Current Conditions
Temp5.5 C
RH16 %
WindNNW 0 mph
Mauna Kea Observatories Forecast
5 PM HST Tuesday 12 November (0300 UTC Wednesday 13 November) 2019
Cloud Cover and Fog/Precipitation Forecast
The summit will remain clear, dry and stable throughout the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 3.5 C this evening and 3 C tomorrow morning. Winds will be from the NW at 5-15 mph, with seeing near 0.35-0.4 arcseconds. Precipitable water is expected to be in the 3-4 mm range for the night.
The tradewind inversion will continue to cap the fairly limited supply of low-level moisture primarily near 8 thousand feet and ensure the summit remains dry and stable through at least Thursday night. Building instability may begin to erode the inversion and enhance the low-level cloud flow through Friday, perhaps allowing the atmosphere to turn saturated for Saturday and Sunday. This will raise the stakes on fog, ice, high humidity and/or flurries at the summit for Friday and Saturday night. Daytime clouds will be minimal and short-lived through Thursday, but could begin to pick up on Friday and turn extensive over the weekend.

Skies overhead will remain predominately clear for the next 2 nights, but isolated to scattered high clouds may drift overhead for Thursday night. Thicker clouds may begin to fill in from the SE and/or develop overhead, contributing to extensive cloud cover, if not overcast skies for Friday and especially Saturday night.

Precipitable water is expected to linger in the 3-4 mm range for tonight, slip toward 2.5-3.5 mm for Wednesday night and probably 2 mm for Thursday night, then jump back to 4+ mm for the following 2 nights.

Calm stable skies will likely allow seeing to settle in near 0.4 arcseconds for the next 2 nights, and probably into early Thursday evening. However, building instability/moisture, free atmospheric turbulence and perhaps light boundary layer turbulence will begin to degrade seeing through the latter night and contribute to bad seeing for Friday and Saturday night.

No change since the morning forecast....A relatively flat mid-level ridge will continue to sit to the north of the state, while the westerly jet maintains a fairly zonal orientation well to the north for the next 2-3 days. As a result, this will allow large-scale subsidence to prevail in the area, which will help maintain a well-defined inversion near 7-8 thousand feet and ensure a dry/stable and calm air mass through Thursday night. Calm skies will likely keep seeing near 0.4 arcseconds during most of this time, through a slight increase in summit-level winds could contribute to some minor degradation during Thursday night. There is also a possibility that stray clouds will drift in from the tropics as an incoming westerly trough, diverts flow aloft to a more SW direction during that night. There is a fairly strong possibility that this trough will eventually deepen and dig toward the state, destabilizing the air mass beginning Friday morning. It will also veer low-level flow off toward the SE, allowing deeper low-level tropical moisture to fill into the area later that day. The building instability and moisture will likely begin to break down the inversion through that night, while upper-level divergence begins to fill into the area around Saturday morning. This combination will likely lead to a saturated/unstable air mass near the Big Island probably for the remainder of the weekend. As a result, this will significantly increase the risk for fog, high humidity, ice, thick widespread clouds and flurries at the summit for Friday and Saturay night. There is also a possibility for convection in the area particularly after midnight on Friday.
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)
Tue Nov 12 - 8 PM0-5Clear0 / 03.5NW/5-150.3-0.53-4
Wed Nov 13 - 2 AM0-5Clear0 / 03NNW/5-150.25-0.453-4
2 PM0-20Clear0 / 09NE/5-15NaN3-5
8 PM0-5Clear0 / 04NE/5-150.35-0.552.5-3.5
Thu Nov 14 - 2 AM0-5Clear0 / 03ENE/5-150.3-0.52.5-3.5
2 PM0-20Clear0 / 09S/5-15NaN2-4
8 PM0-208-90 / 04S/5-150.35-0.552-2.5
Fri Nov 15 - 2 AM0-208-90 / 03S/10-200.35-0.652-2.5
2 PM60-804-1065 / 307.5S/10-20NaN4-8
Sat Nov 16 - 2 AM80-1004-975 / 402S/10-200.7-1.38-12
2 PM80-1004-1095 / 754SW/10-20NaN8-12
Sun Nov 17 - 2 AM80-1004-1090 / 65-1WSW/10-201-28-12
2 PM80-1004-1095 / 702W/10-20NaN8-12
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
Tue Nov 12 - Wed Nov 13 17:52 18:59 5:13 6:20 18:05 7:41 99 3 57.6 17 06
Wed Nov 13 - Thu Nov 14 17:52 18:59 5:14 6:21 18:49 N/A 96 4 51.3 20 11
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
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Wednesday 13 November 2019.
Additional Information
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