NWS Anchorage, AK wrote its last area forecast discussion before the first event at Dec 9, 4:57 AM AKST, 43 minutes earlier.
Area forecast discussion, Dec 9, 4:57 AM AKST, 43 minutes before
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
457 AM AKST Mon Dec 9 2024
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
A stalled trough sits over Prince William Sound this morning with
showers moving over the coastal mountains. A stronger occluded
front and associated upper-level shortwave over the western Gulf
overnight are both now moving northeast into the northern Gulf
and eventually into Prince William Sound by around midday Monday.
These features are already bringing about a second round of
precipitation and strong winds to the Southcentral coast with
widespread gales and embedded storm-force gusts over the open
waters.
Winds have also increased again for Seward and Whittier this
morning as the front approaches. A more north-south oriented
pressure gradient has allowed winds on the Anchorage Hillside to
subside overnight; however, the gusty winds of yesterday will
return later this morning for all favored gap and high elevation
locations. For the Anchorage Hillside, gusts 55 to 70 mph are
possible again Monday. For Whittier and Portage, gusts 45 to 60
mph area also possible. Gusts 30 to 45 mph are also likely for
the Matanuska Valley.
Precipitation is also overspreading the Kenai Peninsula. Again,
the strong southeasterly flow should keep the bulk of the
precipitation along the mountainous terrain; however, given the
strength of the approaching shortwave and strong jet in the upper
levels, periods of very light precipitation across Cook Inlet
north into the Mat-Su Valleys cannot be ruled out.
Just like yesterday, temperatures are below freezing with
northerly winds this morning for Anchorage, extreme western
Matanuska Valley, and southern Susitna Valley. With warmer air
aloft and, northerly winds at the surface through this afternoon,
and some precipitation making it over the higher terrain, pockets
of light freezing rain for these locations is possible this
morning.
As for precipitation amounts, this system is tapping into copious
amounts of moisture stemming from an atmospheric river originating
over the Pacific. Kodiak received over 4 inches of rain since
yesterday as the front slowed in its eastward progression
yesterday. Another 1 to 3 inches of rain are likely from Seward to
Cordova today.
Similar conditions are expected across Southcentral late Monday
into Tuesday as yet another frontal system moves from the western
Gulf to Prince William Sound. An additional 1 to 3 inches of rain
is possible from Kodiak to Prince William Sound with this next
event.
-TM/Rux
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3)...
A low pressure system in the southeastern Bering Sea continues to
drive the active weather pattern across Southwest Alaska and the
Eastern Aleutian chain. Widespread areas of rain showers across
the Bering Sea and into the Eastern Aleutians, with some
diminishing shower presence over Southwest Alaska. The primary
impact driven by the low's position is strong and gusty winds
through the Kamishak gap, pouring into the Greater Bristol Bay
area. As these winds are expected to have peaked earlier this
morning, winds up to 50 mph are possible the remainder of this
morning through locations such as Iliamna, Kokhanok, and up into
the Lower Kuskokwim Valley near Aniak. These winds will come down
later this afternoon, providing a reprieve in strong winds for the
evening and overnight period.
Beginning early Tuesday morning, another low pressure system will
cross the southern Alaska Peninsula and enter the eastern Bering
Sea, elongating and merging with the current low pressure system.
This new combined system is expected to bring another, potentially
stronger swath of gale force winds south of the Alaska Peninsula
and in the southeastern Bering as well as gusty winds through
Kamishak Gap once again for Bristol Bay and the Lower Kuskokwim
Valley. Wind gusts Tuesday afternoon up to 65 mph are possible
near the mouth of the Kamishak Gap near Kokhanok, with locations
downstream such as New Stuyahok and Igiugig to see gusts up to 55
mph. Widespread rain showers across Southwest Alaska will be
possible through Wednesday morning, with the greatest rainfall
amounts expected for the Alaska Peninsula and areas most
susceptible to southeasterly upslope flow in southwest Alaska.
Temperatures are expected to remain warm enough to keep
precipitation as all rain through Wednesday morning, except for
snow showers at high elevations. Following the passage of this
next system, the pattern appears to quiet down, suggesting a
potentially broad showery pattern across the Bering Sea,
Aleutians, and Southwest Alaska with the low losing strength and
spinning out in the northern Bering, and a weak ridge building in
over the Central Aleutians.
-CL
&&
.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...
On Thursday, a negatively-tilted trough extends east over
Southwest Alaska and into the Gulf from a broad upper low over
the far western Bering Sea. Enhanced lift provided by the trough
and weak southerly flow will support light rain showers along the
north Gulf coast, with potential for light snowfall for inland
portions of southern mainland Alaska. The trough cuts off into a
weak upper low that shifts into the eastern Gulf for Friday,
focusing the best potential for precipitation in eastern Prince
William Sound and the Copper River Basin. Meanwhile, cold air from
the Interior filters south, trending temperatures down for the
latter half of the week into the weekend.
Out west, a longwave trough remains anchored near Kamchatka. This
brings a strong gale to storm force low into the far western
Bering for Thursday and Friday. Its front pushes to the Southwest
coast by Friday, but there is significant uncertainty in
precipitation type, with temperatures marginal either rain or snow
are possible depending on solution. A ridge builds off to the
east into the Gulf, trending precipitation chances down over
Southcentral Alaska for the weekend. There are, however,
indications in the model guidance that the front along the
Southwest coast sweeps inland and brings another surge of moisture
and precipitation into the southern mainland by Sunday, but there
is significant spread in the areas that are most favored, with
potential for both coastal and inland precipitation. Late in the
weekend, a large storm or hurricane force low looks to approach
the Aleutians, bringing moderate rainfall to the islands and the
southern Bering.
Quesada
&&.AVIATION...
PANC...A complex weather situation will persist around the
airport through Monday. With winds at the terminal expected to
remain mainly northwesterly through around noon today,
temperatures will remain at of slightly below freezing. This was
the cause of the freezing rain yesterday with southeast winds
aloft bringing in warmer air over the below zero surface
temperatures in the northwesterly winds. Because of the similar
set up this morning, any precipitation would likely fall as very
light freezing rain. This combination of northwest surface winds
abruptly becoming southeasterly around 500 to 1000 ft will mean
the redevelopment of wind shear in the area beginning early to
mid- morning Monday. By early Monday afternoon strong
southeasterly winds should push over the airport and both end the
wind shear while turning any precipitation at that point to all
rain. These winds should persist through much of Monday night and
then diminish.
&&