WEATHER DISCUSSION: Weak high pressure will continue to create valley inversions on Sunday in western Montana, including the Helena valley. Patchy, dense fog and cold temperatures will continue. The frigid temperatures for eastern portions of the Hi-Line will begin to let up on Sunday as the next storm system moves in from the south.
Snow develops along I-90 after lunchtime on Sunday, pushing into the Helena area around dusk. A few snow squalls are possible which could result in low visibility and dangerous travel. Accumulating snow should remain south of Route 200.
An arctic cold front pushes in from the north Monday evening. Snow showers will break out across north central and eastern Montana as the front passes through. Accumulations should stay on the lighter side, with heavier amounts possible for northern slopes of the Little Belt, Highwood and Snowy mountains.
Frigid air is in place behind the cold front, temperatures will fall into the single digits above and below 0 on Monday night. This round of arctic air looks to be short-lived as a strong, downslope wind warms temperatures closer to normal midweek.
SATURDAY NIGHT: Mostly clear. Temperatures falling into the single digits for the Hi-Line and Helena valley. Overnight lows in the single digits below zero in northeastern Montana, mid to upper 10s for the Rocky Mountain Front and central Montana.
SUNDAY: Increasing clouds, with snow showers developing in the Helena area around dusk. Highs in the upper 20s and lower 30s. Mostly cloudy overnight, snow showers likely. 1-3" of snow accumulation south of Route 200, less than 1" north of Route 200. Overnight lows in the upper 0s and lower 10s.
MONDAY: Snow showers in the morning, followed by overcast skies. Temperatures will be in the 10s throughout the morning and afternoon, with falling temperatures throughout the evening. Snow showers developing after dusk, overspreading north central Montana overnight. Overnight lows -5 to 5 for central Montana, 10s for the Helena area.
TUESDAY: Frigid, with snow showers tapering and gradual clearing. Total snow accumulation 1-3". Highs in the upper 0s and low to mid 10s. Mid 20s for the Helena area.
WEDNESDAY: Mostly sunny and breezy. A sustained SW breeze at 10-20 MPH gusting to 35 MPH. Highs in the low to mid 30s. Mostly clear overnight as temperatures fall into the 10s.
THURSDAY: Mostly sunny. Highs in the upper 20s and lower 30s. Overnight lows in the mid to upper 10s.
FRIDAY: Sun and clouds. A few, spotty snow showers possible, especially along the Continental Divide. Highs in the upper 20s and lower 30s. Overnight lows in the mid to upper 10s.
SATURDAY: Partly cloudy with highs in the upper 20s.