Gale Warning 323, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
419 PM AKDT Sun Apr 28 2019

.ANALYSIS AND UPPER LEVELS...
High pressure continues to keep its hold over most of the
mainland. An area of low pressure in the North Pacific extends a
warm front over the northwestern Gulf. This has allowed for
clouds to move in over the southern Kenai Peninsula. Surface
observations also show rain continuing over Kodiak Island.

Out west, a vertically stacked low centered south of Shemya
continues to move northward. Its associated front extends over
the central Bering. Satellite imagery shows plenty of marine
stratus in place over the western and central Bering, while skies
are generally clear over the eastern Bering thanks to the
influence of the ridge over the mainland.

&&

.MODEL DISCUSSION...
The forecast challenge continues to be the placement of an upper
level low over Southcentral for Monday and its interaction with
the lifting warm front currently over the Gulf. The NAM solution
brings in more moisture from the Gulf, resulting in more
precipitation for the northern Gulf coast Monday night into
Tuesday. Although the GFS is still the driest solution for
Southcentral, it has fallen into better agreement with the NAM and
EC solutions. A blended approach was used for the afternoon
forecast package.

&&

.AVIATION...
PANC...VFR conditions will persist even as clouds increase. Gusty
southerly winds will continue through the late afternoon and
evening hours, with light winds resuming after dark. Flow will
become northerly Mon, but there will still be a slight chance for
some southeast winds to clip the terminal.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through
3...Tonight through Wed)... Cloud cover and rain will return to
Southcentral Alaska tonight from a warm front tracking up from the
Gulf. The rain will begin along the southern Kenai Peninsula and
spread north on Monday. Heaviest amounts will be over the eastern
Kenai Peninsula with the Kenai and Chugach Mountains protecting
areas to their west from anything more than intermittent, light
showers. Showers will diminish on Tuesday as the front weakens and
pushes off to the northwest. Wednesday will see more fair
conditions as weak ridging settles in over the area.

&&

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

Another beautiful day is playing out across southwest Alaska, with
mainly sunny skies being observed. The exception to this is from
the Alaska Peninsula up towards Iliamna, and the Kuskokwim
Mountains to the northwest of Dillingham. Here, moisture continues
to increase, courtesy of a low that's located well south of the
Alaska Peninsula. Satellite water vapor loops show this stream of
moisture has a weak tropical connection, which combined with
orographic lift and diurnal heating has fostered the increase in
clouds.

Of more significance is a front currently over the western
Bering/Aleutians. This front will approach the coast for Tuesday
before stalling. Then a weak wave of low pressure rides north
along it from the North Pacific. This will bring a renewed surge
of moisture, with additional disturbances crossing the region
helping to boost ascent (lift) in the atmosphere. This all leads
to increasing rainfall potential for the Tuesday into Wednesday
time period.

&&

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

A ~975 mb low continues to approach the western Bering/Aleutians,
with a very strong tropical feed noted in the latest water vapor
loops. This system had some thunderstorms developing along the
front and near the low earlier. However, the core of the cooler
air aloft is becoming somewhat displaced as the system begins to
occlude. Thus, thunderstorms were left out of the forecast. The
main impacts from the front will be widespread rainfall, some of
it heavy at times, and sustained winds increasing to gales.

This front will then trek eastward through Tuesday evening, before
stalling across the eastern Bering and Alaska Peninsula. It
outruns its upper-level support and due to a weak wave of low
pressure riding north from the Pacific.

&&

.MARINE (Days 3 through 5)...
Winds are expected to be below gale force Thursday through
Saturday for the entire forecast area. However, there is a risk of
gales with a front moving through the western Aleutians Friday if
it ends up being a little stronger than currently advertised.
Forecast confidence is high for the northern Gulf of Alaska, and
only moderate for the Bering Sea and Aleutians.

&&

.LONG TERM FORECAST (Days 3 through 7)...
On Wednesday there will be an upper level high over northern
Alaska, an upper low over the Yukon Territory and the Alaska
Panhandle, and an elongated and negatively tilted upper low over
the Bering and Aleutians. There is also an upper high over the
Gulf extending southward. The main forecast challenge is in how
these features change over time. The current consensus is that the
upper high over northern Alaska will retreat northward through
the extended period. The Yukon low will weaken through Saturday,
then move eastward. The Bering/Aleutian low is expected to slowly
consolidate and move eastward, with its center near the eastern
Aleutians by Monday morning. Thus the forecast is for a slow
moving and somewhat stable pattern. The models are in better
agreement today than in previous days, and the forecast confidence
is near to above normal.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 173 175 176 178 185 412 413 120 131 138.
FIRE WEATHER...NONE.

&&

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