NWS Anchorage, AK wrote its last area forecast discussion before the first event at Feb 9, 5:56 AM AKST, 19 minutes earlier.
Area forecast discussion, Feb 9, 5:56 AM AKST, 19 minutes before
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
556 AM AKST Wed Feb 9 2022
.ANALYSIS AND UPPER LEVELS...
A deep upper level low centered near Hooper Bay is pivoting to
the east. The associated upper level trough extends southward
across Southwest Alaska and the Bering Sea, and cold Arctic air
continues to flood into the region as far south as the Aleutians.
On visible satellite imagery, cloud streets are still seen
streaming off the sea ice edge and across the Bering as the cold
air moves over the warmer sea water. The resulting snow showers
continue for the Pribilof Islands and Aleutian Chain. A
southwesterly upper level jet over the Gulf is supporting an
elongated surface low located southeast of the Kenai Peninsula as
it tracks towards Prince William Sound. The front extending from
this low has moved inland, but it produced snow for the north Gulf
Coast earlier this morning. An upper level shortwave will help
snow linger into the afternoon over the region. Strong cold air
advection behind the low is creating gusty southwesterly winds in
Homer and surrounding areas. These winds combined with snow
showers and recent snow will result in areas of blowing and
drifting snow, with localized low visibilities, primarily from
Anchor Point to Homer.
With the Arctic airmass sitting over Southwest and southerly flow
bringing warmer air into Southcentral, an impressive temperature
gradient has set up across the Alaska Range. Temperatures at 850
mb over western Alaska are around -20 to -30C, whereas
temperatures on the eastern side of the Alaska Range are only
around -8C.
&&
.MODEL DISCUSSION...
In regards to the surface low currently headed northward towards
Prince William Sound, all models have shifted the low slightly to
the east, so this could mean that Anchorage, Mat-Su, and the Kenai
Peninsula end up getting less snow from the system.
Models are still struggling with the complex surface low with
multiple centers that will move northward towards the Aleutian
Islands and Bering Sea this evening through Thursday. The GFS and
NAM look the most similar as both hint at widespread gale force
winds with the system, and a low pressure system could possibly
develop from the parent low near Kodiak Island on Friday. If this
low does end up developing, there could be stronger winds through
Shelikof Strait and the gaps and passes along the coast. There is
another North Pacific low that will move over the western
Aleutians early Friday morning, and model agreement is already
fairly decent with this system in regards to its track and
strength.
&&
.AVIATION...
PANC...VFR conditions are expected to drop to MVFR conditions
around noon today. Ceilings will come down with light snow moving
over the terminal as the next system approaches. MVFR conditions
are expected to lift back to VFR conditions later this afternoon
as the system passes and snow diminishes. Light westerly winds
will give way to gusty southerly winds briefly this afternoon.
&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Friday night)...
A low over the northern Gulf will track quickly into Prince
William Sound this morning, then rapidly weaken as it pushes
onshore midday. Warm air advection east of the low center will
lead to mostly rain for Cordova and perhaps a brief mix of rain
and snow for Valdez and the southern Copper River Basin. While the
upper level jet has veered eastward toward Southeast Alaska, a
series of upper level short-waves will help focus the heaviest
precipitation from eastern Prince William Sound to the eastern
Copper River Basin. Light snow falling across much of the rest of
Southcentral Alaska this morning, will diminish as we head through
the day.
Meanwhile, a deep and cold upper level low along the west coast
will begin to track eastward today, leading to moderate to strong
cold air advection from west to east across the Gulf and
Southcentral today through tonight. The cold air advection and
pressure gradients will be strongest over the western Gulf,
leading to widespread strong and gusty winds across the coastal
waters as well as Kodiak Island and the southern Kenai Peninsula.
Based on the track of the surface low, this is a favorable
scenario for strong winds coming through Kamishak Bay to head
right for Kachemak Bay and Homer. The winds will rapidly move into
Homer during the mid to late morning, which will cause the fresh
snow on the ground to blow and drift. Also expect some snow
showers to develop due to the cold air advection over the open
waters of southern Cook Inlet and upslope flow as it hits the
hills of Homer. Thus, there could be brief periods of
significantly reduced visibilities from the snow showers and
strong gusty winds. The strongest winds will last all the way
through the afternoon before diminishing this evening, while snow
showers should diminish by mid to late afternoon.
