textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- A backdoor cold front continues to bring cooler temperatures and northeast winds of 20 to 30 mph across western Montana today.

- Boaters on Flathead Lake should anticipate choppy conditions returning today due to gusty northeast winds.

- A warming trend begins Wednesday, though a disturbance will bring showers to northwest Montana late Wednesday, followed by showers and isolated thunderstorms along the Continental Divide on Thursday.

A positively tilted ridge of high pressure building along the West Coast is keeping the Northern Rockies under northerly flow aloft. A north to south oriented jet streak will become situated over western Montana today. Closer to the surface, cooler, dense air to the east and warm air to the west will result in a strong easterly pressure gradient over western Montana. The bottom line is that strong northeasterly winds will continue this morning, turning more northerly later in the day. Winds speeds will remain below advisory criteria, but do expect choppy conditions on Flathead Lake throughout the day. Temperatures today will stay around normal for this time of year.

The tight pressure gradient will relax on Wednesday as the ridge of high pressure moves over the Northern Rockies. The ridge will shut off the gusty northerly winds and initiate a warming trend, with western Montana valleys returning to the 70s and the lower valleys of north-central Idaho pushing into the 80s. However, this will not be a completely dry ridge. Most guidance indicates a disturbance will ride over the top of the ridge late Wednesday into Thursday. This atmospheric forcing will initially trigger showers across northwest Montana late Wednesday, particularly impacting the Glacier Park region. As the system progresses on Thursday, instability will increase slightly, shifting the threat southeastward and bringing showers and isolated thunderstorms primarily along the Continental Divide. Some ensemble solutions (about 40%) show another weak disturbance on Saturday bringing widespread rain.

AVIATION

VFR conditions will prevail across the Northern Rockies airspace. The persistent easterly or northeasterly winds of about 20-30 knots continue at KMSO and KGPI, while KHRF and KSMN will see a shift to northerly winds by about 05/2200Z. Winds remain elevated into tonight before relaxing on Wednesday as a ridge of high pressure moves over the Northern Rockies.

MSO WATCHES/WARNINGS/ADVISORIES

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