Gale Warning 414, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
523 PM AKDT Sun Sep 15 2019

.ANALYSIS AND UPPER LEVELS...
There is an upper level low over southern Alaska that is moving
rapidly eastward. The associated front currently stretches from
the Lower Kuskokwim Valley southeast through Cook Inlet then south
across the central Gulf. Rain and showers are occurring over much
of southern Alaska with this front. A triple point surface low is
developing just south of the Kenai Peninsula, with gale force
winds over portions of the Gulf and south of the Alaska Peninsula.
There is a flat upper level ridge over the central and western
Bering Sea, with westerly winds over the central and eastern
Bering. A warm front is working its way into the central and
western Aleutians from the south.

&&

.MODEL DISCUSSION...
The numerical models are in rather good agreement for the short
term portion of the forecast (through Tuesday afternoon), even
with a quite progressive pattern. Therefore forecast confidence
is higher than normal for this time of year.

&&

.AVIATION...
PANC...MVFR conditions in rain are expected tonight. After the
rain ends late tonight, MVFR ceilings are expected to hang on for
a bit and then improve to VFR by late Monday morning. The threat for
southeast winds to hit the terminal this evening is all but over
as of 5pm.

&&

.FIRE WEATHER...
Wetting rains are expected over most of Southcentral tonight. The
overall pattern for the rest of this week will be very fall-like,
with wetting rains expected every 2 days or so.

&&

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

Precipitation continues across Southcentral, driven by a broad
upper low centered over Southwest AK. A triple point low
developing near the southern Kenai Peninsula will slowly shift
eastward and deepen tonight, enhancing precipitation over Prince
William Sound and the eastern Kenai Peninsula. Southeast gap winds
over Southcentral will diminish tonight, while gales will develop
over wide swaths of the Gulf as the surface low deepens.

The upper is tracking southeastward, and will become stacked by
late tonight. Precipitation will diminish into showers, clearing
up from west to east as conditions stabilize. Monday will be a
mostly dry day, though some lingering showers are possible in the
periphery of the low in eastern Gulf and in the Wrangells. Gusty
offshore winds are likely along the north Gulf coast as the Gulf
low exits to the east, particularly in Seward/Resurrection Bay and
Whittier/Passage Canal.

A trough with Arctic origins will track southward Monday night
into Tuesday, enhancing north flow and bringing a cooling trend,
with possible precipitation in the northern Susitna Valley/
northern Copper River Basin.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1-3: Sun-Tue)...

The front across the southwest brought average rainfall amounts
around one half inch today. The front moves east overnight with
rain tapering off quickly late this evening. Showers remain in the
forecast through Monday as upper level waves continue to propagate
around the upper low digging southeast. By Monday evening...most
of the area will see a brief break in the rain. A low dropping
south from the northwest coast will push a front to the Kuskokwim
Valley Monday which should bring a showers mainly along the
Western Alaska Range. Patchy fog is expected to develop Monday
night as winds go light and temperatures drop toward dewpoint
values.

Tuesday and Wednesday will be a wet forecast as the next Bering
front rides in along the subtropical jet stream. The frontal
boundary arrives along the Southwest Coast early Tuesday
morning...pushing quickly across the Delta and Bristol Bay...then
across to the Alaska Range Wednesday evening. The associated low
moves inland from the Bering Wednesday morning and continues track
eastward through the afternoon while weakening. Rain tapers off
significantly from west to east as the low center moves across the
Alaska Range.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1-2: Sun-Mon)...

The next low pressure system moves to the Western and Central
Aleutians this evening. The track of this system is relatively
slow as the low center deepens to 990 mb and crosses over Adak to
the southern Bering late Monday afternoon, with the associated
front pushing across the Eastern Aleutians and the Pribilof
Islands. Expect gale force winds around the core of the low and
moderate to heavy rain. Tuesday morning...the low begins to pick
up pace on an eastward track. The front races quickly across the
eastern Bering including the Alaska Peninsula by Tuesday
morning. The low center reaches the Pribilof Islands Tuesday
evening pushing inland over the Kuskokwim Delta by Wednesday
morning.

Colder air advects across the northern Bering on Wednesday in the
wake of the low. The next North Pacific warm front moves to the
Western Aleutians Wednesday morning limiting the advancement of
the Arctic air.

&&

.MARINE (Days 3 through 5)...
There is high confidence that a low in the eastern Bering early
Wednesday will help to bring gale force winds around the eastern
Aleutians and Alaska Peninsula. Small craft westerly winds look
likely for most of the Gulf of AK. As the low moves over mainland
Alaska through the day on Wednesday the winds will diminish.

Out west, there is lower confidence that a North Pacific low
approaching the western Aleutians on Wednesday will bring gale
force winds to the area. These winds are expected to drop to small
craft level on Wednesday. Winds look to stay light Thursday and
Friday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
There is good agreement amongst the models of an unstable pattern
remaining over southern Alaska through the weekend. This would
keep a chance of showers for most locations. However, the
Aleutians and north Gulf coast will see more activity with a
series of lows tracking through the area from west to east while
staying just south of the Aleutians.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 411 413 150 155 177 178 351 352 119 120 131 132 138.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...MM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
MARINE/LONG TERM...DK