Small Craft Advisory 461, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
501 PM AKDT Tue Jun 14 2022

.ANALYSIS AND UPPER LEVELS...

The upper low that was over the YK Delta is continuing to move
northwest. A low is parked south of Kodiak Island and a north-
south deformation band is bringing precipitation to the Middle
Kuskokwim Valley to the Bristol Bay area. Rain is also being
reported east along the northern side of the western Gulf low to
include Iliamna, Kodiak Island, and the southern Kenai Peninsula
coast. Southwest wildfires are ongoing and although there is rain,
smoke and haze will likely continue to be dispersed over
Southwest Alaska.

In contrast, high pressure over the mainland interior. Cumulus
clouds with partly clouds skies stretches from the Copper River
Basin to the Kuskokwim Delta and eastern Bering Sea, where a
building ridge separates the two aforementioned lows. Further
west, high clouds reach over a ridge axis located over the central
and eastern Aleutians well ahead of the next major low system
from the North Pacific. On precipitable water satellite imagery,
this low is carrying relatively more moisture than this area has
seen in a while.

&&

.MODEL DISCUSSION...

Models continue to be in good synoptic agreement in the short
term, thus the going forecast is remaining on track. While the
potential still remains, NAM is more aggressive with the widely
scattered thunderstorms than the GFS for on Wednesday afternoon.

As the western Gulf low begins to pull away from Kodiak Island and
the ridge builds ahead of the next major North Pacific progresses
east, the timing of the front slightly differs between models and
from run to run. The location of the front with time will depend
upon the strength of the ridge and its ability to slow the low
down. Models indicate that the energetic forcing along the front
begins to break down once it reaches Southwest Alaska and the
western Gulf sometime during the first half of Thursday. What
transpires down stream and with the second front that follows
going into the weekend for Southcentral is less certain and will
make a difference in the precipitation field and resulting QPF.

&&

.AVIATION...

PANC...VFR conditions are expected to continue. Light and
variable winds at the surface will gradually increase and become
south to southeasterly as Turnagain Arm winds also increase later
this evening. Winds will decrease again later tonight.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Today through Friday
afternoon)...

Cloud cover has increased today as winds aloft have switched to a
more southeasterly flow pattern. This has caused the smoke to
largely depart the Anchorage area. The cloud cover should help
limit the thunderstorm activity this afternoon/evening, however
storms remain possible near the Alaska range. Steady rain will
continue over Kodiak through the evening on the northern edge of a
Gulf low. Slightly more widespread thunderstorms will be possible
Wednesday, generally between Cantwell and Paxson, as clearer
skies will lead to more daytime heating/instability. Conditions
will remain generally quiet elsewhere into Friday. A broad low
will move into the central Bering Friday morning. Its associated
front will gradually move into Southcentral through the day,
leading to increased clouds, precipitation chances and cooler
temperatures.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Thursday night)...

An axis of light rain and cloud cover is persisting across
portions of the Lower Kuskokwim Valley and Bristol Bay this
evening, as most of Southwest remains in a col between the low
lifting towards the Bering Strait and another low over the Gulf.
This persistent cloud cover is holding down temperatures quite a
bit this afternoon, with areas from Sleetmute to King Salmon
barely pushing above 50F for afternoon highs. An area of ridging
aloft should build back over Southwest by tomorrow, with
associated subsidence helping skies clear out and allowing
temperatures to rebound well into the 60s. There may still be a
few showers and isolated thunderstorms that get going along parts
of the western Alaska Range by the afternoon, but overall coverage
of any lightning activity will be limited. Even though recent
cooler temperatures and clouds/rain have improved weather
conditions near ongoing wildfires, areas of smoke and haze will
continue to impact parts of the area at times, especially near
the larger fires.

By Thursday, a front will approach the Southwest Coast, resulting
in increasing southeast winds and cloud cover spreading inland
from south to north through Thursday night. Thus, expect the
highest temperatures around 70F or so across the Lower Kuskokwim
Valley, where the upswing in cloud cover will be most delayed and
warmer low level temperatures hold on for the longest. The entire
frontal zone will progress inland on Friday, sending perhaps the
best chance for widespread rainfall in weeks across the region
along with noticeably cooler air (high temperatures no higher
than 60F) and dense overcast skies. There remains some uncertainty
for the degree of moisture advection into more interior parts of
the outlook area with the front, but the current expectation is
for around 0.1 to 0.3 inches of new rainfall between Thursday
night and Friday evening. In any case, this should extend a
welcome break from the volatile fire weather conditions we've seen
in days prior.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Today
through Thursday night)...

The main feature in play for the next few days will begin to
impact the western Aleutians tonight, as a gale force North
Pacific low and front move into the Bering between now and
Thursday. East to southeast gale force winds and rain will
progress quickly from west to east on Wednesday, with the front
approaching the Pribilofs and Dutch Harbor areas by Wednesday
night. The front is expected to weaken below gale force as the
parent low becomes increasingly occluded and drifts over Atka by
Thursday afternoon, with the front and associated rain clearing
out of the eastern Aleutians and Pribilofs by Thursday night.
Areas of rain will persist along portions of the Aleutian Chain
near the low's weakening center, with the best chance for rain
shifting east towards the Alaska Peninsula with the low/front on
Friday.

&&

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

Bering/Aleutians Forecast confidence remains high from Friday
through Sunday as there is good ensemble agreement with respect to
the placement and intensity of synoptic scale features. Winds are
expected to remain below gale force with no high seas expected.

Gulf of Alaska Forecast confidence remains high from Friday
through Sunday as there is good ensemble agreement with respect to
the placement and intensity of synoptic scale features. Winds are
expected to remain below gale force with no high seas expected.

&&

.Long Term Discussion (Days 4 through 7: Saturday through Tuesday)...

Forecast confidence with respect to the overall synoptic pattern
remains high for the extended period due to a high degree of
ensemble agreement. Low pressure is forecast to move eastward
along the Aleutian Islands into the Gulf of Alaska. This low will
increase the probability of wetting rain across Southcentral and
Southwest Alaska as easterly waves associated with this low will
continuously move over the area. Forecast confidence is lower with
respect to finer details in the mesoscale as well as exact
precipitation amounts.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warnings 155 165 170-178 413 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...TM/VR
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AS
MARINE/LONG TERM...ED