348
FXAK68 PAFC 211256
AFDAFC
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
456 AM AKDT Wed May 21 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
An upper-level shortwave and associated weakening surface warm
front are moving across the Kenai Peninsula early this morning. A
strengthening southerly flow aloft ahead of the front is helping
to advect moisture from Prince William Sound to Cook Inlet.
Although there are some light returns showing up on radar over
Cook Inlet as of 4 AM, the precipitation is having a tough time
reaching the ground due to drier air near the surface.
These features will weaken over the next few hours, with a more
potent shortwave trough, surface low, and attendant occluded
front quickly becoming the main players for Southcentral Alaska
later today. This low will push its front into the central and
western Gulf today, spreading gusty southeasterly winds and rain
into Kodiak Island this morning and up into the eastern Kenai
Peninsula by afternoon. A coastal ridge will build along the
north Gulf Coast in advance of the front, and will help drive
fairly potent gap winds through Turnagain Arm, Knik Valley and
Copper River Valley from around noon today through late this
evening. Southeasterly gusts up to 30 to 40 mph will be common
along parts of the Turnagain Arm, as well as parts of the
Anchorage Hillside and western side of the Anchorage Bowl.
Similar wind gusts are also expected across parts of the Mat
Valley and Copper River Basin. While it will certainly be a
blustery day in places, the interior valleys should stay fairly
dry thanks to the strong southeasterly flow developing north of
the Gulf low/front and downslope drying in the lee of the
mountains.
From Thursday into Friday, a transition to a quieter, warmer and
drier pattern will begin as the Gulf low moves off into the
Northeast Pacific and as prevailing winds aloft begin to turn more
easterly to northeasterly. This should draw warmer and drier air
into Southcentral from the Interior and Yukon, especially on
Friday. It`s looking like quite a pleasant close out to the work
week on Friday afternoon, with increasingly clear skies and a
decent chance for valley temperatures to approach or exceed 60
degrees Fahrenheit. An easterly wave moving out of the Yukon and
across Southcentral Friday afternoon may produce a few scattered
showers and isolated thunderstorms across portions of the western
Copper Basin, Mat-Su Valleys, and Anchorage Bowl.
-TM/AS
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA AND BERING SEA/ALEUTIANS
(Days 1 through 3)...
Scattered showers are moving across the Southwest mainland this
morning while a low occupies Bristol Bay. The strongest winds will
be diving down across the Alaska Peninsula peaking around 10AM
AKST. Closer to 4PM AKST the low drops south of the AKPen and
settles into the Souther Gulf. Almost simultaneously, a second
low from the North Pacific enters into the western Bering near
Attu. This second low tracks across the southern Bering and
crosses back in to the North Pacific over Unalaska by Friday
afternoon. Wind from this low will be weaker than its predecessor,
and precipitation from this system is not expected to advance
beyond the western Alaska Peninsula. Between these lows, an area
of high pressure sweeps across the central Bering, arriving at the
Southwest mainland by Thursday and persists into the weekend.
Ridging over the western mainland will bring warmer temperatures,
and reduced cloud cover will give rise to convective showers.
This pattern should persist while the next system sweeps across
the Bering sea Friday and Saturday. Widespread gales will be
limited to the western and central Aleutians, however several
bands of rain are anticipated to reach the mainland later in the
weekend.
&&
.LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)...
A number of upper level low centers progress from the Russian Far
East across the Bering and Alaska Peninsula into the Gulf of
Alaska through the forecast period. Main jetstream energy remains
across the North Pacific into the new week, with shortwaves
passing through the pattern. Most of the active weather will be
occurring over the Southern portions of the state. Ensemble
forecast models handle the features overall with some variations
in timing of individual events.
Lingering showers are expected over the Southern half of Mainland
Alaska through the weekend. A well developed low and front
pushing across the Western Aleutians and Bering brings moderate
rain and locally gusty winds across the region. This front moves
over the Central and Eastern Bering on into Western Alaska, the
AKPEN and Kodiak Island Sunday before spreading across
Southcentral Alaska through Tuesday. Locally moderate rain moves
further into the Interior with the front extending across the
coasts. The supporting surface low crosses the AKPEN Monday and
slips South of Kodiak Island through Tuesday.
- Kutz
&&
.AVIATION...
PANC...VFR conditions and light winds will persist through this
morning. Southerly winds will increase with gusts to 25kt possible
this afternoon.
&&
$$
851
FXAK69 PAFG 202118
AFDAFG
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
118 PM AKDT Tue May 20 2025
.SYNOPSIS...
Showers in the Western and Central Interior. Isolated
thunderstorms in the Eastern Interior. Light snow showers along
the Eastern North Slope. Temperatures warm through the end of the
week.
&&
.KEY WEATHER MESSAGES...
Central and Eastern Interior...
