textproduct: Juneau

SYNOPSIS

Key Messages:

- Quieter weather for the first part of the work week with light rain showers possible and potential for overnight fog.

- A fast moving low moving just south of the panhandle will bring a period of moderate rainfall Tuesday for the southern panhandle.

- A larger, impactful system to move into the Gulf midweek and impact SEAK by late week, bringing moderate to heavy rain and elevated winds.

SHORT TERM

Multiple rounds of light showers are expected to continue pushing into the northeast Gulf coastline early this week, the first wave continuing to push in tonight into the northern panhandle, and the next coming after a brief break during the day Tuesday. These showers tonight into Tuesday will bring higher precipitation amounts along the NE Gulf coast around Yakutat, alongside chances for more convective cells developing and potential lightning just along the outer coast. Some storm cells moving inland may bring a strike or two along the Fairweather range, but much of this convective activity is expected to remain offshore.

The southern panhandle will begin to see more clearing by later tonight as a weak ridge of high pressure continues to build, before the high begins to shift northeastward into British Columbia overnight as a low approaches from the south. This fast- moving low pressure system will begin to move in towards Haida Gwaii Tuesday morning, clipping the southern panhandle through the day Tuesday. This system is expected to largely stay south of Frederick Sound, with the confidence in rainfall amounts between 0.50 to 1.25 inches remaining higher for the Annette Island, Ketchikan, Misty Fjords, and Hyder areas.

Overnight tonight into the morning brings more of a break for the central panhandle, namely northern PoW Island northward to Icy Strait, with fog potential looking possible across the area through the morning. The highest chances for this look to be around Klawock up to Angoon overnight, before the Gustavus to Juneau area beginning to see potential begin slightly later, closer into Tuesday morning. The southern panhandle may see another period of clearer conditions and potential fog Tuesday night to Wednesday, as ridging builds over the area while another shortwave moves into the northern panhandle.

LONG TERM

Weather for the long term continues to look unsettled as forecast guidance continues to show multiple lows moving into the panhandle for the end of the week and into the weekend. Forecast guidance still shows some uncertainty with the exact location and strength of the low moving in for Thursday. This low will track around the parent low which looks to remain near Kodiak Island. While the parent low remains in the Western Gulf, some forecast guidance is pointing towards a low forming on the triple point convergence for Friday which could bring another shot of moisture and winds to the panhandle.

Attention then turns towards the weekend as deterministic and ensemble forecast guidance have the remnants of Typhoon Koguma moving into the Gulf and interacting with the low that has been lingering in the area. Right now, guidance is split on whether this system that develops moves north into the southern panhandle or dives south. Right now, Euro/EPS guidance wants to bring the low north along Haida Gwaii Sunday evening into Monday morning before moving into the Southern Panhandle. The GFS/GEFS wants to bring the strengthening low up to Haida Gwaii before diving south in British Columbia and the PNW. Canadian/GEPS is leaning more towards the Euro solution but not as strong and does not move the low as far north. Due to the uncertainty of this track, a lot of uncertainty remains regarding the weather for the weekend and start of next week.

AVIATION.../Through 6z Wednesday/

Mostly VFR to MVFR conditions prevail across the panhandle through Monday night. Multiple organized bands of showers are expected to move through the northern panhandle Tuesday, with MVFR conditions expected for PAYA and extending into the Icy Strait Corridor. Through the afternoon, guidance has shown some indication for CIGs to start to break up in the northern panhandle, though showers will still be possible. VFR conditions are prevailing for the southern half of the panhandle tonight, with clear skies in the central panhandle and a thin mid-level layer moving over the southernmost panhandle. Fog development has begun to take over parts of the central panhandle, mainly for PAPG and PAWG, and LIFR conditions are expected to persist through the early morning. A fast moving system is expected to jump up from the south Tuesday morning and bring periods of MVFR conditions with light rainfall and CIGs AoA 1500 ft to parts of the southern panhandle through the afternoon. This system is expected to begin to move out by the end of the period, at the same time as the next organized band of showers begins to move into PAYA again. Overall, the active period continues with breaks possible between showers.

MARINE

Outside: As of Monday morning, ASCAT passes across the Gulf show diminishing southwesterly flow, with winds at or below moderate breezes. Seas are southwest and also diminishing, with coastal buoys reporting 6 to 8 ft near 6 to 9 seconds. Monday night southwest flow continues to feed smaller systems into the Gulf bringing periods of fresh to strong breezes, mainly to Cape St. Elias and Dixon. However, southwesterly seas continue to remain at or below 8 ft through Wednesday morning.

Wednesday afternoon east to southeast winds build in the eastern Gulf, reaching near gale force over much of the coast by early Wednesday evening and fresh seas building to 10 to 12 ft. Thursday morning conditions continue to deteriorate as a front moves into the coast, with gales to strong gales impacting many areas and seas reaching 20 to 25 ft in the northern Gulf, seas near 15 ft south of Edgecumbe. Southwesterly winds of fresh to strong breezes persist Friday with thunderstorms possible along much of the coast.

Inside: Across the inside, for the most part winds remain at or below moderate breezes with areas of fog remaining the primary threat Tuesday and Wednesday mornings. Mariners navigating southern Clarence Strait and Revilla might see the higher end of moderate breezes, perhaps fresh breezes, as a low moves into Dixon Tuesday into Wednesday. Thursday a large system moves into the Gulf freshening up the winds across much of the inner channels to 20 to 30 knots, with localized areas of gales possible, and bringing heavy rainfall. Thunderstorms are likely to impact the Panhandle Friday bringing gusty winds. Active weather persists through the weekend.

HYDROLOGY

Impressive plume of moisture looks to be associated with the incoming atmospheric river Thursday morning. Strong WWA ahead of the moisture looks to raise freezing levels to above 5000 ft, with an atmosphere relatively saturated. Associated PWAT via ensemble mean looks to exceed the 95th percentile for this time of year for the southern panhandle. This coupled with the strong flow aloft means that IVT will likely exceed 500 kg/ms at around 80%. The big question here is timing of this moisture, and if any mesoscale features will keep this flow of moisture directed at the southern panhandle for longer. Dynamics continue to favor higher rain rates, with divergence aloft and stronger 850-700 mb southerly flow. Rain rates could exceed 0.3 in/hr for longer periods of time, and exceed 0.5 in/hr at elevation. Flooding is certainly possible with this rainfall intensity, but uncertainty in duration (see long term) has cast some doubt on overall impact level. Stay tuned for updates as the event approaches.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Dense Fog Advisory until 11 AM AKDT Tuesday for AKZ326. MARINE...Small Craft Advisory for PKZ652.