textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Showers and isolated thunderstorms through Wednesday, mainly across northwest Montana and over the Continental Divide.

- Return to summer-like conditions as moderating temperatures are expected late week into next weekend.

After a cold start this morning, temperatures moderate through Saturday. A few showers or isolated thunderstorms will be possible this afternoon in northwest MT and along the Continental Divide. A few showers on Monday were able to produce 0.10 to 0.15 inches and with similar precipitable waters today, similar results are expected. Most showers however will be characterized as very light.

Wednesday the models are attempting to close off a low pressure system over eastern Alberta and western Saskatchewan. The results for us still seem up in the air, however there are hints of an upper level cold front pushing southwest across western MT. If this was to happen, disorganized shower activity may become organized along that boundary as it moves southwest. Our current forecast keeps the favored area for precipitation from the Flathead and Mission Valleys and eastward along the Continental Divide. Missoula south through the Bitterroot and I-90 west of Missoula will see lighter precipitation but potentially an isolated thunderstorm. Thunderstorm activity will be scattered through northwest MT and along the Continental Divide. Graupel, small hail, and gusty outflows 25-35 mph will be possible. Of note, the core of the cold trough will be well north and east of the Northern Rockies and snow levels will be 6500 feet and higher.

Beyond warming, the longer term does not favor precipitation until potentially Sunday. Model cluster analysis is split between fading or developing high pressure 56% and a trough with positional and timing differences 44%, more to come.

AVIATION

Once again northwest Montana and along the Continental Divide will see isolated showers and thunderstorms. Brief lowering of visibility and a few strikes of lightning will be possible.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Frost Advisory until 9 AM MDT Tuesday for Bitterroot/Sapphire Mountains...Flathead/Mission Valleys...Lower Clark Fork Region...Missoula/Bitterroot Valleys.

ID...Frost Advisory until 9 AM MDT /8 AM PDT/ Tuesday for Eastern Lemhi County...Northern Clearwater Mountains...Southern Clearwater Mountains.

Frost Advisory until 9 AM PDT Tuesday for Orofino/Grangeville Region.