Current Conditions
Temp5.1 C
RH4 %
WindNNW 18 mph
RoadOpen (4x4 only)
Mauna Kea Observatories Forecast
5 PM HST Friday 05 February (0300 UTC Saturday 6 February) 2016
Warning(s)
Strong winds on Sunday
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 8 C this afternoon and 3 C for the night. Winds will be from the SW at 5-15 mph for today, increasing to 10-20 mph for the morning hours. Seeing will be near 0.45-0.5 arcseconds, while precipitable water is expected to linger near 0.65-0.7 mm for the night.
Discussion
The tradewind inversion will continue to cap low-level moisture at or below 9 thousand feet and ensure the summit remains dry and stable through late tomorrow morning. There is a strong possibility that the inversion will briefly weaken as instability passes through the area, which will increase the risk for fog and ice at the summit for Saturday night (particularly the second half); precipitation is unlikely. The inversion will quickly recover and strengthen near 7 thousand feet through Sunday, ensuring the summit steers free of moisture for the remainder of the forecast period. Daytime clouds will be minimal and short-lived through tomorrow, but could pick up over the weekend, then taper again for the early part of next week.

Skies overhead will remain predominately clear of organized/wide-spread clouds throughout the forecast period. However, there is a possibility for lenticular clouds over the summits for Saturday, Sunday and perhaps Monday night. A thick band of clouds may also be visible along the northern and eastern skies for Saturday and Sunday night, respectively.

Precipitable water is expected to linger near 0.65-0.7 mm for tonight, increase toward 2-3 mm and become more highly variable for Saturday night, dip back to 1 mm for Sunday night, then wobble between 1-2 mm for the early part of next week.

Deep subsidence in the area will allow for calm skies and seeing to settle in near 0.5 arcseconds for most of tonight (some degradation is possible toward the end of the night). A significant increase in summit-level winds is expected to stir up boundary layer turbulence and contribute bad seeing for at least Saturday and Sunday night. There is a good chance that winds will taper by Monday morning, allowing for some improvement (toward more poor-like values) for Monday and Tuesday night.

Little change since the morning forecast...A deep ridge currently linger over the state will continue to promote steady/strong large-scale subsidence in the area, which will easily maintain a well-defined inversion near 8-9 thousand feet and ensure a dry/stable summit-level air mass for at least the next 18 hours. Calm skies and very dry mid/upper-level air embedded in the ridge will also allow seeing to linger near 0.45-0.5 arcseconds and 0.65-0.7 mm for tonight. Unfortunately, a sharp developing trough is still slated to rapidly dig in from the north, bringing cold/unstable upper-level air to the area, which will likely weaken the inversion between late tomorrow evening and late Sunday morning. While the bulk of the moisture associated with the low will remain off toward the north of the state, there is still a possibility for short-lived fog and ice at the summit mainly for the second half of Saturday night. In addition, winds will begin to increase near sunrise tomorrow, likely peaking in the 60-80 mph range early Sunday afternoon. Last few model runs suggest that winds will taper rather quickly as the trough shifts eastward over the following 24-36 hours and is expected to settle back in near 20-25 mph for Monday and Tuesday night. Regardless, there is a very good chance that boundary layer turbulence will contribute to bad seeing for Saturday and Sunday night and probably poor seeing for the following 2 nights. Fortunately, the inversion is set to recover as dry/stable air fills in the wake of the trough and a ridge building in from the west for Sunday night and likely most 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 Feb 05 - 8 PM0-5Clear0 / 03SSW/5-150.4-0.50.6-0.8
Sat Feb 06 - 2 AM0-5Clear0 / 03WSW/10-200.4-0.60.55-0.75
2 PM0-204-4.2510 / 05WSW/20-35NaN2-4
8 PM10-304-4.550 / 10-1WSW/25-400.8-1.62-3
Sun Feb 07 - 2 AM20-404-675 / 15-3WSW/40-601-22-3
2 PM10-305-6.525 / 01NW/60-80NaN1-2
8 PM0-205-70 / 0-5NW/50-701-30.8-1.2
Mon Feb 08 - 2 AM0-205-60 / 0-4NW/35-501-20.8-1.2
2 PM0-205-60 / 03W/20-35NaN1-2
Tue Feb 09 - 2 AM0-205-5.50 / 00W/15-300.5-12-3
2 PM0-20Clear0 / 06W/15-30NaN2-3
Wed Feb 10 - 2 AM0-5Clear0 / 01WNW/20-350.5-1.11-2
2 PM0-20Clear0 / 06.5WNW/20-35NaN1-1.5
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
Sat Feb 06 - Sun Feb 07 18:26 19:32 5:40 6:46 5:56 16:57 2 20 15.2 -15 50
Sun Feb 07 - Mon Feb 08 18:26 19:32 5:40 6:45 6:46 17:57 0 21 11.7 -13 07
Mon Feb 08 - Tue Feb 09 18:27 19:33 5:39 6:45 7:35 18:58 1 22 07.9 -9 35
Tue Feb 09 - Wed Feb 10 18:27 19:33 5:39 6:44 N/A 19:59 4 23 03.5 -5 27
Wed Feb 10 - Thu Feb 11 18:28 19:33 5:39 6:44 N/A 20:59 10 23 58.7 -0 59
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 8 February 2016.
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