Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 061259
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
359 AM AKST Fri Dec 6 2019

.ANALYSIS AND UPPER LEVELS...

An upper level ridge over the eastern Bering is slowly becoming
more amplified and moving eastward over Southcentral. A strong
upper level low centered northwest of Shemya is producing gale
force winds over the central Bering as its associated front
approaches the southwest coast. Scattered snow showers continue to
linger over both the Kuskokwim Delta coast and inland Bristol Bay
area. Meanwhile, a weak trough at the surface has generated some
light snow showers over the Cook Inlet region this morning ahead
of a larger front approaching from the west.

&&

.MODEL DISCUSSION...

Models have come into slightly better agreement regarding key
features in the upper levels, however they still struggle to
resolve the positions and tracks of several surface lows moving
over the southern half of the state this weekend. Forecast
confidence remains below average beyond 48 hours as the models
still differ greatly.

&&

.AVIATION...
PANC...Low stratus and fog continue to linger over the area. Light
snow showers will continue through the early morning, leading to
MVFR conditions before improving by midday.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The weak weather system over the area this morning will dissipate
this afternoon as a weak and transient ridge builds over the area.
Strong southerly flow aloft will push into Southcentral beginning
tonight. This will bring a stronger weather system, and also a
considerable warming trend. This makes forecasting precipitation
type a bit more challenging, as the warmer air clashes with the
cold air over the region. Snow should change quickly to rain late
tonight along coastal eastern Kenai Peninsula and western Prince
William Sound as a strong southerly surface wind develops. For
inland locations the transition will take a little longer, with
rain mixing in over the western Kenai fairly early Saturday
morning, then work its way up the Inlet to the Anchorage area by
late morning and into the Matanuska Valley in the afternoon.
Farther north, the colder air should remain in place probably
through Saturday night. Winds will also increase for some areas,
with strong winds through Turnagain Arm and possibly on the Upper
Hillside of Anchorage this afternoon through Saturday afternoon.
For the lower elevations of Anchorage, strong winds are not
expected.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A front over the eastern Bering is on its way to southwest Alaska.
It will reach the coast this morning and initially bring snow to
the area. Stronger winds will also accompany the snow with the
Kuskokwim Delta seeing enough snow and wind for blowing snow
conditions. The front is pulling up warm air from the North
Pacific that will begin to transition the snow over to rain this
afternoon. The Kuskokwim Delta will hold on to cold air at the
surface with northeast winds that will bring a potential for light
freezing rain in the evening before switching to rain. Tonight
into Saturday, another low will approach bringing back some cold
air and transitioning precipitation back to snow. Snow will then
diminish through the day Saturday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A low over the western Bering has its front extending through the
northern Bering and then south through the eastern Aleutians. The
front is bringing rain to the islands. However, the parent low is
advecting cold air back over the area behind the front. Another
low will approach the Alaska Peninsula from the North Pacific this
afternoon bringing another round of rain to the area. A generally
unstable pattern will set up on Saturday with several small lows
moving through a broader area of low pressure over the Bering. The
result will be snow showers over the western Bering/Aleutians
with rain showers over the eastern Bering/Aleutians.

&&

.MARINE (Days 3 through 5)...

The biggest features of concern in this period will be a strong
decaying low over the northern Bering and a developing system
over the Gulf of AK. First, in the northern Bering, there is high
confidence in a strong system that will be weakening starting on
Sunday. Lingering gale force winds will be moving out of the area
with this system. A broad trough of cold air across the Bering
will keep a small area of gales across the western Aleutians on
Sunday, but these will move out of the area to the south on Monday.
Then in the Gulf of AK, a developing system is riddled with
uncertainty at this time. However, we are trending things into the
gale force wind range to start the week with this forecast
package. It is certainly possible this system could bring storm
force winds (particularly in the Barrier Jet region), however, we
will wait to see a few more model runs before we make that call.

&&

.LONG TERM FORECAST (Days 3 through 7: Sunday through Thursday)...

The long term continues to be a mess, quite frankly. Models are
decidedly poor in performance, changing enough each day this week
to have low confidence in them. Therefore, our forecast for the
long term will be one of persistence and hedging towards the
trend this winter of cycles of warming and cooling.

What this means for Southcentral is that we will continue to
forecast a warm-up to start the long term, with sustained warmth
through the week. This is sticking with this season`s trend
mentioned above by bringing us out of our current cold snap.
Models are showing a series of lows and general southerly flow
which is why we can at least expect that warmth to continue. Even
with their fickle nature this week, they would be hard pressed to
completely shift this pattern. Preliminarily for next week, there
looks to be a compact low moving north along the Gulf coast
Monday into Tuesday. Then, a larger and more powerful low looks
to enter the western Gulf Wednesday into Thursday. Bottom
line...warm, wet, and possibly windy weather for next week
especially along the coast.

For the Bering, Aleutians, and Southwest AK...the longwave trough
holds over the area which will continue to circulate low pressure
systems within it through early next week. Models are hinting at a
shortwave ridge entering the Bering Wednesday, briefly calming
things midweek. Another large and powerful low looks to enter the
western Bering and Aleutians Thursday. All the while, the
previously mentioned powerful low in the western Gulf that
develops midweek will have at least some play on weather in
southwest AK with easterly winds. However, the Alaska Range will
probably block most weather. Details are yet to emerge for out
west in all locations, but do expect unsettled weather for the
foreseeable future.



&&


.AFC WATCHES/WARNINGS/ADVISORIES...

PUBLIC...Winter Weather Advisory...155.

MARINE...Gale: 119, 130, 131, 132, 139, 150, 155, 160, 165, 172,
178, 179, 180, 181, 185, 352, 414.
         Heavy Freezing Spray: 181

FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KO
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
MARINE/LONG TERM...MSO/BB


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