Current Conditions
Temp4.4 C
RH26 %
WindNE 3 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
10 AM HST (2000 UTC) Friday 24 November 2017
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will be mostly dry and stable throughout today and tonight, while scattered high clouds will continue to approach the summit skies from the SW and stream over, likely increasing as time goes by.
Summary of Key Meteorological Variables
Summit temperatures will be near -1.5 C this evening and -2.5 C tomorrow morning. Winds will be from the WSW at 5-10 mph, with seeing near 0.7-0.75 arcseconds. Precipitable water is expected to be in the 2 to 2.5 mm range for the night.
Discussion
The tradewind inversion will continue to cap the low-level moisture near 8-9 thousand feet and ensure the summit remains mostly dry and stable for at least another night. The inversion is likely to lift and weaken throughout Saturday and vanish complitely by early Sunday morning. The risk for fog, ice and high humidity will increase in time through the weekend and will be rather elevated from Sunday and through the rest of this forecast period.

Scattered high clouds will continue to approach the summit skies from the SW and stream over today. Cloud coverage is expected to increase as time goes by through the weekend and mostly cloudly skies are expected from Sunday through at least Monday, when a brief clearing trend might begin.

Precipitable water is expected to range between 2 and 2.5 mm tonight. It will reach the 4 mm threshold by Saturday afternoon/evening and will exceed it through the rest of this forecasting period.

Observing conditions will be less than average tonight, as cloud cover increases and so does turbulence in the free atmosphere, and will be unoperable from Saturday night and throughout the rest of this forecast period.

The current weather scenario is dominated by a ridge to the NW of the State and the associated high surface pressure, and a through to the East of the State slowly moving eastward, which is causing the Sub Tropical Jet (STJ) to linger just slightly South of the Big Island and slowly rebounding northward. As a result high clouds and mid level moisture are advected over the area from the SSW. This will cause the inversion to lift in time and instability to increase from Saturday and through the rest of this forecast period. Risks are therefore high for fog, ice and high humidity from early Sunday morning and onward. Precipitation is also possible. Observing conditions will be very poor and unoperable from the second part of this weekend and for most of this forecast period.
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 Nov 24 - 2 PM20-407-100 / 03NE/5-10NaN1-2
8 PM30-507-100 / 0-0.5SSE/5-100.55-0.851-2
Sat Nov 25 - 2 AM50-707-100 / 0-2.5WSW/5-100.6-0.92-2.5
2 PM50-706-100 / 02SSW/5-15NaN2-3
8 PM60-806-1040 / 5-1.5SSW/10-200.7-1.14-6
Sun Nov 26 - 2 AM80-1005-1080 / 30-2.5SSW/15-250.7-1.14-10
2 PM80-1004-1090 / 501WSW/20-35NaN8-14
8 PM80-1004-1095 / 60-1WSW/15-301.3-1.78-14
Mon Nov 27 - 2 AM80-1004-1095 / 80-2.5SW/15-301.3-1.78-14
2 PM70-904-1095 / 801S/10-20NaN10-16
Tue Nov 28 - 2 AM60-805-995 / 80-2NE/5-150.8-1.210-16
2 PM60-806-980 / 501NNW/5-15NaN10-16
Wed Nov 29 - 2 AM40-606-970 / 40-1.5NNE/5-150.8-1.26-10
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
Fri Nov 24 - Sat Nov 25 17:51 18:58 5:20 6:27 N/A 23:13 37 21 21.5 -15 31
Sat Nov 25 - Sun Nov 26 17:51 18:58 5:20 6:28 N/A 0:05 46 22 10.3 -12 30
Sun Nov 26 - Mon Nov 27 17:51 18:59 5:21 6:28 N/A 0:57 56 22 59.2 -8 51
Mon Nov 27 - Tue Nov 28 17:51 18:59 5:21 6:29 N/A 1:50 66 23 48.7 -4 40
Tue Nov 28 - Wed Nov 29 17:51 18:59 5:22 6:30 N/A 2:45 76 0 39.4 -0 07
Forecast Issued by: Tiziana Cherubini
Next update at 5 PM HST Friday 24 November (0300 UTC Saturday 25 November) 2017.
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
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