Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 271319
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
519 AM AKDT Wed Mar 27 2024

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

A weak shortwave currently pushing north of Anchorage into the
Susitna Valley and lifting north from the Gulf Coast into the
Copper River Basin continues to weaken today as it pushing north
over the Alaska Range. Precipitation will decrease through the day
today, however, very light rain or snow showers or drizzle could
linger along the western slopes of the Talkeetna, Chugach, and
Kenai Mountains as weak (10 knots or less) westerly flow confined
to the lowest levels of the atmosphere (below 850 mb) brings in
colder air near the surface. The same airmass will also trigger
some weak offshore/northerly gap winds through the coastal
mountains. Some model guidance suggests that weak cyclonic flow
lingering aloft could support weak upslope precipitation, however
it materializes, through as late as Thursday, for which a slight
chance of precipitation is maintained in the forecast. Elsewhere,
conditions appear dry and calm, with partly to, in some places,
mostly sunny skies. Light rain and snow showers will continue to
diminish through the day as the system lifts to the north.

By Friday a low in the Bering Sea pushes a front into the western
Gulf of Alaska which brings the next round of active weather
through the weekend to SouthCentral Alaska. The exact track of
this next storm remains uncertain uncertain at this time. A more
westerly track will produce strong winds for Anchorage along with
moderate to heavy rain along the Gulf Coast and heavy snow in the
mountains. A more easterly track will bring the potential for
moderate rain or snow for Cook Inlet areas, Anchorage, Mat-Su and
and heavy coastal rain or rain-snow mix at sea level and heavy
mountain snow.

-CC

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, the BERING SEA and the
ALEUTIANS (Days 1 through 3: Tonight through Saturday)...

The unsettled pattern across Southwest Alaska and the Aleutian
Chain continues through the work week as an upper-level low
pressure system remains anchored over the central Bering Sea. An
associated surface low in the vicinity of St Matthew Island is
producing scattered, light snow and gusty conditions along the
Pribilofs through tonight. This surface low continues to push
cooler temperatures into coastal Southwest. This cooler, slightly
drier air will allow temperatures to cool overnight, and reduce
the presence of showers across Southwest Alaska. Clearer skies
have lead to temperatures overnight to drop more dramatically than
this past weekend; however, overnight low temperatures are likely
to remain at or above zero, with the coldest temperatures
observed in the Kuskokwim Delta and Lower Kuskokwim Valley.

Thursday morning attention shifts to a north Pacific low that
will increase winds across the Aleutians before crossing into the
Bering. A brief period of heavy snow and strong winds are
possible before temperatures quickly warm above freezing. This
low is expected to bring widespread gales (>34 kts) and areas of
storm-force (>48 kts) gusts to the Aleutians and Southern Bering.
The front on the leading side of the approaching low will likely
be fairly progressive, sweeping across the Aleutian Chain into the
Pribilofs Thursday, and into Southwest Alaska by Thursday night.
The Central and Eastern Aleutians will likely see a quick shot of
moderate to heavy rain/snow showers as the front sweeps across
with the precipitation coming down as rain, or melting fairly
quickly once on the ground as snow.

The latest model runs suggest that an elongated low will track
northeast until reaching the Pribilofs by late Thursday
night/Friday morning with the associated front and widespread
southerly winds across southwest Alaska. While the low is over the
Pribilofs, they will likely see up to 4 inches of snow
accumulation over the course of Thursday, with gusts up to 30 mph.
Given the elongated shape of the low at this time, it is difficult
to determine when the period of strongest winds may be.
Regardless, periods of blowing snow are possible through Friday
morning. The low is then expected to continue pushing northeast,
toward Nunivak Island and the Kuskokwim Delta late Friday. The
front on the eastern side of the low, pushing into Southwest
Alaska by late Thursday night, is expected to produce widespread
gusty and snowy conditions, initially. Some areas across southern
Bristol Bay into the AK Peninsula may see a transition to rain,
but elsewhere across southwest Alaska should maintain snow given
residual colder air in place. This system has the potential to
produce blowing snow and blizzard conditions for most of the
Southwest coast Friday night into Saturday. Snow accumulation
expected is, 2-3 inches for most interior areas, with the highest
amounts of 5-6 inches for the northern side of Bristol Bay from
Dillingham to Togiak, and the Kuskokwim Delta coast, including
Kipnuk, Kwigillingok, and Nunivak Island. However, there is still
some uncertainty at where the freezing level will establish across
this region, which would severely impact both the accumulation of
snow on the ground, and the ability for the snow to loft with the
gusty winds. As such, Winter Storm Watches have been issued for
both Bristol Bay and the Kuskokwim Delta, with a focus near the
coastal areas of those regions. Stay up to date with our latest
forecast for news on updates to these statements.

-CL

&&



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

An active pattern more reminiscent of autumn than spring persists
through midweek next week. A positively tilted, upper-level trough
remains in place, extending from the Seward Peninsula to western
and central Aleutians. At the surface, a surface low looks to be
positioned off the wet coast of Alaska with its occluded front
extended from the Y-K Delta southeast to the norther Gulf coast.
The front, along with the bulk of the warmer air aloft, will slide
east toward the Alaska Panhandle for Saturday as colder air wraps
around the upper level trough and advects over the Southern
Mainland.

A second surface low will develop over the Northern Pacific and
drive north as its deepens, aided by a strong jet streak and
potent shortwave trough, toward the Alaska Peninsula. Guidance
quickly diverges on the track of the low, with the EC
deterministic driving the low into Bristol Bay and the GFS
deterministic pushing the low first to the eastern Kodiak Island
coast then into Prince William Sound by Sunday morning. Their
respective ensemble runs show a large range in the potential
track; however, the GEFS does place the low west of its respective
deterministic run. Whatever the track, the common theme is
copious moisture streaming into the Southern Mainland for the
weekend. Heavy rain is all but certain for the coast. The greater
uncertainty is the extent of cold air and how much can hold on
over interior Southwest and Southcentral Alaska for snow to fall.
A more western track in the low would also potentially limit
precipitation amounts in the lee of the coastal mountains, but
could bring significantly higher winds to places like Anchorage,
Palmer, and interior Bristol Bay (Koliganek). This system exits to
the north and east through Sunday night.

Model divergence becomes even greater following the weekend
system; however, the GFS, EC, and GEM all show the potential for
yet another system lifting into the western Gulf from the north
Pacific. This feature may interact with a polar trough and surface
cold front diving south from the Bering Strait. Much like the
previously mentioned system, this next low would likely bring
another round of moderate to heavy precipitation to the coast for
Monday. If these features phase, as the GFS is hinting, it could
result in moisture being drawn north through Cook Inlet and into
the Mat-Su Valleys just as colder air is advecting in from the
west. The result would be the potential for snow late Monday into
Tuesday from Kenai to Talkeetna.

As this system exits to the east late Tuesday, a deepening low
over the western Aleutians will move east pushing a warm to the
Southwest Alaska coast. This system looks to to bring not only
wind and abundant moisture to the Bering and Aleutian Chain, but
also a much warmer airmass that could move over the western half
of Alaska, and perhaps even farther east, for midweek.

-TM

&&

.AVIATION...

PANC...Low stratus and MVFR conditions have persisted through the
morning hours and have likely staved off any threat of fog.
Intermittent light rain to taper off before noon with light and
variable winds continuing through Thursday. A chance for light
precipitation redevelops this evening/tonight as yet another
trough lifts across PANC with MVFR ceilings to persist through the
period.

-BL

&&


$$


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