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 272255 AFDAJK

Southeast Alaska Forecast Discussion National Weather Service Juneau AK 155 PM AKST Mon Jan 27 2020

SHORT TERM. Very active and high impact weather pattern continues in the short term. High winds, heavy snow and rain, and very high seas are expected over the next 48 hours and potentially longer.

Currently SE AK is between systems as a large upper trough remains centered over the western Gulf. Expansive cold airmass is noted over the western and central Gulf and some of this air will be streaming eastward over SE AK over the next 24 hours. This cold air will be modified somewhat by its traverse over the warmer Gulf waters and thus will not be as deep or as cold as the airmass that was in place ahead of the system from a couple of days ago. A shortwave rotating around the main upper trough will enhance snow shower activity through the night over the NE Gulf coast and thus have extended the Winter Weather Advisory there through midnight to account for this. Winds remain strong out of the south over upper Lynn Canal this afternoon due to strong SW flow over the mtns and the resulting lee troughing effect increasing local pressure gradients. These winds should gradually diminish Tuesday as the next storm approaches from the S.

Attention then turns to the vigorous PV max now seen on GOES 17 WV imagery over the NPAC along 50N 160W. All guidance indicates that as this PV lifts into the Gulf on Tuesday, that some degree of phasing will occur between it and the polar trough over the western Gulf. Surface low will deepen to around 955 mb on Tuesday over the western Gulf. Rapidly occluding and storm force front will move into the eastern Gulf Tuesday night and across the Panhandle Wednesday morning. Surface wave looks to form on the front and track either along or just E of 140W late Tuesday night. This is a very favorable track for high winds over the southern Panhandle and Gulf coastal areas. Low level wind fields are quite impressive, with 80 to 90 kt of SE flow at 925 and 850 mb. Forecast profiles from hi-res models show 50 to 55kt as low as 500 ft near Ketchikan, Sitka, and Prince of Wales Islands late Tuesday night. Surface pressure gradients will favor high winds over much of the southern and central panhandle with the PASI-PAKT gradient peaking at 16mb late Tuesday night. Storm force winds will spread from the eastern Gulf into Clarence Strait with gales over many of the rest of the inside waters S of Lynn Canal. Wind gusts to 60 mph or higher are expected in land areas adjacent to these channels so went with a High Wind Warning for a large part of the southern and central Panhandle for this time frame.

Further north, at least some colder air will be in place so that heavy snow will once again be an issue for far upper Lynn Canal. 60 to 80 kt of deep S'ly to SE'ly moisture transport will likely lead to snowfall rates of 2 inches per hour at times for the Haines and Klondike Highways. With the cold air source being a longer trajectory over the Gulf, think that sea level Haines and Skagway will be able to transition to a rain/snow mix by Wednesday morning as a mix out of the cold air will occur. Further up the highways, heavy snow will continue through Wednesday. When it's all said and done, expect yet another 12 to 24 inches of snow for areas already hard hit by last weekends storm. Highest amounts will be over the upper elevations of both highways.

Confidence is high on the impact of this storm but a bit lower in the details, such as timing of the high winds and snow to rain changeover etc.

LONG TERM. /Wednesday through Sunday/ . The active weather pattern appears very likely to continue in the extended range into the weekend. The split flow pattern that is in place is challenging in the sense that Southeast AK could experience rain or snow, but small details that are difficult to devine in the long term forecast are not quite available. We do know that precipitation will likely continue to fall each day through Saturday, and if snow does fall, it could be impactful.

Ensemble agreement is good in the overall synoptic pattern over the Gulf of Alaska. Large upper trof will remain in place across the western parts of AK extending over the W gulf. Early Wednesday an upper shortwave rotating around the trof will move N across the eastern gulf and lift across the panhandle. At the surface the low pressure system remains and issue with a complex of multiple waves possible as the low moves northward into the N gulf through Wednesday. Low level temperatures will briefly warm as the front lifts north across the panhandle early Wednesday, but colder air is expected to wrap in behind the low and across the E gulf and panhandle later in the day. Currently expecting this system to provide a rain/snow mix across the Icy Strait corridor, including Juneau, while the more impactful snowfall is likely across the N Lynn areas including Haines and Skagway where temperatures will likely remain near or below freezing.

Another wave will move NE out of the NPAC into the SE gulf by Thursday morning. This system has the potential to the be an impactful wind event where and if it makes landfall across the panhandle. Operational models all depict a rapidly developing low, but handle the details very differently. The placement of the low will also determine where impactful snow will be possible Thursday. Did increase winds to gales in the E gulf but future work will need to be done with better consensus. By Friday, there is more disagreement between the models, but still expect a surface low to be churning in the N gulf through Saturday. By Sunday there is a chance for a brief break as a ridge moves east across the gulf and panhandle. Overall forecast confidence is average.

AJK Watches/Warnings/Advisories. PUBLIC . High Wind Warning from 6 PM Tuesday to 3 AM AKST Wednesday for AKZ023-026>028. Winter Storm Warning from 6 PM Tuesday to 6 PM AKST Wednesday for AKZ018-019. Strong Wind until midnight AKST tonight for AKZ018. Winter Weather Advisory until midnight AKST tonight for AKZ017. MARINE . Gale Warning for PKZ041>043-051-052. Small Craft Advisory for PKZ012-021-022-031-033-036-053.



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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
FFIA2 - Five Finger, AK	50 mi	74 min	SSE 15 G 20	39°F			1004 hPa (-0.4)

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	78 min	Var 3	10.00 mi	Overcast	36°F	33°F	89%	1006.7 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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Weather Map

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GEOS Local Image of PacificNorthwest    EDIT
NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
Link to Loop

Other links: Northern Pacific     Contential US     Full GOES-East

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Wind Forecast for (23,6,7,8)

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Ground Weather Radar Station Biorka Is., AK

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