Gale Warning 544, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
513 AM AKDT Sat Oct 1 2022

.ANALYSIS AND UPPER LEVELS...

A broad upper low continues its eastward progression across the
western Bering Sea this morning. While it's no longer producing
hurricane force winds, gale to storm force winds will be common
across the southwest Bering through the morning hours along with
seas to 20+ feet. An occluded front extends southeastward from the
northern Bering and is currently pushing inland of Southwest
Alaska with scattered showers and small craft winds offshore of
the coast. At the tail-end of the front, located south of the
Alaska Peninsula, a triple point low is beginning to form and will
lift into the Kenai Peninsula over the next 24 hours. High
pressure is noted over Southwest Alaska, which has promoted clear
skies through much of the overnight hours and the development of
fog and low stratus. Some locations have managed to drop to below
freezing where skies have remained clear.

Meanwhile, an area of low pressure over the eastern Gulf is
lifting northward into the eastern half of the Copper River Basin
with more rain. The pressure gradient due to the low over the
eastern Gulf is maintaining enhanced westerly winds from Portage
Pass into Prince William Sound and also over the northern Gulf.
Small craft winds will be common through the morning hours while
gusts to as high as 35 mph will be possible through the passes and
especially across passage canal. The low and its associated
shower activity will press eastward and out of the region through
the course of the day with westerly winds diminishing by this
afternoon. The rest of Southcentral should remain dry until later
tonight with the arrival of the triple point low.

&&

.MODEL DISCUSSION...

With landfall of a broad extratropical low, the remnants of
Kulap, now within 48 hours, models are coming into better
agreement overall with its track. Latest models suggest pressures
will weaken into the mid or upper 990 millibars before pivoting
across the Kuskokwim Bay Sunday evening. Westerly winds just
below gale force are currently forecast over Bristol Bay. The
next low into the western Bering is being handled somewhat better
by models, with a low tracking across the Western Aleutians on
Sunday morning before amplifying over the southern Bering Monday
afternoon. The low's track thereafter becomes more uncertain as
models diverge in solutions. All models eventually take the low
southeastward across the Eastern Aleutians Monday into Tuesday,
though timing and strength discrepancies abound.

&&

.AVIATION...
PANC...VFR conditions to prevail on Saturday. Overcast ceilings
at around 5000 ft are helping to limit nighttime radiational
cooling. Thus, the development of meaningful fog is not
anticipated through the morning hours. Winds to remain light and
variable through tonight, although a brief period of southerly
winds to around 10 knots may develop this afternoon as low
pressure over the eastern Copper River Basin begins to amplify
before shifting into Yukon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Monday night)...

A low which crossed the eastern Gulf overnight will lift quickly
inland to the Yukon this morning, trailed by a strong upper level
short-wave. Steady rain over the eastern two thirds of the Copper
River Basin will diminish from west to east through the morning
hours. Showers will linger along the Wrangell Mountains and Alaska
Range through this evening thanks to a weak short-wave marching
eastward across interior Southcentral. Further west, after some
morning fog, expect sunshine for a good portion of the day from
the Susitna Valley south to the western Kenai. The aforementioned
weak short-wave and westerly flow will likely hold in clouds for
the interior Kenai, Anchorage, and portions of the Matanuska
Valley - with just a chance of clouds breaking up this afternoon.

The reprieve from rain and clouds will not last long, with a
trough over the Bering Sea reaching the western Gulf and Kodiak
Island this morning then quickly lifting northward to Southcentral
this afternoon through tonight. A weak triple point low and
frontal system will accompany the trough, tracking quickly across
Kodiak Island this afternoon and pushing onshore along the north
Gulf coast tonight. The combination of forcing mechanisms will
lead to rain overspreading Southcentral tonight. A series of
short-waves will move in behind the first, leading to periods
of rain through Sunday night.

The upper level flow will quickly amplify on Monday as a new
Bering trough digs down into the North Pacific, causing ridging
downstream from the Gulf of Alaska up to Southcentral. This will
bring an end to most of the rain. More significantly perhaps, the
upstream trough will continue to dig underneath the ridge as we
head to Tuesday. Expect a return of moderate to heavy rain for
Kodiak and the Gulf coastal areas. However, with the upper low
settling down in the Pacific, inland areas of Southcentral could
actually see a longer duration of dry weather.

