Current Conditions
Temp-0.5 C
RH96 %
WindSW 26 mph
Mauna Kea Observatories Forecast
5 PM HST Friday 09 December (0300 UTC Saturday 10 December) 2016
Fog, high humidity and ice
Chance for rain/snow and convection
Moderate winds
Cloud Cover and Fog/Precipitation Forecast
Fog, high humidity, ice, clouds and light stratiform flurries/rain will continue to plague the summit through the night. There is also an outside chance for periods of heavy snow and convection in the area through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near -2 C, with winds from the SSW at 25-40 mph for this evening, decreasing to 15-30 mph by the end of the night. Seeing and precipitable water are expected to exceed 1 arcsecond and 4 mm, respectively, through the night.
A saturated air mass between at least 12-16 thousand feet will allow fog, hig humidity as well as periods of ice and light flurries/rain to plague the summit probably through the next 4 nights. There is a possibility for additional moisture at different levels in the atmosphere as well as periods of instability moving through, which could allow for the development of isolated convection in the area, periods of heavy snow and/or light/moderate stratiform rain/snow mainly over the next 24 hours and again between Sunday afternoon and early Tuesday morning. The inversion is expected to finally rebuild near 7 thousand feet through Tuesday, which should help diminish the risk for moisture at the summit for that night. Extensive daytime clouds are expected through Monday, but could taper for Tuesday and especially Wednesday.

Banding overcast thick clouds will continue to stream over the summit area, blanketing skies through early Sunday morning. While there is a very good chance that the bulk of the upper clouds will shift off toward the east, broken mid-level clouds may still linger in the area, contributing to periods of extensive cloud cover through Monday night. Clear skies are expected once these clouds finally shift off toward the east for Tuesday night.

Precipitable water is expected to exceed 4 mm through the next 4 nights. There is a possibility that PW could dip toward 1 mm for Tuesday night.

A mixture of boundary layer turbulence, upper-level instability/turbulence, poor/wet conditions and/or cloudy skies will contribute to bad seeing through Monday night. While the atmosphere is expected to dry out and stabilize for Tuesday night, boundary layer turbulence will limit much improvement in seeing for that night.

Very little change since the morning forecast...The trough to the NW of the state will continue to gradually march eastward, before finally shifting east of the Big Island around Tuesday morning. Unfortunately, its associated band of moisture/clouds along its eastward flank will keep the atmosphere between 12-16 thousand feet quite saturated, allowing extensive fog and high humidity to plague the summit through the next 4 nights. Initially, the air mass below 10 thousand feet will remain fairly dry and stable, which should limit the risk for convection in the area through this evening. However, thick overcast clouds will continue to stream over the Big Island, which could allow for light/moderate stratiform rain/snow at the summit through sunrise Sunday. In addition, there is a chance that an embedded short-wave trough will help briefly saturate and destabilize the entire atmosphere, increasing the risk for periods of heavy snow and convection in the area between midnight and tomorrow evening. The upper atmosphere is expected to dry out as this SWT shifts eastward, which may open skies a bit for Sunday. However, the large-scale trough will still persist to the NNW, drawing more mid/low-level moisture in from the tropics for that day and especially Monday. There is a chance that this trough will briefly dig southward, further destabilizing the atmosphere, organizing the moisture in the area (into a front) and thus increasing the odds on convection in the area and heavy snow at the summit on Monday and into Tuesday. As mentioned previously, the trough and its associated band is expected to shift east of the Big Island around Tuesday morning, allowing a ridge to build in from the west during that day. This should help quickly rebuild the inversion near 7 thousand feet and allow dry and stable conditions to return to the summit for that night and Wednesday night. Long term projections continue to suggest that another low/trough will rapidly dig in from the north during the latter night, deepening and settling in to the NW for Thursday onward. This could bring another round of moisture/instability to the area for the latter part of next week.
WRF Astronomical Observing Quality Guidance
Cloud Cover and Precipitable Water Analyses
MK CN² Profiles
5 Day Forecast Summary (Graphical Trend)
HST Cloud Fog/Precip Temp Wind Seeing PW
Cover (%) Height (km) Probability (%) (Celcius) (Dir/MPH) (Arcseconds) (mm)
Fri Dec 09 - 8 PM80-1004-10100 / 90-2SSW/25-401-210-15
Sat Dec 10 - 2 AM80-1004-10100 / 90-2SSW/15-301-210-15
2 PM80-1004-10100 / 901SW/5-15NaN10-15
8 PM80-1004-1095 / 800SSW/10-200.8-1.68-12
Sun Dec 11 - 2 AM80-1004-1095 / 750SW/10-200.8-1.66-10
2 PM80-1004-895 / 801SW/15-30NaN8-12
8 PM50-704-695 / 90-1SW/15-300.8-1.88-12
Mon Dec 12 - 2 AM60-804-795 / 90-1SW/20-351-28-12
2 PM80-1004-995 / 90-0.5WSW/25-40NaN8-12
Tue Dec 13 - 2 AM60-804-690 / 75-4WSW/35-500.9-1.96-10
2 PM20-404-4.540 / 54WNW/30-45NaN2-4
Wed Dec 14 - 2 AM0-20Clear10 / 02NW/25-400.7-1.31-2
2 PM0-20Clear5 / 07WSW/10-20NaN1.5-2.5
Rise and Set times for the Sun and Moon
Night (HST) Sun Set Twilight End Twilight Beg Sun Rise Moon Rise Moon Set Illumination (%) RA DEC
Fri Dec 09 - Sat Dec 10 17:53 19:02 5:28 6:37 N/A 3:22 81 1 48.3 6 58
Sat Dec 10 - Sun Dec 11 17:53 19:02 5:28 6:37 N/A 4:25 90 2 46.5 11 14
Sun Dec 11 - Mon Dec 12 17:54 19:03 5:29 6:38 N/A 5:29 96 3 47.5 14 50
Mon Dec 12 - Tue Dec 13 17:54 19:03 5:30 6:38 16:52 6:34 99 4 50.7 17 26
Tue Dec 13 - Wed Dec 14 17:55 19:03 5:30 6:39 17:51 7:38 100 5 55.1 18 46
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 12 December 2016.
Additional Information
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