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KEY MESSAGES

- A very subtle weather disturbance will bring a chance for a rain/freezing rain/snow mix tonight with light accumulations, if any.

- Temperatures and chinook winds will increase sharply on Tuesday; a High Wind Warning has been issued from the Little Rocky Mountains through Fort Peck Lake.

- Warm and dry conditions will continue through the end of the week. Any remaining snow pack will initially slow the impact of warming temperatures, especially SW of Fort Peck Lake.

DISCUSSION

WEATHER PATTERN OVERVIEW:

Ahead of the approaching chinook, a small embedded short-wave impulse is expected to bring a mix of rain/freezing rain/snow from west to east tonight through the overnight hours. Accumulations will be light if any at all.

The broad ridge of high pressure is already making it's impact felt as warming temperatures are already pushing into the Intermountain West region. Our local impacts in NE Montana will show up as a strong chinooking WNW wind, starting early Tuesday. Lately HREF wind model has been mostly accurate, and it is showing gusts to 60 mph easily reaching through most of our western CWA Tuesday morning through Tuesday evening. I chose to upgrade the High Wind Watch to a High Wind Warning and include northern Valley County.

Expect widespread rapid snowmelt over the next few days, and eventual snow melt for Petroleum County. Flatwillow Creek and other area drainages will need to be closely monitored for high water and flooding concerns.

This ridge will remain over the western states through the end of the week with warm and generally dry weather. The next chance for any precipitation will be later this weekend.

FORECAST CONFIDENCE & DEVIATIONS:

Deviated on winds through Tuesday night due to incoming chinook by blending NBM90/NBM.

Confidence is moderate for temperatures through Tuesday for southwestern areas with significant snow cover to melt.

Confidence is moderate to high for wind gusts up to 60 mph in the High Wind Warning area.

AVIATION

LAST UPDATE: 1915Z, Monday, March 16

FLIGHT CATEGORY: VFR

DISCUSSION: The beginnings of a chinook aloft will increase high to mid level cloud cover into today.

As the warm front and embedded disturbance ahead of the the chinook approached our region, a light wintry mix of rain/freezing rain/snow will be possible during the tonight and overnight hours. Precipitation amounts look minimal with only a hundredth at max, and chances themselves are below 50%. Hence the PROB30s at best.

LLWS: Low level wind shear is expected across the terminals from beginning around 08Z or 09Z and remaining throughout the TAF cycle.

WIND: This afternoon, from the S and SE around 10 to 15 kts. Tonight light and variable ahead of the chinook. Tomorrow (Tuesday), from the WNW at 25 to 30 kts sustained, gusting around 50 kts at times. The wind will calm again later Tuesday night.

GGW WATCHES/WARNINGS/ADVISORIES

High Wind Warning from 2 AM to 6 PM MDT Tuesday for Central and Southeast Phillips-Central and Southern Valley-Garfield-Northern Phillips-Northern Valley-Petroleum.

High Wind Warning from 8 PM this evening to 6 PM MDT Tuesday for Southwest Phillips.