Gale Warning 667, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
451 AM AKST Tue Nov 8 2022

.ANALYSIS AND UPPER LEVELS...

The upper-level ridge continues to build east into Canada, with
its axis located over the Alaska Panhandle this morning. In the
wake of the ridge is an upper trough that spreads across the
entire Bering and Aleutian Chain, with associated weak pressure at
the surface. As a result, rain showers and broken skies currently
dominate most of the far western domain. The strong front that
recently swept across Southwest is now pushing east across
Southcentral and the Gulf, gradually weakening at the same time.
Downsloping is keeping the Anchorage area and western Kenai
Peninsula on the drier side while the remainder of Southcentral
continues to get precipitation. Southerly warm air advection with
the front is leading to a rain/snow mix for a majority of the
coastal Southcentral locations, and precipitation further inland
remains as snow.

&&

.MODEL DISCUSSION...

The primary model disagreement in the short term is still in
regards to the low that forms near Kodiak Island late tonight into
Wednesday. While overall agreement is getting better and there is
consensus for the low to remain near Kodiak Island through
Wednesday morning, agreement diverges through the rest of the day
Wednesday and into Thursday. The GFS continues to be the more
southern solution, bringing the low into the southern Gulf late on
Wednesday. This solution would decrease chances of precipitation
for the Anchorage area in addition to keeping temperatures cooler
for much of Southcentral.

&&

.AVIATION...

PANC...VFR conditions will persist through the TAF period.
Southeasterly Turnagain Arm winds will diminish this morning, and
winds over the airport will remain light and out of the north-
northeast.

&&

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

Light snow will continue along coastal areas through the morning
under a front, transitioning to a mix or all rain by this
afternoon with warming surface temperatures. A second front will
track through the Gulf tonight into Wednesday, bringing another
round of steady precipitation along the coast. Highest amounts of
2 to 3 inches are expected in the Whittier area, with areas in the
lee of the Chugach including Anchorage and the Mat-Su remaining
mostly dry in a downsloping pattern. Gusty southeasterly winds
through Turnagain Arm will persist through Wednesday before
diminishing as the aforementioned front dissipates inland. More
widely scattered rain/snow showers will continue Thursday as the
associated low fills in and weakens.

&&

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

An upper level shortwave moving east across the Aleutian Chain
this morning will merge with a complex low with multiple centers
near the Alaska Peninsula this afternoon. By the overnight hours
the two upper level waves will organize into one, with the
dominant surface low forming south of the Alaska Peninsula and
eventually east of Kodiak Island by Wednesday morning. The
resultant evolution will bring widespread precipitation to Bristol
Bay, the Alaska Peninsula and Lower Kuskokwim Valley through
Wednesday afternoon. The Kuskokwim Delta should stay mostly dry
from this system, but areas south and east of Bethel may get some
rain and snow. For precipitation type, expect a transition from
rain to snow from northwest to southeast as colder air moves in
from the northwest. Snow totals are expected to range from two to
seven inches across Bristol Bay and the Lower Kuskokwim Valley.
The overall influence of this system will wane overnight Wednesday
into Thursday morning, though upslope areas near the Alaska Range
and Kuskokwim Mountains may have lingering precipitation into the
day Thursday. An additional weak low is expected to move through
overnight Wednesday, but snow accumulations will be marginal and
the timing and strength of this system is uncertain.

&&

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

Fairly calm westerly winds and brief rain showers will persist
over most of the Bering and Aleutian Chain through Wednesday
morning with no major surface features present other than the
aforementioned low near the Alaska Peninsula discussed in the
Southwest section. However, by Wednesday afternoon a strong low is
expected to move south of Shemya before taking an eastern turn
and following the 50th parallel through Thursday while slowly
weakening. Storm force winds and rain are expected along the
front, which will impact all of the Aleutian Chain through
Thursday.

&&

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

The pattern will start out on Friday with a very large low
centered over the eastern Bering, with cyclonic upper flow
extending well away from the center across most of the Aleutians
and over Southwest. A broad small craft to gale strength wind
field should be affecting much of the same region at the surface,
along with precipitation mainly in the form of rain across the
Aleutians. More of a mix of rain and snow will be likely along the
low's front as it moves into Southwest during the day on Friday.
Another low is set to be moving into the western Bering/Aleutians
by this point in time as well, which will begin to merge with the
initial system and reinforce deep troughing over the Bering
through at least Saturday. Meanwhile, things should be starting
out fairly quiet over Southcentral, where a sharp upper ridge will
initially be in place. However, this ridge axis will begin to
shift east with time, allowing heavier precipitation and strong
south to southeast flow to spread into the eastern Kenai Peninsula
and Prince William Sound region by late Friday into Saturday.

From the rest of the weekend into early next week, models
continue to signal the development of a blocking pattern over the
Alaska region. The aforementioned upper ridge is currently
projected to strengthen dramatically northwest Canada and mainland
Alaska through Monday, becoming a robust Omega block. This should
cause the upper trough/low upstream over the Bering to stall in
place, perhaps eventually pinching off into a cutoff low as
another strong ridge builds into the western Bering on Monday. The
most active weather during this stretch will be focused where
deep, persistent southerly flow pushes into the coast, or along
the Alaska Peninsula, across Kodiak Island and over portions of
the northern Gulf coast, where precipitation will be greatly
enhanced by onshore and upslope flow. Very warm temperatures
compared to average are likely across nearly the entire eastern
half of the outlook area for this timeframe as warm, moist air is
forced north around the blocking high. Daytime temperatures in the
30s to 40s are likely across even some more interior valleys of
Southcentral and Southwest from Saturday to Monday.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 119, 120, 125, 130-132, 138, 139, 150, 155,
					   160, 175, 177, 351, 352.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AF
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CJ
LONG TERM...AS