NWS Anchorage, AK wrote its last area forecast discussion before the first event at Jan 12, 5:51 AM AKST, 11 hours 17 minutes earlier.
Area forecast discussion, Jan 12, 5:51 AM AKST, 11 hours 17 minutes before
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
551 AM AKST Wed Jan 12 2022
.ANALYSIS AND UPPER LEVELS...
A broad upper low continues to remain nearly stationary over the
central Aleutians. Scattered rain/snow showers persist as colder
air wraps around it. Farther east, a front is lifting northward
across the southwest mainland, brining scattered snow showers to
Bristol Bay and the Kuskokwim Delta. A number of shortwaves
embedded in the overall southerly flow aloft are continuing to
drive light precipitation along the Gulf coast this morning. Some
mixed precipitation has been observed, however not to the extent
of yesterday. Overcast skies are seen farther north over the
Susitna Valley and Copper River Delta, however these areas remain
generally dry away from higher elevations.
&&
.MODEL DISCUSSION...
As has been the case over the past few nights, subtle difference
exist with shortwaves embedded in the southerly 500 mb flow across
Southcentral. However, no matter the timing, precipitation looks
to be confined to coastal areas. The next major system will enter
the Gulf late Wednesday into Thursday. All models show a
relatively strong front entering the Gulf this evening. The GFS
was originally much farther south with the associated low than
other models, however they have now come into better agreement
with the precipitation reaching the Gulf coast by Thursday
morning.
&&
.AVIATION...
PANC...
VFR conditions will persist this morning. Light snow will develop
early this afternoon and continue through the evening, bringing
MVFR ceilings/visibilities. VFR conditions will return by Thursday
morning. Light winds will persist.
&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2...Wed and
Thu)...
An active weather pattern will remain in place through the end of
the week. First up in chronological order is another shortwave
lifting north across Southcentral this morning. This wave is
slightly stronger than the one on Tuesday morning, thus, it is
bringing a bit more cross barrier flow over the mountains. This is
helping to create some localized downsloping conditions with the
net result being predominantly dry weather for the population
centers (Kenai, Palmer, Anchorage, etc). It is a different story
from the coastal sites where mixed precipitation will continue
this morning from Seldovia over to Cordova. While most of these
coastal areas have warmed up enough to turn the precipitation over
to all rain, Valdez has been able to hold onto some colder air.
Thus, precipitation will fall as freezing rain through the morning
and a Winter Weather Advisory is in effect. As the current system
lifts inland through the day, cross barrier flow is expected to
weaken. This should allow precipitation to fill in over the
Anchorage Bowl, Eagle River, and up through the Mat-Su Valleys.
Most of this will fall as snow, but there could be some embedded
sleet/ice pellets initially as the warm air aloft erodes. Any snow
accumulation is expected to be rather light, on the order of 1 to
maybe 2 inches.
Then attention will shift to a much stronger system developing
over the Gulf late tonight. This system could create a myriad of
weather concerns across the area. Winds will increase quickly to
gale- force across most of the marine areas as the front
associated with this developing low moves north. This front should
arrive in Prince William Sound by daybreak Thu morning. Upon
arrival, expect increasing southeast winds from Whittier up
through much of Portage Valley and Turnagain Arm. Gusts to 60 mph
will be possible at sea level with stronger gusts over the higher
terrain. Further inland, winds will shift out of the northeast and
start to increase from the Mat Valley down through Anchorage.
While this certainly does not look anywhere near as strong as the
wind event from early last week, it could produce gusts in the
30-40 mph range Thu afternoon and into the evening.
As with the last system, most of the precipitation will be
confined to the coast. However, this system does have a deep
moisture tap and strong upper level jet support, so it could
produce 2 to 4 inches of QPF in about 36 hours from Seward through
Whittier. Snow levels will rise to between 1,000-1,500' courtesy
of the warm air this storm will bring to the coast. The
combination of upper level support and abundant moisture means
that even the inland locations that might typically be downsloped
could see some "spill-over" precipitation as well. We do expect
some cold air to hold on late Thu into Fri for inland valleys
which could result in another round of mixed
precipitation/freezing rain.
&&
.MARINE (Days 3 through 5: Friday through Sunday)...
Going into the weekend, an upper trough stretching across Bristol
Bay to the Eastern Gulf will bring periods of unsettled weather
with rain and snow showers to the Southwestern Alaska and Gulf
coastlines through the weekend. Winds will remain below gale force
over the Gulf with seas on Friday around 15 ft subsiding to below
10 ft on Sunday. However, to the west, another cluster of
elongated troughs along the Aleutian chain will very slowly move
east, with gale force winds approaching storm force in the western
Aleutians. These winds will increase seas to around 20 ft at
times south of Aleutians and in the Bering Sea throughout the
weekend.
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA (Day 1 through 3: Today
through Fri night)...
Throughout Wednesday, light snow will continue to fall as a
shortwave moves north across the Southwest. Accumulations will be
about 1 to 2 inches, with slightly higher amounts along the
Kuskokwim Delta coast.
The next round of precipitation arrives Thursday morning, when a
North Pacific low pushes its front into the Southern Mainland.
Temperatures will climb with the arrival of this front, with highs
in the 30s for Bristol Bay and in the 20s across the Kuskokwim
Delta and Lower Kuskokwim Valley. Precipitation looks to be
mostly snow, with the highest amounts occurring along the
Aleutian Range and Kuskokwim Mountains due to upsloping.
Downsloping will bring warmer and drier air to locations on the
lee side of the Aleutian Range, such as King Salmon and Iliamna.
While some rain or rain/snow mix is possible in these downslope
areas, wet-bulbing looks to cool temperatures enough to support
mostly snow. By Friday, northerly flow and cold air advection will
bring a return to cooler temperatures across the Southwest. As
there is uncertainty with the track of the low by Friday, snow
amounts on Friday are also uncertain and will continue to be
refined.
&&
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Day 1 through 3: Today
through Fri night)...
A stacked low lingers near the Central Aleutians until Thursday,
when it is displaced by a North Pacific low tracking towards the
AKPEN. The biggest change with this incoming low will be in the
Eastern Aleutians, where winds will become northerly and
temperatures will cool. Otherwise, conditions remain largely the
same elsewhere until Friday. Broad northerly flow, colder
temperatures, and snow showers will persist for the Central and
Western Aleutians, as well as much of the Bering Sea. Over the
Northern Bering and near the ice edge, heavy freezing spray will
remain a concern due to cold air advecting off land. As the low
weakens and moves towards the Kuskokwim Delta, the shift to an
onshore flow pattern will cause heavy freezing spray to diminish.
On Friday night, a low tracking northeast towards the Western
Aleutians will bring rain and increased winds.
&&
.LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)...
The relatively warmer and wetter pattern experienced this week
will continue through this weekend. Periods of rain and snow
showers, which could be heavy at times will be possible along the
Gulf Coast and Southcentral Saturday. A brief period of dry
weather is possible Sunday through early Monday across
Southcentral. Rain and snow from another elongated low stretching
along the southern portion of the Aleutians into the Bering Sea
will gradually push precipitation east along the Aleutian chain
towards Southwestern Alaska this weekend into early next week.
&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory: 131.
MARINE...Gale Warning: 119 120 125 130-132 138 139 150 155 185 351
352.
Heavy Freezing Spray Warning: 185 412 414.
FIRE WEATHER...NONE.
&&
SYNOPSIS AND MODEL DISCUSSION...AP
SOUTHCENTRAL ALASKA...MSO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KC
MARINE/LONG TERM...VR