Small Craft Advisory 170, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 PM AKST Thu Feb 24 2022

.ANALYSIS AND UPPER LEVELS...

An upper level ridge remains in place across Southeast Alaska
with an extension of this ridge towards the North Slope of Alaska.
Across the far western Bering and North Pacific is a strong upper
level low/trough that continues to rotate upper level shortwaves
around it. In between these two big features is deep, moist,
southerly flow aimed right at southern Alaska. As a result, when
looking at radar imagery this morning, rain sometimes mixed with
snow was falling in places such as Whittier, Portage, and Seward.
In conjunction with the rain was gusty winds with Portage gusting
as high as 50 kts (55 mph) earlier this morning. Koliganek in
Bristol Bay was also gusting upwards of 56 kts (64 mph) earlier
this morning. Embedded in the deep southerly flow were various
different upper level shortwaves with the first one moving through
Southcentral this morning resulting in the aforementioned rain
and winds. Another upper level shortwave was seen moving northward
east of Kodiak. Lastly, a much stronger and more defined upper
level shortwave was seen south of King Cove moving northward. This
latter shortwave will be responsible for the increase in precipitation
and precipitation rates across coastal areas (Prince William
Sound and eastern Kenai Peninsula) of Southcentral tonight through
Fri morning.

&&

.MODEL DISCUSSION...

Models are in fair agreement on the synoptic scale features and
the upper level pattern out through Day 3. The main focus this
forecast package was to continue fine tuning the winds for the
Upper Hillside of Anchorage and Turnagain Arm in association with
another much stronger upper level shortwave depicted across all
model guidance moving northward on Friday. This same upper level
shortwave with its corresponding surface low are expected to move
from southeast to northwest across the eastern Bering Sea on
Friday which may result in strong gusty winds (potentially high
winds) for the Kuskokwim Delta coastline. Therefore, updates were
made to increase the winds in this area, especially for the
backside of the low.

&&

.AVIATION...

PANC...VFR conditions are expected throughout the entire TAF
package. Light and variable winds are expected throughout the day,
though, though winds should become more consistent out of the
north this evening. Gusty northerly winds may develop with gusts
to around 20 mph between 25/12z-26/00z before becoming
southeasterly after 26/00z as the surface front passes by. With
the low track so far west into the central Bering Sea, this is not
a great case for a strong bend of Turnagain winds into Anchorage.
Therefore, it looks like the terminal will be on the northern
periphery of the Turnagain Arm jet, likely limiting wind gusts to
25 kt or less.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (This evening through
Sunday afternoon)...

Lingering precipitation along the coast will intensify again late
tonight into the first half of Friday as another frontal system
extending from a surface low south of the Alaska Peninsula lifts
to the northern Gulf. Precipitation will continue to fall as rain
along the coast, snow at higher elevations, and a mix of rain/snow
for parts of interior Kenai Peninsula. A series of upper level
shortwaves will lead to gusty winds across Turnagain Arm, peaking
Friday morning (with strong winds also near Portage Valley) and
then diminishing late Friday while the upper level waves and
aforementioned low move north away from the region. Subsequently,
precipitation will gradually taper off Saturday morning and give
way to calmer conditions. The Anchorage Bowl and western Kenai
Peninsula are expected to stay relatively dry through this weekend
as a result of downsloping from strong southeasterly winds
running up against the Kenai and Chugach Mountains. By Sunday
afternoon, a low pressure system will track into the northern Gulf
and lead to a good chance of more precipitation along the coast,
though it looks quite a bit lighter compared with the current
system.

&&

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

Through tonight expect winds to gradually increase across the
AKPen and Bristol Bay as a low pressure system moves towards the
AKPen. This low will also spread precipitation across the area
into Friday with a bulk of the precipitation near coastal areas
and offshore, while areas west of mountain ranges will see
downsloping which will minimize precipitation. Most of this
precipitation will be in the form of rain near sea level, with
snow confined to the higher mountains. As this low moves across
the eastern Bering Sea, pressure rises on the back side of the
low will result in further strengthening of the winds along the
Southwest coast Friday afternoon and evening. This will bring the
threat of high winds across the Kuskokwim Delta Friday evening
through Saturday morning. A high wind watch has been issued for
coastal areas of the Kuskokwim Delta with gusts to near 70 mph
possible. Sea ice is currently 5 to 12 miles offshore with the
threat of some ice closer to the shore line. However, this low
will quickly move northwest by Saturday morning into the northern
Bering, so with this quick movement we expect sea ice moving near
the shore to be a minimal threat as the winds will quickly weaken
on Saturday. Temperatures will also cool a few degrees on Friday
which will bring the chance of snow mainly to coastal areas with
minimal snow accumulations expected. Saturday looks to be a
quieter weather day with cooler temperatures, winds decreasing and
the clouds thinning out as weak ridging begins to edge into the
area. Sunday will be another quiet day with the cooling trend
continuing as weak high pressure edges into Southwestern Alaska.

