National Weather Service United States Department of Commerce


000
FXAK68 PAFC 140045
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
445 PM AKDT Sun Jun 13 2021

.ANALYSIS AND UPPER LEVELS...

The upper levels feature a large upper level ridge extending
southwest to northeast across nearly all of mainland southern
Alaska this afternoon. A low and associated front are moving
across the northern Bering, and may bring some light rain and wind
to the Hooper Bay area this evening. meanwhile, a compact upper
low is spreading rain over the eastern Aleutians and into the
southern Bering south of the Pribilofs.

Extensive cloud cover has overspread the coast and Kuskokwim Delta
this afternoon, with a mix of sun and clouds with an extensive
Cumulus field developing for the Lower Kuskokwim Valley, and along
the Alaska Range. The clouds have grown upscale into towering
cumulus near Eureka, with partly cloudy conditions over much of
the rest of Southcentral. The morning fog and stratus has
dissipated along the coastal Kenai Peninsula, including Seward,
with some remnants remain over portions of Prince William Sound.
Once again most high temperatures today are in the 60s and 70s,
except 50s along the Bering coast where the cloud cover is
extensive.

&&

.MODEL DISCUSSION...

The models are in good agreement through Tuesday afternoon. The
main forecast challenges continue to be onset of sea breezes, high
temperatures, and afternoon minimum relative humidity values.
Forecast confidence is high.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Sunday night through Wed)...

Hot and dry conditions are expected over inland areas through
Tuesday as a ridge of high pressure remains parked over the
region. Expect high temperatures to push 80 degrees in parts of
the Mat-Su Valleys and Copper River Basin Monday with low 80s
possible on Tuesday. Coastal areas are unlikely to break 70 the
next two days due to strong sea breezes. Thunderstorm activity
will be limited due to strong subsidence aloft with only a slight
chance for a storm over the eastern Alaska Range.

Tuesday evening will begin a pattern change as a series of
easterly waves move in from the Panhandle/Southern Yukon Territory.
There is considerable uncertainty amongst the models with these
features, particularly the northern extent of the precipitation
field and shortwaves. Models often break down ridges too quickly,
so there`s a chance these waves may remain over the northern
Gulf. At this time the Prince William Sound and southern Kenai
Peninsula look the most likely to receive rain. With these
shortwaves there is always potential for convective activity over
the Copper River Basin and Talkeetna Mountains. However,
overrunning cloud cover prior to the arrival of the easterly waves
could limit instability from building throughout the day
Wednesday. Regardless, expect a pattern change towards overcast
skies and cooler temperatures on Wednesday. Southerly gap winds
are also likely to increase Wednesday as a coastal ridge builds
in.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 3...Tonight
through Wed afternoon)...

An upper level ridge will remain dominant across much of Southwest
Alaska, especially interior locations through Wednesday afternoon.
This will result in plenty of sunshine and warm temperatures.
Breezy conditions are expected Monday for much of Southwest with
winds southerly around 12-20 mph as the pressure gradient builds
across this area. This will be due to a frontal system
approaching from the Bering. These winds will diminish Monday
night though as the gradient weakens over the area. Temperatures
each afternoon will be a bit warmer with 60s and low to mid 70s
widespread. Some areas especially near Sleetmute Tuesday afternoon
and Wednesday afternoon may approach 77-80 degrees meaning summer
is in full swing.

For the Kuskokwim Delta, expecting this area to be more under the
influence of a frontal system approaching the area from the Bering
Monday. This frontal system is expected to bring coastal locations
of the Kuskokwim Delta periods of rain overnight through the day
Monday becoming more showery in nature after Monday afternoon.
Some of the rain may reach areas just west of Dillingham across
coastal Bristol Bay Monday morning/afternoon, though, not
expecting any rain to make it past Dillingham at this time.
Temperatures will remain cooler across the Kuskokwim Delta as a
result with 40s along the coast and 50s to possibly low 60s
inland. Tuesday night through Wednesday, the upper level ridge
builds over the Kuskokwim Delta leading to improving and warmer
conditions for Wednesday.

Lastly, an easterly wave is expected to cross the Alaska Range
Wednesday. As a result, there is the potential for increasing
showers and possible wet thunderstorms Wednesday afternoon. This
was left out for this forecast package though due to uncertainty
yet. Therefore, check back for subsequent updates.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 3...Tonight
through Wed afternoon)...

A low pressure system south of Adak currently will continue moving
northward into the Bering tonight. This low will phase with a
frontal system already present across the northern Bering. As a
result, moisture will stream north along it bringing rain and
unsettled conditions to the Pribilofs tonight through Monday
afternoon. The front that will bring rain to the Pribilofs will
undergo frontolysis (stretching apart of a front) Monday night.
However, a potent upper level low currently over the North
Pacific moves eastward tonight through Monday afternoon
reinvigorating the southern part of the front keeping areas
around Dutch Harbor unsettled through Wednesday. Winds will also
be gale force through the bays and passes along the eastern
Aleutian Chain as the front moves through tonight through Monday
evening.

