Wildfire in Alaska, June 9 to 10, 2022

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
507 AM AKDT Thu Jun 9 2022

.ANALYSIS AND UPPER LEVELS...

The main synoptic feature continues to be a vertically stacked low
in the Gulf of Alaska. A robust shortwave associated with this
low is slowly moving out of Southeast Alaska and into
Southcentral this morning. Cloud cover is increasing with this
shortwave, and the Middleton Island radar is showing a band of
rain moving towards Southeast Prince William Sound. Ahead of this
shortwave, favorable dynamics overnight have led to showers and a
few thunderstorms along the Chugach Mountains (from the Mat
Valley down to Anchorage) and also along the Alaska Range in
Bristol Bay.

Further west, parts of the Kuskokwim Valley and Bristol Bay are
seeing visibility reductions due to smoke from nearby fires.
Visibility is also reduced along the Alaska Peninsula, where the
fog and low stratus blanketing much of the Bering Sea is slowly
creeping onshore. Otherwise, the Bering Sea remains fairly quiet
except for a compact upper level low bringing rain to the Eastern
Aleutians.

The final feature of note is a broad upper level low currently
over the Yukon Flats, which is visible on water vapor satellite
imagery. As this low dips southward, it will influence weather in
the Southern Mainland for today and tomorrow.

&&

.MODEL DISCUSSION...

Overall forecast confidence is fair. Model agreement for the
upper level low currently over the Yukon Flats looks about the
same as yesterday. The GFS remains the clear outlier and has had poor
run-to-run consistency. The NAM, Canadian, and Euro are in good
agreement, and their trajectories for this low have changed little
since yesterday. Model agreement has also improved with the
easterly wave coming off the low in the Gulf. As such, confidence
is increasing with this afternoon's showers in Southcentral.
Further out, the broad upper level low that pushes south from the
Arctic through late Saturday night is also relatively well-handled
by the global models.

&&

.AVIATION...
PANC...Expect periods of rain showers through the day. VFR
conditions should persist, though ceilings and visibilities may
drop to MVFR with the heaviest of showers this morning. Lighter
rain showers will develop again in the afternoon and evening,
before tapering off into the overnight hours.

&&

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

An upper level trough is digging southward out of the interior of
the state this morning. This is a subtle but important feature
that caused the late development of thunderstorms over the
Matanuska Valley northern parts of Anchorage last evening. The
trough has caused lift over the Anchorage and Matanuska areas and
is the reason the showers persisted all night. This trough will
keep the unstable atmosphere over northern Cook Inlet producing
showers throughout the day. A second feature is an easterly wave
that is just reaching the Copper River Delta early this morning
and will bring some rain to the north Gulf coast and then Copper
River Basin. This easterly wave will stall out somewhere over the
Chugach and Talkeetna mountains as the source low it is rotating
around is to the south of the Gulf of Alaska. The main uncertainty
with this wave is if it is able to phase with the upper level low
moving into Southwest Alaska from the Interior. This will
determine whether the rain from the easterly wave stops over the
Talkeetna and Chugach Mountains or is able to bring rain to the
Susitna Valley southward to the Kenai Peninsula tonight into
Friday. At this time the rain stalling out over the mountains
looks more likely.

The weather for Friday and Saturday will be highly dependent on
the behavior of a second (but stronger) upper level low in the
interior. The atmosphere will remain fairly unstable over
Southcentral these days and there will likely be mainly afternoon
and evening showers each day. However, there is a chance the low
could bring some more extensive rain to the Susitna Valley
southward to the Kenai Peninsula on Saturday. In short, there is
a bit of uncertainty with how all this showers activity will play
out into the weekend.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2: Today and
Friday)...

Hot and dry conditions are expected to continue for the next two
days across Southwest Alaska. This will only continue to add insult
to injury for the already many wildfires (seen on various
satellite imagery) that continue to burn throughout the area. A
Red Flag Warning is in effect for the Middle Kuskokwim Valley
through 10 PM this evening for hot, dry, and windy conditions due
to hot temperatures 73 to 77 degrees, low min RH values near 15
percent and sustained winds greater than or equal to 15 mph. In
addition to the hot and dry conditions, a rigorous upper level
shortwave diving southward from the Alaska Interior will help to
ignite widely scattered wet thunderstorms this afternoon and
evening along the Western Alaska Range with more isolated wet
thunderstorm activity towards the southern Kilbuck and Ahklun
Mountains. Some of the storms will be capable of producing
frequent lightning, gusty winds, and small hail especially near
the Western Alaska Range. Areas of fog have worked into areas from
Nelson Lagoon to King Salmon this morning but expect this to mix
out by mid to late morning before potentially settling back in
overnight tonight into Friday morning.

Expect most of the activity to wane during the overnight hours
especially for the Ahklun and southern Kilbuck Mountains as
subsidence moves into the area behind the leading shortwave. Much
of Bristol Bay should also see activity wane down by midnight and
result in a mostly clear to partly cloudy night with temperatures
in the upper 40s to low 50s. Then, another upper level low is
expected to dive southward hugging the Western Alaska Range for
the day on Friday. As a result, expect another afternoon and
evening of potentially isolated wet thunderstorms mainly confined
to the Western Alaska Range.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2:
Today and Friday)...

Quiet conditions are expected to continue across the Bering and
the Aleutian Islands for the next few days as northerly flow
remains. Much of the Bering and Aleutians remain under low
stratus along with patchy areas of fog this morning. This is
expected to continue today, tonight, and through the day Friday.
The one exception to the fog and low stratus continues to be from
the Pribilof Islands north and east where dry air is trying to
hang on creating for a topsy turvy forecast. Overall, expect
Saint Paul and Saint George to remain down in the fog and the low
stratus a majority of the time the next two days. However, with
the higher sun angle and daytime heating this time of the year,
some peeks of afternoon sun cannot be completely ruled out. The
sun helps the atmosphere to mix drier air not too far above the
surface down to the ground during the day causing the fog to lift
for a period of time each afternoon before settling back in
during the evening hours.

&&

.MARINE (Days 3 through 5)...
Expect winds less than 35 kts and seas less than 20 ft for the
Day 3 through 5 period.

&&

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

The odds tilt in favor of an upper level pattern change during the
extended period. Deep upper level troughing across the Alaskan
mainland on Sunday will weaken through Wednesday. As the upper
trough weakens, upper-level ridging is expected to gradually build
across the Alaskan mainland Tuesday and Wednesday. There is good
ensemble agreement that the ridge-axis will remain east of
Southcentral Alaska. This will increase the probability for
moisture to enter the region from the central North Pacific. A
surface low is expected to move northeastward from the central
North Pacific to over the Gulf on Tuesday and Wednesday. This will
increase the probability for wetting rain across the region as a
series of easterly waves associated with this low move over the
area. Conditions will be drier over Southwest Alaska, though there
remains a chance for moisture associated with these easterly waves
to enter Southwest. There is lower forecast confidence with
respect to specifics on this low as there are minor disagreements
in the placement of this low. We are also monitoring a second low
pressure system that is forecast to move northeastward from the
western Pacific to over the southwestern Bering/Aleutians
Wednesday afternoon. Forecast confidence remains very low with
respect to this feature as there are major discrepancies between
guidance with respect to the position and intensity of this low
pressure system.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...Red Flag Warning: 153.

&&

SYNOPSIS AND MODEL DISCUSSION...KC
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MV
MARINE/LONG TERM...NS/ED