Graphical Hydro Meteorological Discussion

182
FXAK68 PAFC 241330
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
530 AM AKDT Thu Apr 24 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
through Saturday Night)...

Satellite imagery reveals an occluded, mature and now-weakening low
pressure system drifting northeast in the direction of Yakutat. As
with yesterday, multiple shortwave troughs rotating around this low
will continue to push rain and high-elevation snow into portions of
Southcentral Alaska. The bulk of heavy precipitation will remain
confined to the Prince William Sound region and adjacent mountains.
That said, it`s likely portions of the Copper River Basin,
Talkeetnas, and even areas west into Anchorage and the Mat-Su will
see spotty shower activity today as the aforementioned shortwaves
swing through.

Although the mid/upper-level low lifts into Yukon Friday, unsettled
weather will persist as the Aleutian Low broadens and anchors
cyclonic flow across the North Pacific, steering embedded shortwave
troughs towards the Gulf of Alaska. One such wave and associated
frontal boundary will push into the Gulf Thursday night, bringing
rain and breezy conditions to Kodiak Island before reaching the
southern Kenai later in the day. A more robust trough will rotate
into these regions on Saturday, bringing heavier precipitation to
Kodiak and then the Kenai Peninsula and eventually Prince William
Sound. At the time, it appears much of the area lee of the mountains
will remain downsloped and dry through the weekend.

Temperatures through the period will remain near or above average
for most locations. Model guidance has been consistently too cold,
so forecast temps have been raised to compensate for the recent
bias. On the note, models have also been struggling to capture our
near-daily convective showers across the region, perhaps owing to
the cold bias and resultant lack of forecast instability. Have also
raised PoPs in areas today and tomorrow to adjust for the recent
bias.

-Brown


&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

The front of a Bering Sea system approaches the southwest
mainland, bringing snow and rain mainly to the Bristol Bay area
and the Wood River Mountains late on Thursday. Colder air
wrapping in behind the low will sweep light snow across the
western Aleutians, however, in the eastern Aleutians, temperatures
will likely remain high enough to support rain. Light amounts are
expected for the Kuskokwim Delta and Valley, with little to no
snow accumulation. After the front passes, much of the area will
remain in a cloudy, showery regime of mixed precipitation through
the weekend. The responsible low pressure system will approach the
western mainland and stall between the Pribilof Islands and
Bristol Bay by Saturday morning. Widespread gales over water are
expected to weaken as the front reaches the mainland. Gap winds
won`t be very strong across the Alaska Peninsula, though there
may be some enhancement through channeled terrain.


&&


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

The long term continues to be characterized by upper level
troughing over the Bering, leading to an active weather pattern
for the Aleutians and southern mainland Alaska. An upper level
shortwave will traverse northwards across Southwest Alaska as a
closed upper low slides eastward towards the eastern Bering by
Monday morning. A surface low lifting from the AKPen into the
eastern Bering looks to bring a wave of precipitation across
Southwest and the AKPen through Monday, likely beginning as rain
for lower elevations before transitioning over to snow as
precipitation from this system tapers off. This low sends its
front across the Gulf and Southcentral bringing rain to Kodiak
Island and the northern Gulf coast and snow to higher elevations
through Tuesday morning as the front pushes inland. Precipitation
associated with this system is expected to be predominantly light,
though locally moderate rainfall is possible along the eastern
Kenai Peninsula and Western Prince William Sound.

By Monday morning, an upper level low lifting out of the North
Pacific supports a deepening surface low south of the western and
central Aleutians. This low is expected to continue to track
eastward south of the Aleutians and AKPen through the remainder of
the forecast period. Some light precipitation is possible for the
Aleutians as the system skirts to the south of the island chain
through the early part of next week, though even a slight shift in
the track to the south may limit precipitation. As the low nears
the Gulf, the focus for Tuesday into Wednesday shifts towards
another round of potentially heavier precipitation for the AKPen,
Kodiak Island, and northern Gulf coast. The greatest chance for
heavy rain and snow at elevation will likely again be along the
eastern Kenai Peninsula and Western Prince William Sound given the
southeasterly flow in the Gulf. Northwesterly flow and cold air
advection on the back side of the low may enhance northwesterly
gap winds through the eastern Aleutians and AKPen Tuesday into
Wednesday.

-JH

&&

.AVIATION...

PANC...VFR conditions will generally prevail through the TAF
period. Through Thursday afternoon, there is a small chance that
ceilings could briefly drop to MVFR if a shower passes over the
terminal. A weak Turnagain Arm wind is expected to set up also on
Thursday afternoon, but this may fail to materialize if pressure
gradients do not align correctly.

&&


$$

168
FXAK69 PAFG 232256
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
256 PM AKDT Wed Apr 23 2025

.SYNOPSIS...Very quiet weather across northern Alaska will
continue through Thursday before winds increase across the Arctic
Coast, bringing blowing snow. Northeast winds will be breezy
across the Interior through Friday. Showers in the Interior will
be mostly isolated and light through Friday before conditions
completely dry out Friday night. A warm front will bring a mix of
rain and snow the the West Coast Friday through Sunday.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...

-Northeast winds peak Wednesday evening with gusts up to 30 mph
along highway summits. Winds may mix down into the valleys with
gusts 20 to 25 mph possible Wednesday evening. NE winds remain
elevated through the end of the week.

-Temperatures remain steady through the end of the week with highs
in the 40s to near 50 and lows dipping down below freezing in
most places.

-Isolated rain showers possible in the afternoons. Showers will
fall as snow in elevated terrain with low to no accumulations.
Showers become more numerous Thursday in the eastern Interior.

-Southerly gap winds through Alaska Range passes are likely
beginning Sunday.

