textproduct: Glasgow

KEY MESSAGES

- Areas of rain lasting through Monday evening. Overnight temperatures tonight and Monday have a decent chance of being expected to be at or near freezing, coldest on Monday night.

- A Lake Wind Advisory is in effect through midnight tonight.

- Although the trough will weaken a bit early this week, waves of energy will bring a few isolated thunderstorms on Tuesday and Wednesday to various parts of the area.

DISCUSSION

WEATHER PATTERN OVERVIEW:

A strong upper trough will keep cool conditions through Monday night before the trough weakens a bit and temperatures climb closer to normal by Wednesday. Rain showers are mostly west of a line from Scobey to Circle currently, and the upper trough will help bring scattered rain showers to the whole area through Monday evening before clearing to the east. Although most locations are expected to accumulate less than five hundredths during this time, a few isolated locations may see up to two tenths of an inch of rain. There is a brief period with 10 to 15 percent chance for thunder this afternoon. Windy conditions on Fort Peck Lake will eventually come down a bit after midnight tonight.

Tonight and tomorrow night there is potential for multiple locations to drop below freezing. However, the thick and low cloud cover will be overhead, which keeps temperatures from dropping. Monday night has the best chance of dropping below freezing since cloud cover is expected to be somewhat scattered that night. With these cooler temperatures, make sure to protect sensitive vegetation.

The upper trough will continue to remain over the area after Tuesday, although a bit weaker than this weekend. This will likely allow shortwave troughs to sneak through the overall flow, bringing some isolated thunderstorm action to the area. There are 500 millibar temperatures expected to be around -20 to -25 celsius, which often lines up with at least isolated convection. The best chance for general thunderstorms is in the western half of the area on Tuesday afternoon, especially with CAPE values up to around 200 J/kg and lapse rates around 9 to 10 Celsius degrees per kilometer. Current model plumes suggest weak instability in the ~300 J/kg MLCAPE range during Wednesday afternoon, but low forecast RH may suggest it as a wind event.

FORECAST CONFIDENCE & DEVIATIONS: The only deviation was the PoP grid on Tuesday afternoon for isolated thunderstorm opportunities.

There is high confidence of rain showers occurring in various parts of the area through Monday evening and low clouds staying over the area through at least tomorrow evening.

There is high confidence the Lake Wind Advisory will be canceled at midnight. There is low to moderate confidence of temperatures dropping below freezing tonight and tomorrow night.

There is moderate to high confidence of isolated thunderstorms occurring on Tuesday and Wednesday in a portion of the area, with low confidence from Thursday going forward.

AVIATION

LAST UPDATED: 1830Z

FLIGHT CAT RANGE: MVFR, IFR after 00Z.

DISCUSSION: Low overcast skies with moderate confidence in scattered rain showers occurring through tomorrow afternoon. There is high confidence of ceilings as low 1000 feet, and moderate confidence in ceilings dropping as low as 500 feet from 00Z tonight through 18Z Monday. The chance of seeing a weak thunderstorm this afternoon is 10 to 15 percent, so we opted to leave it out of TAFs.

WINDS: For KSDY, southeast at 5 to 10 knots becoming northwest at 10 to 20 knots after 21Z, becoming north at 10 to 18 knots after 12Z Monday. For all other sites, northwest at 12 to 25 knots with gust to 34 knots, decreasing to 8 to 16 knots after 02Z, becoming north after 12Z.

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory until midnight MDT tonight for Central and Southeast Phillips-Central and Southern Valley-Garfield-McCone- Petroleum.