textproduct: Glasgow

KEY MESSAGES

- Expect showers and thunderstorms starting early this morning in the west and spreading east through the day.

- A marginal risk exists for today and some storms could become severe with large hail in the afternoon over the Yellowstone Valley.

- A slow warm up is expected Tuesday through Friday. Another system will arrive around Friday with ample rain possible through the weekend.

DISCUSSION

WEATHER PATTERN OVERVIEW: A weak low level jet is expected to kick in this morning, and with only a small amount of elevated capping overnight in the southern part of the area, a strong thunderstorm or two is possible across the Yellowstone Valley. Gusts up to 50 mph and hail are the main hazards. The cooler surface temperatures will allow the hail to stay together instead of melting right away on its way down to the ground. Strongest cell look to occur between Noon and 6PM.

The upper trough will slowly break down and move east through Wednesday. So, a weak ridge will be able to build in by Friday. The northeast part of the area will be in the periphery of the trough, so there are still chances for showers and storms through Wednesday afternoon. A weak round of showers and storms is expected to make its way in for Thursday & Friday as the trough starts to rebuild.

By Friday night the ridge exits and a new PCNW trough arrives. With this arrival will be ample precipiation through the weekend and possibly into early next week. THere is also a chance for the start of this passage to contain severe weather as it first moves in and breaks down the ridge.

FORECAST CONFIDENCE & DEVIATIONS: Only deviations from NBM were to remove 6-hour jagged edges from hourly PoPs in the NBM PPI01 and creat a more seamless transition from hour to hour.

There is MODERATE to LOW confidence in low clouds in fog this coming morning.

There is HIGH confidence is regional storms today and MODERATE confidence of strong storms occurring in the southeast this afternoon.

There is MODERATE confidence in showers and storms over the weekend.

/GAH

AVIATION

LAST UPDATE: 0620Z

FLIGHT CAT RANGE: VFR - MVFR

DISCUSSION: A stalled boundary oriented N/S over KGGW has allowed for low clouds to form east of it. At higher elevations these clouds may sneak in as fog and briefly drop of to IFR Between 09Z-15Z Monday morning.

Another round of showers and thunderstorms are expected across the region moving west to east and will begin impacting KGGW at 09Z and gradually spread east to all terminals by 18Z. MVFR Visibility may be possible in heavy downpours. Showers and thunderstorms should exit around 04 to 05Z this evening. There is a chance (5-20%) for an isolated Severe cell with large hail at KGDV from 18 to 00Z this afternoon. But, this is not high enough to include in the TAFs directly yet.

WIND: Light and variable through this morning. Becoming N ands then NW at 10 kts or less through the afternoon. Gusty erratic winds are possible near any thunderstorms. Backing NW to W at less than 10 kts Monday night.

GAH

GGW WATCHES/WARNINGS/ADVISORIES

None.