381
FXAK68 PAFC 010019
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
419 PM AKDT Fri May 31 2024

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

An area of low pressure will continue to linger in the western
Gulf of Alaska through Sunday afternoon. A surface warm front
associated with this system will quickly occlude as it lifts north
into the northern Gulf Friday night. Widespread rain and easterly
gales will accompany the front spreading to the immediate
Southcentral coast. Farther west, strong northeasterly winds and
steady rain will continue for Kodiak Island as a lingering trough
axis over the region phases with the occluded front while also
serving as the focus for continued moisture advection.

For Saturday morning, expect generally clear and dry conditions
from Cook Inlet north into the Mat-Su Valleys and Copper River
Basin as an upper- level ridge builds over the region out ahead of
the aforementioned low. Subsidence with this ridge should keep
any low-level and mid- level cloud cover to a minimum and allow
for daytime temperatures to push well into the 60s for many
locations, with the warmest temperatures over the Susitna Valley
and Copper River Basin.

The occluded front reaches the coast Saturday with rain across
the immediate coast and increasing chances for afternoon showers
inland as an upper-level shortwave ahead of the surface front
moves inland. Increasing clouds and scattered showers will keep
temperatures a few degrees cooler than Friday for interior
Southcentral. The low center also begins to track west on
Saturday in response to the longwave upper-level trough also
lifting northwest. This westward jog will allow a second round of
strong winds and heavier rain showers to move back over the
northern Gulf and Kodiak Island. The gusty winds and precipitation
will likely persist across Kodiak Island and the northwestern
Gulf of Alaska through Sunday afternoon as the low drifts slowly
south of Kodiak Island.

Conditions should improve again for Sunday with only a few
isolated showers as the upper level wave moves north into the west
central part of the state.

&&


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

Radar imagery and area observations show light rain continues across
coastal southwest Alaska, primarily around the Kuskokwim Delta, in
response to an upper-level shortwave moving across the area
coincident with a weak surface front. This first bout of
precipitating activity will diminish this evening into the overnight
hours. This lull will be brief as an occluded front off the low in
the Gulf pushes across the Alaska Range, bringing light rain back
into Bristol Bay tonight.

On Saturday, warming conditions and more unstable conditions will
be supportive of more numerous showers across the Lower Kuskokwim
Valley and interior Bristol Bay. There are indications that
convection will continue overnight with the support of a
combination of the theta-e ridge and easterly shortwaves tracking
in from Southcentral Alaska. The area of greatest instability
shifts toward the Kilbuck/Ahklun Mountains and potentially even
into the Kuskokwim Delta for Sunday as the low in the Gulf shifts
northwest. However, there is some uncertainty in the exact
placement of the greatest instability and therefore exactly where
showers will set up. Conditions appear, at best, marginal for
thunderstorm development, with a warm layer above 600 mb likely
keeping convection too shallow for more than a stray lightning
strike or two. Currently, though, lightning is not expected.
Monday will be quite similar to Sunday with precipitation focused
again across or near the Kuskokwim Mountains.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Tonight through Monday)...

A ~980mb low analyzed near the Rat Islands will gradually move east
and weaken over the next as it moves towards and dissipates into the
Gulf of Alaska. A weak front currently stretches out ahead of the
low, moving through the eastern Aleutians and Pribilof Islands. This
front will continue to push into the Alaska Peninsula later today
into the overnight hours before shearing out over the eastern Bering
Sea Saturday morning. Light rain showers near the center of the low
track east along the Aleutian Chain through Saturday as well, before
dipping back into the North Pacific. Much calmer and drier
conditions are in store for the Bering Sea and Aleutians on Saturday
despite a broad trough lingering behind the exiting low. This is
short-lived, however, as northerly winds increase over the western
Bering/Aleutians in response to the remnants of Typhoon Ewiniar
passing well to the south of the Aleutians on Sunday. Northerly
winds spread eastward to cover much of the Bering for the start of
next week, but remain below gale force.

&&


.LONG TERM FORECAST (Days 4 through 7) Tuesday through Friday...

A broad upper-level trough over the Gulf of Alaska will continue
to persist through Wednesday evening, producing easterly waves
that will carry over Southcentral. As showers form from these
waves, precipitation totals will mostly be light. However, as
increased convective activity is currently expected over the
Copper River Basin through midweek, higher local amounts of
rainfall are possible with this system. The biggest chance for
widespread and heavier precipitation will be Tuesday into early
Wednesday as the majority of easterly waves will pass over the
region at that time.

The trough will start to dissipate and merge with a new trough
in the eastern Bering and Aleutians Wednesday night. Widespread
showers will be possible over Southwest as the trough lingers over
the Bering and slowly moves westward through the remainder of the
forecast period. Stronger winds will not be a major concern since
the low will be vertically stacked and past its peak intensity.
The track of the trough by Friday and into next weekend becomes a
bit more uncertain with current model guidance. Some models are
suggesting that the trough lingers over the central Aleutians
while others shift it much further south and east well outside of
the forecast region.

-BS

&&
.AVIATION...

PANC...VFR conditions and light winds will persist.

VFR conditions and light winds will persist through early
afternoon. Gusty winds are expected to pick back up out of the
south from Turnagain Arm this evening. These winds will likely
persist through late evening before diminishing again overnight.

-CC

&&


$$