Latest Forecast for Mauna Kea Observatories
830 AM HST (1830 UTC) Tuesday 28 January 2014

Warnings
Fog, ice and high humidity
Chance for convection and snow
Strong winds through this evening

Cloud Cover and Precipitation Forecast
Fog, ice, clouds and high humidity will continue to plague the summit through the night. There is also a chance for convection and snow, particularly for this afternoon.

Summary of Key Meteorological Variables
Summit temperatures will be near -2 C this evening and -6 C for the night. Winds will be from the south at 20-35 mph for this afternoon, but will briefly pick up for this evening, then taper while switching to a more northwesterly component through the night. Precipitable water and seeing are expected to exceed 4 mm and 1 arcsecond, respectively.

Discussion
The atmosphere near the Big Island will remain saturated and quite unstable through tomorrow afternoon. Although the upper-half of the air mass will dry out thereafter, the inversion will remain weak/indistinct and the air mass below 15-18 thousand feet will remain fairly moist probably through the weekend. As a result, there is a moderate/high risk for fog, ice and/or high humidity throughout the forecast period (especially over the next 24 hours). There is also a chance for convection and snow at the summit, mainly through tomorrow afternoon. Extensive daytime clouds are expected throughout the forecast period.

Broken to overcast thick clouds will continue to blanket summit skies through tonight, then will the upper clouds will start to shift eastward just after sunrise tomorrow. While this may help open up skies for that night, there is a good chance for residual mid/summit-level clouds in the area mainly through Thursday night, perhaps even Friday night. Clearer skies should prevail for Saturday night.

Precipitable water will likely linger near or exceed 4 mm throughout the forecast period.

Boundary/low-level turbulence as well as moisture and instability will contribute to bad seeing for tonight. The boundary layer turbulence is slated to subside for the remainder of the forecast period, but the moisture and perhaps instability will remain. In addition, there is a possibility for lingering low-level turbulence for tomorrow evening. Nonetheless, seeing should return toward 0.7-0.8 arcseconds for tomorrow night, improve slightly for Thursday night and perhaps dip to 0.5-0.6 arcseconds as relatively calm skies prevail for Friday and Saturday night.

A trough passing to the north of the state will continue to destabilize the atmosphere while its associated cold front stalls out near the Big Island over the next 24 hours. While the trough is slated to rapidly lift northeastward, which may help to stabilize at least the upper-half of the air mass thereafter, it will leave its remnant cold front to decay in the area probably well into the weekend. This will allow the lower half of the atmosphere to remain quite moist with a indistinct/elevated inversion as the ridge fails to re-establish itself in the area during that time. Consequently, there is a moderate/high risk for fog, ice and high humidity throughout the forecast period. Flurries or light rain are also possible at almost anytime, though the odds favor the next 24-36 hours in particular. There is a chance for deep convection in the area as well as short-lived periods of heavy snow, mainly while the atmosphere remains very saturated and unstable through early tomorrow morning. Winds will also fluctuate quite a bit over the next 24 hours, but is slated to become quite weak and variable for the remainder of the week. This may allow for more short-lived afternoon convection to develop along the slopes (driven by land heating throughout the day, an abundant supply of moisture and lingering instability) over the next several days; any afternoon convection should subside as the sun sets. Nonetheless, expect poor/wet summit-level conditions probably throughout the forecast period.