Warning(s)
Fog, ice and high humidity
Chance for thuderstorms and heavy snow
Strong winds
Cloud Cover and Fog/Precipitation Forecast
Fog, ice, thick clouds and snow are expected throughout the night. There is good chance for deep convection developing in the area mainly through midnight.
Summary of Key Meteorological Variables
Summit temperatures will be near -5 C this evening and -6 C tomorrow morning. Winds will be from the WSW at35-50 mph for the night. Seeing and PW are expected to exceed 1 arcsecond and 4 mm, respectively, through the night.
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Discussion
The atmosphere near the Big Island will remain saturated and unstable, resulting in mostly inoperable conditions (extensive fog, ice and flurries) through at least the weekend. There is also a possibility for convection developing in the area, which could deposit heavy snow at the summit particularly for this evening, but may pop up occasionally into Sunday evening. While there is a chance that the upper air mass will begin to dry out late for the early part of next week, the inversion will remain rather indistinct as low-level moisture persists, likely contributing to poor/wet conditions for Monday and Tuesday night. Extensive daytime clouds are expected throughout the forecast period.
Thick clouds to the north and south are expected to merge in the area, while deep convection develops over the Big Island by this afternoon/evening. These clouds will contribute to mostly overcast skies probably for the next 2 nights, then will begin to push off toward the east, leaving patches of mid/low-level clouds in the area through Tuesday night. Still, there is a good chance that extensive cloud cover will prevail at the summit through at least Monday night.
Precipitable water is expected to exceed 4 mm through the next 5 nights.
A mixture of boundary layer turbulence, instability and/or moisture will contribute to poor/bad seeing through the next 5 nights.
No changes since the morning forecast... A relatively deep tropical upper-tropospheric trough (TUTT) will continue to stretch out from the west coast toward the state, before becoming more shallow as it reaches out toward Guam. The TUTT will promote widespread instability in the area and keep the mid-level ridge displaced off to the NW well into next week. A sharp/deep upper-level trough embedded in the TUTT will continue to dig in from the NW and deposit a low just north of Kauai. This low will provide fresh dynamic and thermodynamic instability, which will dismantle the inversion and saturate the bulk of the air mass near the Big Island early this afternoon. That could allow for development of deep convection in the area, which may deposit heavier snow at the summit and contribute to blizzard-like conditions at the summit for at least the early part of tonight. There is a chance that the low/trough will shift subtly eastward, which will take the area of convection to the eastern skies for early Saturday morning. However, the low is expected to retrograde and/or expand westward by that afternoon, then will slowly dissipate in the area over the remainder of the weekend and early part of next week. Nevertheless, this will likely allow for the return of deep moisture/instability to the area, perhaps resulting in another round of convection near the Big Island (and moderate/heavy snow at the summit) through Sunday evening. The bulk of the organized moisture is expected to disband and/or shift off toward the east thereafter, but persistent instability and the absence of a prominent ridge will limit/prohibt the inversion from restrengthening until the middle part of next week. There is also a possibility that building trades will usher rather unstable low-level clouds in from the NE and provide fresh fuel/moisture to the area early next week. As a result, there is a good chance that inoperable conditions (extensive fog, ice, high humidity and light flurries) will plague the summit between early this afternoon and late Tuesday night. Lastly, due to the depth of the TUTT and its southern counterpart, aka the sub-tropical jet, a tight wind gradient will persist in the area, contributing to more moderate/strong summit winds throughout much of the forecast period. There is possibility for gusts exceeding 50 mph and blizzard-like conditions mainly as the low deepens to the north over the next 24 hours.
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