West Coast and Western Interior...

-North and Northeasterly winds increase along the West Coast
Wednesday and Thursday to sustained speeds of 10 to 20 mph.
Kivalina and Red Dog Dock may see stronger winds with gusts up to
35 mph possible. Sustained northerly winds through the Bering
Strait and across western St. Lawrence Island will be stronger
with sustained speeds of 20 to 25 mph peaking Friday evening with
gusts up to 35 mph.

-Showers remain isolated along the West Coast and Western Interior
through Thursday before a front brings a band of rain and snow
to the YK Delta and lower Yukon Valley Friday and moving up the
coast through the weekend.

North Slope and Brooks Range..

-Northeasterly winds 15 to 20 mph across the Arctic Coast today
will increase to 20 to 25 mph Friday with gusts 40 to 45 mph by
Friday afternoon. These decrease slightly to gusts up to 35 mph
on Saturday. Blowing snow is likely, but blizzard conditions are
not anticipated at this time.

-High temperatures will be mainly in the teens on the North Slope
with 20s in the Brooks Range.

&&

.FORECAST ANALYSIS AND DISCUSSION...Most of northern Alaska
currently lies in a col between a vertically stacked low pressure
system in the Gulf of Alaska and a high to the north of Wrangel
Island. There is weak ridging over the far eastern interior.
Surface high pressure in the Arctic has a NE gradient draped
across the central and eastern Interior. Otherwise, the pattern is
weak with weak flow and non impactful amounts of moisture. The low
in the Gulf of Alaska will bring a backdoor warm front to the
eastern Interior late tonight through Thursday before weakening
near Yakutat on Friday. A weak low pressure system will move into
the southern Bering Sea Thursday night, bringing another warm
front to the west coast. This front will arrive at the Yukon Delta
coast Friday morning and continue to push north, bringing a mix of
rain and snow. Impacts will be limited and no products are
currently planned. Models are in poor agreement on the timing and
how far east precipitation will reach. At this time, prefer the
NAM for limiting the easterly extent, but the ECMWF for faster
northward progression of the front. High pressure in the Arctic
will increase easterly winds across the Arctic Coast beginning
Friday morning. Blowing snow is likely but at the time do not
expect blizzard conditions. Winds will diminish Monday.

&&

.EXTENDED FORECAST DAYS 4-7...Broad troughing will persist over
Alaska through next week with periods of weak southerly flow
possible as the storm track continues to bring low pressure
systems across the Aleutians and into the Gulf of Alaska. This
will bring continued quiet weather to most of northern Alaska with
temperatures near seasonal norms. Showers across the Interior will
be very limited with most precipitation along the west coast and
in the southwest Interior, though amounts there look to be light
as well.

Coastal Hazard Potential Days 3 and 4...None

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Heavy Freezing Spray Warning for PKZ806.
Brisk Wind Advisory for PKZ811-812-857-858.
Heavy Freezing Spray Warning for PKZ816.
Small Craft Advisory for PKZ816.
Brisk Wind Advisory for PKZ817.
Brisk Wind Advisory for PKZ851-854.
&&

$$

Chriest

802
FXAK67 PAJK 241820
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
1020 AM AKDT Thu Apr 24 2025

..New 18z Aviation Discussion...

.SHORT TERM...
Vertically stacked low in the central Gulf will continue to track
NE through the day Thursday and weaken. Observations show the
warm front that pushed into the panhandle on Wednesday has
somewhat stalled, or otherwise jumped from Northern Lynn Canal
into the interior, as Haines reports ENE wind with gusts to around
25 mph, while Eldred Rock reports a light southerly wind. Follow
up cold front extending from the low will gradually push into the
panhandle this morning leading to a transition from blanket
stratiform precipitation to showers by the afternoon. Once again
rain is expected at sea level while at the higher elevations of
the Klondike Highway temperatures will remain cool enough for wet
snow and some minor accumulation.


.LONG TERM.../Friday through Wednesday/...
The low currently in the Gulf is expected to continue tracking
northeast in the Gulf by Friday. Showers will diminish into the
evening Friday as the low center moves inland and weakens.
Relatively drier conditions are expected for Southeast Alaska into
the weekend given the exiting low pressure system. Light rainfall
may persist as the axis of moisture shifts increasingly over the
southern portion of the region, including Sitka and Prince of
Wales Island. Ensembles trend towards the open wave trough
solution. From there operational models diverge. Another surface
low and associated front is expected in the western gulf and
impacting SE AK early Monday into Tuesday. Model agreement is
increasing towards a elongated northwest oriented trough to push
over much of SE AK, bringing a return to widespread rainfall and
near gale-force winds along the Gulf coast waters.

&&

.AVIATION.../Through 18z Friday/...
Currently, an occluding front overstretches south to north across
the panhandle this morning leading predominate MVFR flight
conditions with CIGS AoB 3000ft and intermittent vsbys down to 4SM
within the heaviest showers. For the rest of today, expecting
predominate MVFR conditions to continue with widespread rain
through early afternoon, a brief break possible with rain becoming
more isolated and showery in nature behind the front with CIGS
increasing to upper end MVFR to low-end VFR flight conditions,
AoB 5000ft, with an underlying SCT deck. Not expecting widespread
visibility issues, however, any issues should be isolated and
short- lived in nature within heavier showers, down to 4 to 6SM.

Expect SE-ly LLWS near 30kts around 2000ft and turbulence
associated with the occluding front over interior SEAK TAF sites
through early afternoon, quickly dissipating through 00z.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ641>644-651-652-661>664-671-672.

&&

$$

SHORT TERM...STJ
LONG TERM....CL
AVIATION...NM
MARINE...STJ

Visit us at http://www.weather.gov/Juneau