cool temperatures across North-central, Central, and Southwestern Montana this afternoon. This afternoon snow will linger across the Little Belts and western Fergus County. This snow will gradually end by this evening. This evening into tomorrow morning another shortwave will move south from Canada. This will bring gusty winds to North- central, Central, and Southwestern Montana. The strongest winds will be near the mountains of North-central Montana. On Wednesday northwesterly flow aloft remains which will cool down temperatures to around seasonal averages with dry conditions. On Thursday a surface high slides south from Canada into North Dakota. This combined with northwest flow aloft will pull some cold air from Canada into North-central, Central, and Southwestern Montana. The coldest temperatures will be in Hill and Blaine County.

On Friday northwest flow aloft will remain over North-central, Central, and Southwestern Montana. This will keep the cold and dry conditions over the area. On Saturday the northwest flow aloft over North-central, Central, and Southwestern Montana will remain, but the cold air will begin to slowly move out of the area. On Sunday an upper-level ridge will begin to move over North-central, Central, and Southwestern Montana. This will allow temperatures to warm up with mostly dry weather. On Monday the upper-level ridge remains over North-central, Central, and Southwestern Montana. This will allow temperatures to warm up further with dry weather. -IG

- Forecast Confidence & Scenarios:

Tonight through Wednesday morning there is greater than a 60% chance for wind gusts of 55 mph or greater in Blaine County, portions of Fergus County, and near the Sweet Grass Hills. Given that the impacts from the wind in Northern Blaine County and Fergus County are expected to be limited and isolated, a High Wind Warning was issued for the Bears Paw Mountains (Southern Blaine County) and the Sweet Grass Hills from midnight tonight to 8 AM tomorrow morning. Future shifts will continue to evaluate Northern Blaine County and Fergus County for the need to add them to the High Wind Warning.

On Thursday morning there is greater than a 50% chance for low temperatures below zero along most of the Hi-Line. On Friday morning there is a 25 - 50% chance for low temperatures of 20 below zero across Hill and Northern Blaine Counties. Elsewhere across North- central Montana there is greater than a 30% chance for low temperatures of 10 below zero Friday morning. -IG

AVIATION

20/18Z TAF Period

As the front continues to move south over central and southwest Montana, winds will increase right as the front passes along with light snow showers that will primarily impact slantwise visibility. Low-VFR to IFR CIGs are expected through the morning before gradually lifting towards the late afternoon hours.

The next weather disturbance arrives on Wednesday with some increasing low to mid-level clouds after 21/12Z which will bring back low-VFR CIGs and periods of mountain obscuration across the region. -thor

PRELIMINARY POINT TEMPS/POPS

GTF 18 27 6 16 / 0 10 0 0 CTB 15 25 1 12 / 0 0 0 0 HLN 14 28 9 22 / 0 0 0 0 BZN 9 28 7 24 / 0 0 0 0 WYS -5 25 -4 25 / 0 0 0 0 DLN 10 32 10 28 / 0 0 0 0 HVR 14 23 1 8 / 0 0 0 0 LWT 15 22 4 13 / 0 10 0 0

TFX WATCHES/WARNINGS/ADVISORIES

High Wind Warning from midnight tonight to 8 AM MST Wednesday for Bears Paw Mountains and Southern Blaine-Eastern Toole and Liberty.