Mauna Kea Weather Center Forecast

Maunakea Observatories Forecast
5 PM HST Friday 03 February (0300 UTC Saturday 4 February) 2023

Warning(s)
Chance for fog/ice and high humidity
Increasing risk for flurries through the weekend

Cloud Cover and Fog/Precipitation Forecast
There is a moderate (increasing) risk for periods of fog, ice and high humidity, especially toward the end of the night; flurries are also possible mainly near sunset. Broken to overcast thick clouds will continue to spread in from the west, blanketing much of the sky for the night.

Summary of Key Meteorological Variables
Summit temperatures will be near -2.5 C this evening and -3.5 C tomorrow morning. Winds will be from the ESE at 10-20 mph, while seeing will be near 0.9-1 arcsecond for the night. Precipitable water is expected to exceed 4 mm through the night.

Discussion
An influx of instability is expected to deepen the surrounding low-level cloud field, allowing the air mass up to at least 18 thousand feet to become somewhat saturated as the night progresses and especially over the following 2 nights. This will increase the risk for fog, ice, high humidity and flurries over at least the next 3 nights. There is also an outside chance for convection in the area (mainly along the eastern skies) between sunrise Saturday and late Sunday evening. The air mass will begin to dry out on Monday, but the inversion will be slow to rebuild, which may allow for more periods of fog, ice and high humidity through Tuesday night. Extensive daytime clouds are expected through Tuesday, but could taper for Wednesday.

Broken to overcast thick clouds will continue to spread in from the west, blanketing the sky probably through Sunday evening. There is a good chance that these clouds will begin to break up and shift off toward the east thereafter, opening up skies by early Monday morning. There is still a possibility for residual low-level clouds in the area for Monday night; clear skies will prevail for Tuesday night.

Precipitable water is expected to linger near or exceed 4 mm probably through Monday night, but could slip toward 2 mm (or less) as Tuesday night progresses.

A mixture of moisture, instability, strong free atmospheric turbulence and/or bouts of boundary layer turbulence will contribute to poor/bad seeing over the next 5 nights.

Little change since the morning forecast...The remnant upper-low to the west is set to be swept up by a short-wave trough digging in from the NW and will begin to make a push through the area over the next 12-18 hours. Fresh instability provided by the short-wave trough (SWT), combined with residual deeper patches of moisture embedded in the low will likely help dismantle the already indistinct inversion and probably saturate most of the air mass near the Big Island between this evening and late Sunday night. There is still a possibility for some drier pockets of air in the area as widespread deep moisture is not expected to surround the state, which will help limit the risk for heavy snow at the summit. However, there is a good chance for another round extensive fog, ice, high humidity and periodic flurries at the summit between between late this night and late Sunday night. There is also an outside chance that convection will develop along the eastern Big Island slopes as the trades begin to develop, deep moisture persists in the area and dynamic instability associated with the SWT passes through around Sunday. This SWT will eventually depart eastward and allow a rather deep low-level ridge to continue to fill in from the west early next week. While this may allow for large-scale subsidence to return to the area around Tuesday, residual moisture will likely get caught up in the rather deep/strong low-level trades and may prevent the inversion and could contribute to more poor conditions for Monday night and perhaps into early Tuesday evening.

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
HST	Cover (%)	Height (km)	Probability (%)	(Celsius)	(Dir/MPH)	(Arcseconds)	(mm)
Fri Feb 03 - 8 PM	80-100	6.5-9	40 / 10	-2.5	ESE/10-20	0.7-1.1	4-6
Sat Feb 04 - 2 AM	80-100	6.5-9	60 / 20	-3.5	ESE/10-20	0.7-1.3	4-6
2 PM	80-100	4-9	90 / 60	-1.5	ESE/15-30	NaN	4-8
8 PM	80-100	4-9	90 / 30	-5	S/10-20	1-1.4	6-10
Sun Feb 05 - 2 AM	80-100	4-8	90 / 40	-5	SSW/10-20	1-2	6-10
2 PM	80-100	4-9	95 / 90	-1.5	WNW/5-15	NaN	8-12
8 PM	80-100	4-8	95 / 90	-4	N/5-15	1-2	6-10
Mon Feb 06 - 2 AM	60-80	4-7	90 / 65	-4.5	ESE/10-20	0.8-1.6	6-10
2 PM	80-100	4-8	95 / 65	0	NE/10-20	NaN	4-8
Tue Feb 07 - 2 AM	20-40	4-5	75 / 25	-3	ENE/15-30	0.7-1.3	3-5
2 PM	60-80	4-6	75 / 25	1	ENE/15-30	NaN	4-8
Wed Feb 08 - 2 AM	0-20	Clear	40 / 10	-1.5	ENE/15-30	0.6-1	2-4
2 PM	0-20	Clear	10 / 0	3	NNE/10-20	NaN	1.5-2.5

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
Sat Feb 04 - Sun Feb 05	18:25	19:31	5:41	6:46	17:30	7:21	100	9 06.2	21 51
Sun Feb 05 - Mon Feb 06	18:26	19:31	5:40	6:46	18:23	N/A	99	9 54.6	17 51
Mon Feb 06 - Tue Feb 07	18:26	19:32	5:40	6:46	19:14	N/A	97	10 40.9	13 06
Tue Feb 07 - Wed Feb 08	18:27	19:32	5:40	6:45	20:04	N/A	93	11 25.6	7 49
Wed Feb 08 - Thu Feb 09	18:27	19:33	5:39	6:45	20:54	N/A	88	12 09.6	2 12

Forecast Issued by: Ryan Lyman
Next update at 10 AM HST (2000 UTC) Monday 6 February 2023.

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.
NWS Hawaiian Islands Synoptic Discussion and Guidance
Honolulu National Weather Service Data and Products

Current Conditions
Temp		-3.2 C
RH		67 %
Wind		N 12 mph
Road		Closed