Gale Warning 602, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
449 AM AKST Sun Nov 3 2019

.ANALYSIS AND UPPER LEVELS...
High pressure continues to dominate over the Gulf, keeping upper
level flow along the north Gulf coast out of the west. The ridging
is also helping to bring more warm air to the southern mainland as
a long fetch of warm air rides over the ridge from the North
Pacific. Another area of high pressure sits over the northern
Bering helping to keep weak outflow winds over southwest Alaska.
Underneath the effects of the high pressure, the southern
mainland is seeing areas of fog and stratus lasting through the
night.

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.MODEL DISCUSSION...
The models are in good agreement through the short term for the
main synoptic features leading to high confidence with the
pattern. However, fog and stratus will continue to be a forecast
challenge for areas around the southern mainland.

&&

.AVIATION...
PANC...Light winds will persist. Fog and stratus will dissipate
in the early afternoon and then VFR conditions will persist. There
is a chance that fog could return tonight as there is
disagreement amongst the models on how dry conditions will be.
This leads to lower confidence tonight.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
(Sunday through Tuesday)

Fog has once again reasserted itself across much of the region,
with the lowest visibilities along the eastern side of the Cook
Inlet from north of Kenai, through Anchorage, into the Palmer
area. Here, visibilities have mainly been in the 1 to 3 mile
range, occasionally down to 1/4 of a mile. Otherwise, its been
less of a impedance for the morning drivers. This has occurred as
winds remain light, and a strong inversion (area of warmer air
aloft that acts like a "lid", preventing air to rise) which has
allowed surface moisture from our recent rainfall to remain
entrenched near the surface.

Aiding this process is an area of low pressure in the north
Pacific, and its attendant warm front stretching across the
southern Gulf. This front should spread rainfall far enough north
to reach the southern coast, before stalling once again.
Meanwhile, an area of low pressure stretched from eastern Russia,
across the Seward Peninsula, then across central portions of the
state. With our region being "sandwiched" in between, look for the
morning fog to gradually dissipate as it once again lifts into a
stratus deck by late morning. The good news is, the high pressure
will slide by just north and east of the Copper Basin, while the
front to the south approaches. This results in a tightening
pressure gradient, allowing increasing northerly winds to develop,
which should be sufficient to mix out the air enough from north
to south to allow the fog to become less of an issue for
tonight/Monday morning. These winds will get funneled through area
gaps/passes, with the strongest winds expected in the Broad pass,
Thompson Pass, and near Palmer as the Matanuska wind cranks up
somewhat.

This pattern begins to change for Monday and Tuesday, as the area
of high pressure slides into Canada, and a frontal system
approaches the western Bering/Aleutians. In advance of this
approaching western front, a few disturbances move into the
Bering. Southerly flow on the backside of the high and ahead of
these disturbances look sufficient to finally pull the front and
moisture northward into the southern Mat-Su Valleys and Copper
Basin, based on the latest model runs.

&&

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

With broad high pressure persisting over the Bering Sea/ eastern
Siberia, offshore flow and a cooling trend will continue over the
Kuskokwim Delta. Though it's tough to rule out fog with such a
clear night, it's most likely that persistent dry northwest flow
will stave off fog. Meanwhile, a low in the North Pacific is
lifting a warm front towards the AKPEN, which could bring some
precipitation into the Bristol Bay area this afternoon, but more
likely precip will be contained to the AKPEN/Alaska Range today.
Tonight into Monday, another front associated with that low
complex will push into the AKPEN again, and should track farther
north than today's front. Precipitation is likely in Bristol Bay
Monday morning, and precipitation types are a challenge. With warm
southerly flow aloft, precipitation in low lying areas will
either be rain, or freezing rain. Surface temperatures Monday
morning will be the deciding factor. With steady cloud cover and
no great source of cold air advection, it will be hard for coastal
areas, including Dillingham, to get much below freezing. Thus,
though there's a decent chance of brief freezing rain along the
coast, it's unlikely that any ice will stick thus impacts should
be minimal. Farther inland, e.g., Koliganek and New Stuyahok,
conditions will be colder and could see some icing. With southeast
flow, expect a transition to rain later in the day. Precipitation
will spread north into the Kuskokwim Valley/Delta Monday night
into Tuesday morning. Freezing rain is of particular concern, and
really the only factor diminishing confidence is that it's still a
few days out and models have had some inconsistency with the
progression of the front.

&&

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

A warm front associated with a North Pacific low is lifting
northward over the AKPEN into Bristol Bay, bringing small craft
advisory level conditions and precipitation. Meanwhile, high
pressure over the Bering Sea/ eastern Siberia continues,
maintaining mostly benign conditions and general anticyclonic flow
in the western Bering. As the warm front continues northward
Monday, small craft advisory level winds and seas will spread to
the central Aleutians, Kuskokwim Delta coast and Pribilof
Islands. A storm force low will approach the western Aleutians
Monday into Tuesday.

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.MARINE (Days 3 through 5: Monday through Wednesday)... A
moderately strong low south of the Alaska Peninsula may produce
gale force wind south of the Alaska Peninsula and Eastern
Aleutians through Tuesday. A strong low is moving into the
western Bering Sea Tuesday and storm force winds are possible
along and in advance of its front across the western Aleutians and
western Bering Sea offshore regions Tuesday.

&&

.LONG TERM FORECAST (Days 3 through 7: Monday through Saturday)...
The models are in good agreement amplifying the ridge into the
Bering Sea at the surface and aloft Monda.y through Wednesday. As a
result strong low pressure and a front move into the western
Bering Sea and moderate low pressure remains south of the Alaska
Peninsula. The models then depart from yesterday's solution that
held the low south of the Alaska Peninsula, and now are trending
to a low over or crossing the Alaska Peninsula Wednesday as the
Ridge in the Bering retrogrades west and weakens. With this in
mind, and the lacking consistency in the model solutions, we will
trend toward the ensemble solutions that are keeping a low in the
Gulf of Alaska and along or south of the Alaska Peninsula while
maintaining the high pressure over northeast Alaska. Over the
Bering Sea and Aleutians the trend will be to hold weak high
pressure over the west central Bering with moderate to strong lows
in the extreme western Bering Sea and Kamchatka Peninsula.

The models persist with bringing colder conditions to the Copper
River Basin Wednesday, with the much colder air moving in
Thursday. Friday and Saturday solutions are hinting at a return to
the warmer air for the Copper River Basin, however, confidence in
the models is low at that time.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gales...127.
FIRE WEATHER...NONE.

&&

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