Small Craft Advisory 102, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
521 PM AKST Fri Feb 1 2019

.ANALYSIS AND UPPER LEVELS...
A slow transition to a new pattern is evident on satellite and
radar today. The ridge that has been in place is yielding to
multiple waves coming in from the broad trough over the Bering.
First, the fog that has lingered across much of Cook Inlet
dissipated quickly this morning. Offshore flow remains gusty
through the Copper River Basin down through the port of Valdez.
Gusts as high as 63 mph have been reported at the Valdez Airport.
The first wave is a warm front moving into SW AK. Radar shows
light snow stretching from King Salmon up through Bethel with
visibilities and ceilings dropping in response. There is just
enough persistent offshore flow to create some isolated pockets of
blowing snow, mainly along the coast.

A secondary warm front is over the Western Bering. Along this
boundary, we can already start to see a new area of low pressure
developing. Gale-force winds continue across the Central
Aleutians. This system is bringing up a healthy round of warm air
and all of the precipitation associated with it is rain, some of
it moderate at times from Adak to Atka.

&&

.MODEL DISCUSSION...

Models are in general good agreement as the pattern changes this
weekend. With this consensus, a blend of models was used
throughout the Gulf and Southcentral. The low in the western
Bering is being well handled, especially regarding the intensity
and location of the low as it moves into the northern Bering
Saturday morning. Come Sunday evening, while synoptically the
models are showing a similar North Pacific low approaching the
Aleutian chain, they have yet to lock onto an agreed upon
solution. The American models are showing a closed low system with
varying strengths southeast of Adak, while the EC is depicting
more of a troughing feature. With this in mind, the GFS was chosen
as the model of choice in southwest Alaska.

&&

.AVIATION...

PANC...VFR conditions with light north winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

A front along the Southwest slides across Kodiak Island and the
southern Gulf tonight. Snow will be the main form of precipitation
across the island, except for the southern end where temperatures
will be warm enough to support a wintry mix. Otherwise, the
conditions across the mainland will see dry conditions through
Saturday afternoon under the influence of the mainland ridge. A
few showers will develop across the gulf as a weak mesoscale low
forms due to the off shore flow. Showers are not expected to move
into coastal areas, but it cannot be ruled out being so close to
the vicinity.

The biggest challenge in the forecast is the next front that
begins to push across from the Southwest Saturday night. This
system is expected to slowly move across Cook Inlet to the
Susitna Valley as the driving surface low fills on its northerly
track across the Bering Strait. Light snow is expected to spread
across the Kenai, Anchorage Bowl and Matanuska Valley on Sunday;
although accumulations will be limited as southeasterly flow
increases at the onset of this first front of the week. During
this time, snow accumulation amounts are expected to be highest
across the Susitna Valley and west facing slopes of the Talkeetna
Mountains...including Hatcher Pass.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The upper level trough over the area will move east and dissipate
tonight. A front will reach the Kuskokwim Delta coast tonight, and
work its way eastward across the area through Sunday afternoon.
This system is moving quite slowly with precipitation spreading
eastward, and also slow to end on the back side with only the
Kuskokwim Delta being dry by Sunday afternoon. The front will
bring a surge of warmer air to southwest Alaska, with
precipitation starting as snow and then changing to rain. There is
a chance of freezing rain in the lower Kuskokwim valley as low
level cold air should be slow to scour out.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The storm force low centered just north of the central/western
Aleutians this afternoon will rapidly move north across the
central Bering tonight. The associated front will be slow to exit
the eastern Bering, finally moving inland late Sunday night into
Monday morning. Behind this system, generally southerly flow
will then persist across the Aleutians and Bering with mild
temperatures. The air mass will also be fairly moist for the
central and western Bering/Aleutians with some showers expected
through Sunday afternoon. With the warm temperatures these will
generally be a mix of rain and snow, changing over to snow for the
western Bering Saturday night and Sunday as some slightly colder
air moves in from the west.

&&

.MARINE (Days 3 through 5)...
Confidence is gaining on mid to high end gales happening from the
central Aleutians and east towards Bristol Bay Sunday night and
again Monday evening, as a deepening north Pacific low moves into
the Bering. The first bout of low end gales will be from the east
as a front slides to the north. Monday, winds will become
southwesterly behind the front and ramp up. We feel pretty
comfortable seeing mid to high end gales with 20+ ft seas. Storm
force winds are possible, but guidance is not as firm on that
outcome.

.LONG TERM FORECAST (Days 3 through 7)...
The long range hemispheric pattern is not changing much through
next week. A large and complex upper level low remains anchored
across Siberia and keeps the Bering as well as all of Alaska in
the continued cross hairs for active weather. Three systems will
impact the region through next Friday, keeping the area under
southwesterly flow and warming over time. Southwest Alaska will
keep warming to above normal for this time of year. Southcentral
will see the return to near freezing temperatures during the day
and overnight lows in the upper teens on nights that clouds clear.
With the successive frontal passages, snow looks to be a
possibility across the area with the Susitna Valley being the
biggest winner for totals. Anchorage will likely see the usual
mountain blockage for the majority of the events. Challenges for
precipitation type forecasting do not look to be a problem until
later in the week. We should remain locked in with enough cold air
at the surface, and minimal warming aloft, to see primarily snow.
Thursday and beyond it will become more of a challenge as
stronger warm southwesterly flow bleeds into southcentral. This
could elevate the chances for mixed precipitation type, but
confidence that far out is quite low. The Copper River Basin is
the only area that will keep winter-like temperatures this coming
week. Temperatures should raise 20 to 25 degrees over the past few
days. While a significant jump, highs will still remain in the
teens with overnight lows still slipping below zero.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 170 172 173 174 177-185.
		 Storm 175 176.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MSO/RA
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BL
MARINE/LONG TERM...SS