Current Conditions
Temp0.2 C
RH17 %
WindN 6 mph
RoadOpen (4x4)
Maunakea Observatories Forecast
5 PM HST Friday 01 July (0300 UTC Saturday 2 July) 2022
Moderate/strong winds
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for periods of fog and high humidity, mainly during the second half of the night; precipitation is not expected. Scattered to broken thin high clouds will continue to fill in from the west and dissipate in the area throughout the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 1 C this evening and 0.5 C tomorrow morning. Winds will be from the ENE at 30-45 mph, while seeing will exceed 1 arcsecond. Precipitable water is expected to be in the 2-3 mm range for the first half of the night and 2.5-3.5 mm range for the second half.
Although tradewind inversion will remain fairly well-defined at or below 12 thousand feet, patches of deep low-level moisture are set to pass through the area and combined with stiff easterly trades could allow for short-lived fog, ice and high humidity (precipitation is unlikely) at the summit over the next 2 nights. The inversion is set to recover, diminishing this risk through Sunday night and should allow for dry/stable conditions again by Monday and Tuesday night. Some afternoon clouds are possible for today and could turn extensive with the possibility of isolated convection along the Big Island slopes over the weekend, only to taper again for the early part of next week.

Scattered thin high clouds will continue to fill in from the west and dissipate in the area for tonight. Thicker mid/summit-level clouds may develop and/or drift in from the east for Saturday night, while more scattered to broken high clouds are expected to spread in from the south and may contribute to brief periods of extensive cloud cover for Sunday night and early Monday evening. These clouds will move off to the north during the latter night, leaving mostly clear skies for Tuesday night.

Precipitable water is expected to start out near 2 mm for this evening, but will increase toward 3+ mm as the night progresses and probably 4+ mm (and somewhat variable) for Saturday and Sunday night. There is a good chance that PW will slip to 1 mm for Monday night, then trend toward 2 mm for Tuesday night.

Boundary layer turbulence will contribute to bad seeing through Saturday night, perhaps even into Sunday evening. Instability and moisture may also negatively impact seeing for Saturday night. Improving conditions and diminishing summit-level winds should allow seeing to settle in back near 0.5-0.6 arcseconds as relatively light flow prevail in the free atmosphere for Sunday night. However, a subtle increase in mid-level flow could result in minor boundary/low-level turbulence, which could disrupt seeing for the early part of next week.

Little change since the morning forecast...The surface/mid-level ridge will continue to sit to the north of the state and promote steady/strong large-scale subsidence in the area, negating most of the instability associated with the tropical upper-tropospheric trough (TUTT) to the west well into next week. While this subsidence will help maintain an inversion at or below 10-11 thousand feet, patches of deep low-level clouds associated with an old tropical wave will continue to make a push through the area over the next few nights. These clouds, combined with increasing deep easterly trades and orographic lifting, may periodically punch through the inversion and allow for short-lived fog/high humidity at the summit for tonight. The easterly trades are also expected to stir up boundary layer turbulence and contribute to poor/bad seeing through at least Saturday night. The core of this tropical wave is expected to pass through the area, while an upper-level low embedded in the TUTT develops to the north over the weekend. This combination (of cold upper-level air/instability and tropical moisture) may help erode/lift the inversion and further increase the risk for extensive fog, high humidity, ice and/or light rain at the summit mainly for Saturday night. Afternoon convection may also develop along the Big Island slopes, particularly before the upper-level low departs westward early Sunday morning. There is a chance that conditions will improve and summit-level winds will taper as the both the low and the tropical wave shifts further westward and allows the mid/surface-level ridge to regain control of the air mass late Sunday night and especially for the early part of next week. However, summit-level humidity may remain on the high side until the tail end of the tropical moisture shifts around sunrise Monday. There is also a chance that mid-level flow will subtly pick up again as the ridge expands to the NNW of the state 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 (%) (Celsius) (Dir/MPH) (Arcseconds) (mm)
Fri Jul 01 - 8 PM40-609-1015 / 01ENE/30-450.9-1.72-3
Sat Jul 02 - 2 AM30-509-1025 / 00.5E/30-450.8-1.62.5-3.5
2 PM60-804-865 / 253E/25-40NaN4-8
8 PM20-406-850 / 10-2SE/20-350.7-1.33-5
Sun Jul 03 - 2 AM20-406-840 / 10-2.5SSE/20-350.7-1.33-5
2 PM50-704-860 / 154SSE/20-35NaN4-8
8 PM30-508-1030 / 50SE/10-200.475-0.7253-5
Mon Jul 04 - 2 AM50-708-1020 / 00SE/5-150.4-0.63-5
2 PM40-608-100 / 07E/5-15NaN2-4
Tue Jul 05 - 2 AM20-408.5-100 / 03E/10-200.525-0.7751-2
2 PM20-408-100 / 08.5ESE/10-20NaN2-3
Wed Jul 06 - 2 AM0-20Clear0 / 03ESE/10-200.525-0.7751.5-2.5
2 PM0-20Clear0 / 08SE/5-15NaN2-4
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
Sun Jul 03 - Mon Jul 04 19:15 20:29 4:24 5:38 N/A 22:54 24 10 54.0 11 31
Mon Jul 04 - Tue Jul 05 19:15 20:29 4:25 5:38 N/A 23:28 32 11 39.4 6 14
Tue Jul 05 - Wed Jul 06 19:15 20:28 4:25 5:38 N/A 0:03 42 12 24.9 0 32
Wed Jul 06 - Thu Jul 07 19:15 20:28 4:25 5:39 N/A 0:38 53 13 11.6 -5 23
Thu Jul 07 - Fri Jul 08 19:15 20:28 4:26 5:39 N/A 1:15 64 14 00.7 -11 17
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 5 July 2022.
Additional Information
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