Small Craft Advisory 149, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
235 PM AKDT Sun Oct 8 2017

.SYNOPSIS...
Aloft...
A long wave trough over mainland Alaska will progressing east and
will move into NW Canada tonight. A second long wave trough over
the Sea of Okhotsk and western Bering Sea will progress east of
the Bering Sea Wed and expand into mainland Alaska late in the
week. A series of strong short waves will move northeast across
the Bering Sea into the West Coast of Alaska through this week
making for a very stormy week with several storm surge events for
the West Coast of Alaska and possible coastal flooding or high
surf. This will also bring several potential significant snow
events to the Interior of Alaska.

A vertically stacked low in Prince William Sound will move near
Yakutat by 4am Mon then continue east. Weather associated with
this will be addressed with its surface frontal system below.

A short wave trough that lies from Point Hope to Anvik will move
to Wainwright to Denali by 4am Mon, to Barrow to Eagle to Northway
by 4pm mon, then continue east. Snow showers east of this trough
will taper off along and west of the trough with a brief break in
the clouds.

Surface...
A 1004 mb Low 100 nm north of Barter Island will weaken slowly
through Mon. Very cold air with 850 mb Temperatures ranging from
-6C to -12C lies west of this low. This feature is causing northerly flow of that cold air over open water and will cause lake affect type snow showers over the Arctic Coast tonight. Due to shallowness of flow only expect 1-2 inches of snow along the Arctic Coast through Mon. This will also cause freezing drizzle tonight in areas of super cooled fog.

An occluded front associated with the vertically stacked low in
Prince William Sound lies from the low to Minchumina to Old Crow
will stretch east of the Alcan Border tonight. Rain is now
occuring in most areas along and east of this front, changing to
snow above 2000 feet along the front with the snow level rising to
3000 ft along the Alcan Border.

An Arctic front stretching from Inuvik to Old Crow to Galena to
McGrath will move to Inuvik to Dawson to Northway by 4am Mon and
then move south of the Alaska Range Mon. Snow level will lower to
the surface along and west of the Arctic front. Expect 2 inches
of snow above 2000 ft in the Eastern Interior tonight, with up to
6 additonal inches in the Alaska Range near Denali Park. At
Valley level expect 1 inch tonight but it should melt soon after
falling.

A 974 mb low in the far western Bering Sea will move to 60 nm
North of Cape Navarin as a 978 mb low by 4am Mon with an occluded
front extending from Anadyr to Provideniya to Cape Romanzof. By
4pm Mon the low will be at 985 mb 200 nm north of Cape Navarin
with the occluded front from Anadyr to Point Hope to the Yukon
Delta. At 4am Tue the low will by 995 mb 150 nm northwest of
Gambell with the occluded front from Anadyr to Point Lay to
Anaktuvuk Pass to the the Yukon Delta with and Arctic front from
Bettles to Fairbanks to Northway. By 4pm Tue the low will be 1002
mb 60 north of Shishmaref with the the occluded front from the low
to north of Point Hope and then east just north of the Arctic
Coast to Demarcation Point to Arctic Village to Bethel with an
arctic front from Fort Yukon to Eagle. Expect 0.50 to 1.00 inch
of liquid with this occluded front from the Brooks Range south,
with the heaviest amounts over the Central and Western Interior
where the front stalls. Precip will start as snow as the occluded
front overruns the arctic air that cover the Interior and West
Coast by Monday. Precip will switch quickly to rain over the West
Coast so only expect 1 inch of snow there. As the front moves
inland the arctic air will be more entrenched the further east the
front moves so that the Western Interior will see 2-4 inches of
snow Mon (though most will melt after turning to rain), the
Northern and Central Interior will see 4-7 inches of snow Mon
night through Tue night over hills while valley location see 2-4
inches. Will issue Winter Weather Advisory for Zones 218 219 220
221 222 for Mon night through Tue night for 2-4 inches of snow in
valleys and 4-7 inches of snow above 2000 feet.

Also accompanying this low will be brief southeast gales over the
Bering Sea just ahead of the front becoming southwest 25-35 kt
trailing the occluded front. Will see southwest 40kt over zone 213
Mon and Mon night as the poison tail portion low moves over that
area. This will bring sea levels up 2-5 ft along the entire West
Coast from Point Hope to Cape Romanzof, with the greatest rises in
eastern Norton Sound. Will issue a coastal flood watch for this
in zones 211, 212, and 214, high surf for zones 213 207 209 and
210.

&&

.DISCUSSION...
Models initialize too weak on ridging aloft over NE Alaska as
shown by Fairbanks 12Z RAOB which GFS/NAM/Canadian and ECMF
initialize at 20DM too low on heights. This may also be due to
the lack of ROABs at Barrow and Kotzebue at 12Z. The ridge will
be weakening today, so this may slow the weakening by an hour or
two today from what models would indicate. Otherwise, models in
pretty good agreement through 4pm Tue, with the GFS/ECMF in good
agreement on short wave features through 4pm Wed. After that time
the GFS and ECMF maintain good agreement on long wave pattern into
next weekend with fair agreement on short wave through then.

The surface low now bombing out in the western Bering Sea will be
the main feature through Wed and appears to be quite similar in
the GFS/ECMF solutions. NAM is definitely the odd one out after
4pm Tue, so we will stick with the GFS/ECMF. A second and much
deeper Bering Sea low late in the week is handled similarly by the
GFS/ECMF and will need to be watched closely for coastal impacts.

Coastal Hazard Potential Days 3 and 4...
Potential surge 2-5 feet Tue along all of West Coast.
Surge height will decrease Tue night and Wed, then rising again
Wed night through Fri with flooding possible Thu and Fri.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory for AKZ207-AKZ209-AKZ210-AKZ213.

Coastal Flood Watch for AKZ211-AKZ212-AKZ214.

Winter Weather Advisory for AKZ208-AKZ217-AKZ218-AKZ219-AKZ220-
AKZ221-AKZ222-AKZ225.

Small Craft Advisory for PKZ200-PKZ215-PKZ220.

Gale Warning for PKZ210.
&&

JB OCT 17