(ABOVE) Hawaii Island Weather Alert map plots the area under a National Weather Service Blizzard Watch

NEWS BRIEF

• A powerful low in the mid levels of the atmosphere is expected to develop near the islands tonight and
  Tuesday, bringing very strong, dangerous winds to the summits of Mauna Kea and Mauna Loa on the Big Island. Gusts of 95 miles per hour are possible Tuesday night into Wednesday.
• A Winter Storm Watch for the summits has been cancelled and replaced with a Blizzard Watch. A band of deep moisture could spread over Hawaii Island on Tuesday / Wednesday bringing with it the possibility of 6 inches of snow above 12,000 feet.The high winds could create deep drifts.
• Temperatures will be in the upper 20’s to lower 30’s with wind chills in the teens.
• The combination of wind and snow would bring “extremely hazardous and potentially life-threatening conditions” for anyone attempting to drive or hike to the summits, says the National Weather Service.

PRIMARY SOURCES

There is still some uncertainty as to whether or not the deep moisture will extend over the Big Island or remain just to the east. Even if the heavy snow does not materialize, very strong winds are expected.National Weather Service on Dec. 22

Here is the discussion posted to the Mauna Kea Weather Center webpage:

The airmasses above the islands is destabilizing rather quickly. The inversion over the Big Island is expected to vanish throughout today. This is allowing the mid and low level moisture to reach the summit already. Expect fog tonight. Precipitation is likely in the form of ice, snow and flurries tonight, and it possible Tuesday night as well. The atmosphere will remain unstable throughout at least the next three days while it will start slowly stabilizing on Christams day.

Mid-high clouds will start approaching the summit today. As the atmosphere destabilizes and the inversion lifts and vanishes, low-mid clouds will continue to raise up to the summit level throughout this evening/night. The summit skies will be therefore occluded tonight and through the following two nights. They might start open up a bit on Thursday and through Friday.

Precipitable water will exceed the 4 mm threshold tonight and Tuesday night. It is likely to linger close to 4 mm on Wednesday night, and decrease and be close to 2 mm on Thursday. The models project a further decrease, between 1 and 1.5 mm, on Friday nigth.

Observing conditions will be unoperable/very poor at least throughout Wednesday night. An improvement is possible for the following two days.

A weakening cold front is moving through the island chain today, advecting low-mid clouds toward the Big Island. Meanwhile an upper level trough is approaching the State from the NW. This trough is projected to stall west of the Hawaiian Islands and develop into a mid level low (kona low) which is expected to rapidly advect sub-tropical moisture and clouds over the Island’s chain from this afternoon and through Wednesday. The latest model runs projects this mid-upper level low to follow a more northern path than initially anticipated. In this scenario the Big Island will be less affected than expected. Still atmospheric instability will rapidly increase today and winds at the summit are picking up and are likely to reach warning levels tonight. Fog is very likely and precipitation in the form of ice/snow/flurries is also likely for tonight and possibly tomorrow. Overall observing conditions will be very poor/unoperable at least through Wednesday night. The more northern path though will allow the environment to dry and stabilize sooner than initially anticipated. PW might drop below the 4 mm threshold on Thursday and sky might start opening up then. As a word of caution, kona lows are very difficult to predict in term of their paths and evolution. Stay tuned with next forecast updates on this feature future developments.Mauna Kea Weather Center on Dec. 22 at 5 p.m. HST