NWS Anchorage, AK wrote its last area forecast discussion before the first event at Mar 2, 5:48 AM AKST, 10 hours 14 minutes earlier.
Area forecast discussion, Mar 2, 5:48 AM AKST, 10 hours 14 minutes before
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
548 AM AKST Wed Mar 2 2022
.ANALYSIS AND UPPER LEVELS...A 972 mb occluded low sits nearly
stationary over the western Bering this morning. Its front
extends north of the Pribilof Islands and southward across the
Alaska Peninsula. Gale southeasterly winds exist immediately
northeast of the low and across the northern Bering. An area of
westerly gales have overspread the Western and Central Aleutians
within a region of strong cold air advection around the backside
of the low. Subsequently, areas to the south of the low and its
associated front are experiencing colder temperatures with
scattered light snow showers noted over portions of the Aleutians.
A triple point low has also developed on the tail end of the
aforementioned front roughly 150 nautical miles southeast of Sand
Point and is tracking northward toward Bristol Bay. A small swath
of gales and higher gusts may accompany the low across the Alaska
Peninsula into Bristol Bay through this afternoon. Elsewhere,
general high pressure is noted inland of the Southwest coast. Much
of the widespread low level stratus has lifted and is now being
overspread by higher clouds aloft, thanks to pressure height falls
with an approaching front. Otherwise, winds over much of
Southwest are mild at 15 mph or less.
Further east and across Southcentral a ridge of high pressure
over the eastern Gulf is being broke down by an upper trough
approaching Kodiak from the Alaska Peninsula. Precipitation across
much of Southcentral has come to an end this morning with the
lone exception existing over the eastern Copper River Basin where
a weak shortwave is skirting the region. Southerly onshore flow
into the Gulf coast, however, will likely result in at least
isolated areas of showers within upslope flow across the higher
elevations.
&&
.MODEL DISCUSSION...Models remain in good agreement with the
overall synoptic pattern the next 48 hours with a large upper low
pushing into the eastern Bering late Thursday into early Friday.
Main concerns entail the strength and exact track of the low which
will determine the intensity and coverage of winds across the
Aleutians into Southwest. For this forecast package have leaned
toward the GFS and NAM, which both depict a deeper low, with
widespread gales and storm force winds across the eastern Bering
from the Eastern Aleutians, up the Alaska Peninsula and into
Bristol Bay and the Kuskokwim Delta. Forecast confidence at this
time is above average. The potential for high winds and blizzard
impacts will continue to be monitored.
&&
.AVIATION...
PANC...VFR conditions and light east to southeast winds to
persist into Thursday.
&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Friday night)...
A short-wave trough will continue to lift northward across
Southcentral today, but forcing is very weak, so don't expect
more than isolated to scattered snow showers. Meanwhile, a
low south of the Alaska Peninsula will track north into Bristol
Bay, while an associated front tracks north and east across the
Gulf of Alaska. Precipitation and winds will spread across Kodiak
Island today then to the eastern Kenai Peninsula and Prince
William Sound regions tonight through Thursday. A series of out
of phase short-wave troughs will also lift north across the Gulf
and Southcentral. None of these look particularly strong, so
precipitation will generally be light, with some enhanced
precipitation in upslope flow. While the airmass is generally
cold enough aloft to support snow, gusty surface winds moving
off the Gulf will warm surface temperatures along the coast
to above the freezing mark. Expect a changeover to rain on Kodiak
island, while north Gulf coast and Prince William Sound
communities will likely mix with rain at times. The population
centers look like they will remain mostly dry with this system
due to the weak dynamics and some downslope flow. There could be
a brief period of light snow inland as the upper trough passes
over Southcentral Thursday afternoon through evening.
