Current Conditions
Temp1.9 C
RH14 %
WindSSW 8 mph
RoadOpen
Mauna Kea Observatories Forecast
5 PM HST Monday 30 March (0300 UTC Tuesday 31 March) 2015
Warning(s)
None
Cloud Cover and Fog/Precipitation Forecast
The summit will remain dry and stable, but there is a possibility for a thin band of high clouds passing through the area during the second half of the night.
Summary of Key Meteorological Variables
Summit temperatures will be near 1 C this evening and 0 C tomorrow morning. Winds will be light and from the south, with seeing around 0.55-0.6 arcseconds. Precipitable water is expected to be in the 0.8-1 mm range through most of the night (it may creep beyond 1 mm just before sunrise).
Discussion
The tradewind inversion will continue to cap low-level moisture at or below 8 thousand feet and ensure the summit remains dry and stable through at least Wednesday night. Moisture and instability are slated to gradually build into the area, which could help breakdown the inversion and increase the risk for fog, ice and perhaps light flurries at the summit for Thursday and especially Friday night. Daytime clouds will be minimal and short-lived through Wednesday, but could pick on Thursday and turn extensive for Friday and over the weekend.

Skies will start out predominately clear for this evening, but a narrow band of high clouds is slated to pass overhead between early tomorrow morning and late that afternoon. This should allow fore clear skies for most of tomorrow night, but broken to overcast high clouds are expected to fill in overhead beginning early Wednesday afternoon and may blanket summit skies for much of that night and especially Thursday night. There is a possibility that these clouds will thicken during the latter night, but may break up a bit for Friday night.

Precipitable water will linger near 0.8-1 mm for much of tonight, but could creep past 1 mm just before sunrise tomorrow and start out near 2 mm for that evening. Although it should slip back toward 1 mm by the end of Tuesday night, there is a very good chance it will increase to 1.5-2 mm for Wednesday night, 3-4 mm for Thursday night and probably 4+ mm for Friday night.

Despite relatively calm skies aloft, light low-level turbulence will likely contribute to slightly poorer than average seeing for tonight. There is a possibility that building upper-level turbulence and perhaps boundary layer turbulence will further degrade seeing as the week progresses.

Subtle changes have been made mainly to the wind forecast...The mid/low-level ridge will continue to sit over the state for the next few days, but will gradually weaken during this time and may fall apart all together as a trough/low develops to the north around Thursday/Friday. Nonetheless, strong/steady large scale subsidence will prevail in the area, which will help maintain a well-defined inversion near 8 thousand feet and ensure the summit remains dry and stable through at least Wednesday night. Unfortunately, the westerly jet is slated to bulge southward and drift over the summit area during the next 48 hours. This will not only increase turbulence in the free atmosphere, but bring broken to overcast high clouds to the area after Tuesday night. The decay of the ridge will also allow mid/low-level moisture and perhaps instability to build into the region beginning late Thursday afternoon. This may help weaken the inversion and increase the risk for fog, ice and light flurries at the summit for that night and especially Friday night. Upper-level instability will be fairly insignificant, which will help minimize the risk for heavy snow and/or widespread/organized convection during that time and over the weekend.
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)
Mon Mar 30 - 8 PM0-10Clear0 / 01SSE/0-100.5-0.70.8-1
Tue Mar 31 - 2 AM0-209-100 / 00SSW/0-100.55-0.650.8-1.2
2 PM20-409-100 / 04WSW/10-20NaN2-3
8 PM0-20Clear0 / 0-1W/5-150.6-0.81.5-2
Wed Apr 01 - 2 AM0-10Clear0 / 0-1W/5-150.55-0.751-1.5
2 PM20-409-100 / 04.5SW/5-15NaN1-2
8 PM60-808-100 / 0-0.5W/5-150.6-0.91.5-2
Thu Apr 02 - 2 AM80-1008-100 / 0-1W/5-150.6-0.91.5-2
2 PM80-1008-1020 / 53.5SW/5-15NaN2-4
Fri Apr 03 - 2 AM80-1007-1020 / 5-2W/5-150.6-13-4
2 PM80-1004-1040 / 202WSW/5-15NaN3-6
Sat Apr 04 - 2 AM60-804-850 / 20-2WSW/10-200.7-1.34-8
2 PM60-804-860 / 202NW/5-15NaN4-8
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
Mon Mar 30 - Tue Mar 31 18:44 19:49 5:03 6:08 N/A 4:05 85 9 45.7 9 12
Tue Mar 31 - Wed Apr 01 18:45 19:50 5:02 6:07 N/A 4:42 91 10 32.0 5 48
Wed Apr 01 - Thu Apr 02 18:45 19:50 5:01 6:06 N/A 5:19 96 11 17.9 2 09
Thu Apr 02 - Fri Apr 03 18:45 19:50 5:00 6:05 17:21 5:56 99 12 03.7 -1 37
Fri Apr 03 - Sat Apr 04 18:46 19:51 4:59 6:04 18:09 6:33 100 12 50.0 -5 22
Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Tuesday 31 March 2015.
Additional Information
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