Current Conditions
Temp3.5 C
RH12 %
WindNE 0 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Monday 24 October (0300 UTC Tuesday 25 October) 2016
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while scattered high clouds drift in from the west and dissipate over/near the Big Island for tonight.
Summary of Key Meteorological Variables
Summit temperatures will be near 4.5 C this evening and 4 C tomorrow morning. Winds will be from the east at 5-15 mph, with seeing around 0.6-0.65 arcseconds. Precipitable water is expected to be in the 1-1.5 mm range for the night.
The tradewind inversion will continue to cap low-level moisture primarily near 7 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.

More scattered high clouds are expected to spread in from the west and dissipate over or near the Big Island for tonight. The bulk of these clouds will begin to pass along the western and southern skies for the following 2 nights, with more organized broken/thicker clouds drifting in from the north late Thursday night. The latter set could result in periods of extensive cloud cover for Friday night.

Precipitable water is expected to linger near 1.25 mm for tonight, slip toward 0.9-1 mm for tomorrow night and likely bottom out near 0.8 mm for Wednesday night. It is then set to trend toward 2 mm through Thursday night and probably 4 mm for Friday night.

Lingering low-level turbulence will likely keep seeing near 0.6-0.65 arcseconds for tonight, but is set to subside allowing seeing to improve toward 0.45-0.55 arcseconds as relatively calm skies prevail for the following 3 nights. An increase in upper-level turbulence may degrade seeing once again for Friday night.

No change since the morning forecast....A persistent mid/upper-level ridge to the north will continue to promote steady/strong large-scale subsidence in the area through the week. This subsidence will easily maintain a well-defined tradewind inversion primarily near 7 thousand feet and ensure the summit remains dry and stable through the next 5 nights. A weak sub-tropical jet is expected to linger overhead, send mainly dissipating high clouds over/near the summit area for the tonight and possibily tomorrow night. The jet is set to weaken as an upper-level ridge passes to the north late Tuesday night and into Wednesday. This will help augment subsidence in the atmosphere and likely drive PW below 1 mm for those nights. Seeing should also respond to the calm flow embedded in the ridge and slip toward 0.45-0.5 arcseconds during that time. Unfortunately, a new trough is expected to brew to the north and dissipate the ridge beginning late Thursday. Right now, it doesn't look like this trough will disrupt the stability of the atmosphere much, but could bring broken/thick clouds to the area especially for Friday 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)
Mon Oct 24 - 8 PM10-309-100 / 04.5ENE/5-150.55-0.751-1.5
Tue Oct 25 - 2 AM10-309-100 / 04E/5-150.5-0.71-1.5
2 PM10-309-100 / 09.5N/0-10NaN1-1.5
8 PM0-20Clear0 / 04NE/0-100.45-0.650.9-1.1
Wed Oct 26 - 2 AM0-20Clear0 / 03.5NE/0-100.45-0.550.8-1
2 PM0-20Clear0 / 09NE/5-15NaN0.8-1.2
8 PM0-20Clear0 / 03.5ENE/5-150.4-0.50.7-0.9
Thu Oct 27 - 2 AM0-20Clear0 / 03ENE/5-150.4-0.50.7-0.9
2 PM0-20Clear0 / 08NE/0-10NaN0.8-1.2
Fri Oct 28 - 2 AM20-409-100 / 02.5NE/0-100.4-0.61-2
2 PM40-608-100 / 06ENE/0-10NaN2-4
Sat Oct 29 - 2 AM60-807-100 / 01NNE/5-150.5-0.83-4
2 PM60-807-100 / 05.5ENE/0-10NaN3-6
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
Mon Oct 24 - Tue Oct 25 18:01 19:06 5:06 6:11 2:08 N/A 24 10 23.5 9 09
Tue Oct 25 - Wed Oct 26 18:00 19:05 5:07 6:12 2:59 N/A 16 11 10.9 5 33
Wed Oct 26 - Thu Oct 27 18:00 19:05 5:07 6:12 3:48 N/A 9 11 57.0 1 46
Thu Oct 27 - Fri Oct 28 17:59 19:04 5:07 6:13 4:37 16:29 5 12 42.2 -2 02
Fri Oct 28 - Sat Oct 29 17:58 19:04 5:08 6:13 5:26 17:06 2 13 27.2 -5 44
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 25 October 2016.
Additional Information
For public road conditions and snow report message please call (808) 935-6268.
This message is also available at the MKWC road conditions page.
NWS Hawaiian Islands Synoptic Discussion and Guidance
Honolulu National Weather Service Data and Products