Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 111248
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
448 AM AKDT Thu Oct 11 2018

.ANALYSIS AND UPPER LEVELS...
The pattern is signified by an upper level low anchored over the
eastern Bering. Multiple shortwaves are rotating around the main
low with the strongest pushing through the eastern Aleutians
bringing rain to the islands. This setup is bringing southwest
flow to the southern mainland with scattered showers over
southwest Alaska and along the north Gulf coast.

&&

.MODEL DISCUSSION...
The models are in good agreement for the most part with the main
synoptic features through the mid term. The 00Z runs were having
some issues with a low approaching the western Aleutians Friday,
but the 06Z runs seem to have a better handle on it.

&&

.AVIATION...
PANC...VFR conditions will persist. Winds will stay out of the
south around 10 kt and gust into the mid teens through tonight.
Turnagain Arm winds will increase overnight tonight but should
remain south of the airport.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Rain showers will linger over the area today, mainly near the
coast and along the Alaska Range and Talkeetna mountains. This is
due to weakly unstable southwesterly flow. The next front will
slowly make its way from west to east across the Gulf later today
into Friday. It will briefly stall out in a north/south
orientation stretching from Kodiak Island through the Kenai
Peninsula and into the Susitna valley on Friday. Winds will once
again ramp up through Turnagain Arm. Some gusty winds will also
move into the Anchorage Bowl on Friday, but not as strong as those
on Wednesday. Rain will be likely at some point Friday for much
of Southcentral, though downsloping will limit precipitation from
the western Kenai through Anchorage and the Matanuska valley. A
system to the east of the front will move into the Gulf rapidly
from the south on Friday night. This will bring strong winds and
more rain to the northern Gulf beginning Saturday morning.

&&

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

Southwest winds and a cyclonic onshore flow is helping to maintain
a decent amount of moisture across the region, with fairly
widespread showers continuing to move across most locations. This
looks to continue through at least the morning hours. By early
afternoon, another deepening low will race northeastward towards
the eastern Bering, before it turns more north. An associated weak
warm front will loft north with the low, and a trailing weak cold
front will slide east. Ahead of either of these features, winds
will increase somewhat with widespread rainfall developing. This
storm will have less of a tropical connection compared to the past
few. That said, some of the rainfall will occasionally reach
moderate intensity.

As this low reaches Nunivak Island late Thursday night, it`ll
encounter the low from the former tropical system, and they`ll
rotate around one another in a Fujiwhara-like fashion near Saint
Matthew Island. This will keep southwest Alaska in a continued
broad cyclonic flow, conducive to maintaining a showery regime
through Friday, before the lows consolidate/fill and edge eastward
for Saturday, bringing a somewhat more steady rainfall to the
coast.

&&

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

Another deepening low will lift from the east central Bering this
morning, towards Nunivak Island by midnight tonight. This low will
spread a weak cold front eastward, with widespread rainfall
developing along and ahead of it. Winds will remain in small
craft criteria, except south of the AKPEN, where sustained gales
are likely through Friday morning, before gradually subsiding.

Further west, cyclonic flow around a St. Matthew Island low will
keep showers in the picture for all of the Bering and Aleutians,
with sustained small craft criteria winds expected across the
western half of the Bering and Aleutians. This looks to continue
through late Friday, as models have slowed down the frontal timing
of a cold front associated with a Kamchatka low. This system
looks to bypass the western Aleutians to the west and south for
Friday into the weekend. However, it`ll pass close enough to bring
widespread rainfall (some moderate to heavy at times) and
sustained gales to the western portions of the Bering Sea and
Aleutian chain, with rainfall spreading eastward along the chain
through Saturday.

&&

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

A strong low located south of Adak on Saturday night is
forecast to make its way towards mainland Alaska, and will be the
cause of much of the active weather across the area through the
long-term. The long-term models are all in impressive agreement on
the forecast behavior of the low, which adds confidence to the
forecast that is not commonly there. The low center is expected
to track eastward but remain well south of the Aleutians until it
crosses the Alaska Peninsula near Cold Bay during the day Monday.
The low will be a large one, and as such will impact many
communities well away from the center. The front wrapping around
the low pressure center is expected to approach and move in to
Southwest Alaska on Sunday evening, despite the low center still
located south of Cold Bay at that time. This is testament to the
large area that will be affected by the low. Overnight Monday
night into Tuesday, the low center will track northward to near
Kuskokwim Bay, slowly weakening as it goes, then will remain
nearly stationary over the Kuskokwim Delta through Wednesday
night.

Across Southcentral, rain ongoing from a low that will impact the
area during the day Saturday will diminish Saturday night. High
pressure briefly moves in during the day Sunday, which looks to be
by far the nicer of the two weekend days. Winds will be on the
increase through the gaps late in the day Sunday into the night,
as a strong warm front lifts northward into the area. The rain,
heavy at times will persist across much of Southcentral through
the day on Monday, and continue into Monday night. With the
stationary low over Southwest Alaska keeping the overall
atmospheric flow out of the south to southwest Tuesday and
Wednesday, a continuation of cloudy and showery conditions is
likely to persist.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gales...130 132 150 155.

&&

$$

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



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