textproduct: Glasgow

DISCUSSION

KEY MESSAGES: - The High Wind Watch has been upgraded to a High Wind Warning for all of northeast Montana.

- The active and windy day will suddenly include colder and snowier conditions by Wednesday evening.

WEATHER PATTERN OVERVIEW:

A strong low pressure system developing off the Canadian Rockies will strengthen even more as it approaches our region tomorrow (Wednesday morning). Model agreement is lining up very well to support a widespread, long-duration wind event across our entire northern Rockies and northern High-Plains regions. The High Wind Watch from earlier has now been upgrade to a High Wind Warning.

Morning winds will generally be from the south, but a turn more from the west will signal the arrival of the stronger winds. Timing will begin around 9 AM for Zortman, around 11 AM for Malta and Winnett, around 1 or 2 PM for Glasgow, Opheim, and Jordan, around 3 PM for Scobey, Wolf Point, and Circle, around 4 PM for Plentywood, Culbertson, Sidney, and Glendive.

Recent warming and melting has provided plenty of evaporation, and the approaching low pressure system will create just enough convection instability to support scattered rain showers and an isolated thunderstorm during the mid-day hours. Indeed, the convective outlook from SPC has most of our region outlined for general thunderstorms. Later by Wednesday evening, a strong cold front will push south from Saskatchewan and bring a round of snowfall to many locations. While snowfall amounts are not expected to be much more than an inch or two, the persistent strong winds could easily lead to periods of near-white out conditions or snow squalls. The question mark is whether or not it ends up being a short duration snow squall or will the snow last 3+ hours to meet the criteria for a blizzard warning. Any snow cover that remains from the current warm weather will be crusted and not blow. So, any blowing snow that occurs will have to come from new snow.Travel during all this time will be dangerous, especially for high- profile vehicles.

The strong winds will quickly diminish overnight Wednesday night, becoming near calm Thursday morning.

The next following snow storm will be on Friday and confined more toward the northeast corner of the state and northern North Dakota. FORECAST CONFIDENCE & DEVIATIONS:

Blended best model agreement I could find for precip, snow, and winds for Days 1 and 2.

Confidence is high for the strong winds Wednesday afternoon and night. Confidence is moderate for snow and blowing snow Wednesday night but low on whether or not it will last long enough to meet blizzard conditions.

AVIATION

UPDATED: 2200Z / 3 PM / Tuesday, Dec 16

FLIGHT CATEGORY: VFR becoming MVFR just after the end of this TAF cycle. Then isolated periods of VLIFR in possible snow squalls Wednesday evening.

DISCUSSION: A strong low pressure system is approaching the region from the Canadian Rockies. Confidence continues to increase for a widespread High Wind event for most of the day (Wednesday late morning through midnight).

WINDS: Tonight, near calm, then overnight increasing from the south around 5 to 10 kts. Wednesday morning from the south and southwest around 15 to 20 kts. Wednesday mid-day from the southwest at 20 to 25 kts. Wednesday afternoon from the west at 30-40 kts and gusts to around 50-55 kts. Wednesday evening/night from the west at 50 kts and gusts in excess of 60 kts. Thursday 12Z, winds finally diminish back down to less than 20 kts.

LLWS: There will be periods of LLWS throughout the TAF cycle.

GGW WATCHES/WARNINGS/ADVISORIES

High Wind Warning from 8 AM Wednesday to 3 AM MST Thursday for Central and Southeast Phillips-Central and Southern Valley- Daniels-Dawson-Eastern Roosevelt-Garfield-McCone-Northern Phillips-Northern Valley-Petroleum-Prairie-Richland-Sheridan- Southwest Phillips-Western Roosevelt-Wibaux.