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Alaska Area Forecast Discussions


000
FXAK69 PAFG 162142
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
142 PM AKDT Wed Jun 16 2021

.SYNOPSIS...Isolated thunderstorms this evening and overnight in
the Interior with some widespread showers. Showers will be mainly
northwest and north of the Yukon River Thursday afternoon.
Temperatures cooler with lows overnight in the mid 40s to lower
50s, and highs Thursday in the 60s to lower 70s. The Arctic will
be partly cloudy west of Nuiqsut with a mix of clouds to the east
as the front decays in the area. Isolated thunderstorms in the
Brooks Range mainly east of Anaktuvuk Pass this evening. The West
Coast will remain pleasant with mostly clear north of Galena and
mostly cloudy to the south. Some isolated thunderstorms in the
Upper Kuskokwim Valley tonight, may move into the Lower Yukon
Delta. Temperatures will be warming along the coast.

.DISCUSSION...

Models...The 16/12Z solutions continue the good run to run
consistency they have had the last few days with this system.
Solutions have a good handle on the shortwaves moving around the
low to the south that will be impacting the southern Interior, and
continue to handle the ridging very well. Going with a blend of
the solutions and maintaining continuity with the previous
forecast. Will be leaning a bit more on the solutions that are
producing higher QPF with the upslope component expected along the
north slopes of the Alaska Range. Convective indicies look good
for Isolated thunderstorms, and support some localized ares of
scattered thunderstorms. Lifted Index in the -2 to -6 range with
CAPE values ranging up to 1300 J/kg. Expect the high convective
indicies through the night will support isolated embedded
thunderstorms. For the remainder of the elements leaned heavily on
continuity with only some minor adjustments.

Aloft...At 500 hpa...Ridging with a 569 dam high over Old Crow
extends west over the Brooks Range, then northwest over Wrangel
Island. A weakening branch of the ridge extends from Tanana
southwest over Bethel. A shortwave swinging around a 555 dam low
over the Gulf of Alaska is moving through the area this afternoon.
Tonight the ridging will continue to rotate to the northeast as
the high move over the Northwest Territories. A second, stronger,
wave will be swinging around the low and will move over the
Southeast Interior in the early morning hours, and continues to
swinging around the low to be over Fairbanks by noon on Thursday.
By Thursday afternoon the high will be 300 nm east of Eagle at 571
dam, while the ridge axis will lie northwest over the Eastern
Arctic. The second axis will lie over the Eastern Brooks Range to
Ambler, then southwest over Norton Sound and Nunivak Island. The
first shortwave will continue to move around the ridge and will
lie northwest to southeast over the Central Arctic Coast. At 850
hpa...Dome of warm air with temperatures approaching +17C over the
Interior is being pushed north today as the shortwave aloft
pushes west across the Southern Interior. By Thursday afternoon
the dome of dome of +10C temperatures and warmer will be over the
Upper Yukon Flats, Eastern Brooks Range, and Eastern Arctic Coast.
Friday those warmer temperatures will spread west over the
Central Brooks Range and the Upper Kobuk Basin.

Surface...Front that was over the West Coast and moved across the
Arctic lies from Old Crow to Bettles to McGrath as it continue to
decay. Thermal low is over the Upper Yukon Flats near Fort Yukon
with the thermal trough extending north over Arctic Village,
southeast over the AlCan Border Crossing, and west to Huslia. High
pressure has moved over the Coastal areas around the low pressure
between the ranges. High pressure will persist over the Arctic and
West coasts with low pressure over the Interior, while a 1013 mb
low will develop this evening over the Upper Kuskokwim Valley
and drift southwest to the coast by Friday morning.

Arctic Coast and Brooks Range...Front that moved across the area
yesterday is stalled over the Eastern Brooks Range and the Eastern
Arctic Coast. Mostly clear from Nuiqsut northwest, with cloudy
conditions to the southeast. Isolated thunderstorms in the Eastern
Arctic Plain and Brooks Range again this evening, and expect that
will continue for a few more days. Stratus is always hanging just
offshore, so a change in winds can bring it over the coast at any
time. As the surface winds move from more offshore to more
onshore you can expect those low clouds to move in. Inland areas
will see some clearing as the old front dissipates. Along and near
the coast from Utqiagvik west, southwest 5 to 15 mph becoming
northeast to east at 5 to 15 mph, while to the east of Utqiagvik
wind will be east at 5 to 15 mph. Inland winds will be variable,
mainly northeast to 10 mph. Temperatures along and near the coast
in the upper 40s to mid 50s, while inland areas will be in the 50s
to around 70 for highs, while lows on the coast will be in the
40s and inland around 50.