Another piece of energy is expected to move into the western
Aleutian Islands overnight with rain and breezy conditions. This
system continues moving eastward through the Chain bringing
unsettled conditions to Adak and Atka Monday evening through
Tuesday night. This low will continue weakening as it moves into
the North Pacific Tuesday evening.

&&

.MARINE (Days 3 through 5: Wednesday through Friday)...

A well-developed low tracks south of the Aleutians through
Friday. Its front will bring gusty winds less than gale force over
the Central Aleutians increasing Thursday diminishing Friday.
Seas to 16 feet near the Central Aleutians building Thursday
subsiding Friday. A moderately strong and elongated North Pacific
Low remains nearly stationary through Friday. Its front spread
gusty winds less than gale force over the Gulf through Friday.

&&

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

The long-term models have come into significantly better
agreement over the runs 24 hours ago. As usual, while details are
still highly in doubt, the timing and strength of the disturbances
causing active weather are in better agreement. Starting on
Wednesday, an inverted trough will make its way northwestward
across the Gulf, causing rain to develop over much of Southcentral
by Wednesday afternoon. Again, exact timing on that remains in
question. Meanwhile, quiet weather will persist over Southwest
Alaska and much of the Bering on Wednesday. A small and compact
low may produce some shower activity over the eastern Aleutians as
well. The gap winds will reintensify on Wednesday

On Thursday, the Southcentral disturbance will be over Southwest
Alaska, causing some shower activity there as Southcentral dries
out. The timing will depend on how fast that disturbance moves,
which there is some uncertainty about. The Bering will remain
generally quiet, with the usual widespread stratus and some shower
activity towards the western Bering.

By Friday a rex block pattern sets up with the large blocking
high over the northern half of the state and weak lows moving
across the Gulf and eastern Aleutians. The easterly flow should
bring somewhat cooler air in across the mainland.

For this weekend a stronger upper level low moves north out of
the Pacific towards the Bering, causing unsettled and wet weather
especially across Southwest Alaska. Depending on the strength and
track of the low, that wet weather could spread east into
Southcentral as well.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 165 170.
FIRE WEATHER...NONE.

&&
$$

SYNOPSIS AND MODEL DISCUSSION...JPW
SOUTHCENTRAL ALASKA...CJ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MV
MARINE/LONG TERM...MK/JPW


000
FXAK69 PAFG 132054
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
1254 PM AKDT Sun Jun 13 2021

.SYNOPSIS...Not much change from yesterday, for the Central and
Eastern Interior and north to the Eastern Arctic Plain, isolated
to scattered thunderstorms and showers this evening and again
Monday. Temperatures rising in the Interior into the 70s and 80s
for Monday. A weather front has moved to the West Coast spreading
showers to the coastal areas and some clouds to the inland areas.
The Arctic continue to be a challenge with Cloudy conditions and
periods of dense fog.

.DISCUSSION...

Models...The 13/12Z solutions are in very good agreement on
holding the ridge over the state through next weekend even though
there are some minor differences. A couple waves moving east
across the Arctic may impact the solutions more that they are
indicating, so will keep a watch on them. There is agreement on a
system moving north up the western flank of the ridge next Sunday
night and Monday that will bring the next major change. At 13/15Z
surface solutions initialized well against the local analysis.
Convective indicies are fair to good the next couple day. The big
question is how much will the ridging aloft suppress convection.
Lifted Indicies range from +1 to -3, and CAPE values range up to
around 1200 J/kg. Thunderstorm activity will generally be east of
Tanana and extend from the Eastern Arctic Plain south to the
Alaska Range. For precipitation will be going with an equal blend,
but will be filling in some of the holes to capture the isolated
to scattered thunderstorms and showers. 850 hpa temperatures
rising into the teens above the next 3 to 4 days east of Ruby, and
will be above 0C for the rest of the forecast area, so surface
temperatures will be rising. Going with an equal blend for winds
today through Monday. Will need to make some adjustments to the
winds near the Alaska Range Passes for Monday evening as the
thermal trough sets up along the north slopes of the range and
winds will kick up and be gusting to around 25 mph.

