Current Conditions
Temp5.6 C
RH15 %
WindNNW 0 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Thursday 05 May (0300 UTC Friday 6 May) 2016
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, but there is a possibility for lingering high clouds mainly along the eastern skies for this evening.
Summary of Key Meteorological Variables
Summit temperatures will be near 2.5 C this evening and 2 C tomorrow morning. Winds will be from the SSE at 5-15 mph, with seeing near 0.55 arcseconds. Precipitable water is expected to be in the 2-2.5 mm range for the night.
The tradewind inversion will continue to cap low-level moisture near 7-8 thousand feet and ensure the summit remains dry and stable for tonight. There is a possibility that building/persistent upper-level instability coupled with abundant supply of low-level moisture lingering in the area will weaken and/or lift the inversion toward 12 thousand feet and increase the risk for periods of fog and high humidity at the summit for the following 4 nights; nighttime precipitation is unlikely. Daytime clouds will be minimal and short-lived for today, but could turn extensive, with the possibility for afternoon convection through Monday.

Skies are set to open up for most of tonight (and likely most of tomorrow night) as the high clouds continue to move eastward over the next 6 hours. However, more widespread high clouds are expected to stream in from the west through Saturday, and will probably contribute to extensive cloud cover mainly between sunrise Sunday and early Monday evening. There is a chance that these clouds will sag a bit southward, opening up skies to the north for Monday night.

Precipitable water is expected to linger primarily in the lower-half of the 2-3 mm range for the next 2 nights, but will likely increase toward 3+ mm for the remainder of the forecast period.

Light/moderate turbulence in the free atmosphere will likely allow seeing to linger near average-like values for tonight. However, an increase in upper-level turbulence and instability will likely contribute to poorer than average seeing over the next 2 nights. Turbulence in the free atmosphere is expected to strengthen, which will probably further degrade seeing for Sunday and Monday night.

Minimal change since the morning forecast...The mid/low-level ridge is set to shift off toward the SE as a late season low develops to the north of the state over the next 24-36 hours. Fortunately, strong large-scale subsidence will prevail in the area, which will easily help maintain the inversion near 7-8 thousand feet and ensure the summit remains dry and stable for tonight. And while the bulk of the instability associated with the low is expected to linger further off toward the north, there is a very good chance that the low's associated cold front, currently organizing to the NW, will shift southeastward over the next 24-36 hours, then stall out over the Big Island area between late tomorrow evening and into the early part of next week. This band could lift/weaken the inversion toward 12 thousand feet and increase the risk for fog and high humidity at the summit after tonight; nighttime precipitation is unlikely as the mid-level air mass should remain relatively dry. In addition, there is a somewhat remote possibility that daytime heating will help fire off afternoon convection along the slopes over the weekend. Finally, it looks like this low's parent trough will help strengthen and pull the sub-tropical jet back over the state late in the weekend. This jet could significantly increase turbulence in the free atmosphere and usher widespread high clouds to the area for Sunday and Monday night.
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)
Thu May 05 - 8 PM0-208.5-90 / 02.5SSE/5-150.5-0.62-2.5
Fri May 06 - 2 AM0-5Clear0 / 02S/5-150.5-0.62-2.5
2 PM40-604-560 / 157WSW/5-15NaN3-6
8 PM0-5Clear50 / 52.5W/10-200.5-0.82-3
Sat May 07 - 2 AM10-309.5-1050 / 52WNW/10-200.5-0.82-3
2 PM60-804-1060 / 157W/10-20NaN3-6
8 PM20-409-1040 / 52.5W/5-150.5-0.83-4
Sun May 08 - 2 AM40-609-1040 / 52W/5-150.5-0.93-4
2 PM80-1004-1070 / 206W/5-15NaN3-6
Mon May 09 - 2 AM60-808-1050 / 50WNW/5-150.6-13-4
2 PM60-804-1070 / 205WNW/10-20NaN3-6
Tue May 10 - 2 AM50-709-1040 / 50NW/5-150.6-1.12-4
2 PM0-209-1050 / 106NNE/5-15NaN2-4
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
Thu May 05 - Fri May 06 18:56 20:06 4:31 5:40 5:49 18:11 0 2 38.0 10 46
Fri May 06 - Sat May 07 18:57 20:06 4:30 5:40 6:43 19:16 1 3 37.7 14 09
Sat May 07 - Sun May 08 18:57 20:07 4:30 5:39 N/A 20:20 4 4 38.3 16 32
Sun May 08 - Mon May 09 18:58 20:07 4:29 5:39 N/A 21:22 10 5 38.7 17 47
Mon May 09 - Tue May 10 18:58 20:08 4:28 5:38 N/A 22:21 17 6 38.0 17 50
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 6 May 2016.
Additional Information
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