Current Conditions
Temp10.5 C
RH33 %
WindNNE 15 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
10 AM HST (2000 UTC) Wednesday 20 June 2018
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit skies will be predominantly clear today.
Summary of Key Meteorological Variables
Summit temperature will be near 11C this afternoon, 4C this evening and 3.5C tonight and tomorrow morning. Precipitable water will range between 3 and 4 mm through the night. Winds will be weak at 10 to 20mph, decreasing further through the second part of the night. Observing conditions are on an improving trend and seeing will be in the 0.55-0.65 range.
Discussion
The tradewind inversion will continue to cap the bulk of the low level moisture below summit level through the forecast period. Nevertheless the mid level atmosphere are slow to dry and moisture will still linger around today and through the first half of the night. The inversion is expected to weaken/lift some later on Friday, but it is not expected to vanish completely.

Summit skies will be predominantly clear throughout the forecast period.

Precipitable water will range between 3 and 4 mm tonight, between 2.5 and 3 mm on Thursday night and will drop in the 1.5 to 2 mm range finally by Friday night. It will decrease further to linger closer to 1 mm (1 to 1.5mm) on Saturday night and to 1.5 mm on Sunday night.

Observing conditions are on an improving trend as airmasses slowly dry out and winds at the surface taper. Chances are for average seeing conditions tonight and tomorrow, possibly degrading during the second half of the night then. Conditions are expected to be average but with some degree of variability through the rest of the forecast period as winds at the surface will be picking up some and will therefore be stirring up some ground layer turbulence then.

As a weak front slowly drifts to the East and the weak high pressure ridge remains to the north of the state, the mid level atmosphere slowly dries out and winds at the surface taper. Therefore weather conditions will be generally good and seeing will finally get into more average values. From Thursday a strong surface high pressure will build into the central pacific area and mostly stable conditions will persist through the rest of the forecast period. The upper level low the models still project to develop East of the islands should remain far enough not to greatly impact the summit weather.
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)
Wed Jun 20 - 2 PM0-20Clear0 / 011E/10-20NaN4-6
8 PM0-20Clear0 / 04E/10-200.5-0.83.5-4.5
Thu Jun 21 - 2 AM0-20Clear0 / 03.5ENE/5-150.45-0.753-4
2 PM0-20Clear0 / 010ENE/10-20NaN3-4
8 PM0-20Clear0 / 03.5NE/10-200.5-0.82.25-2.75
Fri Jun 22 - 2 AM0-20Clear0 / 02.5NE/15-200.6-12.5-3
2 PM0-20Clear0 / 09ENE/15-20NaN1.5-2.5
8 PM0-20Clear0 / 02.5ENE/15-200.5-0.91.5-2
Sat Jun 23 - 2 AM0-20Clear0 / 02ENE/10-200.4-0.81.5-2
2 PM0-20Clear0 / 09ENE/10-20NaN1.5-2.5
Sun Jun 24 - 2 AM0-20Clear0 / 01.5NE/15-250.4-0.81-1.5
2 PM0-20Clear0 / 09ENE/15-25NaN1-2
Mon Jun 25 - 2 AM0-20Clear0 / 01.5ENE/15-250.5-0.91.25-1.75
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
Wed Jun 20 - Thu Jun 21 19:13 20:27 4:20 5:34 N/A 1:25 60 12 48.1 -0 43
Thu Jun 21 - Fri Jun 22 19:14 20:28 4:20 5:34 N/A 2:05 70 13 37.3 -5 19
Fri Jun 22 - Sat Jun 23 19:14 20:28 4:20 5:34 N/A 2:44 79 14 26.2 -9 37
Sat Jun 23 - Sun Jun 24 19:14 20:28 4:21 5:35 N/A 3:25 87 15 15.4 -13 28
Sun Jun 24 - Mon Jun 25 19:14 20:28 4:21 5:35 N/A 4:07 93 16 05.2 -16 40
Forecast Issued by: Tiziana Cherubini
Next update at 5 PM HST Wednesday 20 June (0300 UTC Thursday 21 June) 2018.
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