Small Craft Advisory 552, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
455 PM AKDT Wed Jul 31 2019

.ANALYSIS AND UPPER LEVELS...
There is split flow over in the jet stream over Alaska. A
northern stream polar jet is driving a deep closed low and trough
eastward across northern Alaska. The tail end of a cold front
pushing inland is approaching the Kuskokwim Valley and Kuskokwim
Delta, with scattered showers out ahead of it. In the southern
stream, a high amplitude trough is lifting northward into the
western Bering Sea, with a moderate strength surface low and
frontal system tracking in the vicinity of the western Aleutians.
Rain and wind are spreading across the western to central Aleutian
Islands. An upper ridge is amplifying out ahead of the trough
across the central to eastern Bering Sea. Widespread low clouds
and fog dominate this area. Continuing downstream, a weak trough
and low centered over the southern Alaska Peninsula is exiting
slowly to the southeast. Areas of light rain and low clouds are
lingering along the Alaska Peninsula and into Bristol Bay. Lastly,
a short-wave ridge over Southcentral is providing mostly dry
conditions. Advection of mid to high clouds over top of the ridge
is leading to slightly cooler temperatures today versus Tuesday.

&&

.MODEL DISCUSSION...
Overall, models are very similar with evolution of large scale
features and forecast confidence is above average.

&&

.AVIATION...
PANC...VFR conditions will persist. There may be a period of gusty
south winds this evening with a hybrid of a Turnagain wind and up
Cook Inlet flow.

&&

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

A cold front will push up against the AK Range from the northwest
Arctic tonight into Thursday, bringing increasing cloud cover and
cooler conditions to parts of Southcentral. While some showers
are possible in the Chugach, in general the potential for
precipitation will be concentrated in the Talkeetnas and Alaska
Range. High pressure will persist over the Gulf of Alaska, and
patchy fog is possible tonight into Thursday morning in the
eastern Gulf. As a low approaches from the west, the increased
pressure gradient upstream of the Gulf high will bring areas of
small craft advisory level winds and seas to Cook Inlet and
Shelikof Strait Thursday, spreading into the western Gulf Friday.

A ridge will restrengthen over southern Alaska Friday, and cloud
cover inland will be less widespread than Thursday. A weak
shortwave will pass over top of the ridge Friday, bringing
possible showers to the Alaska Range and Talkeetnas, and likely
just a slight increase in cloud cover elsewhere across
Southcentral. However, Friday should still be a sunnier day than
Thursday for most of Southcentral and temperatures will trend
several degrees warmer than Thursday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3/Wednesday
afternoon through Saturday afternoon)...

A weak low tracking eastward across the Alaska Peninsula is
bringing rain showers and cloudy skies to Southwest today.
Simultaneously, a front approaching the Yukon-Kuskokwim Delta
from the northwest will keep the cloudy and showery pattern
intact overnight tonight. By Thursday morning, a weak ridge
briefly lifts over Southwest, though not much clearing is
anticipated as a strong gale-force front follows on its heels late
Thursday evening into early Friday morning. This front will bring
rain and gusty southwesterly winds to the Southwest coast. While
winds eventually diminish early Saturday morning, expect rain to
continue through Saturday afternoon.

At this time, we are monitoring the possibility for potential
storm surge along the Kuskokwim Bay coast (extending as far north
as Hooper Bay), as high tide occurs in conjunction with
persistent southwesterly flow Friday evening into Saturday
morning. Mariners and coastal residents are advised to stay tuned
to the forecast for updates on this situation.

&&

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

A gale force front moving across the Bering beginning this
afternoon will bring rain and southwesterly flow as it tracks from
west to east. The front is expected to reach the central Bering
by Thursday morning and the eastern Bering by Thursday evening.
Behind the front, expect continued showers and low level stratus
through the early weekend.

&&

.MARINE (Days 3 through 5)...

Beginning the extended period marine forecast on Saturday, a
seasonably strong front will be located over the eastern half of
the Bering Sea. The front will remain mostly stationary through
Sunday before weakening Monday night. This front will support
persistent southerly winds 20-30 knots from the Pribilof Islands
to the Kuskokwim Coast and farther south to Bristol Bay. With this
pattern expect gusty southerly winds at Dutch Harbor eastward to
the Alaska Peninsula.

For the Gulf of Alaska, persistent westerly flow will be occurring
across the Gulf and will persist into the next week. The strongest
gap flows will continue to favor the Barren Islands, Shelikof
Straight, and the southern coast of Kodiak Islands with winds
approaching 25-30 knots at times.

&&

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

Beginning the long term forecast period on Saturday, there will be
weak ridge over Southcentral with a strong shortwave trough and
associated surface low tracking overtop of it. The front will
extend from the North Slope down to the Central Aleutians, and
this will be bringing rain to parts of Southwest Alaska. Strong
cross barrier flow will bring in a much warmer and drier airmass
east of the Alaska Range into Southcentral, but there will be
quite a bit of cloud cover with it. The front will remain quasi-
stationary through Monday, with energetic upper level shortwaves
moving along it, briefing bringing rain chances farther south into
the Susitna Valley and interior Southcentral mountains. Overall
the pattern looks to hold steady through most of next week as the
upper ridge generally remains over Southern Alaska with transient
waves passing through. What does this mean? Generally wetter and
cooler across Southwest Alaska with warmer and overall drier
across Southcentral.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 412 413 175 177 178 181.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...MM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...JA