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Alaska Area Forecast Discussions


000
FXAK69 PAFG 061314 CCA
AFDAFG

Northern Alaska Forecast Discussion...CORRECTED
National Weather Service Fairbanks AK
414 AM AKST Fri Dec 6 2019

.SYNOPSIS...
A weather system will move north along the west coast tonight
through the weekend bringing a mixture of snow, freezing rain,
strong winds and blowing snow. Cold temperatures will persist
today across Interior; however, a warming trend will begin tonight
and continue through the weekend and into early next week as
southerly flow develops over the Alaska Range for the weekend.

&&

.DISCUSSION...
The 6/00z model suite initialized well against the the 00z surface
analysis and verified well against the 06 surface analysis. Overall
the models are in decent agreement in the short term with the
synoptic scale pattern; however there are still differences with
the low that will move north along the west coast this weekend,
both in terms of the strength and the placement of the low moving
north along the west coast.

Central and Eastern Interior: High pressure over the central and
eastern interior will begin to retreat north and east as a strong
front moves north and east into the Lowe YK Delta and Western
Interior. Clouds will move into the southern interior late tonight
and will push into the northern interior Friday. The clouds
combined with a warming chinook over the Alaska Range will bring
much warmer temperatures Saturday for the southern interior
especially in the hills and higher locations. The cold airmass
will be slower to mix out of valley locations. High temperatures
today will not budge much from the 20s below in the Fairbanks area
but will begin to climb late tonight especially in the hills as
clouds move in. Temperatures on Saturday are expected to rise
into the single digits and lower teens with cloud cover and
warming from ongoing chinook pushes north. Southerly gap winds
will develop in the Alaska Range on tonight where a Wind Advisory
has been issued from tonight through Sunday morning. By Saturday
we expect wind gusts around 60 mph in the passes of the Alaska
Range which will persist into Sunday morning.

West Coast and Western Interior: The west coast will receive a
quick one-two punch today and into the weekend. A front
associated with a low in the western Bering will push into the
Yukon Delta this evening and will continue to move north along
the coast Saturday. A 960 mb low will move into Bristol Bay
Friday evening. By Saturday morning this low will be over Nunivak
Island. During the day the low will track towards St. Lawrence
Island; however, there are still significant differences in the
exact track and strength of this low and another low that is
racing north out of the Northern Pacific toward Bristol Bay on
Saturday morning. The when and where of how these two lows merge
and the subsequent track of the merged low through the
southeastern Bering are still not being resolved well by the
models. A broad forecast brush was used to paint where the
heaviest snow and strongest winds are expected to occur as a
result. The merged lows are expected to bring snow and stronger
winds on tonight and Saturday for for areas south of the Seward
Peninsula and Saturday and early Sunday for areas from the Seward
Peninsula north. Warmer air will move in aloft over the Yukon
Delta this evening. This will cause snow to change over to
freezing rain There is still some uncertainty in the exact
placement of the heaviest snow minor differences in the track will
impact where the heaviest snow will fall. At this time the
heaviest snow is expected to fall in and near the Nulato Hills
while the greatest risk for freezing rain and sleet remains in the
Lower YK Delta. At this time 4 to 8 inches of snow is expected in
the Nulato Hills with 2 to 4 inches expected elsewhere. Ice
accumulations of a glaze to one tenth of an inch are expected in
the Yukon Delta Friday this and Saturday. As the front moves
north on Friday, south to southeast winds 25 to 35 mph with gusts
to around 55 mph are expected to develop along the Norton Sound
Coast and over St Lawrence Island, with the winds expected to
continue into Saturday. Another system looks to move north along
the coast on Monday.

Will need to closely monitor Little Diomede Island for the
potential for sea ice that is currently positioned along the
north coast of the Seward Peninsula to push south and west toward
Little Diomede Island as strong north to northeast winds buffet
the area for the next couple of days.

Coastal Hazard Potential Days 3 and 4...None.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Advisory for AKZ226.

Winter Storm Warning for AKZ213.

Winter Weather Advisory for AKZ207-AKZ209-AKZ210-AKZ211-AKZ212-
AKZ214-AKZ215-AKZ216.

Heavy Freezing Spray Warning for PKZ210-PKZ220-PKZ225-PKZ230.

Small Craft Advisory for PKZ220-PKZ225-PKZ230.

Gale Warning for PKZ200-PKZ210.

Brisk Wind Advisory for PKZ200-PKZ215.
&&

$$

CCC DEC 19


347
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



000
FXAK67 PAJK 061301
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
401 AM AKST Fri Dec 6 2019

.SHORT TERM...Upper ridge will build strongly into the Gulf today
and shift slowly eastward through Saturday night. By late Saturday
night this ridge axis will be directly over the Panhandle.

One or two slugs of low to mid level WAA and isentropic ascent
will affect mainly the northern Panhandle over the next 48 hours.
The first will be this afternoon and will be accompanied by a weak
surface wave which will lift into the northern Gulf this evening
and die in place. As the ridge axis slides eastward Saturday into
Saturday night, stronger WAA will commence for the NE Gulf and
northern third of the Panhandle. Kept precipitation chances across
the north today and increased precipitation chances for Saturday
and Saturday night as a result. Stubborn cold air continues to
hang on over the far northern channels where snow is still being
reported. Surface gradient should continue to allow cold air to
hang on through at least Saturday in these areas and so expect
generally 1 to 2 inches of new snow accumulation in the
Haines/Skagway areas today and perhaps again on Saturday before
the cold air gets scoured out for good.

Winds over the inside waters will be on the downward trend today
as the gradient relaxes. As stronger low level SW flow impinges on
the NE and E Gulf coast tonight and Saturday, an increase in the
winds over the outside Gulf waters is expected as a weak barrier
jet takes shape. For now kept things in the 25 to 30 kt range for
the immediate offshore waters.

Southern areas will have a relatively nice end to the week and
early weekend as low and mid level ridging leads to weak offshore
flow.

.LONG TERM.../ Sunday to Friday as of 10 pm Thursday / Ridge axis
aloft at 500 mb is pushed east of the Southeast Alaska panhandle
by Sunday night but the upper trough to the west is trying to
nose further into the western gulf. As it does a long southerly
fetch aloft will move to the eastern half of the gulf which will
lead to increased onshore flow of warm and moist air.

The flow pattern will have some rain for the central gulf coast,
perhaps over to the Icy Bay-Yakutat Bay region on Sunday and as
the ridge shifts eastward the increase in clouds over at least the
northern panhandle will happen along with a small bump in rain
changes. Mid to long range model solutions still hanging on to
the idea that a significant frontal band will spread in around
Tuesday with a followup around Thursday. Will need to keep a
watch and monitor this situation as it develops.

With the overall southerly flow pattern, temperatures should
remain above average for the season. And no strong wind events are
expected through the week.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ041>043-051-052.

&&

$$

DEL/Bezenek

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