Latest Forecast for Mauna Kea Observatories
10 AM HST (2000 UTC) Thursday 14 January 2021
Cloud Cover and Precipitation Forecast
The summit will remain dry and stable, while isolated to scattered high clouds pass along the northern skies mainly during the first half of the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 6 C this afternoon and 0.5 C for the night. Winds will be from the east at 5-15 mph for today, easing and switching to a more SSE direction through the night. Seeing will be near 0.5-0.6 arcseconds, while precipitable water is expected to be in the 2.5-3.5 mm range for the night.
A fairly well-defined inversion will continue to cap low-level moisture near 7 thousand feet and ensure the summit remains dry and stable through at least Saturday night. Building instability will begin to erode the inversion and increase the risk for fog, ice and flurries at the summit through Sunday night and especially for Monday evening. Daytime clouds will be mimimal and short-lived through Saturday, but could pick up on Sunday, turn very extensive with the possibility for thunderstorms on Monday, then taper again through Tuesday.
THere is a chance for isolated to scattered high clouds passing along the northern skies for this evening. These clouds will shift eastward thereafter, leaving predominately clear skies through Sunday evening. Patches of mid/summit-level clouds may fill in from the WNW early Monday morning and may contribute to periods of extensive cloud cover (particularly along the northern half of the sky) before passing eastward through Tuesday.
Precipitable water is expected to slip into the 2-3 mm range for tonight, trend toward 1 mm through Friday night, increase back to 2-3 mm for Saturday night, and probably 3-4 mm through Sunday night and 4+ mm for Monday night.
Easing winds above the summit, combined with a drier more stable air mass will allow seeing to improve toward 0.5-0.6 arcseconds for tonight. There is a chance for a brief increase in winds, which could stir up boundary layer turbulence and contribute to a degradation in seeing for tomorrow evening. Seeing is set to improve again as winds subside through that night and eventually settle in near 0.5 arcseconds as relatively light/laminar northerly flow prevails in the free atmosphere for Saturday night. However, an increase in instability, boundary layer turbulence and the possibility for moisture and an elevated inversion will likely result in poor/bad seeing for Sunday and Monday night.