Aloft...At 500 hpa...Ridging is building in over the state with a
559 dam high over Denali this afternoon, and ridging extending
northeast to Banks Island, and southwest over Bristol Bay, then
south over the Pacific. The low in the northwest Territories has
moved to 200 nm west of the MacKenzie Delta at 548 dam and is
starting to move northeast. In the Arctic the low that was over
the Bering Strait for the longest time is exiting to the north and
is 500 nm north of Oliktok Point. In the Bering Sea 536 dam low
is just south of the Gulf of Anadyr and is moving northeast, with
a trough extending south to a 541 dam low 300 nm south of the
Aleutians that is moving east. A broad area of lower heights
remains off the Canadian and Pacific Northwest Coasts with a 548
dam center 500 nm west of Coos Bay, OR. Ridging will continue to
build and expand over mainland Alaska with a 564 dam high over
Central and another over Denali Monday afternoon. Ridging will
extend north over 150W, and south over Kodiak Island and 150W. The
low to the west will move over the Chukotsk Peninsula at 533 dam
with a strong shortwave extending southwest from the low, while
the low south of the Aleutians will move to 250 nm south of Dutch
Harbor. Broad area of low heights remains off the Canadian Coast
with a 551 dam low 200 nm west of Vancouver Island. Tuesday
afternoon the ridging will lie over the Beaufort Sea, then
northeast to southwest over the state to Nunivak Island with a 567
dam center over Venetie. The low over the Chukotsk Peninsula will
move over the Western Arctic 300 nm northeast of Wrangel Island
with the shortwave moving over the Northwest Arctic Coast and the
Bering Strait. Troughing will remain to the south with the low off
Vancouver Island moving to 400 nm south of Yakutat at 553 dam. A
wave moving around the low will extend east over British Columbia
that will be moving over the southeast Interior later in the week.
At 850 hpa...Temperatures warming over mainland Alaska and the 0C
isotherm has been pushed west and northwest of the mainland. A
dome of warm air with temperatures near +10C continues to develop
in the Southeast Interior and temperatures will warm to around
+13C by Monday afternoon, and +16C by Tuesday afternoon. The +10C
isotherm will lie from Oliktok Point to Bettles to Minchumina by
Monday afternoon and hold there into Wednesday.

Surface...Weak low pressure across the Interior between the ranges
this afternoon. The thermal trough lies from Eagle to the Eastern
Brooks Range and a second branch lies from Eagle to Fairbanks to
Galena. A 1018 mb high is 150 nm north of Utqiagvik. A 997 mb low
has moved to 200 nm west of St Lawrence Island, and a 997 mb low
has moved to Atka. High pressure remains over the Northeast
Pacific extending north over the southwest mainland, Kenai
Peninsula, and Prince William Sound. Monday afternoon the high in
the Arctic will be in the Central Beaufort Sea at 1020 mb, while
weak high pressure will extends south over the Central and Eastern
Interior to a 1018 mb high 400 nm south of Prince William Sound.
Low pressure associated with the low to the west will push over
the West Coast with a 998 mb low near St Lawrence Island, and a
999 mb low 300 nm south of Dutch Harbor. The thermal trough will
lie from the AlCan Border crossing to Delta Junction to
Minchumina with a second branch extending north along the AlCan
Border to the Eastern Brooks Range.

Arctic Coast and Brooks Range...A weather front will spread
showers over the Northwest Arctic Coast tonight, but stays west of
Utqiagvik. Low clouds and fog will continue to be an issue from
Utqiagvik east with areas of dense fog along the coast. In the
Plains some clearing will bring warmer temperatures, and in the
Eastern Plains some isolated thunderstorms again today.
Inland temperatures much warmer with less clouds so the plains
will see highs in the 60s today and around 70 Monday, while the
Brooks Range will have highs around 60 today and in the mid to
upper 60s Monday. Along the coast highs will be in the upper 30s
to mid 40s today and Monday. Areas of fog along the coast with
visibility reduced to less than one half mile at times. Winds
east at 5 to 15 mph tonight, with winds becoming southwest to the
west of Wainwright Monday.

West Coast and Western Interior...A weather front is spreading
showers up the coast and showers will continue into early Tuesday
before tapering off as the low moves into the Arctic. Quiet in the
inland areas around the Middle Yukon Valley and the Upper
Kuskokwim Valley through Monday as high pressure builds into the
area. High temperatures continue warming in those inland areas and
will be in the upper 60s to around 70 today and the low to mid 70s
Monday. Along the coast high will only reach the 40s to around 50
with the cloudy conditions and showers. On St Lawrence Island
temperatures will be in the mid 30s to around 40. Winds will be
generally light and variable east of the Nulato Hills, while winds
along the coast will be turning from the southeast to
south as the low moves up the coast. Winds will be increasing
along the coast to 10 to 20 mph.

