textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Breezy, warm, and dry conditions are expected through the weekend.

- A 75 percent probability exists for a cool, wet, and breezy weather system early next week.

Today will be the warmest day into the weekend. Temperatures in western Montana will range from the upper 80s to low 90s, while north-central Idaho will see highs in the low 100s in the lower elevations. There will be just enough instability and moisture for isolated thunderstorms to develop over Lemhi County and southwest Montana this afternoon and evening. There are some cloud streets that have formed over the Flathead Valley area, so we have introduced a slight chance for showers this afternoon. Otherwise, mostly dry conditions will prevail, with wind gusts around 20 to 25 mph across the Northern Rockies. The weak front that will traverse across north-central Idaho this evening and tonight will create elevated fire weather conditions.

Saturday will be slightly coolerpossibly even a few degrees below normalbut will remain dry and breezy across the region. Minimum relative humidity values dropping into the upper teens and low 20s, combined with gusty winds, will create near-critical fire weather conditions, particularly across southwest Montana and north-central Idaho. Currently, there is a 50 to 70 percent probability that gusts will exceed 25 mph across western Montana. A shortwave trough across the Canadian border may bring just enough instability and lift for a few isolated showers and thunderstorms in northwest Montana, north of Highway 2.

On Sunday there will be increasing high clouds, breezy afternoon conditions, and mild temperatures. The greater chance(50-70%) for wind gusts exceeding 20 mph is found along the Divide, Southwest Montana and Lemhi County.

By Monday, a slow-moving cut-off low pressure system will be situated over central Washington into Oregon. The frontal zone associated with this feature will be quasi-stationary from north-central Idaho into western Montana. It could be a good setup for post-frontal showers that could be light to moderate in intensity Monday morning. Depending on how much sun we get, will determine how intense the thunderstorms will be. The University of WA WRF that goes out to 120 hours depicts scattered storms across northwest Montana Monday evening, but an isolated supercell thunderstorm across southwest Montana.

As the upper trough begins to eject to the northeast by Tuesday morning, the stronger lift associated with it will induce more widespread showers and thunderstorms, mainly across northwest Montana. This is the area where the NBM has the highest probability for precipitation amounts greater than 0.09" (50-75% chance). There could be northeast winds that develop in this region, but right now they don't look to be as strong as what was experienced this past Monday and Tuesday.

A general warm-up is expected later next week into the following weekend. With the upper level flow oriented in a southwesterly direction, this could bring possible thunderstorms back to the region.

AVIATION

A west to southwest flow will remain over the Northern Rockies today, promoting warm, mostly dry, and breezy conditions across the region. Westerly winds with gusts between 2025 kts are expected at KMSO, KHRF, KBTM, and KSMN this afternoon by 18/2100Z. Winds are expected to relax after 19/0300Z this evening. Weak instability will allow for isolated convection over Lemhi County and southwest Montana this afternoon, potentially impacting KSMN and KBTM between 18/2100Z and 19/0200Z.

MSO WATCHES/WARNINGS/ADVISORIES

MT...None. ID...Red Flag Warning until 10 PM PDT this evening for Palouse/Hells Canyon.