textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Scattered showers and thunderstorms are ongoing this afternoon and into tonight.

- Expect daily showers and thunderstorms for the rest of the week.

- Daytime high temperatures increase through the upcoming holiday weekend.

Satellite imagery early this afternoon indicates a closed low pressure system spinning over south-central Canada. To the west, another trough over southeast Alaska is accelerating northwesterly upper level flow against a broad trough of high pressure off the coast of California. The trough to the east is departing after delivering a healthy dose of summertime snow and rain to the Northern Rockies. Low pressure and residual moisture from the departing system will result in continuing showers and thunderstorms this afternoon, and again on Wednesday afternoon. Model soundings indicate weak instability and shear along with slightly-above-average precipitable water, bringing garden variety thunderstorms today (think pea size hail, brief heavy rain, gusty outflow winds of about 30 mph, lightning). Instability and shear increase on Wednesday as a shortwave trough moves through the Northern Rockies, allowing for some slightly stronger, albeit sub-severe, thunderstorms in the afternoon. The focus for convection will be primarily across north-central Idaho, southwest Montana, and along the Continental Divide.

As the week develops, upper level flow becomes westerly and temperatures become seasonable by Friday. There will be enough moisture and instability to not rule out afternoon thunderstorms. By the holiday weekend, temperatures will be slightly above normal, mid to upper 80s in the valleys of western Montana, 90s in the lower Salmon and Clearwater valleys of Idaho.

AVIATION

Lingering showers remain over northwest Montana including KGPI this afternoon. Elsewhere, mostly cloudy skies are what remains from a rather stormy weekend. High resolutions models indicate a round of thunderstorms moving southwest to northeast through north-central Idaho and across the Bitterroot and Missoula valleys this evening. Storms will move out by about midnight. Threats associated with these storms will be brief heavy rain, small hail, lightning, and gusty outflow winds to about 25 knots.

MSO WATCHES/WARNINGS/ADVISORIES

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