National Weather Service United States Department of Commerce


000
FXAK68 PAFC 290205
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
505 PM AKST Wed Feb 28 2024

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

A vertically stacked low remains nearly stationary over the
northern Gulf of Alaska this evening. Along with it an arctic
airmass has permeated all of Southcentral with 850mb temperatures
remaining as cold as -25 degrees and warmer temperatures up to -10
degrees along the Gulf coast. For tonight through the next couple
of days the thermal gradient will maintain a strong pressure
gradient and subsequent gusty northerly winds through
Southcentral. The presence of the sun over Anchorage today has
been deceptive with afternoon temperatures only warming into the
mid and upper teens. Winds, however, have been gusting in excess
of 35 mph in many locations resulting in wind chills at or below 0
degrees. Further north and into the Valley, Palmer has been
gusting in excess of 60 mph. Regardless of where you are located
within the Southcentral forecast area, gusty winds have likely
contributed to areas of blowing snow. Visibilities have largely
remained unaffected. The exceptions being through the Hay Flats
along the Glenn Highway, and also over Thompson Pass where gusts
have approached 70+ mph. Wind speeds remain highest through the
typical coastal bays and passes and this will remain true through
tomorrow and Thursday.

Offshore, satellite-based winds continue to show storm force
winds over the western Gulf/Kodiak Island coastal waters, from out
of the Kamishak Bay area into the Barren Islands corridor. On the
south side of Kodiak Island, from immediately offshore of Akhiok
southeastward, gusts have been approaching hurricane force over
the past couple of hours. Over the next few days, and with little
change to the synoptic pattern, temperatures will remain cold and
winds will remain gusty. Winds will begin to diminish Friday
through Friday night as the last in a series of short-waves moves
through and a high amplitude ridge approaches from the Bering Sea.
Despite a moderating airmass (warming 850mb temperatures),
lighter winds will likely result in the coldest temperatures of
the week on Saturday morning - with widespread sub-zero
temperatures (Fahrenheit) expected.

SEB/BL

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Tonight through Friday)...

A strong upper level ridge has built across much of the Bering
Sea, and with a low pressure system in the central Gulf of Alaska,
gusty winds out of the north continue to flow into Southwest
Alaska. This air is dry and cold, keeping skies clear, which is
helping alleviate the bitterly cold temperatures in areas like the
Lower Kuskokwim Delta. The wind flow itself is also keeping the
air mixing with slightly warmer air aloft. This is all to say that
Southwest Alaska is, and will remain cold the next few days,
however the lack of strong winds and warming during the day reduce
but do not eliminate the threat and impact of dangerous wind chill
temperatures. Proper precautions should still be taken when
operating outside as we approach the weekend in Southwest Alaska.
Earlier today, a Polar low diving out of the northern Bering Sea
crossed the Pribilof Islands and is currently weakening and
making it`s way across the Alaska Peninsula and Eastern Aleutians
out into the northern Pacific.

Further to the West, a robust warm front has pushed into the
Western Aleutians. This system is initially producing snow as it
moves over an area, however transitioning quickly to a rain/snow
mix then to plain rain as warm air behind the front fills in. This
precipitation transition is expected to persist for most areas as
the front progresses eastward steadily up the Aleutian Chain. By
Thursday, a nose of warm air aloft above freezing may begin to
override the very cold air mass in place over the eastern half of
the Bering Sea, setting the stage for a messy wintry mix of
precipitation transitioning from snow and sleet, then freezing
rain, then rain as the front approaches the Pribilofs, eastern
Aleutians and southern Alaska Peninsula between Thursday and
Friday. It is still expected that the initial surge of
precipitation will come in the form of snowfall, followed by gale-
force sustained southerly winds. As such, blowing snow reducing
visibility to one-half mile or less at times is possible for the
Pribilofs early Thursday evening. There is still a fairly high
degree of uncertainty in terms of the exact timing of this
transition for any given location, but the possibility of
accumulating freezing rain amounting to as much as 0.1 to 0.2
inches is becoming more likely at some point between Thursday and
Friday, especially along the southern AKPen and across the eastern
Aleutians. As such, a Winter Weather Advisory has been issued for
the Pribilofs for blowing snow and the potential for freezing
rain. Please see product for more information. This will be highly
dependent on how long surface temperatures can remain at or below
freezing before warmer air moves in and changes precipitation
over to predominantly rain. The Pribilofs meanwhile could get
several inches of snow mixing with sleet and freezing rain at
times, with strong southeast winds likely to cause areas of
blowing snow between Thursday and Friday as well.