-Showers continue this afternoon across the Central Interior.
-Isolated thunderstorms expected in the Eastern Interior,
particularly over elevated terrain in the Fortymile Country and
near the Upper Tanana Valley.
-Moderate southerly gap winds through the Alaska Range passes
tonight through Wednesday night. Gusts up to 35 mph possible
through Isabel Pass and gusts up to 30 mph possible through Windy
Pass.
-A warming trend is expected through the end of the week with
highs in the mid to upper 60s this weekend.
West Coast and Western Interior...
-Northerly Winds 25 mph mph through the Bering Strait and 20 mph
through the eastern Norton Sound.
-Light showers return to the Western Interior this afternoon and
remain through Thursday. Mostly scattered today and then becoming
isolated Wednesday.
North Slope and Brooks Range..
-Light snow showers persist across the eastern North Slope this
afternoon. Additional accumulations an inch or less.
-Northeasterly winds increase across the North Slope to 10 to 20
mph by Wednesday night. Winds get stronger further west.
&&
.FORECAST ANALYSIS AND DISCUSSION...
A stalled front sits over the Central Interior and Brooks Range
between broad troughing along the West Coast and a building ridge
along the Canadian border. Isolated thunderstorms expected today
in the Fortymile Country as the ridge and front interact.
Scattered showers expected across the Interior along the front
this afternoon. A 533 dam low moves through the trough pattern
tonight and causes the trough to dig south into the Gulf of Alaska
by Wednesday afternoon. This weakens the trough along the West
Coast causing the front to fall apart as ridging strengthens in
the Interior. The strengthening ridge will bring a warming and
drying trend through the end of the week. Another 535 dam low
moves through the pattern Thursday and interacts with the previous
low that moved into the Gulf. At this point models begin to have
difficulty determining how these two lows interact with each other
which will change how ridging across the Interior behaves. The
most likely solution is that the second low wraps into the first
one as a shortwave feature, which will strengthen it enough to
potentially break free of the Arctic low pressure at the top of
the trough. Should this occur the ridge will be able to build in
much stronger than previously expected which will strengthen the
warming and drying trend possibly bringing temperatures in the
upper 60s to low 70s to the Interior. A 594 dam high in the north
central Pacific will try to extend a ridge into the Bering Sea
late Friday, but a 521 dam low moving into the Western Bering at
the same time will prevent a ridge from fully forming. These
features will further complicate the mess of lows over southern
Alaska leading to poor forecast confidence on the finer details of
the forecast after Friday. Generally though, ridging will keep the
Interior warmer and drier with afternoon convection possible each
day Friday through the early part of next week.
&&
.FIRE WEATHER...
Showery conditions continue for the Central Interior today.
Showers move into the Southeast Interior this afternoon and will
help to moderate the dry conditions of the past several days.
Another area of showers moves into the Western Interior overnight
tonight. This results in decent chances of wetting rain across
much of the Interior through Wednesday. Showery conditions
diminish Wednesday into Thursday as ridging builds into the
Eastern Interior. This will cause a steadily warming and drying
trend through the end of the week with Interior highs in the upper
50s to lower 60s today rising to into the mid 60s by Friday.
Minimum RHs fall from the mid 30s to low 40s today into the mid
20s to 30s Wednesday and remains steady through Friday. Generally
weak flow aloft will limit winds in the Interior, but some weak
southerly gap winds are possible through the Alaska Range passes
tonight through Wednesday night. Elsewhere northerly winds along
the West Coast slowly diminish through Thursday.
Thunderstorms are expected in the Fortymile Country and Upper
Tanana Valley this afternoon. Mostly isolated, but there is
potential for widely scattered Thunderstorms near Northway and
Eagle. Thunderstorms will be generally confined to elevated
terrain, but may drift north after forming. Isolated thunderstorms
are expected Wednesday afternoon as well, generally confined to
elevated terrain in the Fortymile Country, but may reach into the
Yukon Flats later in the evening.
&&
.HYDROLOGY...
Degraded ice remains in place at the mouth of the Yukon River.
Breakup has yet to begin along the Porcupine, although some of the
upper tributaries are beginning to respond to snowmelt. Enhanced
snowmelt in the Chena Basin will lead to gradual rises in water
levels, although there are no immediate flooding concerns.
&&
.EXTENDED FORECAST DAYS 4-7...
A broad trough extends from the high Arctic through the West Coast
and into the Gulf of Alaska. Models are in good agreement on this
broad pattern. Ridging builds into the Eastern Interior which
will allow for warmer and drier conditions in the Central and
Eastern Interior early next week. Afternoon showers and isolated
thunderstorms are possible most days under this pattern in the
Central and Eastern Interior.
Coastal Hazard Potential Days 3 and 4...None
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ806.
Heavy Freezing Spray Warning for PKZ811.
