Current Conditions
Temp-0.2 C
RH71 %
WindW 16 mph
RoadClosed
Mauna Kea Observatories Forecast
5 PM HST Friday 16 February (0300 UTC Saturday 17 February) 2018
Warning(s)
Fog, ice and high humidity
Chance for isolated convection and flurries
Moderate (tapering) winds
Cloud Cover and Fog/Precipitation Forecast
More periods of extensive fog, ice and high humidity are expected to return to the summit, particularly as the night progresses; there is a possibility for light flurries and convection along the eastern skies mainly toward the end of the night. Isolated/thick clouds are set to develop along the eastern skies and shift back westward through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near -2 C this evening and -3 C tomorrow morning. Winds will be from the WSW at 20-35 mph for today, switching to SW direction and easing to 10-20 mph through the night. Seeing and precipitable water are expected to exceed 1 arcsecond and 4 mm, respectively throughout the night.
Discussion
The atmosphere near the Big Island is expected to grow increasingly unstable beginning late this afternoon, which will eventually help erode the inversion and saturate the air mass as a copious supplly of moisture returns to the area and/or drifts in from the south over much of the weekend and into next week. Consequently, there is a very good chance that for extensive fog, high humidity and ice will plague the summit probably through the next 5 nights. Heavy snow and widespread convection are also possible mainly between late tomorrow afternoon and early Tuesday morning. Extensive daytime clouds are expected throughout the forecast period.

Isolated relatively thick clouds are set to develop along the eastern skies and shift westward over the next 12-24 hours. These clouds will become more widespread through tomorrow, and will blanket summit skies for that night and Sunday night. There is a chance that these clouds will begin to slowly break up late Monday evening, but extensive cloud cover will likely remain an issue well into the middle part of next week.

Precipitable water is expected to exceed 4 mm throughout the forecast period.

A mixture of moderate boundary layer turbulence, instability, moisture and/or mid/upper-level turbulence will contribute to poor/bad seeing throughout the forecast period.

While summit conditions have dried out a bit as the front shifted eastward and the low to the north lifted off toward the NNE early this morning, the residual moisture assocated with the latter will continue to return westward as a new short-wave trough (SWT) digs in from the NW over the next 6-12 hours. This SWT will begin to destabilize the air mass as early as this evening and eventually help spawn a new low just west of the state over the weekend. Nevertheless, the return of the residual moisture combined with building instability will erode the inversion once again, likely allowing more fog, high humidity and ice to plague the summit as the night progresses and probably for the remainder of the forecast period. Conditions are expected to grow progressively worse as deep tropical moisture fills in into the area and widespread convection begins to develop in the area once the low takes shape to the west between late tomorrow evening and most of Monday night. There is a very good chance for heavy snow at the summit during this period, and winds are set to pick up, which could result in blizzard-like conditions with large drifting particularly between Sunday afternoon and Tuesday morning. This new low is expected to lift off toward the NW and/or briefly weaken around Tuesday. While this may help stabilize the air mass as the mid-level ridge tries to build to the east, an abundant supply of moisture in the area, may keep the inversion from rebuilding and allow inoperable conditions to persist into the middle part of next week...perhaps longer.
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 16 - 8 PM40-604.5-695 / 40-2SW/20-350.7-1.36-10
Sat Feb 17 - 2 AM50-704-795 / 60-3SW/15-300.8-1.46-10
2 PM80-1004-9100 / 75-2SSW/10-20NaN8-12
8 PM80-1004-9100 / 85-4WSW/10-201-28-12
Sun Feb 18 - 2 AM80-1004-10100 / 95-4.5SSE/10-201-28-12
2 PM80-1004-10100 / 95-3SSW/20-35NaN8-12
8 PM80-1004-10100 / 95-4SSW/35-501-28-12
Mon Feb 19 - 2 AM80-1004-10100 / 95-5SSW/35-501-28-12
2 PM80-1004-1095 / 90-3SSW/35-50NaN8-12
Tue Feb 20 - 2 AM70-904-1095 / 90-5SSW/40-601-26-10
2 PM80-1004-995 / 85-1SW/35-50NaN6-10
Wed Feb 21 - 2 AM60-804-790 / 75-4WSW/35-500.8-1.84-8
2 PM70-904-890 / 751WSW/20-35NaN6-10
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 17 - Sun Feb 18 18:31 19:36 5:35 6:40 N/A 20:26 6 23 59.7 -4 04
Sun Feb 18 - Mon Feb 19 18:32 19:37 5:35 6:39 N/A 21:18 12 0 47.6 0 16
Mon Feb 19 - Tue Feb 20 18:32 19:37 5:34 6:39 N/A 22:12 20 1 36.5 4 41
Tue Feb 20 - Wed Feb 21 18:33 19:37 5:33 6:38 N/A 23:07 29 2 27.0 8 56
Wed Feb 21 - Thu Feb 22 18:33 19:38 5:33 6:37 N/A 0:04 39 3 19.7 12 50
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 19 February 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