Friday and beyond, this frontal boundary will continue it`s march
eastward reaching the Alaska Peninsula by Friday morning, and
potentially the Southwest coastline by Saturday morning. This will
depend on the strength of the ridge over Southwest at the time,
but may help warm up the area after the series of days with cold
temperatures. Additionally, by late Saturday morning, a new north
Pacific low pressure system appears to approach the western
Aleutians.

-CL/AS

&&


.LONG TERM FORECAST (Days 4 through 7) Sunday through Wednesday...

Forecast models show an active series of moderate amplitude upper
level troughs and ridges moving across the Bering through the
Alaskan Mainland. Model tracks and strengths continue to be more
uncertain through the forecast period. Interior Alaska is
dominated by an upper level ridge, flexing with the transient
shortwaves that have been moving through the pattern. However,
Arctic cold and dry conditions will continue to drain across the
Mainland through the period. Conditions over the Bering remain
under the influence of the broad upper low with surface fronts or
troughs rotating around the Bering through Wednesday. The most
active weather will be widespread precipitation, with snow over
the Northern portions and mixed rain and snow or rain and gusty
winds along the Aleutians. A well developed North Pacific low
spreads its influence across the Aleutians for Tuesday with mostly
rain and gusty winds with areas of gale force gusts moving into
the Alaska Peninsula and Kodiak Island by Wednesday.


Kutz

&&

.AVIATION...

PANC...VFR conditions and strong northerly winds will persist.
The strongest winds are still expected to be this evening with
gusts could reaching up to 35 kt.

-CC

&&


$$


000
FXAK69 PAFG 282210
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
110 PM AKST Wed Feb 28 2024


.SYNOPSIS...

Cold snap persists through at least Friday over the Interior.
Low temps range around -30 to -40 in the cold valley locations.
Wind chills are the main hazards in the short term, however
blowing snow and low visibility is occurring and expected to
continue through Friday morning along with very cold wind chills
from Deadhorse east along the Arctic Coast.

&&


.DISCUSSION...

Upper Level...

497 Dam low center over the eastern Arctic and troughing over
the eastern half of the state. Ridging persists over the western
Bering Sea and is slowly moving east. Cold air from the Arctic
has filtered down over the Interior, and 850 mb temperatures
around -20 to -30 C over much of the CWA through at least Friday.
A weak deformation zone centered between Delta Junction and Tok
will persist and may bring flurries and light snow to that area at
times over the next few days. By Saturday morning, ridging will
have moved over the West Coast, bringing warmer air aloft while
northerly flow will exist over the Western Interior.
Models are in good agreement through the short term.


Central and Eastern Interior...
Colder than normal temps are the story through the work week.
Valley low temperatures will be mostly in the 30s below, with
some 40s below in the Fortymile Country and Yukon Flats especially
by Friday night. Highs will be in the teens and single digits
below zero. Light snow accumulations of two inches or less are
expected from Delta Junction east. Moderating 850 temps expected
over the weekend and early next week bringing some relief to the
Interior.

North Slope and Brooks Range...

Near Blizzard conditions and very cold wind chills are occurring
from Point Thomson east to Kaktovik this morning and are expected
to continue through the week. A Winter Weather Advisory for
blowing snow and cold wind chills in effect for Deadhorse through
Friday morning, and a Wind Chill Advisory for wind chills as cold
as 55 below in effect for Atqasuk through late this evening.
Strong northerly gap winds continue in the Eastern Brooks Range
passes through Thursday.


West Coast and Western Interior...

Mostly quiet conditions are expected through Friday under the
influence of cold northerly flow. Wind chills will be the main
weather concern, with wind chills as low as 50 below expected near
Kotzebue Sound through Thursday morning. A shortwave will bring
flurries or very light snow along the coast from Nome to Point
Hope overnight tonight. By Saturday morning, expect east winds 20
to 25 knots from the Yukon Delta to St. Lawrence Island as a 990
mb low skirts east of the Gulf of Anadyr. Low temperatures will be
in the teens below along the coast and in the 20s and 30s below
inland, with highs from the teens below in the Kobuk Valley to the
single digits above near the coast.

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

Extended Forecast For Days 4 Through 7...

