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 4.5 C today, -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 5 to 15 mph for today, 10 to 25 mph for tonight, and 20 to 35 mph tomorrow morning. Shear is expected to be in the 50 to 60 mph range for tonight and 30 to 40 mph during the morning.

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 mid/upper-level moisture/clouds builds in. As a result, there is a chance for periodic fog/frost and light snow/rain over the next 24 hours. 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 atmosphere becomes entirely saturated through noon on Saturday. Consequently, extensive fog, snow, ice, and likely thunderstorms are expected during that time. There is a chance for drying on Saturday and Sunday nights, but moisture and instability will still linger very close to the Islands. Thus, I suspect at least fog and thunderstorms will still be an issue through Monday, at least.

Thick overcast mid/high-clouds will continue to move in from the southwest and over the summit for the next 24 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 and into Saturday 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 the summit through Sunday night. As a result, skies will likely be almost totally blanketed for the next 3 nights, with a chance for partial clearing on Saturday and Sunday night.

Precipitable water is expected to exceed 6 mm for the next 3 nights. The global model expects precipitable water to drop toward 2-4 mm for Saturday and Sunday night, but just a degree off (west or east) would result in PW > 6 mm. Thus, there are very large uncertainties for those nights.

Observing probably won't be possible for the next 3 nights due to the extensive clouds and fog, among other things. Nonetheless, during any unexpected/unlikely short-lived clearing, expect bad seeing. And while observing probably won't be possible for Saturday night either (this time because of the winds), turbulence in the free atmosphere will likely be very strong. Consequently, seeing will likely be highly variable and bad/lousy. The same will likely go for Sunday night, although the winds will likely be dying.

A fairly broad, but weak, trough continues to slowly march toward the Islands from the west, while still maintaining a fairly deep layer of mid/upper-level southwesterly winds. These winds have been responsible for drawing up ample supply of mid/upper-level moisture and/or thick clouds. Fortunately, the atmosphere below the summit, for the most part, remains fairly stable due to positioning of the low-level ridge just over the Islands. That is expected to change over the next 48 hours though. 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 during the afternoon/evening hours. Nonetheless, 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 eventually places the mid/upper-level low just east or over the Big Island after noon on Saturday. While this would situate the summit on the dry side of the low for Saturday and Sunday nights, I still expect conditions to be very unstable and likely moist during that time. Snow will likely be very isolated and light, but I suspect extensive fog to remain in the area through the weekend. In addition, isolated thunderstorms within the low could pop up at virtually any time. Finally, summit-level winds are expected to exceed 50 mph between noon on Friday and probably into Sunday night, making observing very difficult, if not impossible during that time. All in all, very poor conditions/viewing is expected for the next 3-5 night, with another round of snow penciled in for Friday/Saturday. Looking ahead to the 6-7 nights...models still project another trough to dig in behind the low, thus maintaining the 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