Current Conditions
Temp-0.4 C
RH73 %
WindSW 19 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
5 PM HST Tuesday 17 May (0300 UTC Wednesday 18 May) 2022
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, while scattered high clouds build along the western skies through the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 0 C this evening and -1 C tomorrow morning. Winds will be from the SSW at 15-30 mph, with seeing near 0.8-0.9 arcseconds. Precipitable water is expected to start out near 2 mm, but will increase toward 4 mm by the end of the night.
The tradewind inversion will continue to cap the fairly limited supply of low-level moisture near 7 thousand feet and ensure a dry/stable summit-level air mass for tonight. Widespread mid-level moisture and weak instability are set to build into the area, weakening the inversion and increasing the risk for fog, ice and light flurries/rain at the summit over the next 4 nights (particularly Thursday). Daytime clouds will likely turn extensive through Saturday, only to taper again on Sunday.

Scattered high clouds will begin to build along the western skies for tonight, with thicker more widespread following suit and shifting further eastward after sunrise tomorrow. The latter set will likely blanket skies for at least Wednesday and Thursday night. There is a good chance that these clouds will begin to disperse through Friday, which will help open up skies for that night and especially Saturday night.

Precipitable water is expected to start out near 2 mm for this evening, but will increase toward 4 mm as the night progresses and jump to 8-10 mm for the following 3 nights. There is a chance that it will trend back toward 2 mm by the end of Saturday night.

An increase in boundary layer turbulence and/or deep moisture will contribute to poor/bad seeing probably throughout the forecast period.

No change since the morning forecast...The surface ridge to the NE is expected to strengthen/deepen over the next few days and will continue to promote subsidence in the area probably throughout the week. Unfortunately, this subsidence will help maintain a well-defined inversion near 7-8 thousand feet and ensure a dry/stable summit-level air mass for another 12-18 hours or so. A late season low developing to the NNW is expected to send a frontal band toward the state later tonight. The bulk of the instability/energy associated with the band will remain off to the north, but there is a good chance that widespread mid-level moisture will spread over the Big Island by tomorrow evening, contributing to extensive cloud cover and a dramatic increase in PW around that time. A portion of the inversion may remain intact, but the air mass between 12-20 thousand feet will become fairly saturated, allowing fog, ice and/or flurries at the summit mainly between late Wednesday evening and early Saturday morning. While there is a chance that this moisture will detrain into the area through Saturday, then rapidly push off toward the SW around sunrise Sunday, fog and high humidity cannot be ruled out for Saturday 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 (%) (Celsius) (Dir/MPH) (Arcseconds) (mm)
Tue May 17 - 8 PM20-409-100 / 00SSW/15-300.6-12-3
Wed May 18 - 2 AM30-509-100 / 0-1SSW/15-300.7-1.13-4
2 PM50-704-1040 / 104SSW/15-30NaN4-8
8 PM70-906-1075 / 30-1.5S/15-300.7-1.16-10
Thu May 19 - 2 AM80-1005-1090 / 60-1.5S/20-350.7-1.38-12
2 PM80-1004-10100 / 954WNW/15-30NaN10-15
8 PM80-1004-10100 / 95-1WNW/15-300.8-1.610-15
Fri May 20 - 2 AM80-1004-10100 / 90-1.5WNW/10-200.8-1.610-15
2 PM70-904-995 / 654.5N/5-15NaN10-15
Sat May 21 - 2 AM50-704.5-890 / 500ENE/10-200.6-18-12
2 PM60-804-775 / 304.5ENE/10-20NaN4-8
Sun May 22 - 2 AM20-404.5-660 / 10-0.5NE/15-300.7-1.12-4
2 PM0-20Clear10 / 06.5ENE/20-35NaN2-3
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 May 17 - Wed May 18 19:01 20:12 4:24 5:35 20:56 N/A 92 17 57.0 -27 12
Wed May 18 - Thu May 19 19:01 20:13 4:24 5:35 22:02 N/A 85 19 04.4 -27 24
Thu May 19 - Fri May 20 19:02 20:13 4:23 5:35 23:03 N/A 75 20 09.7 -25 40
Fri May 20 - Sat May 21 19:02 20:14 4:23 5:35 23:57 N/A 64 21 10.7 -22 21
Sat May 21 - Sun May 22 19:03 20:14 4:23 5:34 0:44 N/A 53 22 06.9 -17 51
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Wednesday 18 May 2022.
Additional Information
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This message is also available at the MKWC road conditions page.
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