For the rest of Southcentral, the cold air advection will ensure
any remaining precipitation tonight falls as snow. An upper level
short-wave rounding the south side of the upper low will cross
Southcentral late this afternoon through tonight, followed by a
lower level short-wave late tonight through midday Thursday. These
will produce some light snow, mainly along the south to western
facing mountain slopes.
There won't be much of a break for a new storm moves out of the
Pacific Thursday through Thursday night. Despite quite a bit of
uncertainty in the track of the surface low, confidence is high
that a strong warm front will lift northward across the Gulf and
Kodiak Island Thursday afternoon through Friday afternoon. With
the deep cold airmass in place ahead of this front precipitation
will begin as snow on Kodiak Island Thursday afternoon, then
spread northward to Southcentral Thursday night into Friday.
Warmer air will ultimately result in a change to rain for Kodiak,
and possibly the north Gulf coast. While many of the forecast
details for this storm system remain to be worked out, the general
pattern favors moderate to heavy precipitation along the Gulf
coastal zone, with lighter precipitation inland.
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3:
Wednesday through Friday)...
Upper level flow will begin to shift today with the cold, arctic
airmass begins headed east. A developing shortwave will dip into
the interior Bristol Bay and eastern portions of the Kuskokwim
Valley this afternoon. Along with this wave, a brief snowfall and
increase of winds that should last only last through the daytime.
Temperatures will attempt to moderate through the short term.
Another round of precipitation is possible for the AKPen and
Bristol Bay areas beginning late Thursday into Saturday. At this
time it appears to be only another couple inches possible.
Northeasterly winds will increase with offshore flow during this
time frame for the entire southwest and by Friday night, winds
should decrease from south to north into Saturday.
&&
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Wednesday through Friday)...
Cold, northerly flow will begin to shift later today with the
movement of an Arctic low currently situated over the northeastern
Bering. A cluster of lows will press northward, south of the
Aleutians. One of the eastern lows may continue east towards the
Gulf while a couple of rather disorganized grouping of lows will
continue north to cross the Aleutians. Little agreement in the
models for the exact set up of these lows. However, easterly winds
and offshore flow from the mainland will increase to gale force
by Thursday morning and become more widespread towards the
Pribilofs through Friday morning. This will slow the northward
progression and the lows may stall over the Aleutians. The push
will also bring warmer advection to the Aleutians. Any
precipitation may begin as snow changing to a mix Wednesday night
through Thursday from around Adak to Cold Bay. The conversion to
rain will be possible somewhere between Adak and Dutch Harbor.
Snow and strong winds may lower visibility with blowing snow
possible for the Pribilofs Thursday and Friday.
&&
.Marine (Days 3 through 5: Friday through Sunday)...
Gulf of Alaska:
Cyclonic flow will influence the Gulf. A frontal system will move
into the region Friday bringing widespread gale force winds. The
low will track inland and weaken, expect the winds to slack of on
Saturday. Then another low will move into the Gulf on Sunday but
quickly move inland over SE Alaska.
Bering Sea/Aleutians:
Uncertainty persists with the strength and track of an incoming
North Pacific low. Expect fast moving systems. A North Pacific low
approaches the region Saturday evening. Overall, waves will be
mostly 8-15 ft, with seas peaking around 20 ft where gales are
expected. As winds stay mostly northeasterly through the period,
cold air advection and freezing spray will likely continue to be
concerns.
&&
.Long Term Discussion (Days 4 through 7: Saturday through
Tuesday)...
Models are continuing to indicate an active and wet period for
the North Pacific with the persistence of a longwave trough over
the Bering and the Northwest Pacific. Models are showing back to
back lows moving out of the Pacific. By 96 hrs, there is a
significant amount of models divergence which will impact the
track and the timing of the precipitation. At 500 mb there is an
area of positive height anomalies over the Gulf Of Alaska and SE
Alaska from Day 4 to Day 7. Also there is a broad area of negative
height anomalies over the Bering, SW Alaska and NW Pacific on Day
4. However, the intensity of the anomalies over the Bering wanes
but the anomalies over the NW Pacific get stronger. Expect the NW
Pacific to be an area of cyclogenesis this entire forecast period.
&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning: 119, 120, 130, 131.
Gale Warning: 125, 128, 129, 132, 137-139, 141, 150, 160,
165, 170-173, 176, 177, 179, 351, 352,
412-414.
Heavy Freezing Spray: 130, 138, 139, 141, 160, 165, 179,
185, 412, 414.
FIRE WEATHER...NONE.
&&
SYNOPSIS AND MODEL DISCUSSION...AF
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...VR
MARINE/LONG TERM...PJS