textproduct: Glasgow

KEY MESSAGES

- Fog and low stratus north of the Missouri River and near the Yellowstone Valley will return again tonight into Sunday morning.

- Warmer than average temperatures will persist through Monday.

- An approaching upper-level trough will produce gradually decreasing temps and increased chances for precipitation Tuesday onward.

DISCUSSION

A strong Southwest wind at the surface has been transporting moisture into northeast Montana for the last several days and will persist for yet another evening. With a strong ridge of hotter temps aloft and a lack of mixing during the day an inversion is setting up over the region again an again each night. The inversion, coupled with the moisture, will result in fog and low stratus across eastern portions of the state again tonight.

Fog aside, an upper-level ridge over Montana will result in warmer than average temperatures through Monday.

The ridge aloft will eventually exit eastward ahead of an upper- level trough that that will set over the Pacific Northwest, resulting in SW flow aloft for more normal temps and increasing chances of precipitation beginning Tuesday through the week with Wednesday standing out as a particularly higher chance (30-60%). At this time, the predominant mode is expected to be rain as opposed to snow but we re very close to freezing and this could easily switch in future updates.

FORECAST CONFIDENCE & DEVIATIONS: - Changes from NBM were to add fog to all counties other than Garfield and Petroleum at various points tonight. Though Dense fog does not look likely along main roads or cities.

- Confidence in fog placement Sunday morning is moderate (60%). Confidence in intensity is closer to (30%). - Confidence in fair conditions persisting through Monday is high (90%).

- Confidence in early-to-mid-Week pattern change is moderate to high (83%).

- Confidence in precipitation mode and amounts next week is low (20%).

DON/GAH

AVIATION

LAST UPDATED: 1830Z.

FLIGHT CAT RANGE: VFR - LIFR

DISCUSSION: Expect clear conditions with FEW to SCT low stratus clouds through the afternoon and into the early evening. After sundown low stratus will begin to fill back in with fog in higher elevations. Around 06Z- 12Z a surface trough will pass through the region and begins clearing fog out from west to east. However it may not exit east before sun-up possibly leaving KSDY, KGDV, or KOLF in fog which has to clear after a few hours of sun Sunday morning.

WIND: E-SE at 05 to 15 kts through today and into the evening. Switching to the W at 5 kts or less around early to mid-morning Sunday. Backing W to SW at 10 kts or less Sunday afternoon.

GAH

GGW WATCHES/WARNINGS/ADVISORIES

None.