textproduct: Glasgow

KEY MESSAGES

- Upper ridging will keep highs in the 90s in place through Sunday. Heat related effects are possible especially Saturday when the humidity is a factor.

- There is a low chance of thunderstorms (10-20%) today and tomorrow. However somes cells could become severe in the evening across Phillips county today and the Yellowstone Valley tomorrow afternoon. - A brief cooldown is expected Monday.

DISCUSSION

WEATHER PATTERN OVERVIEW: Forecast begins with a large ridge running from Wyoming up through eastern Montana and through the western Canadian Prairie Provinces. To the west a Low pressure system is moving onshore over southern BC and the PCNW. SW flow resides between these two airmasses which is throwing shortwaves through western and central Montana which periodically moves across eastern MT when they can blunt the ridge a bit.

Today and Sunday: First shortwave bumping up against the ridge over the area is dragging rains showers to the northwest across the CWA this morning. These should clear out about mid afternoon allowing heating to set off a second wave of showers and thunderstorms over central Montana. The Thunderstorms that move northwest through the area are expected to clip Phillips county in our NW CWA sometime after 6PM. HREF showcases a few max wind gusts up to 60 mph coming from cells as they die out in the evening moving across the Blaine/Phillips county border. But doesn't let them move much deeper before dying off completely. SPC has placed a marginal risk over this area for the evening hours. Precipitable WAter is also around 1.6 inches to 1.2 inches and suggests that these storms could be prolific rain producers as they move through and die out. As the storms exit the area overnight the stalled boundary to the east is expected to transition to surface trough and move along behind them. As it does so it will set some showers and thunderstorms off across the area Sunday afternoon. The most severe cells look to be focused across the Yellowstone Valley before jumping the MT/ND border. There is uncertainty here with some CAMs moving the boundary across the border entirely before generating anything leaving the location mostly dry.

Monday through Tuesday with the ridge blunted to the south flow becomes zonal, dry, and cooler with highs in the 80s.

Wednesday through the weekend. The pattern begins to warm up with a return from zonal flow across the region to full on hot ridge Friday and Saturday. There is some suggestion that we may be looking at 100s for highs with excessive heat warnings again if this comes to pass from the ensemble data.

FORECAST CONFIDENCE & DEVIATIONS: Deviation from NBM include attempting to get the rain showers on radar bashed back in place for the next several hours. While default hourly NBM PPI01 has dry conditions across the area this morning, CAMs models are only a little better with the rain existing but over the SE CWA rather than the NW and central where it was occuring on MRMS. With no model data available that looked close enough, ended up blending a few CAMs and then dragging those higher PoPs over the locations expected to be affected through roughly 6PM by hand. For this reason confidence in PoPs for the next several hours is LOW.

AVIATION

LAST UPDATE: 1730Z

FLIGHT CAT RANGE: VFR.

DISCUSSION: scattered rainshowers this morning through the early afternoon may briefly lower ceilings but should generally not go below VFR. A second wave of isolated rain showers and thunderstorms is expected to reach KGGW from the west around 08 to 10Z but again impacts look minimal.

SFC WIND: S to SE at 10 to 15 kts gust 20 through the afternoon hours. backing to the E to SE and reducing to 10 kts or less this evening through tonight. Turning W to NW behind a front mid morning and increasing to 10 to 20 gust 25 kts through the day.

GAH

GGW WATCHES/WARNINGS/ADVISORIES

None.