Warnings
Chance for fog and light snow for the night.
Possibility for thunderstorms.

Cloud Cover and Precipitation Forecast
There is a chance for snow, periodic fog, thunderstorms primarily during the second half of the night. There is a good chance for a partial clearing for the first half of the night, but more thick high clouds are expected to pour in from the northwest during the latter half of the night.

Summary of Key Meteorological Variables
Summit temperatures will be near -1.5 C tonight and -2.5 C tomorrow morning. Precipitable water is expected to be in the 4 to 6 mm range for tonight and 5 to 7 mm range tomorrow morning. Winds will be from the WSW at 15 to 25 mph for tonight and SW at 25 to 35 mph tomorrow morning. Shear is expected to be between 50 to 60 mph tonight and 35 to 45 mph tomorrow morning.

Discussion
While the tradewind inversion will persist at 7-8 thousand feet probably through sunrise tomorrow, mid-level moisture and instability will continue to move in from the northwest through the night and into Friday night. Thus, there is a chance for isolated thunderstorms, periodic fog, and light snow primarily during the second half of the night. The inversion will eventually deteriorate as the atmosphere becomes totally saturated and very unstable between noon tomorrow and noon/evening on Saturday. Thus, widespread (possibly severe) thunderstorms are likely primarily between noon and midnight tomorrow. Moderate to heavy snow, extensive fog, ice, and widespread thunderstorms are expected between noon tomorrow and noon/evening on Saturday. Snowfall after that should be light/minimal, but isolated thunderstorms, periodic fog, and ice may continue for the following 3 nights.

There will be a temporarily relief in the thick uniform high clouds probably through the first half of the night, allowing the skies to actually be visible during that time. However, more thick clouds are slated to slide in from the northwest during the second half of the night, and block 90-100% of the sky between 3-5 am tomorrow and sunrise on Saturday. There is a good chance for another clearing as most of the high clouds shift off toward the east during the following 2-3 nights. But, residual slow-moving mid-level clouds may still linger in the area probably through Tuesday night. In addition to this, more high clouds are expected develop over the Islands and/or move in from the southwest on Tuesday/Wednesday of next week.

Precipitable water is expected to increase from 5-7 mm for tonight to more than 10 mm for tomorrow night. Large uncertainties for the following 3 nights as the latest model run has PW dropping toward 1 mm as the dry side of a low shifts over the summit. While this is very possible, I think PW will likely be somewhat variable bouncing between 1 and 4 mm for Saturday night, then increase slightly toward 4 mm on Sunday night, and 5 mm on Monday night.

Observing may actually be possible this evening, however, seeing will likely be poor/bad due to the moisture/instability building in aloft and moderate turbulence/shear in the free atmosphere. Moreover, thick clouds are expected to move in during the second half of the night. While I still don't think observing will be possible on Friday and Saturday night (due to snow/thunderstorms/fog/ice/winds/clouds and fog/ice/winds, respectively), seeing will be terrible and highly variable on either night as pockets of turbulence, moisture, and instability persist in the free atmosphere. Weak to moderate shear is expected for Sunday and Monday night, but pockets turbulence could still linger in the area for those nights. Thus, seeing will probably be still variable (although not to the same extent as Friday and Saturday) and poor/bad.

A deep strong trough is still slated to dig in over the Islands later tomorrow and cut-off into cold-core low on Saturday. In the process it will send a front/band of thunderstorms/convection through the Island chain, with this front/band passing through the Big Island during the first half of tomorrow night. Ahead of this front/band, severe thunderstorms, similar to what occurred over the northern Hawaiian Islands this afternoon, could develop near the Big Island later tomorrow (particularly during the favorable periods of the diurnal cycle: the early morning and especially afternoon). Once the band moves over blizzard-like conditions are expected as winds top 50 mph, extensive fog make for very poor visibility, and moderate to heavy snow blankets most of the mountain above 11 thousand feet. All in all, I don't think it would be wise to be up on the summit between noon tomorrow and noon on Saturday. After that, the cut-off low is slated to drift east of the Big Island, placing the summit on the very dry and stable side of the low. While this latest model projection shows close similarities to this morning's run, I still don't expect the summit to be crystal clear and bone dry for Saturday night, mostly because of the close proximity of the low. In fact, I suspect isolated thunderstorms could still occur near or throughout the Big Island probably through Tuesday afternoon. Precipitation shouldn't be a problem (unless a thunderstorm pops up over the mountain), but periodic fog and ice will likely be an issue during that time. Finally, another trough is still expected to dig in behind this weekend's trough/low and reinitiate the deep southwesterly flow on Sunday and probably into the middle of next week. This will allow mean humidity to climb back toward 80% as instability builds in again on Sunday and Monday night. It may also allow the high clouds to return after Monday night. All in all, ok/poor Thursday night, not observable on Friday (wet, windy, and wild) and probably Saturday (windy) night, high humidity/ice on Sunday and Monday night.

Astronomical Observing Quality Guidance
Vertical Profiles from MM5 (vertical coordinate is pressure in mb):

Tonight's (Thursday Night) Collage	NOT AVAILABLE
Wednesday Night's Collage (available after 0800 HST on Wednesday)	Seeing Cn2
Thursday Night's Collage (available after 0800 HST on Thursday)	Seeing Cn2