Fast flow aloft will keep the storms coming as we head through
the end of the week and into the weekend. A deep low will track
out of the Pacific and into the eastern Bering Sea Thursday, with
the associated frontal system tracking eastward into the western
Gulf Thursday night. This will bring more precipitation to the
same areas, namely Kodiak, the eastern Kenai Peninsula, and Prince
William Sound. Temperatures look a bit warmer with this front, so
expect mostly rain near sea level. The front will stall over the
Gulf as the parent low tracks north along the west coast of Alaska
and a high amplitude ridge builds from the Gulf northward across
eastern Alaska and the Yukon. This will set up what could be a
much more significant precipitation event for Southcentral as we
head into the weekend, with a strong upper jet and associated
atmospheric river. Stay tuned for details, but this likely will
lead to heavy precipitation along the coast (with rising snow
levels) and widespread snow inland.
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3 - Tonight
through Friday)...
A weakening front will move onshore by this afternoon with
southeast winds around 20 to 30 mph developing along the Bristol
Bay coast with areas of light snow moving inland through tonight.
A low currently south of the Alaska Peninsula will move north up
into the Kuskokwim Mountains by tonight, and this low should
concentrate most of the snowfall up to 1.5 inches over areas west
of Dillingham. Southeast (cross-barrier) flow near the northern
Alaska Peninsula should warm temperatures to around 40F by this
afternoon over southern parts of Bristol Bay, where mainly rain
showers transitioning to a rain snow mix is expected through this
evening. What remains of the front will be slower to move into
the Kuskokwim Delta, with most new snow accumulation up to 1 inch
mainly along the coast expected tonight as the weakening front and
low move through.
A short break in the weather is expected Thursday morning as the
frontal system falls apart over the Southwest interior. However,
the break will be cut short by an approaching much stronger low
pressure system moving into the eastern Bering Sea by Thursday
afternoon. Strong southeast winds gusting up to 50 mph will
develop along the coast and expand inland as the low approaches
the Kuskokwim Bay later tonight as snow possibly mixing with rain
moves in from south to north with the low's attendant front. The
strong southeast flow developing across the entire southwest
should result in downslope drying and warming off of the Kuskokwim
Mountains and Aleutian Range, keeping most of the precipitation
through Thursday night focused along the Kuskokwim Mountains and
the Kuskokwim Delta Coast. Temperatures will likely be cold enough
to see all snow across the Kuskokwim Delta, but warm enough for
the snow to be wet and limit potential for significant blowing
snow. Farther south, there is some concern for elevated water
levels developing along parts of Bristol Bay by late tonight as
winds become more southerly and increase to storm force just
offshore. This would be most likely to be an issue on the north
side of the bay between Dillingham and Togiak, although the
remaining sea ice along this stretch could offer some protection
from any storm surge.
&&
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3 - Tonight
through Friday)...
A weakening low pressure over the western Bering Sea will drift
out of the forecast area by late tonight, with westerly small
craft winds along the Aleutians diminishing by tonight. Snow
showers will continue drifting across the Bering in the mean time,
at times impacting the Pribilofs and the Aleutians as they move
across.
Attention by Thursday shifts to the next more impactful system
expected to move into the eastern Aleutians as a strengthening
North Pacific low crosses into the eastern Bering by Thursday
afternoon. Snow will quickly change to rain as strong southeast
winds develop and warm temperatures well above freezing through
Thursday afternoon, before colder air rushing in on the back side
of the low changes any remaining precipitation to snow by
Thursday night. The bigger story will be the very strong west to
northwest winds expected to develop shortly after the low crosses
into the Bering, with a core of 40 to 60 mph winds expected to
form on Thursday afternoon near Dutch Harbor as rapid pressure
rises occur. A High Wind Watch has been issued for the eastern
Aleutians, including Unalaska, for Thursday afternoon and evening
with the potential for 75 mph wind gusts. Winds will quickly
diminish Thursday night as the low moves away to the northeast,
with cold air rushing in turning any lingering showers near the
eastern Aleutians back over to snow. Farther north over the
Pribilofs, the low will bring a band of snow and gusty northerly
winds across Thursday afternoon and evening, likely leading to
periods of blowing snow and reduced visibilities.
&&
.Marine (Days 3 through 5: Friday through Sunday)...
