textproduct: Great Falls

KEY MESSAGES

- Scattered showers and a few thunderstorms develop later this afternoon and evening, persisting into Saturday.

- Warm and largely dry beginning Sunday, lasting through much of next week.

- Occasionally breezy next week as upper level ridging is briefly broken down at times.

DISCUSSION

- Meteorological Overview:

A quick moving wave cutting through the upper level ridge across the Pacific NW and Northern Rockies will result in increased coverage of showers and thunderstorms the remainder of the afternoon and evening, mainly across Central and North-central Montana. Showers continue through the night and into Saturday before slowly subsiding later in the day.

A drier and warmer stretch then develops Sunday as upper level ridging builds in once again. This largely continues through much of next week, though there will be several attempts to break down the ridge. The first looks to be on Monday as a wave progresses eastward near the Canadian border beginning late Sunday night. Breezy winds will be favored near the Canadian border as this wave passes by Monday. A few showers near the Canadian border cannot be completely ruled out Monday as this wave moves through.

Confidence in when the next attempt to break down the ridge will occur toward the middle of next week is much lower at this time. A more southwesterly flow aloft does look to be in place when the next wave moves through, which would favor a more active thunderstorm day. -AM

- Forecast Confidence & Scenarios:

Winds associated with ridge breakdown late Sunday night and Monday:

The initial wave of stronger winds aloft passes over the Rocky Mountain Front late Sunday night. The lack of any ridgetop stability gives confidence that stronger winds will not be realized at the surface in any widespread fashion in this area. As daytime mixing ensues Monday the stronger winds aloft are already beginning to exit eastward. That said, there does look to be at least a brief stretch in Blaine county and vicinity toward the afternoon where gustier winds will develop. The probability for a 50 mph gust in and around Blaine county Monday is roughly 30%. -AM

AVIATION

08/18Z TAF Period

A shortwave trough diving south from the Canadian Rockies will bring more scattered showers today, producing light rain that will mainly impact the terminals of North-Central and Central MT after 09/01Z. While VFR conditions will prevail across all terminals during the 08/18Z TAF period, the light rain will slightly reduce visibility to low VFR conditions at the impacted terminals at times. -OD

PRELIMINARY POINT TEMPS/POPS

GTF 49 65 43 82 / 20 30 10 0 CTB 46 64 41 79 / 40 40 10 0 HLN 46 69 41 83 / 10 10 0 0 BZN 41 66 37 79 / 10 10 0 0 WYS 35 61 30 74 / 10 10 0 0 DLN 40 68 38 82 / 10 10 0 0 HVR 46 68 39 82 / 40 50 10 0 LWT 44 59 38 77 / 50 60 30 0

TFX WATCHES/WARNINGS/ADVISORIES

None.