&&

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

It's another seasonably cold and mostly clear morning across most
of the outlook area once again. Generally calm winds are
further aiding in efficient surface cooling, allowing a few spots
to surprisingly drop all the way into the upper 20s to low 30s.
However, it should cloud up as the day progresses, as a weak front
associated with the post-tropical remnants of Kulap creeps slowly
northeast. A band of light rain will work across with the front,
but little precipitation will make it into the Middle Kuskokwim
Valley as the front mostly falls apart before reaching quite that
far north. From tonight into Sunday, Kulap's remnants will
approach from the Bering as a rapidly weakening low, and is not
expected to have significant impacts to the coast given it's
rapidly decaying wind field. Even so, there may be elevated water
levels about 2 feet or so above the normal high tide line during
the next couple of high tide cycles through Sunday night, namely
across the Kuskokwim Delta Coast. In addition, there may be higher
than average swells generated by Kulap's remnants reaching the
coast, possibly leading to minor coastal erosion.

Looking forward from Sunday evening onwards, what's left of Kulap
should finally exit the picture as it becomes absorbed by the next
approaching low pressure system approaching the eastern Bering
Sea. This next system should push a front into the coast on
Monday, effectively extending the already wet conditions across
much of Bristol Bay and the Kuskokwim Delta as it moves northeast.
Winds should also pick up substantially out of the southeast with
the approach of the low and front, potentially gusting as high as
30 to 40 mph along mainly coastal areas through Sunday evening.
Fortunately, the lack of an onshore component of flow with this
next system's winds should not be favorable for significantly
higher than normal water levels with high tides from Monday to
Monday night.

&&

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

The post-tropical remnant low associated with former Typhoon
Kulap continues to make steady but slow progress across the Bering
this morning. This system has become stacked and occluded,
meaning it's intensity will continue to come down until it
eventually becomes absorbed by a new system moving along and just
north of the Aleutian Chain by the time it approaches the
Southwest Coast on Sunday evening. In the meantime, mainly
westerly winds up to gale force will continue along most of the
Aleutians and southern Alaska Peninsula (AKPen) well to the south
of the weakening low's center. The new low will come into play by
early Sunday as it moves into the southwest corner of the Bering,
extending rain and a renewed period of gusty west to southwest
winds into the western Aleutians through Sunday afternoon. A
potent shortwave embedded on the south side of the low will then
pivot into the central Aleutians Sunday evening along with a push
of cold air wrapping into the low near the surface. This should
briefly kick up the wind field quite a bit for places like Atka
and Adak, and gusts could briefly pick up to around 50 to 60 mph
as the trough moves past late on Sunday night.

It really looks like more of the same heading into Monday, as
strong, gale force westerlies persist along the Aleutians south of
the main low continuing to drift across the Bering. Perhaps the
only place to escape the winds on Monday will be the Pribilofs, or
in the relative calm near the center of the low.

&&

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

The long term forecast starts with a highly amplified pattern as an
upper level low situated over the Bering takes shape early
Tuesday. Meanwhile, two upper level ridges of high pressure flank
this low, one over the far western Bering, and a second over the
Alaska- Yukon border. For Southcentral, this "blocking" ridge over
the border will create a southerly track for moisture to advect
northward, so would expect unsettled and wet conditions to
continue into next week. By Wednesday, there is relatively good
model agreement that a deepening upper level low over Siberia will
develop and track eastward over the northern Bering. This will
ultimately create a more zonal flow pattern for the southern
Bering and Aleutian Chain, and will introduce a warm and wet air
mass to the Chain for Wednesday with accompanying gusty westerly
winds. By Thursday, a mostly stagnant area of low pressure over
the northern Gulf will usher several upper level waves northward
over Southcentral, resulting in continued southerly flow and
unsettled conditions. Overall, the pattern looks to be active and
unsettled for most of next week.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm 177 413.
         Gale 165 170 173-176 178 185 411 412 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AS
LONG TERM...KO

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
306 PM AKDT Sat Oct 1 2022

AKZ155-021300-
Kuskokwim Delta-
Including the cities of Bethel and Nunivak Island
306 PM AKDT Sat Oct 1 2022

The remnants of former Typhoon Kulap are pushing across the
Bering and weakening quickly as the low moves toward Southwest
Alaska. This low will bring high surf conditions to the Kuskokwim
Bay and areas northwest tonight through Sunday night. The biggest
impact will be at high tide when water levels could reach 1 to 3
feet above the normal high tide line with high surf on top of
that. There is the potential for coastal erosion due to the high
surf.