textproduct: Juneau

SYNOPSIS

Key Messages:

- A brief break in the rain is possible Sunday night into Monday, however another front and round of heavy rain and strong winds push across the Gulf of Alaska into the Alaska Panhandle by Monday night and continues through Tuesday.

- Maritime interests need to pay attention to the strong front projected to move across the Gulf of Alaska by Monday afternoon, bringing Gale Force to potentially Storm Force winds to the central and eastern Gulf Tuesday into Wednesday.

LONG TERM.../Tuesday through Friday/

Tuesday will begin with moderate to heavy rainfall and gusty southerly winds across northern panhandle with an occluded front pushing ashore with a deeper feed of moisture. Throughout the day, a rapidly deepening surface low will lift northeast into the northern Gulf, with a quick moving cold front traversing the Gulf and through the panhandle, clearing the southern panhandle on Wednesday morning. Along and ahead of the front, an atmospheric river will tap into a deeper feed of subtropical moisture, with heavy rainfall and strong winds feeding into the panhandle, with highest rain amounts and strongest winds across the northeast Gulf coast and northern panhandle. South to southeasterly winds will intensify, producing gale-force conditions in inner channels such as northern Lynn Canal and Clarence Strait, with widespread gales (34-47 kt) to storm-force winds (4863 kts) and combined seas exceeding 20 feet along outer coastal waters, mainly from Cape Edgecombe northward.

As the primary low stalls and weakens in the northern Gulf through the end of the week, onshore flow and subtle troughs swinging around the low will keep higher precipitation chances with moderate to heavy showers and gusty winds across SEAK through Thursday. Quite a bit of model discrepancy by the end of the week, but general trend is for the low to weaken further as it shifts southeast, with a ridge of high pressure building in its wake, bringing clearing skies and drier offshore flow.

Persistent onshore flow with mainly cloudy skies and rain will keep temperatures cool and consistent through the period, with daytime highs in the 40s (low 50s possible on Tuesday) and overnight lows in the mid 30s to low 40s.

Snow levels may initially be low enough for snow or rain/snow mix near White Pass early Tuesday morning, but will quickly rise throughout the day as southerly winds pick up ahead of the front. Snow levels will fall down to 1-2kft behind the front Tuesday night/Wednesday and snow showers will be possible along the Klondike Highway and the upper reaches of the Haines Highway through Thursday, although any accumulations look to be light for now.

AVIATION.../through Monday morning/

Across the panhandle this morning, mostly VFR conditions continue to persist with periods of conditions dropping down to MVFR and some isolated periods of IFR ceilings. Showers are expected to persist for the northern panhandle today bringing more showers before starting to diminish this evening. For the southern panhandle, the precip is expected to last a little longer during the day but should come to an later tonight. One concern for the latter half of the TAF period will be how quick do places see clouds clear out and allow for fog development. Currently think that there will be no concerns for LLWS during this TAF period as we see a break between systems.

MARINE.../through Tuesday night/

Outer waters: Broad area of low pressure 80nm S of Yakutat continues to weaken and dissipate through Sunday as a brief period of high pressure moves across the northern Pacific. General westerly winds and diminishing seas prevail across the Gulf and Gulf coast through Sunday night with patchy dense fog possible within southern inner channels Monday morning. Conditions deteriorate from west to east across the Gulf Monday afternoon as a strong system reaches the Gulf coast by Monday night. Hazardous marine conditions are expected to continue Monday night through Tuesday night for the Gulf, and Gulf Coast waters with Gale Force to potentially Storm Force winds to the central and eastern Gulf Tuesday into Wednesday and elevated seas reaching 20 to 30 ft from southern Baranof northward along the Fairweather Grounds to the entrance of Yakutat Bay.

Inside Waters: With a brief period of high pressure moving across the panhandle through Sunday afternoon, winds across the inner channels are expected to diminish through the afternoon, going light across the north and calm and variable for the southern panhandle. Benign conditions continue across the inner channels through Sunday night as the high pressure transits over the southern panhandle. Winds turn predominately southerly and increase through Monday afternoon as a strong front approaches the outer Gulf Coast. By early Tuesday morning, anticipate widespread Strong Breezes to Near Gales across the area to persist through the day, with potential for Storm Force wind gusts up to 50 kts developing within N Lynn Canal by early Tuesday morning.

HYDROLOGY.../Monday night through Tuesday/

A strong system is expected to move into the northern central gulf, reinforcing the existing low pressure system, and drawing a deeper fetch of moisture from northern Pacific. By Tuesday morning, this plume of moisture is expected to shift from southwest to southerly, and is likely to exceed 500 kg/ms IVT for around a 12-18 hour period for any given location in the Icy Strait corridor and NE gulf coast. Expecting Yakutat to be the big winner in terms of rain amounts, with near perfect perpendicular flow, strong WAA in the low levels increasing lift potential, and decent divergence aloft. With this, Yakutat could see upwards of 6 inches during a 36 hour period, which is a little higher than a 2 year ARI event. For the Juneau and Gustavus areas specifically, rainfall amounts look very similar to the previous atmospheric river from last week which put Salmon River and Montana Creek into minor flood stage. Therefore, issued a hydrologic outlook for these areas for expected minor flooding at the least.

AJK WATCHES/WARNINGS/ADVISORIES

PUBLIC...Wind Advisory from 4 PM Monday to 10 PM AKDT Tuesday for Akz017. MARINE...Gale Warning for PKZ652-664-671-672. Small Craft Advisory for PKZ012-013-021-022-032-053-641>644-651- 661>663.