West Coast and Western Interior...Offshore flow bringing some
partly to mostly cloudy skies to the area. Isolated thunderstorms
this evening and Thursday south of Kaltag and west of Marshall.
Temperatures warmer with some coastal locations warming to the
lower 60s, but most in the 50s. Inland Warmer with highs in the
60s to lower 70s. St Lawrence Island a bit warmer as well with
highs in the 40s and lows in the mid 30s. Winds light and
variable, or offshore to 10 mph, except on St Lawrence Island,
winds will be southeast at 10 to 20 mph.

Central and Eastern Interior...Isolated thunderstorms in the
evening and overnight with showers spreading across the area. Some
clearing by Thursday evening. Rainfall amounts around one inch
in the Alaska Range tonight through Thursday will produce rapid
rises in the drainages flowing out of the range with some of the
streams and creeks rising to bankfull by late Thursday.
Backcountry travelers should be cautious as the streams and creeks
can rise rapidly. Temperatures cooling with highs in the 60s to
lower 70s and lows in the 40s to lower 50s.

Extended forecast for days 4 to 7...Ridging aloft hanging on over
the northern half of the state with warmer and drier conditions
and isolated to scattered thunderstorms and showers in the
afternoons and evenings mainly over the Brooks Range and the
Arctic Plain. A low aloft will move over the Southcentral area
Sunday with widespread showers and isolated thunderstorms across
the forecast area for most of the extended period.

&&

.Fire Weather...Isolated wet thunderstorms mainly south of the
Yukon River today and tonight spreading northwest into the Middle
and lower Koyukuk Basin Thursday. Widespread showers tonight, so
any thunderstorms will be embedded in the showers. Rainfall
amounts from the White Mountains south this evening and overnight
will range from 0.10 to 0.50 inch. Additional rainfall Thursday
into Friday morning will bring totals up to one inch in some
places along the Alaska Range. Temperatures cooler the next
couple of day as highs fall into the 60s to lower 70s for most
areas. Relative Humidity values will be higher the next couple
days as well with minimum values in the 30 to 40 percent range.
Overnight Relative Humidity recovery will be good the next few
nights.

&&

.Hydrology...A weather system moving west across the area will
bring some heavy rainfall to the north slopes of the Alaska Range
tonight into Friday morning. Rainfall amounts around one inch will
be possible and will produce rises in the drainages flowing out
of the range with some of the streams and creeks rising to
bankfull by late Thursday. Backcountry travelers should be
cautious as the streams and creeks can rise rapidly. Locally
mudslides will be possible in steep terrain. There are currently
no concerns with the mainstem river north of the Alaska Range. For
the latest river information go to www.weather.gov/aprfc.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

None.

&&

$$

SDB JUN 21


000
FXAK68 PAFC 170042
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
442 PM AKDT Wed Jun 16 2021

.ANALYSIS AND UPPER LEVELS...

An upper level ridge is centered over northern Alaska/Northwest
Canada, with a spoke of the ridge extending southwestward into
Southwest Alaska. The thermal trough and axis of maximum
instability extends across the Alaska Interior then down across
the Kuskokwim Valley. Meanwhile, a short-wave trough is centered
over the Gulf, with its primary trough axis extending eastward to
Southeast Alaska. Along the northern periphery of the upper level
cyclonic circulation, weak waves are tracking westward across
Southcentral Alaska, leading to extensive cloud cover and areas of
light rain or rain showers. Some showers are crossing the Alaska
Range into the Kuskokwim Valley, while others are forming along
the thermal trough. Sunny skies dominate as you head south and
west from here to Bristol Bay, the Kuskokwim Delta and the far
Eastern Bering Sea.

Out west, a mature low south of the Eastern Aleutians is tracking
southward into the Pacific, with rain and winds diminishing
behind it. A low is deepening along the subtropical jet over the
North Pacific to the south of the Aleutian chain, but impacts from
this have not reached the Aleutians. For most of the Bering Sea
and Aleutians weather is currently benign with lots of low clouds,
which is typical for this time of year.

