Warnings
Chance for fog and light snow.

Cloud Cover and Precipitation Forecast
There is a chance for periodic fog and light snow for tonight. Thick overcast clouds will continue to stream over the summit through the night.

Summary of Key Meteorological Variables
Summit temperatures will be near -2 C tonight and -1.5 C tomorrow morning. Precipitable water is expected to be in the 6 to 8 mm range for the night. Winds will be primarily from the south at 10 to 20 mph for tonight and 20 to 30 mph tomorrow morning. Shear is expected to be in the 40 to 50 mph range.

Discussion
Although a weak inversion will continue to keep low-level moisture capped at 8-10 thousand feet probably through Friday morning, summit-level humidity will continue to climb as moisture/clouds builds in aloft. Consequently, there is a chance for periodic fog/frost and very light uniform snow/rain through Friday morning. There is also a chance for isolated thunderstorms to develop, primarily during the afternoon hours. The inversion is expected to breakdown after sunrise on Friday as the entire atmosphere becomes saturated between noon on Friday and possibly Monday morning. As a result, extensive fog, ice, snow, and probably thunderstorms are expected during that time (although the last 2 are more likely between 4-5 PM on Friday and midnight Saturday).

Thick overcast mid/high-clouds will continue to stream in from the southwest and over the summit for the next 12 hours. Most of the high clouds will shift east of the summit after sunrise tomorrow, but scattered to broken mid-level clouds will continue to drift in from the west and southwest through Saturday afternoon. In addition to this, another round of thick high clouds is also slated to slide in from the northwest for most of Friday through Sunday morning. While these clouds should also shift east of the summit after that, scattered to broken slow-moving mid-level will likely linger and/or develop around/over the summit through Sunday night. As a result, skies will likely be almost totally blanketed for the next 4 nights, with a chance for partial clearing on Sunday night.

Precipitable water is expected to exceed 6 mm probably for the next 5 nights. The global model expects precipitable water to drop toward 2-4 mm Sunday night, but just a degree off (west or east) would result in PW > 6 mm. Thus, there are very large uncertainties for that and even Saturday night.

Observing probably won't be possible for the next 3-5 nights due to the extensive clouds, fog, precipitation, and/or winds, among other things. Nonetheless, during any unexpected/unlikely short-lived clearing, expect bad seeing.

Subtle change from this morning's forecast, but not necessarily good...A fairly broad/weak trough continues to slowly march toward the Islands from the west, although it is starting to flatten out. Nonetheless, a fairly deep layer of mid/upper-level southwesterly winds still persists over the Islands. These winds have been responsible for drawing up an ample supply of mid/upper-level moisture and/or thick clouds from the tropics. Fortunately, the atmosphere below the summit remains fairly stable due to positioning of the low-level ridge just over the Islands. Moreover, the flattening of the trough has shifted most of the mid-level moisture further north over the central and northern Hawaiian Islands. However, that is expected to change over the next 48 hours. A second stronger trough is still slated to dig in over the state during the next 2 days, before cutting off into a cold-core low on Friday night. In the process it will send a strong band of convection through the state on Friday, with this band likely passing the Big Island that night. In response to this band and the developing low, the atmosphere is expected to entirely saturated and very unstable throughout Friday and into Saturday. Extensive fog, moderate to heavy snow, widespread thunderstorms, and ice are virtually expected during that time. Strong southerly winds will also plaque the summit for most of the weekend, making blizzard conditions likely for Friday and Saturday. The latest model run now places the mid/upper-level low just west or over the Big Island after noon on Saturday (as opposed to just east of the BI). This situates the summit on the moist and unstable side of the low for Saturday and Sunday nights. While I don't expect snowfall to heavy during those nights, isolated thunderstorms could still pop up within the center of the low and over the Big Island, especially during the afternoon hours of Saturday and Sunday. Regardless, extensive fog and ice will likely continue through the weekend. All in all, expect very cloudy with possible fog/light snow for the next 2 nights, and extensive fog, wind, snow, ice, poor visibility, and thunderstorms on the following 2-3 nights. Looking ahead to the 6-7 nights...models still project another trough to dig in behind the low, but this time a bit further west. This still helps maintain deep moist southerly flow and instability into the middle of next week. The consistency behind this projection should raise some concerns as observing will likely be difficult probably for the next 7 nights.

Astronomical Observing Quality Guidance
Vertical Profiles from MM5 (vertical coordinate is pressure in mb):

Tonight's (Wednesday Night) Collage	NOT AVAILABLE
Tuesday Night's Collage (available after 0800 HST on Tuesday)	Seeing Cn2
Wednesday Night's Collage (available after 0800 HST on Wednesday)	Seeing Cn2