Current Conditions
Temp-0.5 C
RH98 %
WindE 8 mph
Mauna Kea Observatories Forecast
5 PM HST Friday 23 February (0300 UTC Saturday 24 February) 2018
Fog, ice, high humidity, and flurries
Chance for convection and heavy snow
Cloud Cover and Fog/Precipitation Forecast
Fog, ice, high humidity, clouds and flurries are expected to plague the summit through the night. There is a possibility for convection in the area and periods of heavy snow throughout the night.
Summary of Key Meteorological Variables
Summit temperatures will be near -2 C this evening and -2.5 C tomorrow morning. Winds will be from the south at 10-20 mph for today, switching to a more NNW direction for the night. Seeing and precipitable water are expected to exceed 1 arcsecond and 4 mm, respectively, throughout the night.
The atmosphere near the Big Island will remain saturated and unstable through at least tomorrow evening, then will begin a very slow drying trend as the inversion gradually rebuilds near 9-10 thousand feet over the next several days. Still, it is very likely that extensive fog, high humidity, ice and flurries will continue to plague the summit through at least Monday night. There is also a chance for convection in the area and periods of heavy snow mainly over the next 36 hours and perhaps again around Sunday afternoon/evening. The inversion is expected to significantly restrengthen near 8 thousand feet on Tuesday, which should help diminish the risk for moisture at the summit for that night. Extensive daytime clouds are expected through Monday, but should begin to taper on Tuesday and especially Wednesday.

Broken to overcast thick clouds will continue to linger in the area through at least Sunday afternoon. These clouds will begin to slowly breakup later that evening, perhaps opening up skies a bit during the second half of Monday night. However, there is a chance that more widespread high clouds will build in from the NW through Tuesday, contributing to extensive cloud cover for that night.

Precipitable water is expected to exceed 4 mm through at least Monday night, but may slip toward 2-3 mm by the end of Tuesday night.

A mixture of moisture, instability and turbulence throughout various layers of the atmosphere (including the boundary layer) will contribute to bad seeing through the next 4 nights. Seeing may return toward more average-like values as the atmosphere dries and only modest turbulence/shear prevails in the free atmosphere for Tuesday night.

No change since the morning forecast...The strong low/trough to the WNW of the state will very gradually shift off toward the west over the next 48 hours then will begin to weaken, before being reinforced again further westward later next week. Nonetheless, this low/trough will continue to draw deep tropical moisture over the Big Island and promote widespread instability in the area for at least the next 24 hours. While there is chance that the air mass will begin to slowly stabilize as the low shifts westward, an abundant supply of moisture will linger in the area probably into early Tuesday morning. Consequently, there is very good chance that extensive fog/CC, high humidity, ice and flurries will continue to plague the summit through the next 4 nights. There is a high probability for deep convection in the area, which could deposit moderate/heavy stratiform snow at the summit through tomorrow afternoon/evening. There is also a chance that isolated convection could pop up along the slopes, which may result a brief period of moderate snow Sunday afternoon and perhaps again on Monday afternoon. The bulk of the moisture is expected to eventually slide westward as the trough begins to restrengthen around Tuesday. This should allow a well-defined inversion to rebuild near 8-9 thousand feet and significantly reduce the risk for moisture at the summit for that night. However, the sub-tropical jet may reform over or just south of the summit, which could advect broken high clouds through the area and promote modest turbulence in the free atmosphere for that 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)
Fri Feb 23 - 8 PM80-1004-10100 / 95-2WNW/10-201-210-15
Sat Feb 24 - 2 AM80-1004-10100 / 90-2.5NNW/10-201-210-15
2 PM80-1004-10100 / 95-1N/15-30NaN10-15
8 PM80-1004-1095 / 80-2NNW/15-301-28-12
Sun Feb 25 - 2 AM80-1004-1095 / 75-2NNW/15-300.9-1.78-12
2 PM80-1004-1095 / 750WNW/5-15NaN8-12
8 PM70-904.5-890 / 60-1.5NNW/5-150.8-1.66-10
Mon Feb 26 - 2 AM60-804.5-890 / 50-1.5NNW/5-150.8-1.46-10
2 PM80-1004-980 / 400NW/5-15NaN6-10
Tue Feb 27 - 2 AM20-404.5-775 / 25-2.5E/5-150.7-1.34-8
2 PM60-808-1040 / 101.5E/5-15NaN3-6
Wed Feb 28 - 2 AM70-908-1025 / 5-1.5E/5-150.5-0.82-4
2 PM0-208-1010 / 02E/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
Fri Feb 23 - Sat Feb 24 18:34 19:38 5:32 6:36 N/A 2:04 61 5 13.4 18 32
Sat Feb 24 - Sun Feb 25 18:34 19:39 5:31 6:35 N/A 3:05 72 6 14.3 19 48
Sun Feb 25 - Mon Feb 26 18:35 19:39 5:30 6:35 N/A 4:05 82 7 16.7 19 45
Mon Feb 26 - Tue Feb 27 18:35 19:39 5:30 6:34 N/A 5:02 90 8 19.3 18 21
Tue Feb 27 - Wed Feb 28 18:35 19:40 5:29 6:33 N/A 5:55 96 9 20.8 15 40
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 26 February 2018.
Additional Information
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