Small Craft Advisory 383, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
501 AM AKDT Wed May 6 2020

.ANALYSIS AND UPPER LEVELS...
A 550 dm upper level high was observed over Southcentral and
extending into Southwest Alaska this morning with surface high
pressure in place. As a result, mostly clear skies were observed.
Gusty southeasterly winds were present at the Anchorage terminal
and in Palmer at the time of this discussion due to the heating
that occurred over the Susitna Valley during the day. However,
winds were slowly diminishing after the sun set for the night as
the atmosphere decouples.

Multiple upper level lows were present south of the Gulf of
Alaska with a 999 mb low near Southeast Alaska and a more
prominent developing low well southeast of Dutch Harbor. With
these lows meandering in the Pacific an unsettled weather pattern
continues for Kodiak with on and off rain showers. Gusty
northeasterly winds were also present in Kodiak gusting 20-30 kts
at times.

Over the Bering and Aleutians, a frontal system was slowly
migrating eastward bringing rain and gusty southerly winds to the
Aleutian Chain. A stratus deck continued to be observed over the
Pribilofs to Dutch Harbor and Cold Bay.

&&

.MODEL DISCUSSION...
Model guidance remains in very good synoptic agreement through
Saturday. Only minor differences were seen in the model data
mainly in regards to the exact placement of the low pressure
areas. Therefore, confidence remains above average for this
forecast package.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist through the
period. Due to the persistence of the pattern in place, gusty
southeasterly winds are expected to make it into the terminal late
Wednesday afternoon through Wed night.

&&

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

The uncertainty from yesterday about the movement of the low in
the Gulf on Thursday and Thursday night has largely been resolved.
This has led to an marked increase in winds over the Gulf region
as well as increased forecast confidence.

Kodiak Island will see the brunt of this system with strong winds
and heavy rainfall on Thursday. Marine areas near Kodiak have Gale
warnings, though there is a chance Shelikof Strait and the Barren
Islands area may see a short period of storm force winds Thursday.

This system will also bring gusty winds and rain to the north Gulf
coast area but the cross-barrier flow will downslope out most of
the rain for the inland areas on the lee side of the mountains.

&&

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

Isolated showers will continue across the area today as an upper
level low in the Gulf sends several shortwaves across the region.
A rumble of thunder cannot be ruled out this afternoon,
particularly over the Kuskokwim Mountains. Any isolated storms
that do form may propagate into the Kuskokwim Delta area, though
they will be short lived, and will dissipate by the evening
hours. By early Thursday morning, a front arrives over the Alaska
Peninsula from the southeast. Gusty easterly to northeasterly
winds will persist across the greater Bristol Bay area Thursday
before tapering off by Friday morning. A warming trend will
continue through the end of the week with most interior locations
reaching highs in the low 60s.

&&

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

A front currently over the western Bering continues to move
eastward this morning bringing rain and gusty southerly winds
to the Aleutian Chain. This front is expected to weaken
significantly before stalling out just west of the Pribilof
Islands early Thursday morning. Attention quickly shifts to the
western Bering where a strengthening low approaches Thursday
afternoon. The leading front will reach the western Aleutians
Thursday evening, bringing another round of strong southerly flow
and rain for Friday.

&&

.MARINE (Days 3 through 5)..
(Friday through Sunday)

...Bering Sea and the Aleutian Coastal Waters...

Sustained gales are expected for the southern coastal waters of
the Alaska Peninsula Thursday afternoon and evening, mainly east
of the Shumagin Islands. Here, waves building into the 15 to 20
feet range are anticipated.

Otherwise, look for a front to enter the western Bering and
Aleutians on Friday, then it will strengthen with winds
approaching low-end gales on Saturday as it reaches the central
Bering/Aleutians, before weakening on Sunday as it approaches the
mainland. Given a decent fetch length, seas will gradually build
into the 15 to 20 feet range for locations along the front and
across the western portions of the chain.

...Gulf of Alaska...

An area of low pressure just south of the region will bring a
large swath of sustain gales to the Gulf, Barren Islands, and
Kodiak coastal waters on Friday. A few gusts near storm force are
possible. Winds will decrease some as you get near the northern
Gulf Coast. However, due to a long fetch length, seas of 15 to 20
feet will be fairly widespread, with the exception being Shelikof
Straight, where waves of 10 to 15 feet are more likely. These
winds and waves will decrease in intensity for the weekend as the
system moves away from the area.

&&

.LONG TERM FORECAST (Days 4 through 7)...
(Saturday through next Tuesday)

Our long-time resident low just south of the Gulf will continue to
wobble in place, sending multiple shortwaves northwestward into
the mainland. This will bring periods of rainfall to portions of
Southwest and Southcentral Alaska. The exception to this is the
Copper Basin. This area may see less upper-level support, as a
ridge of high pressure tries to build westward from the Yukon. As
it tries to do so, 850mb temperatures climb towards 14 deg. C,
with soundings showing a dry airmass in place by Monday. This
could potentially elevate some fire weather concerns.

Further west, a front located over the central Bering and
Aleutians on Saturday will bring widespread precipitation ahead of
it. This feature will then weaken on Sunday as frontolysis (the
weakening of a front) commences, as it's associated surface low
lifts north towards Siberia. Another low and associated front then
approaches the western Bering and Aleutians by Monday, with
precipitation chances rapidly increasing once again, while also
bringing another surge of warmer air.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 150 138 131 132 352 351 119 120 136 130 137.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MV
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...PD