Small Craft Advisory for PKZ811.
Heavy Freezing Spray Warning for PKZ812.
Small Craft Advisory for PKZ854.
Brisk Wind Advisory for PKZ856.
&&
$$
Stokes
069
FXAK67 PAJK 211302
AFDAJK
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
502 AM AKDT Wed May 21 2025
.SHORT TERM...
As the ridge continues to weaken, chances of showers continue
across SE AK through Wednesday night, before a brief period of
drier weather sets in on Thursday, especially for the northern
half of the panhandle.
A remnant trough over the area the past few days has all but
disintegrated. In its place, more southwesterly onshore flow is
joining forces with an atmosphere saturated up to at least 500 mb
to keep lingering chances of rain in the forecast. Somewhat cooler
air aloft has also injected an element of instability, meaning
that some of the rain will be more convective in nature. The
remnants of a mid level short-wave will move through the panhandle
late Wednesday night into Thursday morning, and given this and
the continuing onshore flow, extended chances of rain across the
area through Wednesday night, and into early Thursday morning
though still anticipate drier conditions to emerge on Thursday.
Past this point, a change in the weather pattern begins to dawn as
a vertically stacked moves out of the Bering Sea and enters the
Gulf of AK.
.LONG TERM...
Looking towards late week, guidance have begun to converge on a
less progressive pattern, with increased cold air descending down
from the Arctic. This cold air will intensify the trough,
increasing the amplitude, and directing the moisture flow towards
SE AK. The result will be multiple waves of moisture moving over
the panhandle beginning this Saturday. Exact details of this
evolving system are hazy, but what can be said is long duration
moderate rain with periods of heavy rain will move into the
southern panhandle. What is uncertain is how far this moderate to
heavy rain producing moisture will move northward. Currently, the
more likely solution is the heavier moisture will be directed at
the southern panhandle with lighter precipitation from Petersburg
up to Juneau. However, trends in ensemble guidance has
probabilities increasing for these much higher than normal
precipitation totals up into the Juneau area. In the southern
panhandle, there is around an 80% chance for 2 inches of rainfall
in 24 hours, while the same percentage chance exists for 1 inch of
rainfall for areas like Juneau, Gustavus, Angoon, and Sitka.
Regardless of either solution, with the current state of rivers,
no flooding is currently expected.
&&
.AVIATION.../Through 12z Thursday/...
No widespread aviation hazards through the TAF period. VFR to
upper- end MVFR flight conditions prevail across the panhandle as
last bits of upper lvl energy shift eastward with isolated showers
lingering through morning.
By 18 to 21z, anticipate improving flight conditions to
predominate VFR with SCT to BKN deck CIGS AoA 4000 to 6000ft with
an underlying FEW to SCT deck. Heavier showers will continue to be
isolated in nature through the afternoon as weak ridging moves in
aloft, with main mechanisms of lift either being convective or
orographic on shore flow. Not expecting widespread visibility
issues, outside the aforementioned isolated heavier shower, but
forecast confidence in airport impacts remains too low to include
in TAFs at this time.
Winds should remain near 10kts or less for majority of the
panhandle, outside of Haines and Skagway, which will see
sustained winds up to 15 to 20kts and isolated gust up to 25 to
30kts through 18 to 00z this afternoon as pressure gradient
tightens.
&&
.MARINE...
Outside: Winds slowly shift from the SW to the SE through
Wednesday across the outer coastal waters and the Gulf as a new
system begins to approach the Gulf from the W. Winds for the outer
coastal waters largely remain between 10 to 15 kt through
Thursday, before a system arriving on Friday sees winds strengthen
up to 20 - 25 kt for areas south of Cape Spencer. Winds across the
central Gulf of AK will strengthen to 20 to 25 kt by Wednesday
night.
Wave heights across the outer coastal waters start Wednesday
between 4 to 5 ft, slowly subsiding to 3 to 4 ft by Wednesday
night, before increasing to 5 to 7 ft on Thursday. Higher wave
heights of up to 8 - 9 ft are anticipated across parts of the
central and northern Gulf by late Wednesday night.
Inside: Inner channel wind speeds will continue to be pretty
light overall through most of Friday - generally out of the south
at around 5 to 10 knots. The main exception to this is Icy Strait
and Lynn Canal, where speeds will be upwards of 15 to 20 knots
at times on Wednesday, with speeds decreasing Wednesday night.
Late Friday into the weekend, wind speeds will increase in response
to the next approaching area of low pressure. While confidence in
speeds greater than 20 kts is high, confidence is speeds greater
than 35 knots is low. So for now, capped wind speeds at 25 to 30
knots. But as confidence in the track and strength of the low
increases, gales may need to be introduced. Stay tuned.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.
&&
$$
SHORT TERM...GFS
LONG TERM....NC
AVIATION...NM
MARINE...GFS
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