Current Conditions
Temp4.9 C
RH9 %
WindSE 16 mph
Mauna Kea Observatories Forecast
730 AM HST (1730 UTC) Friday 31 October 2014
Fog, high humidity and ice
Chance for convection/rain
Cloud Cover and Fog/Precipitation Forecast
There is a moderate/high risk for fog, high humidity, ice, mid/summit-level clouds and perhaps light rain, particularly as the night progresses. High clouds will also build in from the southeast as the night progresses.
Summary of Key Meteorological Variables
Summit temperatures will be near 5 C this afternoon, 0.5 C this evening and -0.5 C tomorrow morning. Winds will be from the east at 5-15 mph for today, increasing to 15-30 mph through the night. Precipitable water and seeing are expected to linger near or exceed 4 mm and 1 arcsecond, respectively, through the night.
The tradewind inversion is expected to breakdown, allowing the atmosphere up to 15 thousand feet to turn fairly saturated over the next 12-18, which will increase the risk for fog, high humidity and rain at the summit for the next 2 nights. Although the inversion is slated to restrengthen through Sunday, mid-level moisture is projected to pour into the area, which won't help to decrease the odds on fog/rain at the summit until the atmosphere begins to dry out through Monday night. Drier more stable will return to the summit for Tuesday night. Extensive afternoon clouds are possible through Monday, and there is a possibility for afternoon convection along the slopes mainly for tomorrow.

There is a possibility that a patch of mid-level clouds will move clouds will move in from the east, while banding mid/upper-level clouds build in from the southeast at the night progresses. The former set of clouds is slated to dissipate through tomorrow, but the latter is set to blanket summit skies for Saturday and Sunday night. Although these clouds will begin to breakdown and shift subtly eastward through Monday, it will still contribute to extensive cloud cover for that night and could block the southeastern skies for Tuesday night.

Precipitable water is expected to linger near or exceed 4 mm probably throughout the forecast period.

Boundary layer and/or upper-level turbulence will contribute to poor/bad seeing through Monday night. There is a good chance that seeing will improve toward average/poor values (perhaps even better) as the turbulence subsides for Tuesday night.

A persistent upper-level trough currently sitting over the state is expected to deepen, spawn an upper-level low to the southwest and destabilize the atmosphere in the area through much of the weekend. In addition, a remnant patch of moisture from a stalled cold front is slated to move through the Big Island, erode the inversion and signficantly increase the risk for fog/high humidity, ice and perhaps light rain at the summit and convection offshore through the night. Although this moisture is slated to shift off toward the southwest through tomorrow, the inversion is not expected to recover as the low begins to pull deep tropical mid/upper-level moisture/clouds over the Big Island through the remainder of the weekend and into Monday. Instability associated with the low may also spark more isolated convection in the area, through it should be limited to the early morning or afternoon hours, through the weekend. Conditions and skies will start to improve as the low lifts off toward the north and the mid-level moisture detrains into the surrounding atmosphere once the southwestern edge of mid-level ridge settles back in over state late Monday and into Tuesday. However, there is a very good chance that banding high clouds will continue to little skies to the southeast into the middle part 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 Oct 31 - 2 PM40-604-625 / 105E/5-15NaN2-4
8 PM40-604-650 / 250.5ENE/10-200.7-1.13.5-4.5
Sat Nov 01 - 2 AM60-804-890 / 50-0.5E/15-300.9-1.54-8
2 PM60-804-1090 / 605ESE/15-30NaN4-8
8 PM80-1007-1090 / 401ESE/15-300.8-1.23.5-4.5
Sun Nov 02 - 2 AM80-1006-1090 / 400ESE/15-300.9-1.34-6
2 PM80-1004-1090 / 505SSE/15-30NaN6-10
8 PM80-1005-1075 / 251ESE/15-300.9-1.36-10
Mon Nov 03 - 2 AM80-1005-975 / 250.5SE/15-300.8-1.26-10
2 PM70-904-875 / 155SSE/15-30NaN6-10
Tue Nov 04 - 2 AM60-806-1040 / 51SSE/5-150.7-1.14-8
2 PM50-708-1010 / 07.5SE/5-15NaN3-6
Wed Nov 05 - 2 AM50-708-100 / 02.5E/5-150.5-0.83-5
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
Fri Oct 31 - Sat Nov 01 17:57 19:03 5:09 6:14 N/A 1:26 64 21 44.0 -9 15
Sat Nov 01 - Sun Nov 02 17:57 19:02 5:09 6:15 N/A 2:25 75 22 39.4 -5 00
Sun Nov 02 - Mon Nov 03 17:56 19:02 5:09 6:15 N/A 3:25 84 23 34.5 -0 26
Mon Nov 03 - Tue Nov 04 17:56 19:01 5:10 6:16 N/A 4:24 92 0 29.7 4 09
Tue Nov 04 - Wed Nov 05 17:55 19:01 5:10 6:16 N/A 5:24 97 1 25.3 8 29
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Friday 31 October (0300 UTC Saturday 1 November) 2014.
Additional Information
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