Small Craft Advisory 212, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
323 PM AKST Fri Mar 10 2017

.ANALYSIS AND UPPER LEVELS...

A closed high in the upper-levels over the eastern Bering
continues to keep the weather pattern quiet over Alaska. The ridge
axis extends along the northwest coast of the state, putting the
southern mainland under offshore northerly flow downstream of the
ridge axis. Satellite imagery shows some mid and upper-level
clouds wrapping around the ridge axis into parts of Interior and
Southwest Alaska. Most of this wrap-around moisture is not making
it south of the Talkeetna and Alaska Ranges however, so
Southcentral is enjoying another mainly sunny day. Gusty outflow
winds over Thompson Pass and the Copper River Delta are subsiding
as surface high pressure over the mainland begins to weaken.

&&

.MODEL DISCUSSION...
Models remain in good agreement under high
pressure again today. No significant changes in the East. In the
West, NAM Nest was used to bring higher winds in later on
Saturday. Forecast confidence continues to be high with the
pattern change expected next week.

&&

.AVIATION...
PANC...VFR conditions with continued offshore northerly winds
throughout the day.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Surface ridging across the mainland brings dry and slightly
warmer conditions through the beginning of next week. Winds
generally will stay in a light offshore pattern with typical
gusts along north to south oriented gaps. On Sunday into Monday,
gap winds are expected to increase as low pressure develops across
the east gulf causing the pressure gradient to tighten. This will
also bring stronger north flow along the gulf waters and Cook
Inlet.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Sunny skies, near normal temperatures and diminishing northerly
winds will be the story throughout the Southwest Mainland through
Saturday as Rex block sets up over the Bering Sea. Starting
Sunday this Rex block will shift westward, allowing for a
tightening pressure gradient and increasing northerly winds,
especially along higher elevations around Bristol Bay.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The period of very quiet weather over much of the Bering Sea will
continue into this weekend as a broad Rex block remains overhead.
This will allow winds throughout the region to fall below gale
force this evening with no chance of precipitation in the short
term. This may allow for stratus development over the Western
Bering where the strongest stability exists, however with dry
boundary layers no fog is expected.

&&

.LONG TERM FORECAST (Days 3 through 7...Mon through Fri)...
A pattern change will slowly unfold. This will occur as the ridge
over the Bering very slowly creeps to the west and allows more
energy to spill over the mainland. The energy helps to carve out a
deep longwave trough that will extend from the Arctic through the
Gulf of AK. Within this trough will be plenty of very cold air.
850hPa temperatures over the Interior look to drop to just as or
nearly as cold as they were during the past week. It does look
like the AK Range blocks much of this cold air from intruding into
Southcentral AK. But Southwest AK will not be so fortunate with
low temperatures looking to plunge well below zero by the middle
of next week (13017) March. As this colder air works in, there
could be some light snow that makes it over the ridge. The more
likely impact will be some gusty winds with the robust cold air
advection. And certainly as this cold air spills off the edge of
the ice pack over the open Bering waters, there will be widespread
snow showers spreading across the Aleutians.

The other interesting aspect of the pattern change will be lower
pressure developing in the northern Gulf of AK. There is still a
fair amount of uncertainty with any surface low center that would
develop. However, it does look like enough moisture will make it
back in to the coastal areas that we have increased the snow
chances across that region. If moisture can swing far enough west
into the very cold air, it could lead to some snow threats for
interior portions of Southcentral towards the latter half of next
week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

SYNOPSIS AND MODEL DISCUSSION...RD
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...MO