Current Conditions
Temp1.7 C
RH66 %
WindWSW 0 mph
Mauna Kea Observatories Forecast
5 PM HST Friday 16 March (0300 UTC Saturday 17 March) 2018
Chances for episodes of fog
Cloud Cover and Fog/Precipitation Forecast
Lingering moisture at the summit might still result in episodes of fog particularly this evening.
Precipitation is unlikely.
Summary of Key Meteorological Variables
Summit temperatures will be near 1.5 C this evening and 0.5 C tonight. Winds will be from the NNW at 5-15 mph. Precipitable water is expected to still exceed 4 mm, while there is a chance that, moisture permitting, seeing will range between 0.55 and 0.7 arcsec.
The airmasses are still very moist and dew point is high, in spite of some stability showing up in the soundings. Therefore fog might still be an issue particularly during the afternoon and the evening hours, and possibly through the first half of tonight and tomorrow. The airmasses are supposed to somewhat stabilize from now and through Sunday, with weak inversion showing in the predicted soundings, although the mid-low level moisture will be slow to dry. As a result moisture could pop up at times at the summit throughout the forecast period. More instability is expected from late Monday and onward and the atmosphere will start to fully saturate then. Daytime clouds will be very likely throughout the forecast period.

The bulk of high clouds have cleared from the summit skies. Still daytime clouds might linger at the summit through afternoons and evenings. A streak of thin high clouds is expected to cross the summit sky on Saturday night, while more organized high clouds will start being visible first on the northern horizon on Sunday, then on the southwestern horizon on Monday. They will approch the Big island and are likely to close up entirely the summit sky by late Monday into Tuesday.

Precipitable water will continue to exceed 4 mm throughout the forecast period, but will show a decreasing trend through at least Saturday possibly Sunday, before starting an increasing trend again.

Observing conditions at the summit remain less than optimal as moisture in the air masses continue to linger. There is a chance that seeing will be in the average to less than average range tonight through Saturday night provided moisture settle some below summit level. As shear aloft picks up and so does surface wind, observing conditions will degrade again from Monday and onward.

Not much is changed since the morning forecast ... As the low pressure system responsible for the just past adverse weather passes to the North of the State, a mid-level ridge is slowly filling in from the West. Therefore warmer and more stable airmasses will move over the summit area today. Nevertheless the moisture will be slow to dry out and episodes of fog could still be possible throughout the forecast period, more so during the afternoon and evening hours. Winds at the summit will remain weak through Saturday but are expected to pick up on Sunday and increase afterward as gradients tighten at the surface. A new bout of adverse weather is expected to invest the islands' chain at the beginning of next week, from late Monday through Tuesady and onward as a frontal system will approach the area from the NW and will advect over clouds and more moisture, destabilizing again the airmasses. Temperatures will also be on the decreasing trend then.
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 Mar 16 - 8 PM30-504-570 / 101.5WNW/5-150.41-0.7110-14
Sat Mar 17 - 2 AM10-304-4.530 / 00.5NNW/5-150.45-0.758-12
2 PM60-804-580 / 203.5NW/5-15NaN8-12
8 PM20-404-4.530 / 00.5NW/5-150.4-0.86-10
Sun Mar 18 - 2 AM10-304-4.520 / 00W/10-200.35-0.756-10
2 PM60-804-670 / 203WNW/10-20NaN6-10
8 PM40-605-750 / 00.5WNW/15-250.5-0.96-10
Mon Mar 19 - 2 AM30-505-740 / 0-0.5WNW/15-250.6-16-10
2 PM60-804-780 / 201W/10-20NaN8-12
Tue Mar 20 - 2 AM50-705-790 / 50-2W/15-250.7-1.110-14
2 PM60-804-795 / 800WNW/20-30NaN10-14
Wed Mar 21 - 2 AM80-1004-895 / 80-1.5WNW/15-250.9-1.510-14
2 PM80-1004-895 / 800WSW/15-25NaN12-16
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 Mar 16 - Sat Mar 17 18:41 19:45 5:15 6:20 6:39 18:19 0 23 47.2 -5 15
Sat Mar 17 - Sun Mar 18 18:41 19:45 5:14 6:19 N/A 19:12 1 0 35.6 -0 53
Sun Mar 18 - Mon Mar 19 18:41 19:46 5:14 6:18 N/A 20:06 4 1 24.9 3 37
Mon Mar 19 - Tue Mar 20 18:42 19:46 5:13 6:17 N/A 21:02 9 2 15.5 8 00
Tue Mar 20 - Wed Mar 21 18:42 19:46 5:12 6:16 N/A 21:59 16 3 07.9 12 03
Forecast Issued by: Tiziana Cherubini
Next update at 10 AM HST (2000 UTC) Monday 19 March 2018.
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