Current Conditions
Temp0.3 C
RH100 %
WindN 3 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
10 AM HST (2000 UTC) Tuesday 27 October 2020
Warning(s)
Fog, ice and flurries
Chance for convection and heavy snow
Cloud Cover and Fog/Precipitation Forecast
Fog, ice, thick clouds, high humidity and likely periods of flurries will continue to plague the summit through the night; there is also a possibility for convection in the area and short-periods of heavy snow.
Summary of Key Meteorological Variables
Summit temperatures will be near 2 C this afternoon and -2 C for the night. Winds will be from the south at 20-35 mph for today, switching to a more WSW direction through the night. Seeing and precipitable water are expected to exceed 1 arcsecond and 4 mm through the night.
Discussion
The atmosphere near the Big Island will remain quite saturated and unstable, allowing extensive fog, ice and flurries to plague the summit through the night. There is also a possibility for convection in the area and periods of heavy/wet snow at the summit during this time. While there is a good chance that the upper air mass will dry out through tomorrow, persistent instability and residual low-level moisture will prohibit the inversion from restrengthening until late Saturday night. As a result, there is strong possibility that periods of fog, ice and high humidity will remain an issue into the weekend; nighttime precipitation will subside during this time. Extensive daytime clouds and perhaps afternoon convection are expected through at least Friday, but could taper over the weekend.Thick broken to overcast clouds will continue to blanket summit skies for tonight, but is expected to shift just east of the Big Island by tomorrow evening. However, a narrow band of high clouds may continue to linger overhead through Thursday night, shift just south of the Big Island for Friday night, then slip back in overhead for Saturday night. There is also a possibility for summit-level clouds and an outside chance for lenticular clouds east of the Big Island summits mainly through Friday night Precipitable water is expected to exceed 4 mm probably through Friday evening, but could slip toward 2 mm by sunrise Saturday and especially that night.

A mixture of deep moisture, instability, and turbulence through much of the atmosphere will contribute to poor/bad seeing throughout the forecast period.

A strong/tight low to the NNW will continue will develop and dig southward over the next 24 hours, then will remain quasi-stationary ~500 km to the north of the state before taking off toward the NE on Friday, leaving a residual trough in its wake over the weekend. Unfortunately, as the low digs southward it will send a band of deep moisture through the area, which will saturate the entire air mass, allowing extensive fog, ice, clouds and flurries to plague the summit through late tomorrow morning. There is also a possibility for widespread convection in the area, which could deposit heavy/wet snow at the summit during this period. The bulk of the upper-level moisture is set to slide off toward the SE by tomorrow evening, but instability along the south side of the low will persist in the area while a low-level frontal band-like feature settles in overhead, prohibiting the inversion from restrengthening until the low takes off over the weekend. This will likely allow for more periods of fog and ice at the summit into Friday night, and there is a possibility for the development of isolated convection the area at practically anytime. Strong westerly winds along the southern flank of the low is also expected become an issue particularly for Thursday and Friday night. Winds are set to subside, while the odds on moisture at the summit subsides as the low shifts further eastward particularly after 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 (%) (Celcius) (Dir/MPH) (Arcseconds) (mm)
Tue Oct 27 - 2 PM80-1004-10100 / 902S/20-35NaN10-15
8 PM80-1004-10100 / 95-2SW/20-351-210-15
Wed Oct 28 - 2 AM80-1004-10100 / 95-2WSW/20-351-210-15
2 PM80-1004-1095 / 903WSW/20-35NaN10-15
8 PM60-806-1095 / 75-1WSW/25-400.8-1.68-12
Thu Oct 29 - 2 AM40-607-1090 / 40-1.5WSW/30-451-24-8
2 PM70-904-1095 / 653WSW/30-45NaN4-8
8 PM40-608-1090 / 40-1WSW/35-501-24-8
Fri Oct 30 - 2 AM40-609-1075 / 301.5WSW/35-501-24-8
2 PM60-804-890 / 653WSW/35-50NaN4-8
Sat Oct 31 - 2 AM20-409-1075 / 40-1WSW/30-451-22-4
2 PM60-804-675 / 303WSW/30-45NaN4-8
Sun Nov 01 - 2 AM40-608-1040 / 10-0.5W/20-350.7-1.32-4
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
Tue Oct 27 - Wed Oct 28 17:59 19:04 5:07 6:13 N/A 4:14 91 0 08.7 -4 45
Wed Oct 28 - Thu Oct 29 17:58 19:04 5:08 6:13 16:23 5:02 95 0 52.5 0 16
Thu Oct 29 - Fri Oct 30 17:58 19:03 5:08 6:13 16:56 5:50 99 1 36.2 5 16
Fri Oct 30 - Sat Oct 31 17:57 19:03 5:08 6:14 17:29 6:39 100 2 20.6 10 03
Sat Oct 31 - Sun Nov 01 17:57 19:02 5:09 6:14 18:04 7:29 99 3 06.5 14 29
Forecast Issued by: Ryan Lyman
Next update at 5 PM HST Tuesday 27 October (0300 UTC Wednesday 28 October) 2020.
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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