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KEY MESSAGES

- Gusty winds will slowly reduce through the day today.

- Highs will remain the 60s and 70s through the end of the coming work week.

- Possible rain showers in the southeast portions of the CWA Monday morning. Isolated Thunderstorms may be possible SE of the Yellowstone River.

DISCUSSION

Synoptic Setup: Forecast begins with a ridge running from northern Manitoba into Ontario and down the Mississippi Valley. It then turns back west across the southern plains and into the Hot High pressure over the SW. A broad trough over western half of Canada has begun to break into two parts with the eastern trough running down the Canadian plains and into the Dakotas. The western part begins over roughly British Columbia and moves off shore of the Pacific Northwest and northern California.

Today through Monday: Surface high pressure will move through NE Montana this morning with light winds. Winds will become east to SE this afternoon as the high moves to the east. Zonal aloft this morning will turn WSW this afternoon with an approaching shortwave. The wave will bring some showers and thunderstorms mainly late tonight and early Monday morning along the North Dakota border and the Yellowstone Valley. Look for somewhat warmer temperatures on Monday as the system moves to the east.

Monday night into Wednesday: The western most trough will move inland and dig into the Intermountain West and Four Corners. In response the northern section of the flow will build up into a ridge over Montana that will keep conditions mostly dry through these periods. Tuesday specifically will need to monitored for Fire Weather concerns due to Low RH and gusty winds as the ridge begins to break down.

Wednesday night onwards: Flow will attempt to return to zonal briefly. But, model ensembles begin to break apart on individual waves within the flow with more GFS runs focused on a brief ridge/trough couplet, while EC members slowly orientate flow more to the northwest. Standard deviations amongst ensemble members suggest that no particular run is favored. Therefore, confidence in these periods is low with the expectation of changes in future iterations of the forecast here onward.

FORECAST CONFIDENCE & DEVIATIONS:

Low confidence on western extent of the chances for showers and thunderstorms late tonight and early Monday morning.

Tweaked pops tonight at times to provide better hour to hour consistency. No other deviations from the NBM.

AVIATION

LAST UPDATED: 1730Z

FLIGHT CAT RANGE: VFR - MVFR

DISCUSSION: Expect varying amounts of mid and high clouds moving into northeast Montana through this afternoon. Skies will become BKN to OVC mid-level early this evening and remain that way overnight into Monday morning. Rain showers with MVFR clouds are likely Monday morning around KSDY and KGDV from roughly 12 to 21Z.

SFC WIND: Light and variable at 10 kts this morning becoming E to SE at 5 to 10 kts this afternoon and tonight. Then, reverting back to light and variable Monday afternoon adn evening.

GAH

GGW WATCHES/WARNINGS/ADVISORIES

None.