textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Thunderstorms are possible Saturday afternoon.

- Rain and mountain snow showers return this weekend.

- A return to cooler, more seasonal temperatures by Sunday and Monday.

Today through Friday: Breezy westerly winds will continue this afternoon, though they will be lighter than yesterday. Expect wind gusts up to 25 mph near the Continental Divide and around 20 mph across western Montana and Lemhi County. High temperatures through Saturday will remain 5 to 10 degrees above normal for early April.

By Friday, high clouds will begin moving in from the south as temperatures warm into the 60s and 70s. Showers are expected to reach Idaho and Lemhi counties by Friday afternoon, spreading north through the evening. Because the air near the ground will be dry at first, these showers may produce sudden gusty winds. There is a 15 percent probability of enough atmospheric energy to trigger a few weak thunderstorms, primarily over southern Idaho County and the southern Bitterroot Mountains.

Saturday through Monday: On Saturday, a new storm system will move inland from the Gulf of Alaska. This will bring moist air into the Northern Rockies. As temperatures warm into the 60s and 70s, widespread showers and scattered thunderstorms are expected Saturday afternoon and evening. There is currently a 15 to 35 percent probability for lightning, with the highest risk in western Idaho and Clearwater counties.

As the storm moves inland Sunday, there is some uncertainty regarding its exact path. About 20 percent of forecast models suggest the storm could stall near Yellowstone and develop as a cut-off low pressure system, which would bring moderate to heavy snow to the mountains along and south of the I-90 corridor. If the storm moves through more quickly and remains an open wave, snow levels will remain higher. Regardless, everyone should expect cooler temperatures and widespread valley rain and/or mountain snow.

Extended Outlook: Looking into next week, the active weather pattern appears likely to continue. We may see a brief break with fair weather before another Pacific storm arrives. Current data shows a 50 percent probability of another storm by Tuesday or Wednesday, while 30 percent of models suggest a return to warmer, drier conditions.

AVIATION

VFR (clear) conditions are expected today. Breezy westerly winds will persist through the afternoon, but will be lighter than yesterday. Wind gusts up to 25 mph (20 knots) are possible near the Continental Divide, with gusts near 20 mph (15 knots) elsewhere across western Montana and Lemhi County. Winds will decrease and become light after 8:00 PM MDT this evening.

MSO WATCHES/WARNINGS/ADVISORIES

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