WEATHER DISCUSSION: Steady snow continues to push further south and will come to an end from north to south between midnight and 3 AM. Heavy snowfall rates are possible as the snow pushes through the Helena area and further south towards I-90. Light to moderate accumulations expected with a general 2-5" for most areas. The cloud cover and snowfall keeps temperatures from plummeting tonight as most areas will remain steady in the upper -10s and lower -20s.
A surface high pressure builds over the region later tomorrow, giving way to decreasing cloud cover and allowing temperatures to plummet. How quickly the cloud cover departs determines the extent to which the temperatures fall overnight Wednesday into the Thursday morning. However, it appears many locations experience the coldest temperatures seen in decades. Many areas reach the -30s and -40s with wind chills as low as -60. Frostbite can form on exposed skin in minutes with these kinds of temperatures.
A major warm-up is expected heading into Christmas Eve and Christmas Day. Temperatures could warm up 80+ degrees from the -30s and -40s into the 30s and 40s between Thursday morning and Christmas Eve. As expected, the warmer temperatures comes at the cost of strong winds. Blowing snow and reduced visibility is going to be a huge issue for the Rocky Mountain Front Friday and Saturday. Stronger wind gusts impact the rest of central Montana Christmas Day with 40+ mph gusts creating treacherous travel. Ice jams likely become a concern next week as some areas approach the 50s for high temperatures.
TUESDAY NIGHT: Snow, tapering to snow showers after 3am. Heavier snowfall rates possible for the Helena area and along I-90 between 11pm and 2am. Temperatures falling into the upper -10s and lower -20s. Wind chill as low as -50.
WEDNESDAY: Mostly cloudy and frigid. A sustained NW breeze at 5-10 MPH. Temperatures starting in the -10s, falling into the -20s during the evening. Cloud cover gradually decreases overnight as temperatures fall into the -30s and -40s. Wind chills as low as -65.
THURSDAY: Mostly sunny and frigid. Wind shifts to the SW direction during the morning. Temperatures gradually warm from the -30s and -20s into the -10s and -0s by the evening for central Montana. Remaining in the -10s and -20s for eastern Montana.
FRIDAY: Mostly cloudy. A stray snow shower is possible. Highs in the low to mid 20s for central Montana, 0s and -0s for the Hi-Line and -0s and -10s for eastern Montana. Temperatures remain steady in the 20s in central Montana overnight, as temperatures fall into the -0s and -10s for the Hi-Line and eastern Montana.
CHRISTMAS EVE: Partly cloudy and breezy. A sustained SW wind at 15-25 MPH gusting to 35 MPH at times. Temperatures warming into the upper 30s and lower 40s for central Montana, 20s for the Hi-Line and 0s for eastern Montana. Mostly cloudy and breezy overnight as temperatures fall into the 20s for central Montana, 10s for the Hi-Line and -0s for eastern Montana.
CHRISTMAS DAY: Mostly cloudy, windy and scattered rain/snow showers. Gusts up to 50mph possible. Blowing snow and reduced visibility. Highs in the mid to upper 40s for central Montana, low to mid 30s for eastern Montana. Mostly cloudy with scattered showers continuing overnight as temperatures fall into the upper 20s and lower 30s.
MONDAY: Mostly cloudy and breezy. Highs in the mid to upper 40s for central Montana, low to mid 30s for eastern Montana. Temperatures falling into the mid to upper 20s overnight.
TUESDAY: Mostly cloudy. Highs in the upper 40s and lower 50s.
