Small Craft Advisory 861, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
443 AM AKDT Sat Nov 3 2018

.ANALYSIS AND UPPER LEVELS...

An area of high pressure was centered near Fairbanks, with a low
further south centered near Cold Bay. Normally this would look
like a Rex Block, however it's a progressive pattern, thus
negating the block. A front progressing through the occlusion
process is stretched from the Cold Bay low eastward into the Gulf
with widespread rainfall accompanying it.

Isolated thunderstorms have also developed behind the front
southeast and east of Kodiak. As a vort max in the flow is
supplying additional ascent, and dry advection over the moist
lower levels are interacting with this lift. Producing sufficient
vertical velocities to lift the moisture condensation high enough
for charge separation (high enough into the colder air aloft for
lightning to develop). Strong winds have also been prevalent near
the area of low pressure and the front.

&&

.MODEL DISCUSSION...

All of the short range numerical guidance remains in excellent
agreement at the surface and aloft, leading to a high confidence
forecast.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The front over the northern Gulf will weaken today and then
dissipate tonight. Precipitation with this front will be limited
mainly to the Gulf coast and surrounding mountains. Virtually no
precipitation will make it inland past the coastal mountains as
high pressure remains over the interior, although considerable
clouds are expected. The low responsible for the front will cross
the Gulf from east to west tonight and Sunday. As it does this,
northerly offshore flow will increase with strong gap winds
developing. Southcentral will then return to a period of clear
and dry weather.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2: Today through
Sunday Night)...

Southwest Alaska remains in between high pressure which remains
over interior Alaska, and a weakening area of low pressure
tracking south of Cold Bay this morning. The primary impact from
this meteorological setup is continuing breezy conditions,
primarily through the gaps in the Alaska and Aleutian Ranges.
Isolated rain showers persist near Dillingham, but as the low
weakens, the upslope winds up the Kuskokwim Mountains should cause
a gradual weakening of the shower activity during the day today.
The relaxing pressure gradient between the aforementioned areas of
high and low pressure should also result in diminishing winds
across the area as well today. Otherwise, a quiet weekend is
expected weather-wise, with high pressure keeping conditions dry.
Thus, the two notable points to mention here will be cooling low
temperatures both Sunday and Monday mornings, with Sunday morning
being the colder of the two. Clear skies and light winds will mean
lows will dip to near 0 in portions of the Lower Kuskokwim
Valley. Secondly, warming temperatures in the middle levels of the
atmosphere along with either calm winds or light onshore winds
Sunday Night should result in widespread freezing fog for much of
the area for Monday morning. A saving grace along the Kuskokwim
Delta will be a rapidly approaching front moving in from the
Bering which will increase the cloud cover and the winds ahead of
it, which may scour out the fog during the early morning hours
Monday morning.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2: Today
through Sunday Night)...

The area of low pressure that has caused the active weather across
the central and eastern Aleutians, Alaska Peninsula, and southern
Bering for the past couple days is finally on its way out of the
area. The center is tracking eastward towards the Gulf south of
the Alaska Peninsula. As the low weakens and moves away, winds
will be diminishing especially tonight across the eastern Bering.
The next feature will be a strong cold front expected to move into
the western Bering Sunday morning. Initially through Monday
morning, it will be associated with a low that most of the models
expect will remain centered along the coast of eastern Russia, as
opposed to taking a track further out into the western Bering. The
result of this looks to be a significantly weaker solution as
regards its associated winds, with storm force winds no longer
expected as it tracks through the central and northern Bering late
Sunday night into Monday morning. A renewed blast of cold air will
follow behind the front.

&&

.LONG TERM FORECAST (Days 3 through 7/Monday through Friday)...

Not much change in the extended forecast today for Anchorage
forecast area. Cold and dry conditions are expected to continue
for the mainland, with storms moving across the Bering Sea through
the end of next week. In the upper levels, a strong ridge over the
mainland maintains its hold, keeping a strong low over the western
Bering Sea. This low will track northward through the Kamchatka
Peninsula, bringing gale force winds to the Bering Sea through
Wednesday, but relatively few impacts otherwise. Although the
front from this storm is anticipated to move over the mainland on
Wednesday, it should be relatively weak and precipitation is not
expected to make it very far inland.

As the Bering Sea low weakens, another low is expected to approach
the area from the northern Pacific. Again, the upper level ridge
should help deflect this feature off towards the east. Yesterday's
model runs were in more disagreement on what would happen with
this low, but today, they've come more into alignment, with the
surface low crossing the Gulf of Alaska toward Yakutat late
Wednesday and into Thursday. This should bring some outflow winds
to the Southcentral region, but precipitation impacts are expected
to be confined to the Gulf Coast.

For the end of next week, models are picking up on a stronger low
pressure system crossing the Bering Sea closer to the Aleutians than
the storm we see moving through the Bering earlier in the week.
Models were indicating a similar solution yesterday, so
consistency in the runs leads to more confidence that this will
occur. This track has the potential to bring winds and waves to
the southwest coast, so the forecast bears watching for the next
few days to detect any changing trends.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gales: 120, 130, 139 177, 178, 411, 412, 413.

&&

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JW
LONG TERM...LF