Small Craft Advisory 168, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
512 AM AKDT Tue Oct 24 2017

.SYNOPSIS...
Aloft...
A long wave trough over mainland Alaska and the Bering Sea will
retrograde over the Bering Sea Wed with a ridge building over the
Gulf of Alaska and Eastern Alaska. This will cause moist
southwest flow to develop over Northern Alaska tonight and Wed
that continues into the weekend. Precipitation, strong winds, and
much warmer temperatures will move over Northern Alaska with the
southwest flow Wed and continue into the weekend.

A short wave trough from Kotzebue to Northway will move over the
North Slope of Alaska by 4pm Tue, then dissipate along the Arctic
Coast tonight. Expect isolated to scattered snow showers along
and north of this trough. See surface section below for enhances
areas of snow.

A second short wave trough from Nome to Galena to Dillingham will
move to Kotzebue to McGrath by 4pm Tue, then dissipate over the
Brooks Range by 4am Wed. Another batch of scattered snow showers
with this trough.

A third short wave trough over the YK Delta will move to Galena
to McGrath by 4pm Tue, then merge with the second short wave over
the Brooks Range by 4ma Wed. Some more showers with this.

Surface.... A low pressure trough just north of the Arctic Coast
of Alaska will persist through Wed AM. This will cause weak
offshore winds along the Arctic Coast along with cold temperatures
through tonight.

A 1012 mb low near Minto will move to near Demarcation Point as a
1009 mb low by 4pm Tue, to north of Inuvik as a 1007 mb low by 4am
Wed, and then continue northeast. A cold front extending south
from this low will move to Old Crow to Denali by 4pm Tue, then
persist into Wed. There is snow with the low center and scattered
snow showers along the cold front. Expect less than one inch of
snow with this.

The main feature for this week is a 936 mb low near its minimum
depth now in the southwest Bering Sea. This low will move east
along the Aleutians through 4pm Wed and then move into the
southeast Bering Wed night and Thu. A strong occluded front
stretches from this low to Adak and will move northeast into the
southeast Bering Sea by 4pm Tue, to St Matthew Island to Cape
Romanzof to Dillingham by 4am Wed, to Gambell to Nome to McGrath
by 4pm Wed, to Gambell to Kivalina to a 1004 mb low near Barter
Island by 4am Thu with a trailing front from Barter Island to
Denali. Front will then weaken in place Thu.

Snow will occur ahead of the front, changing to rain after the
front along the West Coast, and changing to freezing rain along
the front over the southern Interior. Expect 4 inches of snow
along the coast along, with 6-8 inches in the Western Interior.
Expect ice accumulation of .10-.25 inch over zones 215 216 and 227
Wed and Wed night, with lesser accumulations over zones 221 and
225 Wed PM and Thu. Freezing rain is possible in zone 222 223 and
226 Wed night into Thu as well.

Expect blowing snow along the West Coast with low visibility
before the front passes. Easterly gales will develop over the
northern Bering Sea ahead of the front tonight and Wed, turning
southeast and decreasing south of the front. Winds will increase
to 20-30kt over Kotzebue Sound Wed Ahead of the front. Will see
winds of 15-25 kt over the Western Interior with the front Wed.

Strong gap flow through Alaska Range passes will develop Wed and
continue into Thu. Chinook flow will develop across the Alaska
Range Wed and then vary from weak to moderate through Thu which
will add to the surface winds and cause temperatures to warm
considerable in the Tanana Valley.

&&

.DISCUSSION...
At H500 models initialize well and similar through 4pm Thu. At
the surface models verify well at 06Z Tue. The GFS deepens the
very strong low in the southwest Bering 5 mb deeper than the NAM
and GFS by 4am this morning, which appears to be happening. The
GFS is also slightly faster with the northeast movement of the
front associated with this low which also appears to be happening.
Thus the GFS is preferred in this strong feature through Thu.
From Thu night into Fri the GFS remains a bit faster with the
weather front moving northeast over Alaska and remains the
preferred model. From Fri into next week the long wave pattern is
similar but there are significant differences in timing and
strength of short waves from the weekend into next week giving a
high degree of uncertainty to the forecast from the weekend into
next week.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
High Wind Warning for AKZ223-AKZ225-AKZ226.

Winter Storm Warning for AKZ215-AKZ216-AKZ227.

Winter Weather Advisory for AKZ210-AKZ211-AKZ212-AKZ213-AKZ214-
AKZ221-AKZ225.

Small Craft Advisory for PKZ200-PKZ210.

Gale Warning for PKZ210.

&&

JB OCT 17