Current Conditions
Temp-0.5 C
RH97 %
WindSW 27 mph
Mauna Kea Observatories Forecast
5 PM HST Tuesday 06 December (0300 UTC Wednesday 7 December) 2016
Fog and high humidity
Chance for ice, rain/snow and convection
Cloud Cover and Fog/Precipitation Forecast
Fog, high humidity, clouds and periods of snow/rain will continue to plague the summit through the night; there is also a chance for ice at the summit and convection in the area.
Summary of Key Meteorological Variables
Summit temperatures will be near 0 C this evening and -0.5 C tomorrow morning. Winds will be from the SW at 20-35 mph for today, easing and switching to the SSW at 10-20 mph as the night progresses. Seeing and precipitable water are expected to exceed 1 arcsecond and 4 mm, respectively.
The air mass between 10-18 thousand feet will remain saturated, allowing extensive fog and high humidity to plague the summit probably through the week; there is also a chance for light flurries/rain and ice during this period. There is a possibility that remainder of the atmosphere will become periodically saturated and unstable particularly between sunrise tomorrow and late Friday morning (and perhaps again over the weekend). This will raise the stakes on heavy snow at the summit and convection in the area during this time. Extensive daytime clouds are expected throughout the forecast period.

A band of broken to overcast mid-level clouds will continue to stream in from the south through the week. In addition, there is a good chance that these clouds will thicken and become more widespread, between sunrise tomorrow and late Friday afternoon. Regardless, these clouds are expected to blanket most if not all of the sky through the next 5 nights.

Precipitable water is expected to exceed 4 mm through the next 5 nights.

A mixture of boundary layer turbulence, upper-level instability/turbulence, poor/wet conditions and/or cloudy skies will contribute to poor/bad seeing throughout the forecast period.

No change since the morning forecast...Deep southerly flow will persist over the state as a quasi-stationary trough sits to the west and a weak ridge prevails well to the east probably into the early part of next week. This will allow a nearly continous supply of tropical moisture to stream over the Big Island, keeping at least the air mass between 10-17 thousand feet quite saturated throughout the forecast period. This will result in inoperable conditions as extensive fog, high humidity and clouds continue to plague the summit during this time. There is also a possibility for periods of ice and/or light rain/flurries at virtually anytime. Deeper more widespread moisture and clouds are expected build over the state as a short-wave trough (SWT) digs in from the NW and enhances the large-scale trough to the west between early tomorrow morning and around Friday morning. This will increase the risk for heavy snow and black ice at the summit, overcast skies as well as convection in the area during this period. Winds are also set to increase back toward 50 mph, which could create more large drifts and blowing snow particularly for much of Thursday. While there is a chance that this stream will weaken a bit and shift subtly eastward again as the SWT departs, mid-level moisture will continue to fill in from the south and/or linger over the Big Island until the next SWT reinforces the large-scale trough (and thus the deep southerly flow) over the weekend. This could help reguvenate the stream of moisture and destabilize the air mass again, which will not help to improve conditions/skies during that time.
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)
Tue Dec 06 - 8 PM70-904-695 / 400SW/15-301-28-12
Wed Dec 07 - 2 AM80-1004-9100 / 50-0.5SW/15-301-210-15
2 PM80-1004-10100 / 901SSW/15-30NaN10-15
8 PM80-1004-10100 / 90-0.5SSW/20-351-210-15
Thu Dec 08 - 2 AM80-1004-10100 / 95-1SSW/25-401-210-15
2 PM80-1004-10100 / 950SSW/35-50NaN10-15
8 PM80-1004-10100 / 90-2SW/20-351-310-15
Fri Dec 09 - 2 AM80-1004-10100 / 75-3WNW/15-301-310-15
2 PM80-1004-1095 / 800WSW/15-30NaN10-15
Sat Dec 10 - 2 AM80-1004-990 / 60-1WSW/5-151-28-12
2 PM80-1004-1095 / 750WSW/10-20NaN10-15
Sun Dec 11 - 2 AM80-1004-1090 / 70-1.5SW/10-201-210-15
2 PM80-1004-100 / 00.5SW/15-30NaN10-15
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
Tue Dec 06 - Wed Dec 07 17:52 19:01 5:26 6:35 N/A 0:26 50 23 06.9 -6 30
Wed Dec 07 - Thu Dec 08 17:53 19:01 5:27 6:35 N/A 1:23 61 23 59.1 -2 11
Thu Dec 08 - Fri Dec 09 17:53 19:01 5:27 6:36 N/A 2:21 71 0 52.6 2 23
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
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Wednesday 7 December 2016.
Additional Information
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This message is also available at the MKWC road conditions page.
NWS Hawaiian Islands Synoptic Discussion and Guidance
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