textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Isolated thunderstorms Lemhi County, ID and southwest Montana today.

- Breezy and warm Fourth of July: Choppy conditions on area lakes. Winds calming skies clearing for evening.

- Localized heavy rainfall threat Monday and especially into Tuesday with showers and storms.

A weak mid-level shortwave lifting through the region today will trigger isolated terrain-induced afternoon showers and thunderstorms. This activity will be confined to far northwest Montana, Lemhi County, and southwest Montana. Storms will be pulse-like and disorganized, presenting minimal threat outside of localized brief rain and erratic sub-severe wind gusts.

On Saturday (July 4th), a stronger trough passing through southern British Columbia will help to flatten the upper level ridge overhead and increase westerly winds. Expect afternoon surface gusts of 20 to 25 mph and sustained winds in the 10-20 mph range which will cause choppy conditions on area lakes. Calmer wind conditions with mostly clear skies are anticipated for the holiday's evening hours.

Warm and mostly stable conditions prevail for most of the region on Sunday. The exception will remain across the southern portions of our forecast area where moisture creeping in from the south will keep isolated afternoon thunderstorm chances in play for Lemhi County and southwest Montana.

The next significant weather feature arrives heading into Monday and especially Tuesday. Model guidance shows a robust surge of subtropical moisture into the Northern Rockies, pushing PWAT values near or above 1.0 inches. An embedded shortwave tracking through this elevated PWAT environment will interact with hot daytime temperatures and subsequent steep low level lapse rates helping to trigger more organized showers and thunderstorms. Given the deep moisture profile, these storms will be highly efficient rainfall producers capable of localized heavy downpours. Outside of Monday and Tuesday's convective potential, the rest of next week looks warm and relatively uneventful aside from the near- daily chances for pop up showers and isolated thunder in southwest Montana.

AVIATION

VFR conditions will dominate the region today. A weak passing disturbance will bring a slight chance of isolated afternoon showers or thunderstorms, with KBTM possibly impacted. Otherwise, diurnal wind patterns will prevail with speeds remaining under 10 knots.

MSO WATCHES/WARNINGS/ADVISORIES

MT...None. ID...None.