Central and Eastern Interior...Isolated to scattered
thunderstorms and showers this evening, and again Monday, but
Monday they will mostly be east of Fairbanks. Winds light and
variable, but some gusty winds to 25 mph can be expected with
thunderstorms. Thunderstorms will also produce small hail and
brief downpours. Rainfall of around one half inch is possible as a
thunderstorm goes directly over an area. High temperatures in the
70s, to around 80 today, with highs in the upper 70s to mid 80s
on Monday. Overnight lows in the mid 40s to mid 50s. Winds
variable to 10 mph. Winds will kick up a bit Monday afternoon and
evening south of Delta Junction gusting to 25 mph out of the
south.

Extended forecast for days 4 to 7...Ridging aloft hanging on over
the state with warmer and drier conditions and isolated to
scattered thunderstorms and showers in the afternoons and
evenings. A low moving up the western flank of the ridge aloft
will spread showers north up the West Coast Sunday and Monday and
will increase chance of Thunderstorms in the Western Interior. A
low will bring some showers to the Northwest Arctic Coast Thursday
then some clearing as high pressure over the Interior pushes
north over the Arctic Coast.

&&

.Fire Weather...Isolated to scattered wet thunderstorm activity
mainly east of Fairbanks this evening expect less coverage of
wet thunderstorms Monday to the southeast of Fairbanks. The
thermal trough lies from Eagle to the Eastern Brooks Range and a
second branch lies from Eagle to Fairbanks to Galena. A weather
front will spread showers north up the West Coast today and
tonight, without much making it into the Middle Yukon Valley.
Temperatures will be warming into the middle of next week with
highs in the Central and Eastern around 80 Monday through
Wednesday. Many locations will see their warmest temperatures so
far this year. Relative Humidity values in the 20s and 30s for
most areas with a few locations falling into the teens. Overnight
Relative Humidity recovery will be fair tonight, but becomes poor
starting Monday and continues poor through most of the week. Near
Red Flag conditions Monday evening south of Delta Junction.

&&

.Hydrology...Yukon River in Canada running near bankfull, but the
gage at Eagle remains well below action stage. Most interior
rivers are showing some diurnal rises and falls as snowmelt
continues at higher elevations, but they continue to run low.
Breakup continues in the Arctic with no known issues. For the
latest river information go to www.weather.gov/aprfc.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Small Craft Advisory for PKZ210-PKZ220-PKZ230.

Brisk Wind Advisory for PKZ245.

&&

$$

SDB JUN 21


000
FXAK67 PAJK 132243
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
243 PM AKDT Sun Jun 13 2021

.SHORT TERM.../Tonight through Tuesday night/ Biggest change (and
challenge) to the short term forecast is the addition of
thunderstorms to the southern half of SE AK.

Several ingredients are there for thunderstorms this evening and
early tonight. Models have a passing vort max overhead. A low
level jet expected at 30 kt from the southeast. Cape values are up
to 300 and LI values are around -1 to -2. Afternoon temps at the
surface have reached 60s to near 70 with dewpoints in the upper
40s to 50s.

Satellite imagery is showing cells beginning to develop around
the Ketchikan to Hyder area in far southern SE AK.

The best setup for thunderstorms is mainly south of Frederick
Sound so for now, have kept thunder out of the forecast for areas
north of Frederick Sound but this may need to be reviewed
depending on how the evening plays out.

Showers are expected to move along the panhandle through Monday
with continued chances for rain on Tuesday as the low looks to
linger in the gulf.

Highs in the short term look warm with most areas getting into
the 60s for both Monday and Tuesday.

.LONG TERM.../Tuesday through Sunday as of 10PM Saturday/...Generally,
dirty ridging stays over the Panhandle through the period. With
this pattern, generally chances of light showery convective
activity is present throughout the Panhandle. To start off the
period, a weak inverted trough and an easterly wave over British
Columbia bring a more organized area of precipitation from south
to north through the Panhandle from Tuesday into Wednesday
morning. A very weak wave moves to our south into the Dixon
Entrance/Graham Island, BC area toward the weekend, which may
bring an enhanced area of showery precipitation to southern parts
of the Panhandle.

Generally, high temperatures look to be the warmest for the
Thursday into Saturday timeframe, primarily in the 60s throughout
the Panhandle. This is supported by warm air advection over the
area as indicated by 850mb operational forecast model
temperatures and GFS and ECMWF extended range MOS guidance.

As for winds, they look to stay at levels or 15 knots or less
over the Panhandle, Gulf waters, and Inner Channel waters for the
majority of the period. The pressure gradient will remain fairly
relaxed through the period, except for the Wednesday evening
through Thursday evening timeframe, when a weakening low moves
into the central and eastern Gulf from the west and dives
southeastward, bringing areas of 20 to 25 knot sustained wind over
the open outside Gulf waters along with its tighter pressure
gradient.

The forecast is blended toward the NBM for the last half of the
long term forecast period, due to some model divergence for that
timeframe.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

$$

CM&GJS/JLC

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