Small Craft Advisory 395, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
416 PM AKDT Wed May 17 2017

.ANALYSIS AND UPPER LEVELS...
The large upper level low remains centered just a little ways
south of the Alaska Peninsula with a broad trough extending to the
northeast of it into the southern half of the state.
The jet stream is running south of this low and remaining south
off the region.

The surface low is weakening just south of Dutch Harbor with what
is left of the front extending into southern Alaska. There is a
wave along the front in the Kodiak area which is enhancing some
rainfall there. The pressure gradient is still running rather
tight along the north Gulf coast bringing in the gusty winds
through channeled terrain.

The atmosphere over southern Alaska is stable this afternoon
which is to be expected in this pattern.

&&

.MODEL DISCUSSION...
Models remain in very good agreement through the remainder of the
week. As has been the case the past few days, the very hi-
resolution models such as the NAMnest and ARW are being used for
the gusty gap winds through the Chugach and Kenai Mountains.

&&

.AVIATION...
PANC...VFR conditions will persist. Gusty Southeast winds will
persist through the evening and eventually lessen overnight, but
may still be an impact for aviation at PANC most of the night.
Tomorrow will see the usual morning lull in winds but then they
will be Southeast and gusty again by early afternoon.

&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The remnants of a frontal system that moved through the gulf
overnight will continue to bring cloud cover and cooler
temperatures to much of Southcentral through Friday. Gusty gap
winds will occur again along Turnagain Arm as well as along the
Knik and Copper River's this evening, however with limited daytime
heating today these will be slightly weaker than the winds
yesterday evening. The area will then remain in a generally
cloudy and showery pattern through Saturday, with rainfall
primarily falling along the Gulf Coast/southern Kenai Peninsula,
while interior Southcentral will stay mostly dry other than a few
stray light rain showers.

&&

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

A stacked low, currently centered south of Dutch Harbor, will be
gradually making its way towards Southwest Alaska over the next
few days. As it does so, a series of upper level waves rotating
around the upper low center will cross over Southwest Alaska. This
pattern will reinforce the cloud cover already in place, keep
precipitation as a constant threat, and ensure temperatures stay
cool. Despite the abundant cloud cover, any precipitation should
be limited to scattered shower activity, so most areas will be dry
most of the time. This cloudy pattern will also help to keep fire
concerns minimal with higher afternoon relative humidity values.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

The area of low pressure centered south of Dutch Harbor will
continue to weaken as it moves eastward over the next day or so.
This will allow for some weak ridging to build over much of the
Bering. This will promote fog and low stratus potential across
large portions of the Bering as a low-level stable layer is
promoted by the warm air aloft. This pattern is expected to
remain relatively steady-state through at least Friday until the
next front enters the western Bering on Saturday.

&&

.LONG TERM FORECAST (Days 4 through 7/Saturday night through Wednesday)...
The extended period starts out with a highly amplified pattern in the
upper levels, which is a bit unusual for this time of year. Two dominant
blocking ridges (one just along the west coast of the Continental U.S.
and another in the Russian Arctic) will cause multiple troughs to converge
upon Alaska, resulting in active weather (aka clouds and rain) across
much of the forecast area.

More specifically, the Gulf of Alaska and southern mainland of Alaska
will be heavily influenced by deep southerly flow along the west side
of the ridge, leading to especially wet conditions along the Gulf coastal
region Saturday night through Tuesday, with clouds and showers occasionally
spreading inland to Southcentral and Southwest Alaska. There will certainly
be some breaks of sun inland, but nothing very prolonged. Thus, expect
temperatures to be near normal for this time of year.

Meanwhile, a series of troughs will cross the Bering Sea with a large
upper level low to follow. This will spread rain eastward to the
Southwest coast by late Tuesday. As the low dives southeastward
into the Pacific the front will likely stall over Southwest Alaska
and the western Gulf, so it could be two or three days of rain across
this region. Ridging out ahead of this will lead to improving conditions
over portions of Southecentral the middle of next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JW
LONG TERM...SB