Current Conditions
Temp3.2 C
RH10 %
WindE 9 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Friday 27 March (0300 UTC Saturday 28 March) 2015
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will remain clear, dry and stable through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 1 C, with winds from the ENE at 15-25 mph for the night. Seeing will be around 0.8 arcseconds, while precipitable water is expected to be in the 0.8-1 mm range for the night.
Discussion
The tradewind inversion will continue to cap low-level moisture near 8 thousand feet and ensure the summit remains dry and stable through the next 5 nights. Daytime clouds will be minimal and short-lived throughout the forecast period.

Skies overhead will remain predominately clear through the next 5 nights, but there is a possibility for stray high clouds passing along the northern skies between late Saturday evening and early Monday evening.

Precipitable water is expected to settle in near 0.8-0.9 mm through Sunday niht, then increase toward 2 mm for Monday night and perhaps Tuesday night.

Lingering low-level turbulence combined with building (light) boundary layer turbulence through the day, will likely contribute to poor seeing for tonight and perhaps early tomorrow night. Both sources of turbulence are slated to subside by early Sunday morning, allowing seeing to improve toward 0.5-0.6 arcseconds for that night and probably Monday night. However, there is a possibility for another brief round of boundary layer turbulence, which could affect seeing for Tuesday night.

Very little change since the morning forecast...A rather broad mid/low-level ridge will continue to build in from the west over the next 12-24 hours and settle in to the north of the state well into next week. Subsidence associated with the ridge will help maintain a well-defined inversion near 8 thousand feet and ensure a dry/stable air mass through the next 5 nights. Winds are slated to increase as the ridge fills into the area, which could affect seeing for much of tonight and perhaps into tomorrow night. However, seeing should slip toward more average-like values once winds taper and the ridge settles in to the north late in the weekend and for the early part of next week. Precipitable water, on the other hand, is expected to benefit from the building subsidence and drop toward 0.8-0.9 mm for the weekend. However, there is a possibility that PW will increase back toward 2 mm as the ridge weakens a tad and allows minor mid/upper-level moisture into the area early next week. Skies will remain predominately clear as the bulk of the clouds pass west to east within a fairly zonal westerly jet well to the north of the state throughout the forecast period.
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 Mar 27 - 8 PM0-5Clear0 / 01ENE/15-250.6-0.90.8-1
Sat Mar 28 - 2 AM0-5Clear0 / 01E/15-250.6-0.80.8-1
2 PM0-20Clear0 / 07E/15-25NaN1-1.5
8 PM0-10Clear0 / 02E/10-200.5-0.80.8-1
Sun Mar 29 - 2 AM0-20Clear0 / 01.5ESE/10-200.5-0.70.8-1
2 PM0-20Clear0 / 07.5SE/5-15NaN0.8-1.2
8 PM0-20Clear0 / 02.5S/0-100.5-0.60.7-0.9
Mon Mar 30 - 2 AM0-20Clear0 / 01.5W/0-100.45-0.550.7-0.9
2 PM0-20Clear0 / 06WSW/5-15NaN1-1.5
Tue Mar 31 - 2 AM0-10Clear0 / 01SW/5-150.45-0.651.5-2.5
2 PM0-20Clear0 / 05W/15-30NaN2-3
Wed Apr 01 - 2 AM0-10Clear0 / 00WNW/15-300.5-0.81-2
2 PM0-20Clear0 / 05SW/10-20NaN1-2
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
Sun Mar 29 - Mon Mar 30 18:44 19:49 5:04 6:08 N/A 3:26 78 8 58.5 12 13
Mon Mar 30 - Tue Mar 31 18:44 19:49 5:03 6:08 N/A 4:05 85 9 45.7 9 12
Tue Mar 31 - Wed Apr 01 18:45 19:50 5:02 6:07 N/A 4:42 91 10 32.0 5 48
Wed Apr 01 - Thu Apr 02 18:45 19:50 5:01 6:06 N/A 5:19 96 11 17.9 2 09
Thu Apr 02 - Fri Apr 03 18:45 19:50 5:00 6:05 17:21 5:56 99 12 03.7 -1 37
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 30 March 2015.
Additional Information
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This message is also available at the MKWC road conditions page.
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