&&

.MODEL DISCUSSION...

Models continue to struggle with the precipitation forecast across
Southcentral and Southwest Alaska as weak and disorganized upper
level impulses track westward across the region. There is better
agreement on a more amplified trough crossing Southcentral
tonight through Thursday morning, then continuing into Southwest
Alaska. Thus, have updated forecasts to reflect an area of steady
rain ahead of this trough. While rain is most likely over inland
areas of Southcentral, there is still some question about how far
south the rain will extend. Notably, Anchorage will be on the
southern periphery of the rain. Looking out through Friday, models
have a good handle on large scale features. The pattern remains
relatively complex, so do expect at least some minor changes to
the forecast each day.

&&

.AVIATION...

PANC...While there may be some fluctuations in the strength of
winds, generally expect gusty southeasterly winds to persist
through Thursday as the surface ridge along the coast remains
firmly in place. Periods of sprinkles or very light rain will
continue through early Thursday, though ceilings are expected to
remain VFR. Steady rain is expected to develop north of Anchorage
as a more significant short-wave trough approaches. If this were
to shift just a little bit to the south, then ceilings could drop
below 5000 ft, but would still think conditions would still
remain VFR (above 3000 ft).

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Wednesday afternoon through Saturday)...

Easterly upper level flow will dominate Southcentral through
Thursday morning as several shortwaves bring enhanced chances of
precipitation. The first wave is located over the Northern Gulf
extending into the Copper River Basin this afternoon. This wave
will continue to produce cloudy conditions across most of the area
with a few showers. Additionally, instability exists across the
Talkeetnas where isolated thunderstorms are expected through this
evening. Another shortwave will move out of the Yukon tonight and
bring an area of rain across Southcentral. With stable conditions
tonight the thunderstorms will die off before midnight with
wetting rains likely across most of the area through Thursday
morning including the Anchorage and MATSU valleys. Thursday
afternoon most of the area of will become sunny with drier
conditions expected and an overall nice afternoon. No
thunderstorms are expected Thursday afternoon or evening as the
atmosphere will be stable, however a few lingering showers are
possible over higher elevations especially the Alaskan Range.

A coastal ridge will continue to produce Turnagain winds bending
into west Anchorage through Thursday but will not be quiet as
strong as today and will taper off by Friday morning as the
pressure gradient weakens.

Friday is expected to be another nice summer day for much of
Southcentral with warm conditions and sun mixed with clouds.
A weak shortwave will move across the Copper River Basin into the
Talkeetnas and Susitna Valley on Friday where isolated showers
and thunderstorms are possible Friday afternoon and evening.

Another coastal ridge develops Friday afternoon through Saturday
with the Turnagain winds redeveloping and turning into west
Anchorage. Saturday is expected to be another warm summer day
with chances of showers and perhaps a thunderstorms mainly over
the Copper River Basin and east towards the Susitna Valley.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3:
Wednesday afternoon through Saturday)...

The easterly wave is responsible for scattered to numerous showers
and isolated thunderstorms over the lower Kuskokwim Valley late
this afternoon into tonight, then continuing on across the
Kuskokwim Delta this evening into late tonight. A separate trough
from the Western Gulf will traverse AKPEN westward leading to
another series of rainfall Thursday morning into early Friday
morning. Models bring another upper North Pacific low closer to
AKPEN on Saturday which could generate rainfall for AKPEN and
Bristol Bay area, but will monitor this situation closely for more
updates. Overall, the short term will bring a continual seasonal
wet pattern, increased clouds and cool overnight temperatures
across the region.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Wednesday afternoon through Saturday)...

Strengthening pressure gradients between the exiting low south of
Eastern Aleutians and the onset of the next North Pacific low
tonight will maintain small craft conditions through at least
Thursday night for several Aleutian Islands. Rain and marine-
layered conditions will linger through Thursday night, then
diminishing by Friday morning until a ridge of high pressure
builds through the Southern Bering and Western to Eastern
Aleutians on Friday morning through Saturday morning. This will
lead to an increased low cloud deck across the Bering. By
Saturday morning, a strong Northwest Pacific Low is expected to
trek towards the Western Aleutians between Saturday morning and
Saturday night, and this could bring another round of increased
rainfall and elevated seas. Stay tuned!

&&
.MARINE (Days 3 through 5: Saturday through Monday)...

