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fxak68 pafc 091635 cca 
afdafc

Southcentral and southwest Alaska forecast discussion...corrected
National Weather Service Anchorage Alaska
735 am akst Mon Dec 9 2019

Analysis and upper levels...

A strong area of low pressure centered south of the Alaska
Peninsula is slowly drifting northward into the eastern Bering.
The associated storm force front is lifting northward over the
southern Mainland, bringing heavy rain and gusty southeasterly
winds to the northern Gulf Coast. Meanwhile over southwest, this
same low is producing gusty northeasterly winds and rain across
the Alaska Peninsula while farther north along the Kuskokwim Delta
coast, temperatures are cold enough for snow. Snowfall combined
with gusty winds has significantly reduced visibility across that area
this morning.

Farther west, weak cyclonic circulation is in place over the
central Bering while another low centered south of Shemya with a
central pressure near 980 mb continues to move eastward, tracking
along the south side of the chain.

&&

Model discussion...

Overall model solutions are in great agreement for the short-term
and the track of the low center as it lifts northward along the
southwest coast of Alaska through Tuesday. Differences arise by
Tuesday night as another North Pacific low tracks northward toward
the southern Mainland. Model solutions continue to differ on the
exact track and location of this low center by midweek. Overall,
forecast confidence is average.

&&

Aviation...
panc...wind shear will continue to be the main threat as another
front lifts inland this morning. Winds will be out of the north
at the terminal while strong southeasterly flow will persist aloft
through the morning. Expect gusty southeasterly flow to arrive at
the terminal by Monday evening.

&&

Short term forecast southcentral Alaska (days 1 and 2)...
a strong weather front will move through the area today. This
will bring very strong winds to Turnagain Arm and the higher
elevations around Anchorage. This system is also loaded with
moisture and is quite warm. Heavy precipitation is expected along
and near the Gulf Coast. Very little precipitation is expected for
inland areas due to strong downsloping easterly winds aloft. The
front will move inland late this afternoon into the evening. The
winds along Turnagain Arm will then diminish. The downsloping
component will also weaken, and some precipitation should work its
way inland. The winds over the Anchorage area will then become
southerly and increase. This will push temperatures into the 40s.
The front will dissipate on Tuesday with precipitation and winds
diminishing considerably. Another front will move into the Gulf late
Tuesday, then move north to near the Gulf Coast late Tuesday night.
This next system will not be as strong as today's (monday) storm,
with winds and precipitation generally staying over the Gulf to just
along the Gulf Coast.

&&

Short term forecast southwest Alaska (days 1 and 2)...

Temperatures will continue to rise above freezing this morning as
a North Pacific low keeps on its path northward through the
afternoon. Many areas in Bristol Bay have already warmed up with
this warm front, causing snow to transition to rain. Areas along
the Kuskokwim Delta coast will continue to see potential blowing
snow out ahead of the front this morning, with gusty conditions up
to 45 mph. However, conditions will improve late this morning
into the afternoon as temperatures continue to rise. Strong winds
will continue across southwest Alaska through Tuesday morning when
the low center moves into the northern Bering. By Tuesday
afternoon, showers begin to taper off across the region before the
next possible system brings precipitation to the Alaska Peninsula
and Bristol Bay for Wednesday.

&&

Short term forecast Bering Sea/Aleutians (days 1 and 2)...

A powerful 950 mb low centered near Port Heiden this morning will
move northward between the pribilofs and southwest Alaska by this
afternoon. Strong winds will persist over the eastern Bering and
in Bristol Bay through tomorrow morning. Meanwhile, northerly
gales this afternoon will continue across the pribilofs and
central Bering. The winds quickly switch over to westerly flow
overnight for the central and western Bering and Aleutians as the
low center tracks into the northern Bering for Tuesday morning.
Rain and snow showers are likely to continue through Tuesday for
much of the Bering and Aleutians.

&&

Marine (days 3 through 5)...

..Bering Sea and Aleutian coastal waters...

A pair of low pressure systems will affect the region. The first
low moves from the northern Bering toward the Kamchatka peninsula
on Wednesday as it retrogrades (moves west), with sustained gales
likely north of 60n and west of 175w. Farther east, a North
Pacific low moving toward the Alaska Peninsula (akpen) will also
bring sustained gales to Bristol Bay and coastal waters of the
akpen. The winds will then subside for both locations on Thursday
and Friday. Seas look to generally remain at or below 15 feet
through the period.

..Gulf of Alaska...

A front will move from south to north across the region on
Wednesday, with sustained gales preceding it. Given a long fetch
length, seas are expected to build into the 20 to 25 foot range
ahead of this feature. The winds will subside for Thursday and
Friday, but the waves will take more time. We expect seas to remain
near 20 feet for the southern and eastern Gulf on Thursday before
decreasing on Friday.

&&

Long term forecast (days 3 through 7)...

Models continue to struggle with the specifics of the long term
forecast, but some general signals can still be gleaned in the
noise. Synoptically, a progressive pattern will persist over the
Bering and Alaska. A vertically stacked low in the northern Bering
Sea Wednesday will continue steering modified Arctic air over the
Aleutians and Bering. The low will continue to gradually weaken
and shift toward Siberia, but in the meantime expect scattered
showers over much of the Bering/Aleutians through Thursday.
Meanwhile, a low that is currently roughly 400 miles southwest of
Shemya will quickly traverse the North Pacific over the next few
days. As this low tracks northeast of 50n 150w it will push a warm
occluded front towards the north Gulf Coast, likely in the
Wednesday to Thursday timeframe. This should trigger a healthy
round of precipitation along the north Gulf Coast and
Alaska/Aleutian Range. South/southeast facing slopes should get
the heaviest precipitation, while areas in the Lee (e.G.,
Anchorage bowl, western Kenai Peninsula, Bristol bay) will be more
of a challenge with shadowing. While it's early to get into
specifics with respect to precipitation type, this looks like a
fairly warm system... the mountains should get snow but in lower
lying areas precipitation type will be a challenge. Friday into
the weekend, models indicate a strong low or series of lows
traversing the Aleutians, bringing a round of strong southerly
winds and precipitation.

In short, temperatures will largely be near or above average with
a southerly component to the flow over southern Alaska for much
of the Wednesday through Sunday timeframe. In addition,
precipitation will mostly be focused along the north Gulf Coast.

&&



Afc watches/warnings/advisories...
public...npw 101, 125. West-southwest 155.
Marine...storms 119, 120, 130-132, 136-141, 351, 352.
Gales 125, 128, 129, 150, 160, 165, 177, 178-181, 185, 411, 412,
414.

Fire weather...none.

&&

$$

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