Current Conditions
Temp-5.5 C
RH88 %
WindS 26 mph
Mauna Kea Observatories Forecast
5 PM HST Friday 15 February (0300 UTC Saturday 16 February) 2019
Chance for fog/ice
Possibility for afternoon convection
Cloud Cover and Fog/Precipitation Forecast
There is a possibility for periods of fog, ice, high humidity and patches of clouds in the area mainly during the first half of the night; precipitation is unlikely.
Summary of Key Meteorological Variables
Summit temperatures will be near -5 C, with winds from the WSW at 5-15 mph for this evening, increasing to 10-20 mph for the morning hours. Seeing will be near 1 arcsecond, while precipitable water is expected to start out near 4 mm, but could slip toward 2 mm by the end of the night.
Although the air mass will continue to dry out over the next 12 hours, widespread instability in the area will keep the inversion rather indistinct/elevated probably well into next week. Nonetheless, this drying trend should help reduce the risk for fog, ice and especially flurries at the summit through tonight and for at least tomorrow night. However, an influx of deep moisture into the area will increase this risk once again as it begins to pass just east of the Big Island through Sunday night and probably shifts over the summit for the following 2 nights. This could bring a round of heavy snow and convection to the area mainly for Monday and Tuesday night. Extensive daytime clouds are expected for today, but may taper a bit over the weekend, only to turn pick up again for the early part of next week. There is also an outside chance for afternoon convection along the Big Island slopes throughout the forecast period.

There is a possibility for patches of low/mid-level clouds in the area, particularly along the northern skies, for tonight. Clear skies will likely prevail for tomorrow night, but patches of thick clouds may begin to pass along the eastern skies through Sunday night and is expected to build overhead, contributing to extensive cloud cover, if not overcast skies fo rthe follwoign 2 nights.

Precipitable water is expected to start out near 4 mm for this evening, but will slip toward 2 mm by sunrise tomorrow and probably toward 1 mm for Saturday and most of Sunday night (an upward trend is possible by sunrise Monday). There is a very good chance PW will increase to 4+ mm again for Monday and Tuesday night.

A mixture of boundary layer and free atmospheric turbulence, as well as instability, moisture and/or an elevated inversion will contribute to poor/bad seeing throughout most of the forecast period. There is a possibility for a brief period of more average-like seeing as winds remain somewhat light and the atmosphere dries mainly during the first half of the Saturday night.

Little change since the morning forecast...The tight low currently sitting overhead will continue to lift subtly northward, taking the bulk of its moisture (in the center) with it over the next 12 hours. While this will help to dry out the air mass, a very broad/strong large-scale upper-level trough will remain quasi-stationary/steady over/near the state and provide very steady widespread instability in the area, prohibiting the inversion from strengthening probably well into the middle if not later part of next week. Nevertheless, the departure the moisture will help reduce the risk for fog, ice and especially flurries at the summit through tonight and especially tomorrow night (there is still an outside chance for afternoon convection along the Big Island slopes throughout the forecast period). However, winds are set to restrengthen again as the low begins to retrograde westward, placing its southern/SE flank over the Big Island as the weekend progresses. In addition, deep moisture flowing out of tropics along this SE flank (of the low) will begin to move over the summit area as the low slips further westward and perhaps digs southward late in the weekend and early part of next week. This will likely start to increase the risk for fog/ice and flurries at the summit as early as Sunday night could bring a very saturated air mass to the area for at least the following 2 nights. The latter may contribute to steady/heavy snow at the summit and perhaps convection in the area between late Monday afternoon and Wednesday night.

Please Note: There will be forecasts on Monday, February 18, in observance of Presidents' Day. The normal forecast schedule will resume on Tuesday, the 19th.
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 15 - 8 PM20-406-865 / 20-5W/5-150.8-1.43-5
Sat Feb 16 - 2 AM0-206-730 / 10-5WSW/10-200.7-1.12-4
2 PM50-704-540 / 151WSW/10-20NaN2-4
8 PM0-10Clear25 / 10-3WSW/10-200.5-0.91.5-2
Sun Feb 17 - 2 AM0-10Clear25 / 10-4WSW/15-300.7-1.11-1.5
2 PM40-604-540 / 201SW/20-35NaN1-1
8 PM0-207-850 / 15-4SSW/30-450.8-1.60.8-1.2
Mon Feb 18 - 2 AM20-406-860 / 20-5SSW/30-451-21-2
2 PM60-804-775 / 40-1SSW/30-45NaN4-8
Tue Feb 19 - 2 AM60-804-890 / 60-6SSW/35-501-26-10
2 PM80-1004-1095 / 750SSW/35-50NaN10-15
Wed Feb 20 - 2 AM80-1004-1095 / 75-5WSW/35-501-210-15
2 PM80-1004-1090 / 652WNW/25-40NaN8-12
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 16 - Sun Feb 17 18:31 19:36 5:36 6:41 N/A 5:21 92 7 53.2 20 50
Sun Feb 17 - Mon Feb 18 18:31 19:36 5:35 6:40 16:32 6:18 98 8 57.8 18 34
Mon Feb 18 - Tue Feb 19 18:32 19:37 5:35 6:39 17:39 7:12 100 10 00.9 14 56
Tue Feb 19 - Wed Feb 20 18:32 19:37 5:34 6:39 18:45 N/A 99 11 01.6 10 15
Wed Feb 20 - Thu Feb 21 18:33 19:37 5:33 6:38 19:49 N/A 95 11 59.6 4 57
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 18 February 2019.
Additional Information
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