textproduct: Juneau

UPDATE

Updated Aviation discussion following 06z TAF issuance.

AVIATION

Flying conditions expected to largely remain between MVFR to IFR across the panhandle as the front continues pushing through overnight. The main front is currently over the southern panhandle, bringing continued rain with CIGs of 1500 ft or less and VIS of 3 to 5 SM, with some intermittent drops to LIFR CIGs and 1 to 2 SM VIS. The rest of the panhandle will see similar conditions dipping from predominantly low-end MVFR down to IFR with periods of LIFR possible overnight as showers continue to push through behind the front into the morning. Low ceilings will linger into the morning even after the precipitation begins to taper off, particularly in areas seeing calmer winds overnight. Flying conditions look to begin to improve late morning into midday for most of the panhandle, though CIGs between 1500 to 2500 ft will remain through much of the day, keeping most areas MVFR still. Improvement to VFR is more likely going into the evening as shower chances decrease, but some areas across the central panhandle may still see MVFR CIGs and some on and off shower activity through the evening.

PREV DISCUSSION......ISSUED AT

SYNOPSIS...

Key Messages:

- An active weather pattern will persist through the weekend as several fronts move over the panhandle.

- A brief lull in heavier rain showers is expected Sunday before a stronger low moves into the Gulf, bringing another round of precipitation through Monday.

SHORT TERM.../through Monday/...Several upper level troughs passing over the region are driving this active weekend pattern, with a weaker digging trough currently moving precipitation through tonight before a stronger low associated with an upper level jet enhances the system on Monday and Tuesday. Organized bands of precipitation should begin to clear out this evening with mainly lighter spotty showers expected tomorrow with daily totals around 0.1 to 0.6. Activity will pick back up overnight Sunday initially near Yakutat, bringing heavier rain rates of 0.1 to 0.2 per hour by early Monday morning. As the front moves south on Monday, expect lower totals for the southern regions, specifically over Prince of Wales Island as most precipitation will be enhanced by higher elevations. 24 hour accumulations from Monday into Tuesday morning are expected around 1.5 to 2.5 over the north and 0.75 to 1.25 over the south. Additionally, while winds will diminish on Sunday, they will increase again Monday morning in Lynn Canal and Stephens Passage, with higher gusts possible over northern land zones.

Across the panhandle today, temperatures remain in the 50s to low 60s. Breaks in rain tomorrow could drive a slight warming trend with highs reaching the upper 50s to mid 60s. The greatest chance for clearing skies tomorrow will be in northern areas. As the next system moves through on Monday, temperatures will cool back down, with most locations remaining in the 50s.

LONG TERM...

Largely uneventful long term in terms of impact, but several interesting features and tidbits. The first being Tuesday morning, as the stronger low moves down from the NE gulf coast towards Dixon Entrance. Rather strong surge of cold air looks to be associated with this low; and with some leeside troughing from northwesterly winds, it could be as low as 990 mb near Yakutat with 850 mb temperatures dropping below 0 C. As a result, expecting lapse rates around the low center to be stronger. With strong vorticity advection, expecting plenty of lift with the possibility of thunderstorms in the outer coast. Most of the rain accumulations look to be on the outer coast with persistent onshore flow, but since this low looks relatively transient, not expecting any one area to have extended periods of moderate to possibly heavy rainfall.

As it moves towards the southern panhandle, another shortwave trough looks to come across the gulf waters, merging with the existing low near the panhandle, strengthening it again. There is some uncertainty on exactly how this shortwave will merge with the ongoing system, but definitely trending towards impacting the Canadian areas.

Going into the mid to late week, high amplitude ridging returns with northwesterly flow, drier conditions, and warmer temperatures.

AVIATION...Difficult day for aviation concerns. Many areas of the panhandle are observing vis around 3 to 5 miles and ceilings down to 1500 ft or less. A few locations are even down to 1 mile vis (Sitka and Yakutat) and a few hundred feet ceilings (also Sitka and Yakutat). This is due to the second of two fronts that are moving through the area today. This front moved onshore early this afternoon and is just reinforcing the already low conditions that many areas were seeing this morning mainly from Cape Fairweather S and E. The low conditions and rain is expected to last into the evening with rain gradually diminishing afterwards with some improvement in vis. However, ceilings will likely stay low for many areas through the night and will not see significant improvement until Sunday morning and even then will likely stay with MVFR conditions.

Surface winds have been somewhat gusty in some areas, but only gusting to around 25 kt today. With the front moving through this evening these winds will likely not diminish until late this evening. Aloft, winds have not been much higher than what is seen at the surface and pilot reports have only had some isolated areas of light turbulence at low altitudes today (and little to no low level wind shear reports). These wind conditions will likely remain consistent through the evening and will likely improve later tonight as the fronts move out of the area and winds lighten.

MARINE...Inner Channels: Inner channel winds today have not been that strong. Highest winds have been on the backside of Douglas Island (E wind 25 kt most of the day), Northern Lynn, and Clarence Strait (20 kt in both places at various points today) so far. At least for this system, right now is about as high as inner channels winds are going to get. The second front that is moving through right now is not as strong as the first one last night was and winds are expected to gradually diminish into Sunday. Likewise seas are around 4 ft or so for most areas and will gradually subside as the winds do. Of greater concern has been the reductions in visibility due to rain and fog. Some areas have been as low as 1 mile and more areas that low will likely be encountered through the evening and overnight before improving Sunday. There is another period of higher winds and seas expected for Monday as a new front moves in at that time. Wide spread southerly winds of 20 kt expected across the northern 2/3rd of the inner channels starting late Sunday night and continuing through Monday night before diminishing. Highest winds will be in Lynn Canal where 30 kt winds could be observed Monday morning.

Gulf Waters: Somewhat active gulf of Alaska over the next few days. At least two lows will be moving SE through the eastern gulf from the Prince William Sound area. Overall the wind pattern over the gulf favors W to NW winds over the offshore marine zones, while the winds directions will be more variable near the coast switching from S and SW ahead of each low, becoming more easterly as the low passes, and finally becoming more N and NW in the wake of the lows. Highest winds will be with the second low that will be moving through Monday into Tuesday with near gale expected for the central gulf waters. Near coastal waters will feature weaker winds of around 20 kt or so even with the second stronger low. Seas will be going up and down as well with up to 8 ft seas for the current system and up to 13 ft seas out in the central gulf for the second system. In between systems on Sunday, seas will be as low as 6 ft. predominate swell will be around 3 to 5 ft out of the W for most of the next few days.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...None. MARINE...Small Craft Advisory for PKZ661>663.