Small Craft Advisory 115, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
751 AM AKST Mon Feb 3 2020

.ANALYSIS AND UPPER LEVELS...
An upper level trough spanning across the Bering and Aleutians
remains the dominant weather system this morning as it sends
multiple short waves to the southern coast. A closed low within
the trough is centered over the Central Aleutians. The next
significant wave is propagating away from the low center and
making progress to the southern Gulf.

At the surface, rain and snow continues to develop along a front
that is now weakening over the northern Gulf. Conditions still
remain gusty across the eastern Kenai Peninsula and western Prince
William Sound, so blowing snow is reducing visibilities to less
than a mile across these locations. A few snow showers are moving
inland from the front with the Northeast Gulf coast in steady
light snow as the front is draped along Prince William Sound. Rain
and snow is also along the Southwest coast from the eastern
Alaska Peninsula to the Kuskokwim Delta, as a boundary extends
across this line and westward along the northern Bering waters.
Warm air intrusion is noted across much of the central and
southern Bering with the warmest temperatures hovering around 40
degrees.

&&

.MODEL DISCUSSION...

Models generally are in good agreement with the active pattern
that continues through Wednesday. There are a few minor
differences with the surface lows development along the next two
fronts progged to cross the gulf today and late Tuesday. Used a
general model consensus for updates with some use of NAM/nest for
stronger winds across the Gulf and surrounding coast.

&&

.AVIATION...
PANC...VFR conditions today are expected to diminish to MVFR this
evening as the next front slowly moves across from the Kenai
Peninsula. IFR conditions may need to be added tonight; however,
there was not enough confidence to add these details at this time.
Winds out of the north today will become light and variable
overnight.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A warm front entering the southern Gulf this morning will lift
northward across the Gulf, helping to strengthen a stationary
front already in place along the North Gulf coast. Thus, expect
gale to storm force winds to persist through the afternoon hours
across the northern to western Gulf coastal waters as well as
southern Cook Inlet. A low will then enter the Gulf tonight and
the front will push onshore and rapidly weaken. The bulk of
precipitation with these fronts will remain along the Gulf coast
and Kodiak Island until this evening. Light snow will then spread
inland tonight with the front and a weak short-wave trough aloft.
A second upper level short-wave will follow shortly behind,
causing snow to linger over interior Southcentral through the day
Tuesday, gradually tapering off during the afternoon hours. With
progressive flow aloft, yet another upper short-wave and surface
front will reach Kodiak Island Tuesday afternoon then up to
Southcentral Tuesday night. This will bring another shot of light
precipitation.

Temperatures will continue to slowly warm as we head through the
next couple days, with all except the Copper River Basin rising
into the 20s by Tuesday. Kodiak will switch back and forth between
rain and snow as each wave/front comes through. The Cordova area
also looks like it will warm up tonight as the front pushes
onshore tonight, leading to a transition from snow to rain tonight
into Tuesday. Expect precipitation type across the remainder of
Southcentral to remain as snow.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 2)...

The latest satellite image has a frontal boundary extending from
Shemya across the Bering and into southwest Alaska. The leading
edge of the cloud shield is already north of the Brooks Range. The
radars at Bethel and King Salmon continue to ping into light
returns over Toksook Bay and near Port Heiden. As of 12z this
morning the temperature at Bethel was 35F which is an increase of
15 degrees from 12z yesterday. As of 12z this morning, Dillingham
was at 26F which is an increase of 26 degrees from 12z yesterday.
There is a broad longwave trough axis over the Bering with a
minor ridge over Lake Clark National Park. There are numerous
shortwaves getting ejected out of the Bering and North Pacific
that will nudge the ridge eastward and bring more moisture to the
region. A new triple point low has formed south of the AKPEN but
this low will quickly move eastward and out of the area of
responsibility.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 2)...

This morning there is a 960 mb low southwest of Adak with an
elongated front over the Bering. This low is already past its
prime and expected to slowly fill this forecast period. The
surface low will cross the chain this afternoon just east of Adak.
Cyclonic flow will continue to influence the region although the
winds will steadily decrease. Looking upstream, the is already a
new low near the Kuril Islands which will move towards the western
Aleutians midweek. The models show a dynamic and progressive
pattern from the western portion of the North Pacific to the
Bering in the form of shortwaves which would suggest that any
additional precipitation over the Bering will be convective. The
jet stream stays south of the Aleutian chain the entire forecast
period.

&&

.MARINE (Days 3 through 5: Wednesday through Friday)...

...Bering Sea and Aleutian Coastal Waters...

Sustained gales are anticipated on Wednesday for the northern
Bering Sea, as the region will get sandwiched between an area of
high pressure over eastern Siberia and an area of low pressure,
with an attendant warm front, moving into the southern Bering.
Here, seas will peak near 20 feet. Lighter winds will prevail
elsewhere for Wednesday. All locations will remain below gales for
Thursday.

Then for your Friday, a stronger area of low pressure and warm
front will make its way into the southern Bering. With the Siberian
high remaining in place, sustained gales will spread from the
western portions of the sea towards the Pribilof Islands by Friday
evening. Given a stronger push of warm air than its predecessor,
given a long fetch length, seas will increase to near 20 feet from
Dutch Harbor westward towards Shemya south of the chain, with
similar heights spreading from the western Bering towards the
Pribilof Islands.

...Gulf of Alaska...

Mainly quiet conditions are expected for the area, with winds
briefly reaching 20 to 30 knots for coastal locations near Kodiak
Island in the Wednesday evening through Thursday morning time
frame. Otherwise, look for seas to average in the 8 to 12 feet
range near the Gulf Coast, with slightly higher seas expected
offshore.

&&

.LONG TERM FORECAST (Days 3 through 7: Wednesday through
Sunday)...

An active weather pattern will be present for the duration of the
long term. Quick moving flow will cause a series of upper level
ridges and troughs to work their way across the Bering Sea and
across Southcentral AK. The long term starts with low pressure in
the Bering, creating stormy conditions there. Southwest flow
riding over the top of a ridge in the North Pacific can be
expected to create active weather (at least a chance of snow) and
warming conditions for Southcentral AK. From there, the long term
plays out with these systems working their way east.

Unfortunately, there is little model agreement on the timing and
placement of the individual weather features within this active
weather pattern. Therefore, all we can really say at this point
is to expect a series of storms to work their way across the
Bering and the Gulf of Alaska, with breaks in the weather in
between. One thing we can say is the pattern looks warm, so we can
expect the colder temperatures we have been seeing to cease and it
should stay that way.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 125.
MARINE...Heavy Freezing Spray Warnings 139 185.
		 Storm Warnings 119 130 131 176 177 178 185.
		 Gale Warnings 120 138 139 411 413.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PJS
MARINE/LONG TERM...PD/BB