textproduct: Great Falls

KEY MESSAGES

- Isolated showers and thunderstorms are possible in Southwest Montana this afternoon and evening.

- Windy and dry conditions are expected on Tuesday.

- Cool and breezy conditions expected on Wednesday with a chance for rain along the Northern Rockies and portions of the Hi- Line.

DISCUSSION

- Meteorological Overview:

A weak shortwave will move across the region today with warming temperatures, breezy conditions along the Rocky Mountain Front, and scattered showers in far southwestern Montana expected.

The upper-level flow becomes more zonal Tuesday into Wednesday with two rounds of strong winds expected to move over the northern half of the state. The first and stronger wave of winds is expected on Tuesday with widespread gusts over 30 mph across the northern plains, gusts up to 50 mph closer to the Rocky Mountain Front, and gusts up to 75 mph possible along the portion of the Northern Rockies highlighted in the High Wind Watch. The second wave of winds on Wednesday will be much weaker comparatively with wind gusts generally staying in the 25 to 35 mph range across much of Central and North-Central Montana. The moisture plume associated with this zonal flow reaches the Continental Divide in the early morning hours on Wednesday with a chance for light rain along the Northern Rockies through the mid-afternoon hours. A few showers may develop across North-Central Montana, particularly along the Hi-Line, but rainfall amounts are expected to remain light.

Weak upper-level ridging briefly builds on Thursday into Friday morning. This will allow for a slight warmup across the region before the models start hinting at the potential for another weak shortwave trough moving across the region Friday afternoon into Saturday.

- Forecast Confidence & Scenarios:

Thunderstorms in Southwest Montana Today: Scattered showers and thunderstorms are possible this afternoon along the Montana/Idaho border into central Madison and Gallatin counties. Precipitation amounts are not expected to be high with generally a couple hundredths of an inch possible. Severe weather is not expected with any of these thunderstorms with only gusts in the 30-40 mph range expected.

Strong Wind on Tuesday: The highest confidence for high winds remains in the portion of the Northern Rockies and Glacier National Park highlighted in the High Wind Watch. Across the rest of the northern plains, there is upper- level support for high winds but no good mechanism to bring those winds to the surface. The one exception might be Cut Bank which is dependent on where mountain wave activity sets up. But even so, confidence is less than 50% across all zones which means that, for now, no expansions will be made to the High Wind Watch.

Elevated Fire Weather Concerns on Tuesday: With gusty winds, minimum RH values in the 20s, and highs in the 70s across much of Central and North-Central Montana, there is a concern for elevated fire weather conditions through the afternoon and evening hours. Conditions are not critical enough to put out any fire weather products but they are elevated enough that ongoing fires or new starts may be difficult to contain at times. Folks should continue to take all preventative measures to reduce sparks. -thor

AVIATION

28/06Z TAF Period.

Mostly cloudy skies are expected across the CWA through the period. Expect some showers overnight over Southwest MT, with a chance for thunderstorms Monday afternoon in the West Yellowstone areas. Breezy winds Mon afternoon will diminish Mon evening. Mountains/passes could be obscured at times across the CWA by showers/clouds. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 73 45 73 51 / 0 0 0 0 CTB 67 42 65 43 / 0 0 0 0 HLN 71 40 74 48 / 0 0 0 0 BZN 68 37 74 42 / 20 0 0 0 WYS 60 28 66 29 / 50 20 0 0 DLN 68 36 75 40 / 0 0 0 0 HVR 72 42 75 44 / 0 0 0 0 LWT 70 41 76 46 / 10 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

High Wind Watch from late tonight through Tuesday evening for East Glacier Park Region-Northern High Plains.