Small Craft Advisory 194, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
403 AM AKST Sun Mar 4 2018

.ANALYSIS AND UPPER LEVELS...
A progressive upper level pattern remains in place over the
region this morning as one system exits the Copper River Basin to
the east and another approaches the Kuskokwim Delta from the west.
An upper trough is leaving clearing skies in its wake across
Southcentral as it departs into the Yukon. Stratus and some patchy
fog has developed in the Cook Inlet region aided by lingering low
level moisture and transient upper level ridging building in from
the west. Farther west, a Bering Sea front is moving into coastal
portions of the Kuskowim Delta accompanied by another round of
snow. The front extends down through the Eastern Aleutians, but
temperatures are warm enough there to support rain at Dutch
Harbor. The rest of the Bering has settled into a cool and showery
southwest flow regime behind the front.

&&

.MODEL DISCUSSION...
Models remain in good agreement in the short term as a series of
disturbances tracks west to east across the Bering Sea and
southern Alaska in the coming days. All of the available 00z
guidance is close on the timing of the next few systems, starting
with the front current moving into Southwest AK and slowly
pushing eastward to Southcentral on Monday. The next system then
follows closely on its heels as another front moves into Southwest
AK Monday night and reaches Southcentral by Tuesday.

&&

.AVIATION...
PANC...Low stratus and patchy fog will linger over the Cook Inlet
region through at least late this morning, bringing IFR/MVFR
conditions to the terminal. Ceilings are expected to gradually
rise over the course of the morning, but may be slow to entirely
dissipate today. Conditions are expected to improve to VFR by 22z.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Expect dry conditions across Southcentral Alaska today as a low
amplitude upper level ridge approaches from the west. Widespread
stratus has developed in the wake of yesterday's light snowfall
across Cook Inlet, the western Kenai Peninsula, Anchorage, and the
Matanuska Valley. There is some patchy fog as well, but mostly
just clouds. Based on the 12Z Anchorage sounding and the GOES fog
thickness product the cloud deck is around 1200 ft thick. Think
there will be some erosion of this cloud deck by midday, but it
will be slow and some clouds will likely persist through the
afternoon - or perhaps even longer. Also expect stratus to set up
shop in the Copper River Basin early this morning as mid level
clouds depart to the east. The remainder of Southcentral will see
some sunshine, especially along the Gulf coast and Prince William
Sound where offshore gap winds will persist. These winds will die
off tonight as the ridge moves overhead.

Another in a steady stream of upper level short-wave troughs will
arrive on Monday. In this case, there will actually be two out
of phase troughs, both very weak. Have backed off PoPs and QPF,
keeping likely chances of snow confined primarily to the mountains
on Monday afternoon. It's looking more and more like the population
centers will only see flurries or nothing at all. Another upper
ridge will build in Monday night, with a good chance of fog and
stratus redeveloping in the Cook Inlet region.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...
A front over the eastern Bering is tracking east and will make it
over the Kuskokwim Delta this morning bringing snow and blowing
snow to the area. It will continue to push inland into tonight
before falling apart. Weak ridging will then move in before
another front comes on Monday night. This front will also impact
the Kuskokwim Delta and bring more blowing snow to the area.
However, this system is stronger with higher snow amounts and
stronger winds expected. This will result in reductions in
visibility that could reach one mile or less. There does remain
some uncertainty with how guidance is handling this feature
resulting in lower confidence in how much snow will fall and how
far visibilities will drop. The front will then push through the
rest of southwest Alaska Tuesday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
The front over the eastern Bering will quickly exit to the east
and will be replaced by weak ridging that will also rapidly track
across the Bering. Another front will soon follow the ridging,
moving in over the western Aleutians tonight. This system is
pulling up warm air from the south and looks to bring a mix of
rain and snow to the islands. The front will move east making it
to the central Bering and Aleutians Monday afternoon and the
eastern Bering and Aleutians by Monday night. Westerly flow with
showers will be left in the wake of this system through Tuesday.

&&

.LONG TERM FORECAST (Days 3 through 7)...

A fast moving frontal system will cross the eastern Bering
Monday evening, to push onshore over Southwest Alaska late Monday
night through Tuesday morning. Snow and blowing snow will likely
be a concern for the Kuskokwim Delta and western Capes with snow
spreading further inland mid morning through early afternoon.
While the upper level trough will be weakening as it crosses into
southcentral Alaska, snow looks likely there as well with light
snow developing Tuesday afternoon then increasing and becoming
more widespread Tuesday afternoon and Wednesday. Following this
system, the strong westerly jet stretching across the Bering will
continue to bring a very active storm track through the end of
the week. A large upper level low will dig southeast across
mainland Alaska around Friday spreading additional cold air across
the state and strong, cold north to northwesterly flow across the
central and eastern Bering, the Alaska Peninsula and eastern
Aleutians.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None
MARINE...Storm Warning 178 411
		 Gale Warning 177 185 412 413

&&

SYNOPSIS AND MODEL DISCUSSION...CB
AVIATION...CB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DWK
LONG TERM...JR