Maunakea Observatories Forecast
5 PM HST Friday 08 May (0300 UTC Saturday 9 May) 2026
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Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for fog and high humidity, mainly toward the end of the night; precipitation is not expected. Broken high clouds will continue to fill out from the west and contribute to extensive cloud cover throughout the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 1.5 C this evening and 1 C tomorrow morning. Winds will be from the south at 5-15 mph for today, easing and switching to a more westerly direction through the night. Seeing will be near 0.6-0.7 arcseconds, while precipitable water is expected to be in the 2-3 mm range for the first half of the night and 3-4 mm range for the second half.
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Discussion
There is chance that the inversion briefly weaken/lift toward 12 thousand feet and increase the risk for short-lived fog/high humidity at the summit over the next 2 nights; precipitation is not expected The inversion is set to recover near 8 thousand feet by late Sunday morning, ensuring dry/stable conditions again for the remainder of the forecast period. Some afternoon clouds are possible for tomorrow, only to taper again for Sunday and early next week.
A steady stream of high clouds will continue to build in from the west contributing to mostly extensive cloud cover probably through the weekend. This stream will begin to breakdown and sag southward on Monday, opening up skies particularly to the north for that night and Tuesday night.
PW is expected to start out near 2 mm, but will increase toward 4 mm by the end of the night through into Saturday night. There is a good chance that PW will dip below 2 mm by Sunday evening and settle in near 1 mm for the early part of next week.
An increase in upper-level shear will likely contribute to slightly poorer than average seeing for Friday and Saturday night. Instability may also weaken the inversion, which could also have an negative impact on seeing during those nights. Seeing may improve again as more lighter more laminar flow begins to fill in overhead and the atmosphere stabilizes late in the weekend and for the early part of next week.
No change since the morning forecast...The mid/surface ridge will continue to sit over the state and promote steady large-scale subsidence in the area into next week. However, a short-wave trough embedded in a rather shallow/flat tropical upper-tropospheric trough (TUTT) extending from the west coast toward the state and out to Guam is expected to pass to the far north over the next 48 hours. In the process, it will inject colder upper-level air into the area, destabilizing the air mass between tomorrow afternoon and sunrise Sunday. This may help weaken/lift the inversion, which could allow for short-lived fog/high humidity at the summit over the next 2 nights. The risk is relatively small, mainly due to the lack of low-level forcing, particularly during the nighttime hours. In addition to the instability, the southern portion of the TUTT, aka the sub-tropical jet (STJ) is set to settle in overhead increasing (upper-level) free atmospheric turbulence/shear and contribute to more average/poor seeing through much of the weekend. The STJ will also bring more widespread high clouds to the area, likely resulting in periods of extensive cloud cover through sunrise Sunday. Seeing and skies are set to improve and clear up as the STJ sags subtly southward late Monday night. The eastward progression of the SWT will allow the ridge to regain control of the air mass in the area by Sunday afternoon. This will rebuild a fairly distinct inversion near 8 thousand feet and ensure dry/stable summit conditions for the remainder of the forecast period.
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5 Day Forecast Summary (Graphical Trend)
| HST |
Cloud |
Fog/Precip |
Temp |
Wind |
Seeing |
PW |
| Cover (%) |
Height (km) |
Probability (%) |
(Celsius) |
(Dir/MPH) |
(Arcseconds) |
(mm) |
| Fri May 08 - 8 PM | 60-80 | 8-10 | 10 / 0 | 1.5 | S/5-15 | 0.525-0.775 | 2-3 |
| Sat May 09 - 2 AM | 60-80 | 8-10 | 15 / 0 | 1 | WSW/0-10 | 0.525-0.775 | 3-4 |
| 2 PM | 60-80 | 7.5-10 | 30 / 0 | 5 | NW/0-10 | NaN | 4-8 |
| 8 PM | 50-70 | 7.5-10 | 20 / 0 | 0.5 | N/0-10 | 0.525-0.775 | 3.5-4.5 |
| Sun May 10 - 2 AM | 60-80 | 7.5-10 | 10 / 0 | 0.5 | NW/0-10 | 0.475-0.725 | 3-4 |
| 2 PM | 80-100 | 7-10 | 0 / 0 | 6 | NE/0-10 | NaN | 2-3 |
| 8 PM | 80-100 | 7.5-10 | 0 / 0 | 1.5 | NE/5-15 | 0.425-0.675 | 1-2 |
| Mon May 11 - 2 AM | 60-80 | 8-10 | 0 / 0 | 1.5 | NE/5-15 | 0.4-0.6 | 0.7-1.1 |
| 2 PM | 40-60 | 8-9 | 0 / 0 | 7 | ENE/10-20 | NaN | 0.8-1.2 |
| Tue May 12 - 2 AM | 20-40 | 9-10 | 0 / 0 | 2 | E/5-15 | 0.375-0.625 | 0.7-1.1 |
| 2 PM | 10-30 | 9-10 | 0 / 0 | 7.5 | E/10-20 | NaN | 1-2 |
| Wed May 13 - 2 AM | 10-30 | 9-10 | 0 / 0 | 2 | ESE/5-15 | 0.4-0.7 | 0.8-1.2 |
| 2 PM | 20-40 | 8-10 | 0 / 0 | 7.5 | E/5-15 | NaN | 1-3 |
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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 May 09 - Sun May 10 |
18:58 |
20:08 |
4:29 |
5:39 |
1:16 |
N/A |
44 |
21 57.5 |
-13 56 |
| Sun May 10 - Mon May 11 |
18:58 |
20:08 |
4:28 |
5:38 |
1:52 |
N/A |
34 |
22 44.4 |
-8 18 |
| Mon May 11 - Tue May 12 |
18:59 |
20:09 |
4:28 |
5:38 |
2:28 |
N/A |
24 |
23 31.3 |
-2 11 |
| Tue May 12 - Wed May 13 |
18:59 |
20:09 |
4:27 |
5:37 |
3:04 |
N/A |
16 |
0 19.5 |
4 13 |
| Wed May 13 - Thu May 14 |
18:59 |
20:10 |
4:26 |
5:37 |
3:43 |
N/A |
8 |
1 10.2 |
10 34 |
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Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 11 May 2026.
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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.
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