Gulf of Alaska: There is high confidence that a front up to gale force
will reach the western Gulf on Friday and push towards the Gulf
coast where a low will form by Saturday. A barrier jet up to gale
force is possible on Saturday as the front reaches the coast and
the low begins to form. Gap winds will then set up on Sunday
through the Barren Islands and typical outflow areas as the low
departs, but with a lack of cold air to the west and over interior
areas, winds should remain at low end gales to small craft. Seas
along the front and barrier jet may reach up to 20 ft should gales
materialize. Bering Sea: There is high confidence a gale to storm
force low will cross the Eastern Aleutians early Friday morning
before moving into the northern Bering and weakening early
Saturday morning. Seas up to 30 ft are possible on the Pacific
side of the chain with up to 25 ft possible north of the Alaska
Peninsula. An additional gale force low is likely to move over the
western Aleutians Friday evening and slowly weaken as it moves
north into Eastern Russia Sunday night. Forecast confidence on the
second low is high and gales are most likely east of the Pribilof
Islands. Seas of 18 to 22 ft are possible with this system.
.Long Term Discussion (Days 4 through 7: Saturday through Tuesday)...
The longwave pattern is expected to amplify over the long term with
a ridge building over the northeast Pacific and broad trough remaining
steady state over the Kamchatka Peninsula and Sea of Okhotsk.
This will place the Southern Mainland in predominantly southerly
flow aloft, which in combination with marginal jet support will
return active weather to the region. On Friday there is good
agreement between deterministic and ensemble forecast models that
a low will form along a front in the western Gulf, which will then
be reinforced by an additional north pacific low as it moves
towards the Prince William Sound and Gulf Coast. Temperatures
aloft appear to be conducive to widespread snow across
Southcentral; however, the low track on Friday can be conducive to
bringing in warm air through Turnagain Arm and the Knik River
Valley, so precipitation may have to overcome low-level warm air
prior to any snow accumulation for these areas. The eventual
development of a closed low in the northern Gulf should help to
pull colder air from the interior areas into the population
centers, but the timing of this transition will impact
precipitation type and accumulations. On Sunday this low departs
rapidly into the Yukon Territory. Model uncertainty increases
drastically after this point, with a closed high developing over
the Alaska Mainland in the ECMWF ensemble and deterministic
models, which would push the storm track south into Southeast
Alaska, while the GEFS and GFS continue to build the ridge and
continue the active storm track into Southwest Alaska.
&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Watch 185.
MARINE...Gale 120 130-132 150 155 160 165 170 171 173-77 180 185 352
411-414.
Storm 172.
Heavy Freezing Spray 180 185.
FIRE WEATHER...NONE.
&&
SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AS
MARINE/LONG TERM...CJSpecial weather statement, Mar 2, 4:01 PM AKST, 1 minute before
SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
401 PM AKST Wed Mar 2 2022
AKZ161-031500-
Bristol Bay-
Including the cities of King Salmon, Dillingham, Naknek,
and Pilot Point
401 PM AKST Wed Mar 2 2022
...STRONG WINDS AND BLOWING SNOW FOR THE NORTHERN BRISTOL BAY
COAST THURSDAY EVENING THROUGH LATE FRIDAY MORNING...
A developing low pressure system entering the eastern Bering Sea
Thursday afternoon will produce strong winds and the potential for
blowing snow for portions of the Bristol Bay region Thursday
evening through late Friday morning. Southeasterly winds of 35 to
45 mph will develop Thursday evening as the low approaches the
Southwest Coast, before shifting southerly through the overnight
hours. The greatest potential for the strongest winds will occur
early Friday morning west of Dillingham when gusts to 60 mph will
be possible. While temperatures are expected to be in the mid-30s,
which are typically less conducive for blowing snow, the strong
winds may combine with the denser, wetter snowfall to produce
hazardous, low visibility conditions at times. Winds will diminish
late Friday morning as the low continues northward across the
Yukon-Kuskokwim Delta.