textproduct: Glasgow

KEY MESSAGES

- Isolated showers will drift across northeast Montana Wednesday as winds begin to pick up ahead of a major pattern shift.

- Thursday and Friday will see the manifestation of that pattern shift with cooler and potentially significantly wetter conditions. Over a 48 hour period, many locations could see north of an inch of accumulated rainfall.

- Precipitation chances don't completely go away this weekend and into early next week, but overall conditions will trend towards drier and warmer.

DISCUSSION

WEATHER PATTERN OVERVIEW:

Today will feature seasonably warm temperatures across NE Montana accompanied by isolated to widely scattered afternoon and evening thunderstorms with a flat ridge over the Northern High Plains. This will allow for Pacific Northwest smoke to spread further into the region. Chances for any specific location to receive any showers or storms through tomorrow is relatively low (<20%) but cannot be completely ruled out.

Toward the middle of the week a potentially significant pattern shift is expected to take place for northeast Montana with an upper trough moving into the Canadian Rockies. This shift will lead to increasing daily chances for showers and thunderstorms, with heavy rain potential as some southwestern monsoonal moisture does transport its way this far north. There will also be a major cooling with this pattern, where highs will be in the 60s and 70s for many places as opposed to the current 80s to 90s.

FORECAST CONFIDENCE & DEVIATIONS:

Generally left the base forecast ride today with little adjustments.

Confidence in any precipitation amounts are increasing even with precipitation amounts continuing to climb for many areas, but this still looks to be a classic setup for a low- confidence/high- impact precipitation event where many locations could get north of 1" of total rainfall Thursday and Friday. Beyond the rain, confidence is moderate in the big temperature swing associated with the major pattern shift that could bring the aforementioned rain. Once the system moves off to the east, confidence goes down with respect to whether or not the region returns to warm and dry, or if chances for rain will persist into the weekend and next week.

AVIATION

Updated: Tuesday, August 11, 1900Z

Expected Flight Category: VFR

Synopsis: Some elevated smoke is still present across Montana, and could briefly lower visibility at some sites while there is still daylight. Otherwise, expect mostly dry conditions through the overnight. Some isolated showers will be possible along and north of the Missouri River valley Wednesday.

Winds: Light and variable winds mostly expected until Wednesday, when winds turn to the east-northeast and increase to 10-20 kts with gusts 20-30 kts.

Cliff

GGW WATCHES/WARNINGS/ADVISORIES

None.