Small Craft Advisory 347, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
531 PM AKDT Fri May 3 2019

.ANALYSIS AND UPPER LEVELS...
An upper wave over the eastern Bering Sea has setup broad southwesterly
flow across much of the northeast Pacific/Gulf of Alaska. A broad
band of cirrus, associated with a strong jet(100kt), was evident
on satellite imagery. Southwesterly onshore flow over the
Southwest mainland continue rain showers. An occluded front over
the western Pacific brought rain and gusty south winds to the
western and central Aleutians. A weak upper level short wave kept
some cloud cover and perhaps some isolated showers along the
Talkeetna Mountains and portions of the Copper River Basin. Gusty
north to west outflow conditions over the eastern Kenai Pen
diminished as warming temps over the interior Kenai Pen weakened
the surface pressure gradients. Gusty westerly winds continue over
Barren Islands.

&&

.MODEL DISCUSSION...
Models adequately handle the synoptic pattern. Higher resolution
models with hand edits for local effects (mainly wind) will be
utilized this forecast cycle in the east. The GFS will be
generally used in the west to capture winds over the western
Bering.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

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

An upper level shortwave trough will move over Southcentral late
this evening into Saturday morning. This will bring scattered
showers to portions of the Mat-Su as well as the Anchorage
hillside and the eastern Kenai Peninsula. Precipitation will fall
mostly as rain, however some higher elevation areas may see snow
as slightly colder temperatures aloft are expected in weak
northerly surface flow. Showers will taper off Saturday morning as
drier air builds in ahead of a weak upper level ridge. A low and
its associated warm front will begin to track near Kodiak Island
Saturday night, with widespread rain and gusty winds eventually
expected for much of Southcentral (except downsloped areas) as the
system lifts northward across the Gulf on Sunday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

Isolated to scattered showers will be possible mainly along the
mountain ranges and across the Kuskokwim Delta through Saturday
night. A transitional surface pattern takes place tonight through
Saturday with a trough across the Southwest lifting north as a
North Pacific ridge builds over Bristol Bay. This ridge should
greatly limit showers Saturday and Saturday night. Southwesterly
flow across the region veers south late tonight with winds
becoming light across Bristol Bay and the Kuskokwim Valley.
Patchy fog may briefly develop during the morning hours this
weekend as stability increases along the building ridge.

Saturday night the next front develops across the Alaska
Peninsula, pushing a boundary north to Bristol Bay early Sunday.
Gusty easterly winds and rain develop along the frontal boundary
which moves northward across the region through early Monday
morning. Another reinforcing upper level wave propagates
northward on Monday keeping higher rain chances for the beginning
of the week.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

A gale force front along the western Aleutians slowly moves north
and east tonight with the boundary expected to stretch along the
Central Aleutians and southwestern Bering Saturday afternoon. Gale
force winds along the boundary taper down by Saturday morning as
the associated low fills on an eastward track; however, small
craft winds will impact the eastern Aleutians as the front slowly
diminishes.

Another low develops south of the Alaska Peninsula Saturday
evening as a strong short-wave rounds the base of the upper level
trough as it centers along the eastern Bering. There is some
uncertainty on the timing and strength of this system as it
organizes quickly and tracks north through Sunday. Yet another
fast mover develops early Monday, and is expected to follow a
similar track across the Southwest. During this same time, the
western Bering pattern becomes relatively benign as a ridge builds
in on Monday.

&&

.MARINE (Days 3 through 5...Mon through Wed)...

A low that gradually moves along the Aleutian Chain this weekend
will eventually center itself over the Pribilof Islands by Tue
and will remain nearly stationary through Wednesday. This will
generate northerly flow and a showery regime over the western
Bering. On the eastern side of the low, southerly flow will
prevail over the Gulf. This will allow a series of North Pacific
lows to track into the Gulf through Wed. Easterly flow along the
northern Gulf coast will briefly generate gale force winds over
the Barren Islands and Hinchinbrook entrance Sun morning through
Sun evening, diminishing to small craft by Mon morning.

Thereafter, it looks like a series of lows will move through the
Gulf through Wednesday. Gale force winds are possible, especially
along the north Gulf coast. Exact track and timing is not certain
at this time, but there is higher confidence this pattern will be
in place through at least mid-week.

&&

.LONG TERM FORECAST (Days 4 through 8...Tue through Sat)...

There is a high level of confidence that a pattern change will be
underway for next week across the northern Gulf coast and Kenai
Peninsula. The two main features that models reflect consistently
are an area of low pressure in place over the eastern Bering and
an area of high pressure over the southeastern Gulf. A cooler,
wetter pattern is very likely as both of these systems work to
advect moist southerly flow over Southcentral. However, there is
high uncertainty in the orientation of the upper level jet. This
yields much lower confidence in where the bulk of the moisture
will be directed and how much will be received. Generally,
unsettled weather conditions can be expected across the southern
Mainland through Saturday.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 173 174 176.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BC
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
MARINE/LONG TERM...KO