Marine Forecasts

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7 Day Forecast for Marine Location Near Kupreanof, AK

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Area Discussion for -

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FXAK67 PAJK 182257 AFDAJK

Southeast Alaska Forecast Discussion National Weather Service Juneau AK 257 PM AKDT Sat Sep 18 2021

SHORT TERM. /Saturday Evening through Monday night as of 2PM Saturday/ . Today has turned out pretty nice for a good portion of southeast Alaska, today. General offshore flow, today has yielded decreasing clouds between broken to clear across the northern 2/3 Panhandle with the clearest skies the more northwestward you go. A low around Graham Island has been bringing rain to the southern quarter of the Panhandle, primarily for the Misty Fjords / Hyder area, today. This will taper to isolated showers over the next 24 hours as the low continues to weaken and move inland. A general ridging pattern is building over the eastern Gulf and Panhandle, which will maintain dominance over the region through Sunday. That will give onshore flow and isolated to scattered shower activity and general decreased cloudiness through Sunday.

A low poised over the northern Gulf and associated cold front will move eastward into the Panhandle for Monday through Tuesday. A long fetch of deep tropical Pacific moisture is indicated by enhanced model forecast IVT and PW values. It will primarily be focused toward the Graham Island, Dixon Entrance, southern Panhandle areas and the western Coast of British Columbia. It looks like an average of 1.5 to 2.25 inches of storm total rainfall will be possible across the Panhandle with that system as it moves through the area with the highest amounts caused by enhancement, due to topographic uplift.

As for winds, sustained valued could get up to around 40 knots or Gale force just off the outer coast and around the Dixon entrance area for the Monday timeframe as the a frontal system approaches the Panhandle from the west. As the front moves through the Panhandle, up to small craft sustained winds can be expected over the Inner Channels through Monday evening. These enhanced winds will be caused by the gradient between a 1028mb high pressure center over southwest British Columbia and the 990mb low over the north- central Gulf. Mariners should use extra caution for the enhanced winds and seas Monday into Monday night as the frontal system approaches.

As for high and low temperatures, an overall combination of MOS guidance, 850mb forecast model temperature advection, and area cloud cover look to yield rather non-impactful temperatures on average for the Panhandle for the short-term forecast period similar to what has been seen over the past several days.

Additionally, for tonight, patchy fog is possible for communities in the northern 2/3 of the Panhandle due to very light to calm winds and decreased clouds mainly between scattered and broken, overnight, giving decent radiational cooling conditions. Evapotranspiration from decent soil saturation from recent rains will contribute to boundary layer moisture, enhancing the change for fog formation.

Forecast confidence is above average for the entirety of the short term forecast period, due to good model agreement.

LONG TERM. /Monday through Friday as of 10 pm Friday/ The extended period will be an active, stormy period for SE Alaska and the surrounding waters as a couple of robust low pressure systems move through the Gulf. An upper level low moves over the region Monday before exiting to the east as an open wave trough Wednesday. Ridging behind the low will quickly move across the panhandle before the next upper level low tracks over the Gulf Thursday, again staying in place for a few days. Although this pattern has above average predictability it continues to have spread within the timing, location and strength.

The Monday gale force low and front showing enhancement over the southern panhandle due to triple point feature. Expecting highest rainfall amounts over the southern Panhandle but model IVT does push the heaviest precip/atmospheric river well to the south of the region. 48 hour rainfall totals of 2 to upwards of 5 inches are possible. Both 25 and 10 year recurrence intervals has 75% plus for upper elevation points or for the far southern panhandle, but due to timing differences went with a broader forecast solution for now. Will be a rather short period of calmer weather Wednesday into Thursday under the upper level ridge. The late week system expected to track across the Gulf of Alaska with very strong maritime winds (potential to be storm force) and wave threats. More heavy precipitation due to a long fetch of moisture pushing northeastward into Southeast Alaska is also expected. But here model recurrence intervals for QPF showing much larger spread.

Operational models were in fair agreement for the Monday system with NAM being the biggest outlier so any changes were done with a GFS/ECMWF blend. Main change was to have the low moving towards the NE gulf and staying intact a bit longer. Beyond that any ensemble guidance at mid levels was telling similar story but here enough spread at the surface to stay with WPC.

AJK WATCHES/WARNINGS/ADVISORIES. PUBLIC . None. MARINE . Small Craft Advisory for PKZ041-042.



JLC/PRB

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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
LCNA2 - Lincoln Rock, AK	48 mi	73 min	W 5.1 G 7	52°F				52°F
FFIA2 - Five Finger, AK	50 mi	23 min	SSW 2.9 G 2.9	48°F			1003.7 hPa (+1.3)
CDEA2 - Cape Decision, AK	69 mi	61 min	W 2.9 G 2.9	50°F			1004.3 hPa	47°F

Wind History for Port Alexander, AK

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
Petersburg, AK	16 mi	27 min	N 0	8.00 mi	Light Rain	47°F	46°F	97%	1005.3 hPa

Link to 5 minute data for PAPG

Wind History from APG (wind in knots)

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Tide / Current Tables for Castle Islands, Duncan Canal, Alaska

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Tide / Current Tables for Wrangell Narrows (off Petersburg), Alaska Current

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