A deep low will approach the Western Aleutians on Saturday, then
remain somewhere in the vicinity through Saturday. There is an
increasing likelihood that winds will reach gale force near the
low center on Saturday, which would impact the Western Aleutians
coastal waters. While the ultimate track of the low is uncertain,
do expect winds do diminish Saturday night through Sunday.

Meanwhile, a low over the North-Central Pacific will track toward
Kodiak on Saturday. While it largely looks like winds will max
out at small craft advisory levels, there is a chance of a gale
force winds Saturday night, most likely from the Barren Islands
southwestward through Shelikof Strait. Winds will then quickly
diminish Sunday as the low weakens.

&&

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

The overall synoptic pattern during the extended period consists
of a deepening Aleutian Low combined with a building upper level
ridge across the eastern Gulf of Alaska. This is a cloudy and wet
pattern for Southcentral Alaska as this pattern is conducive to
prevailing onshore flow. A series of upper level waves will move
through Southcentral during the extended period which will bring
periods of rain and showers. With respect to atmospheric stability,
the southerly onshore flow and ample cloud cover will make for a
less than favorable environment for afternoon thunderstorms in the
Copper Basin and Susitna Valley. Temperatures will also be cooler
than normal during this period across Southcentral due to the
ample cloud cover.

Out west, the deepening Aleutian Low will bring strong
southeasterly gap winds along the Alaska Peninsula and Eastern
Aleutians Tuesday afternoon. For the Western Bering, widespread
northwesterly winds will allow for ample stratocumulus clouds and
light showers.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...RC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
MARINE/LONG TERM...ED


000
FXAK67 PAJK 170740 CCA
AFDAJK

Southeast Alaska Forecast Discussion...CORRECTED
National Weather Service Juneau AK
1140 PM AKDT Wed Jun 16 2021

.SHORT TERM.../ Through Friday / Mostly cloudy skies with
scattered showers over Southeast Alaska this afternoon. There is
a front lifting northward into the Southeast Gulf Wednesday night
and it is expected to shear apart. Part of the energy heads back
to the central gulf with the second part and trailing short wave
to move to Haida Gwaii and the British Columbia Coast. Some of
the associated rain will spread into the southern third of the
panhandle Thursday afternoon. Some of the rains will spread into
the central panhandle Thursday night.

Another feature will try and move across the southern gulf
Friday, however, the consensus is that it will slide south of the
panhandle as well. The remaining shower activity is expected to
end Friday night and early Saturday.

Upper level flow pattern shifts from a zonal to more Southwesterly
so the developing system the later half of Saturday moves
northeast across the gulf toward the NE gulf so the weather front
will be moving towards the NE gulf through Saturday night. Will
need to keep an eye on this one as the various model solutions
have not settled upon a preferred track yet.

.LONG TERM...The main feature of this extended range forecast
period is a front that will impact Southeast Alaska this coming
Sunday. This front will be making its way through an established
surface ridge as it arrives and, as a result, much of it`s energy
will be expended getting to the outer coast. Models diverge
significantly on how far inland and south the precipitation will
reach, with the GFS and ECMWF being in the best agreement on
timing and areal extent of the precipitation coverage. The current
official forecast represents the most aggressive solution, with
categorical PoPs reaching as far south as the Dixon Entrance on
Sunday morning. Best look for indoor activities to celebrate
Father`s Day. Prior to then, easterly wave activity will keep
showers in the forecast for Friday and Friday night. At this
point, Saturday is looking dry, if not sunny, so that may be the
best day to plan outdoor activities for this coming weekend.
Temperatures should top out in the mid to upper 60s on Saturday
with a slight downward trend thereafter. Still, comfortable for
this time of the year and maybe we will see some relief from the
latest hatching of mosquitoes that have been benefiting from temps
in the low 70s. Winds will remain on the light side, as is
typical for this time of the year. Even the Sunday front currently
features only marginal small craft winds.

Forecast updates tonight favored the GFS and ECMWF for wind, PoP
and temperatures. Overall forecast confidence is average.

&&

.HYDROLOGY...Water levels on the Taku River crested this
afternoon at 42.3 feet, flood stage is 43.0 feet. It will start
to recede through the evening and overnight. No reports of
flooding have been received, and the special weather statement has
been updated.

&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ042.

&&

$$

Bezenek/Fritsch

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