Models are in good agreement for ridging currently over the
western Bering Sea to continue to progress eastward over the
Central Interior by Monday morning. This will bring warmer
temperatures to the Interior and possibly precipitation to the
West Coast, though models disagree on the timing of this. We are
favoring a slower solution for the eastward progression of the
ridge and of precipitation moving into the West Coast. This should
result in a gradual warm up of temperatures.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Wind Chill Advisory for AKZ802.
Wind Chill Advisory for AKZ809-812-816-817.
Winter Weather Advisory for AKZ818.
Winter Weather Advisory for AKZ804.
Winter Storm Warning for AKZ805.
Wind Chill Advisory for AKZ848.
Winter Weather Advisory for AKZ850.
PK...Brisk Wind Advisory for PKZ805.
Brisk Wind Advisory for PKZ814-860.
Gale Warning for PKZ815-861.
&&

$$


000
FXAK67 PAJK 282351
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
251 PM AKST Wed Feb 28 2024

.SHORT TERM.../Through Thursday night/ The short range forecast
today is a time of change as the remnants of the system that
brought the snow overnight gives way to increasing northerly
outflow and drier conditions from the north. Currently much of the
panhandle is experiencing numerous snow showers (rain and snow
showers extreme south and outer coast) that are being sent across
the area from the slowly diminishing low in the central gulf.
These showers are much reduced in intensity snow falls not
reaching nearly as much as last night. Still some banding is
noted on satellite imagery along the outer coast so some localized
areas could be seeing some decent snow accumulations if the
showers start training over one area for too long. These showers
will continue to gradually diminish and will be pushed offshore as
northerly outflow increases over the next day or two.

As for the northerly outflow, that is already starting up across
the north with the corresponding cold air temperatures
continuing. Lynn Canal is already showing min gale force winds at
least, and gusty winds are being observed out of the passes near
Yakutat, Taku Inlet, and out of Cross Sound. These winds are only
expected to increase through Thu night as the surface high in the
Yukon steadily strengthens. Freezing spray will become a concern
for northern channels tonight into Thursday night. Winds should be
high enough and temperatures cold enough that heavy freezing spray
might also be observed in northern Lynn tonight, early tomorrow,
and late Thu night.

.LONG TERM.../Friday through the weekend/...Made changes to the
marine forecast based on current marine conditions and strength of
the inversion in Canada. However, regardless of changes, main
takeaway remains the same: cold air is here to stay, with
northerly winds and freezing spray potential.

Similar to previous days, an upper level ridge looks to replace the
trough pattern we have seen for the past couple of days. Guidance
for 500 mb progs have come to much better agreement through the
weekend; however, less confidence towards early next week. GEFS 0z
and 12z runs wants to put a stronger and more progressive trough for
SE AK while the EPS and to some extent the GEPS 0z and 12z runs want
to keep with the idea of the ridge breaking down slower. If the GEFS
solution does come to pass, in particular the 12z and 6z GFS, an
early week storm may be in order. Definitely something to keep in
mind going into next week, however, the likelihood of this solution
coming to pass remains low.

Ultimately what all of this means for the surface: Colder
temperatures, mostly clear skies, and windy conditions. Gap wind
areas such as Taku Inlet, Disenchantment Bay near Yakutat, and Taiya
Inlet looks to be the windiest, with tight pressure gradients from
the previous system dipping blow the panhandle will look to generate
low to moderate gales for Lynn Canal. There is an increased
likelihood of storm force winds out of Disenchantment Bay and a tip
jet at the meeting point of Taiya Inlet and Lutak Inlet. Downtown
Juneau at this time seems to be out of the line of fire for any
mountain wave activity. Critical layer, in particular, looks absent
in the list of ingredients. While this can induce by itself, because
cross barrier flow does not look as intense, it is unlikely that it
will.

Finally, there is freezing spray potential, particularly for the
aforementioned gap wind areas. At this time, the question is not
whether freezing spray will be present, but will temperatures get
cold enough over the water to cause heavy freezing spray. At this
time, temperatures were trended colder due to the extended ridge
pattern aloft.

&&

.AVIATION.../Through Thursday afternoon/...Scattered snow shower
activity will continue to diminish through the period with
attendant improving conditions to both CIGs and VSBY. Low level
southeasterly flow over the southern Panhandle becomes more
easterly further north. Mechanical turbulence not much of a
concern for most locations, but a low over the northern Gulf and
accelerating outflow concentrated in the vicinity of Cape Spencer
and the northeast Gulf coast between Cape Fairweather and Yakutat
will result in LLWS and significant turbulence there.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind through Thursday afternoon for AKZ318.
MARINE...Gale Warning for PKZ012-013-022-053-643-644-651-664-671.
Small Craft Advisory for PKZ011-021-031-032-641-642-652-661>663-
672.

&&

$$

SHORT TERM...EAL
LONG TERM....NC
AVIATION...Fritsch

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