Current Conditions
Temp-1.5 C
RH23 %
WindSSW 11 mph
RoadOpen (4x4)
Mauna Kea Observatories Forecast
5 PM HST Thursday 02 April (0300 UTC Friday 3 April) 2020
Chance for fog, ice and high humidity
Cloud Cover and Fog/Precipitation Forecast
There is a small risk for periods of fog, ice and high humidity throughout the night; precipitation is not expected. Banding high clouds are set to spread in from the south, contributing to extensive cloud cover as the night progresses.
Summary of Key Meteorological Variables
Summit temperatures will be near -2 C, with winds from the SW at 5-15 mph for this evening, switching to more southerly 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 night.
Although the inversion will remain weak/indistinct throughout the forecast period, moisture will be fairly hard to come by, which will minimize the risk for fog, ice and high humidity at the summit for tonight. However, that risk is expected to dramatically increase as deep moisture builds in from the south through tomorrow and into Saturday, likely allowing the air mass to turn quite saturated between Saturday evening and early Tuesday morning. This may also lead to convection in the area and flurries at the summit particularly during that period. Extensive daytime clouds are likely throughout the forecast period.

Banding high clouds are set to rapidly spread in from the south, contributing to extensive cloud cover as the night progresses and probably mostly overcast skies as thicker more widespread clouds develop in the area for the following 3 nights. There is a chance that these clouds will begin to shift off toward the east late Monday evening, opening up skies as that night progresses.

Precipitable water is expected to briefly slip into the 2-3 mm range for tonight, then jump to 4+ mm for the remainder of the forecast period.

There is a possibility that seeing will settle in more average-like values as free atmospheric turbulence strengthens for tonight. Increasing risk for moisture, an deteriorated inversion and persistent free atmospheric turbulence will contribute to poor/bad seeing for the remainder of the forecast period.

No change since the morning forecast...The mid-level ridge will remain rather weak and indistinct, while the low-level ridge shifts off to the east in response to a rather broad low developing to the 1000+ KM NNW over the next 24 hours. The low is set to remain quasi-stationary/steady, allowing widespread albiet weak instability to prevail in the area (with the absence of a prominent ridge) probably throughout the forecast period. While the inversion will remain weak/indistinct in response to this, mid/low-level moisture will be fairly hard to come by over the next 18-24 hours, which will help minimize the risk for fog, ice and high humidity at the summit for tonight. However, the sub-tropical jet is set to shift northward as its drawn toward the low, bringing lots of broken high clouds to the area as the night progresses. These clouds will likely contribute to extensive cloud cover for much of tonight and probably overcast skies for much of the weekend. Deeper moisture may eventually develop in the area and/or drift in from the south, which will begin to dramatically increase the risk for fog, ice and high humidity at the summit early tomorrow afternoon. The air mass will eventually turn saturated by early Saturday evening, further increasing this risk as well as the possibility for flurries at the summit and convection in the area through at least early Tuesday morning.
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)
Thu Apr 02 - 8 PM40-609-1025 / 0-2SW/5-150.5-0.82-3
Fri Apr 03 - 2 AM60-808-1025 / 0-2S/5-150.5-0.82-3
2 PM80-1004-1065 / 201WSW/10-20NaN4-8
8 PM80-1006-1075 / 25-2WSW/10-200.5-0.94-8
Sat Apr 04 - 2 AM80-1005-1075 / 30-2SW/10-100.6-14-8
2 PM80-1004-1090 / 650.5SW/5-15NaN6-10
8 PM80-1004-1090 / 75-1.5S/5-150.7-1.38-12
Sun Apr 05 - 2 AM80-1004-1095 / 90-2SSW/5-151-28-12
2 PM80-1004-1095 / 900SW/10-20NaN8-12
Mon Apr 06 - 2 AM80-1004-995 / 90-2WSW/10-201-28-12
2 PM80-1004-1095 / 900WSW/15-30NaN8-12
Tue Apr 07 - 2 AM40-604-790 / 60-2W/15-300.8-1.64-8
2 PM0-204-565 / 202W/20-35NaN3-6
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
Thu Apr 02 - Fri Apr 03 18:46 19:51 4:59 6:04 N/A 3:09 70 8 45.7 20 46
Fri Apr 03 - Sat Apr 04 18:46 19:51 4:58 6:03 N/A 3:59 80 9 44.7 17 21
Sat Apr 04 - Sun Apr 05 18:46 19:51 4:57 6:03 N/A 4:46 89 10 43.1 12 43
Sun Apr 05 - Mon Apr 06 18:46 19:52 4:56 6:02 N/A 5:32 95 11 40.7 7 09
Mon Apr 06 - Tue Apr 07 18:47 19:52 4:55 6:01 17:29 6:16 99 12 37.7 1 02
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Friday 3 April 2020.
Additional Information
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