Current Conditions
Temp6.1 C
RH10 %
WindS 14 mph
RoadClosed
Mauna Kea Observatories Forecast
5 PM HST Thursday 14 November (0300 UTC Friday 15 November) 2019
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while scattered high clouds spread in from the SW toward the end of the night.
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 SSE at 10-20 mph, with seeing near 0.5-0.6 arcseconds. Precipitable water is expected to be in the 2-2.5 mm range for the night.
Discussion
The tradewind inversion will continue to cap low-level moisture near 6-7 thousand feet and ensure the summit remains dry and stable through early tomorrow morning. An influx of moisture and instability are expected to erode the inversion over the following 24 hours, allowing the atmosphere to turn quite saturated between late Saturday morning and the early part of next week. This will significantly raise the stakes on extensive fog, ice, high humidity and flurries at the summit after tonight. There is also a possibility for convection in the area, which could deposit heavy snow at the summit at virtually anytime during this period, particularly between Saturday evening and Monday morning. Daytime clouds will pick up tomorrow and turn extensive over the weekend and early part of next week.

Skies will remain clear for most of tonight, but scattered high clouds may spread in from the SW toward the end of the night. Thicker more widespread clouds may build in from the SE and NW through Friday, then congregate and develop in the area, particularly along the eastern skies contributing to extensive cloud cover, if not overcast skies before shifting off to the east early Sunday night. Still, there is a very good chance that patches of mid-level clouds will linger in the area probably into Tuesday.

Precipitable water is expected to briefly slip into the 2-2.5 mm range for tonight, then will jump to 4+ mm for the remainder of the forecast period.

Skies will start out relatively calm, with light/deep SE flow at and above the summit, allowing for better than average seeing for most of tonight. Increasing turbulence/instability in the free atmosphere, combined with moisture filling into the area will degrade seeing through tomorrow night (actually as early as the second half of tonight) and probably contribute to bad seeing for the remainder of the forecast period.

No change since the morning forecast...Although the mid-level ridge will continue to shift off toward the east in response to a building trough to the NW, subsidence will still prevail in the area, which will help maintain the inversion near 6-7 thousand feet and ensure a dry/stable air mass for tonight. However, cold air advection associated with the incoming trough, combined with an influx of tropical moisture as low-level winds divert to a more SE direction will begin to dismantle the inversion late tomorrow morning. This will raise the stakes on fog, ice and flurries at the summit through that night. Upper-level divergence will eventually build in overhead as the trough deepens southward and closes in on the state, allowing the atmosphere to turn saturated and both dynamically and thermodynamically unstable, further increasing this risk just after sunrise on Saturday. It could also help fire off deep convection in the area, which may deposit heavy snow at the summit between that afternoon and early Monday morning. Actually the trough will lift off toward the north, but will leave a rather deep mid/upper-level low to meander to the north of the state through Sunday night and into the early part of next week. This low will continue to destabilize the air mass, despite shifting subtly east of the Big Island during the latter part, allowing instability to persit in the area perhaps into the middle part of next week. Consequently, there is a very good chance that the inversion will not restrengthen, which may contribute to more rounds of wet conditions at the summit for Monday and Tuesday 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)
Thu Nov 14 - 8 PM0-5Clear0 / 04.5SSE/10-200.4-0.62-2.5
Fri Nov 15 - 2 AM0-209.5-100 / 04SSE/10-200.5-0.72-2.5
2 PM70-904-1075 / 306SSW/10-20NaN4-8
8 PM60-804-1090 / 501S/10-200.6-18-12
Sat Nov 16 - 2 AM60-804-1090 / 600SSW/5-150.7-1.38-12
2 PM80-1004-10100 / 953SW/5-15NaN10-15
8 PM80-1004-10100 / 900WNW/5-150.8-1.610-15
Sun Nov 17 - 2 AM80-1004-10100 / 90-1WSW/5-151-28-12
2 PM80-1004-995 / 900W/15-25NaN10-15
Mon Nov 18 - 2 AM60-804-890 / 75-4WSW/10-201-26-10
2 PM70-904-890 / 75-2WNW/5-15NaN4-8
Tue Nov 19 - 2 AM40-604-675 / 40-4WNW/5-150.7-1.34-6
2 PM60-804-865 / 300W/5-15NaN4-8
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
Thu Nov 14 - Fri Nov 15 17:52 18:59 5:14 6:21 19:38 N/A 91 5 47.6 22 14
Fri Nov 15 - Sat Nov 16 17:52 18:59 5:15 6:22 20:31 N/A 84 6 45.8 23 03
Sat Nov 16 - Sun Nov 17 17:52 18:58 5:15 6:22 21:29 N/A 75 7 44.9 22 31
Sun Nov 17 - Mon Nov 18 17:51 18:58 5:16 6:23 22:29 N/A 65 8 43.5 20 38
Mon Nov 18 - Tue Nov 19 17:51 18:58 5:16 6:23 23:30 N/A 54 9 40.9 17 31
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 15 November 2019.
Additional Information
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