textproduct: Glasgow

KEY MESSAGES

- Comfortably warmer temperatures expected this weekend.

- Some scattered rain showers and isolated thunderstorms are possible Saturday afternoon and evening.

- Cooler temperatures and more widespread rain showers are possible on Monday and Tuesday.

DISCUSSION

WEATHER PATTERN OVERVIEW:

The 500 mb height field shows a very slow-moving weather pattern over the western U.S., characterized by a fairly-strong ridge of warm high pressure today through the Rocky Mountains and high plains regions. Upstream of the ridge, is a stalled low pressure systems over the U.S. west coast.

The ridge of high pressure will provide NE Montana with warmer than normal temperatures today through Sunday, but as the large west coast system slowly moves inland over the next several days, it will gradually weaken that ridge and introduce less stable and more active weather through short-wave disturbances in the otherwise SW flow aloft. As early as tomorrow, Saturday, some high-resolution model data is beginning to indicate scattered showers and isolated thunderstorms descending from central Montana's higher elevations and pushing through some eastern Montana high plains. For now, Phillips and northern Valley County look like they will see a decent rain shower and a few thunderstorms moving from SW to NE Saturday evening after 6 PM.

Sunday looks to be fairly quiet between storms.

Beginning Sunday evening, the low pressure trough opens up a bit more as it moves over the continental divide. This will focus more widespread rain shower activity through NE Montana. The more stable airmass behind a cool front will likely act to inhibit thunderstorm chances through Sunday night and into early next week, but some of those details still need to get worked out.

That round of unsettled weather will eventually erode away by Tuesday evening.

FORECAST CONFIDENCE & DEVIATIONS:

Only deviations from the NBM Cron was slight adjustments to temperatures and winds using the best agreement from hi-res model data.

There is HIGH to MODERATE confidence in temperatures through Saturday, and MODERATE confidence after this time.

There is AVERAGE to BELOW AVERAGE confidence in the exact placement and timing of thunderstorms outflow winds Saturday evening, but AVERAGE to ABOVE AVERAGE confidence in the overall threat of convective storm activity beginning Saturday afternoon and pushing through into Saturday night.

There is LOW to MODERATE confidence in precipitation accumulation through Saturday evening, and LOW confidence after this time.

AVIATION

LAST UPDATE: 1920Z, Friday afternoon, April 10

FLIGHT CAT RANGE: VFR

DISCUSSION: Clear and sunny skies to begin, then increasing high and mid level clouds toward the end of this TAF cycle. Chances for scattered showers and isolated thunderstorms increase by Saturday afternoon and evening from SW to NE. Specifics for TAF sites will become evident through the daytime hours on Saturday. Some amendments for strong and gusty winds may be needed.

WINDS: Today from the SE at 10 to 15 kts with a few stronger gusts. Tonight, from the ESE around 10 to 15 knots, especially over the higher elevations, then calming by Saturday morning. By mid-day Saturday, winds will turn more from the south ahead of developing rain showers and isolated thunderstorms. Saturday late afternoon and evening, from the S and SW around 15 to 20 mph with some thunderstorms downdraft and outflow winds possible later Saturday evening.

GGW WATCHES/WARNINGS/ADVISORIES

None.