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KEY MESSAGES

- A significant snow event is expected to continue today with the southern zones under a Winter Storm Warning. Most of the rest of the CWA is under a Winter Weather Advisory with the northern zones escaping the brunt of this. - Colder than normal temperatures will persist through Monday, with much warmer temperatures expected by the middle of next week with highs in the 60s and 70s.

DISCUSSION

WEATHER PATTERN OVERVIEW:

The atmospheric river continues to push plentiful moisture from the northern Rockies through the northern plains. For our local region, as of early Saturday morning, the resultant band of snowfall covers most of the state of Montana south of the Hi- Line. Into the early morning hours and through tonight, good model data consensus shows that area of snowfall also pushing further northward to also encompass the Hi- Line. The period of heaviest snowfall with gusty ENE winds seems to be 3 AM to 9 PM. We expect this to result in 9 to 13 inches of snow for our SW zones, 4 to 8 inches for our central and SE zones, and trace to 3 inches for the Hi-Line. It should be noted that during the period of heaviest snowfall, easterly winds are expected to increase to around 20-25 mph with some stronger gusts. We will need to keep a close eye on visibility conditions in case stronger warnings may be necessary.

Winter Storm Warnings remain for the SW zones and Wibaux County. Upgraded Prairie and Dawson Counties to a Winter Storm Warning for today and tonight. The probability of 6 or more inches of snow there is now 50-60 percent for most of those counties. There is a Winter Weather Advisory is in effect for the tier of zones neighboring the warning area. The far northern tier of our zones remain with no headline, being under the threat of less than 2 inches of snowfall. With NE winds feeding dry air into the system, the Canadian Border may end up with little or no snow from this system.

Behind this storm system, an arctic airmass over the southern Canadian Prairie Provinces will drop into eastern Montana later this weekend. Wind chills will drop below zero by Sunday morning across the CWA. Not headline worthy but will be felt as unusually colder than normal for mid-March. This could put some unwelcome stress on newborn and young livestock.

Not to be outdone for drama, on the heels of this cold air mass Sunday and Monday, a strong and very warm ridge of high pressure will quickly move into the region, and bring high temperatures climbing into the 60s degrees possibly warmer by Wednesday. Area creeks, streams, and rivers will need to be watched for ice breaking up and water level rising due to rapid snowmelt. especially through central and southern Montana.

FORECAST CONFIDENCE & DEVIATIONS:

Generally high confidence in the snow forecast today and tonight south of US 2 and low confidence in the snow forecast north of US 2. The dry air on the NE winds will limit snow in the north but it hard gauge at this time how well the dry air will limit the snow.

Low confidence on Sunday night's low as models differ on amount of clouds cover. If skies are clear Sunday night, low will be colder than the going forecast especially with snow covered ground. NBM 10 currently has lows well below zero.

Overall high confidence in the warm up starting Monday west and Tuesday east although snow cover will slow the warm up initially.

Raised pops in the south today for a more consistent and continuous snow forecast. Otherwise, no other changes from the NBM.

AVIATION

FLIGHT CAT: VFR early becoming a mix of MVFR and IFR this morning and continuing through this evening. Conditions improving to a mix of MVFR and VFR late tonight.

DISCUSSION: A storm system will bring heavy snow in a swath from NW Montana to SE Montana and SW North Dakota. Low ceilings will extend north into northeast Montana this morning while snow will reduce visibility to 1SM or less at times today and this evening. Snow will diminish tonight from NW to SE across the region.

WINDS: Will begin to increase from the east to 10 to 20 knots this morning and become NE 15 to 25 knots this afternoon. Winds will become north tonight at 10 to 20 knots and diminish to 5 to 15 knots late tonight.

GGW WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until midnight MDT tonight for Central and Southeast Phillips.

Winter Weather Advisory from 6 AM this morning to midnight MDT tonight for Central and Southern Valley.

Winter Weather Advisory from 6 AM this morning to 6 AM MDT Sunday for Eastern Roosevelt-McCone-Richland-Western Roosevelt.

Winter Storm Warning until midnight MDT tonight for Garfield- Petroleum-Southwest Phillips.

Winter Storm Warning until 6 AM MDT Sunday for Dawson-Prairie.

Winter Storm Warning from 6 AM this morning to 6 AM MDT Sunday for Wibaux.