&&

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

The main weather maker for the short term will be a robust low
pressure system that will deepen through Friday as it crosses the
AKPen and moves into the eastern Bering. This low will produce
gales across the eastern Bering with storm force gusts across the
far eastern Bering near coastal areas of Southwest Alaska. This
low will begin to weaken as it quickly moves into the northern
Bering Saturday morning but Gales near the low are still expected.
By Saturday afternoon this low will move west of the area.
Otherwise weak low pressure will persist across the western and
central Aleutians through Friday. Saturday and Sunday weak
shortwaves will move across the Aleutians and southern Bering with
continued rain and snow showers but winds generally small crafts
or less.

&&

.Marine (Days 3 through 5: Sunday through Tuesday)...

Expect an active storm track across the central to western Bering
Sea and Aleutians, with a series of deep surface lows tracking out
of the northwest Pacific and into the Bering Sea. Right now, it
looks like gale force winds will be the most common condition with
these storms, but there is a chance for small areas of storm force
winds. Conditions look much quieter from the eastern Bering Sea and
Southwest Alaska coast to the Gulf of Alaska waters. There is some
uncertainty in track of lows over the northeast Pacific. One of
these systems could track into the Gulf, but if so it would most
likely be over the eastern Gulf, closer to Southeast Alaska.

&&

.Long Term Discussion (Days 4 through 7: Monday through Thursday)...

The longwave pattern will feature a broad trough over the Bering
Sea and Northwest Pacific. For the Bering, the negative height
anomalies at 500 mb persist through March 3rd. However the
situation is a little more mild for the Southcentral at 500 mb
as they transition from negative to positive. The Bering and the
North Pacific will be major areas of cyclogenesis this forecast
period. The models spin up a number of lows at the surface,
however there is some divergence regarding the tracks of the
surface lows and the intensities. However, all the models are
advertising an active period for the Northwest Pacific and the
Bering Sea. And some of this activity will move into the Gulf of
Alaska. For Southcentral high temperatures for the Anchorage Bowl
and Mat-Su Valleys will be slightly above freezing ranging from
33F-39F. For Southwest Alaska high temperatures along the coast
will be slightly above freezing ranging from 34F-40F but interior
locations will dip below freezing.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Watch 155.
MARINE...Storm Warning 119 130 131
         Gale Warning 120 125 132 136 137 138 139 140 141 150 155
                      160 165 180 181.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MV
SOUTHCENTRAL ALASKA...AF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RC
MARINE/LONG TERM...SB/PS

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
1213 AM AKST Fri Feb 25 2022

AKZ161-260100-
Bristol Bay-
Including the cities of King Salmon, Dillingham, Naknek,
and Pilot Point
1213 AM AKST Fri Feb 25 2022

...STRONG WINDS ACROSS THE BRISTOL BAY REGION THROUGH FRIDAY
EVENING...

Easterly winds will increase across the Bristol Bay region by
early Friday morning as an area of intensifying low pressure
moves north over the Alaska Peninsula. Wind gusts of 60 to 70 mph
are possible across an area from Iliamna to Koliganek and New
Stuyahok. Wind gusts to 50 mph are also possible along the
northern Bristol Bay coast, including the communities of
Dillingham, Togiak, and King Salmon. Winds are expected to peak
early Friday afternoon before slowly diminishing through Friday
evening.

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
329 AM AKST Fri Feb 25 2022

AKZ125-260100-
Western Prince William Sound-
Including the cities of Whittier, Seward, Girdwood,
and Moose Pass
329 AM AKST Fri Feb 25 2022

...LONG DURATION PRECIPITATION EVENT THROUGH SATURDAY MORNING...

A series of surface fronts will impact parts of Southcentral
through Saturday morning with rain along the coast, a mix of
rain/snow for parts of interior Kenai Peninsula, and snow at
higher elevations. Precipitation is expected to increase in
intensity Friday morning with moderate to heavy precipitation
continuing through Friday evening before gradually tapering off
Saturday morning. Additional rainfall amounts of 1.5 to 3.5
inches are possible for Whittier and Portage Valley with up to 1
inch of rain possible for Seward.

Heavy rainfall, combined with melting snow, may create standing
water on roadways where poor drainage exists, particularly in
Portage Valley and Turnagain Pass. Motorists are urged to use
caution while traveling.

In addition to the precipitation, gusty southeasterly winds of up
to 60 mph will continue across Portage Valley and Turnagain Arm
through early Friday afternoon before diminishing Friday evening.

For the latest forecast, visit www.weather.gov/afc.

For the latest road conditions, call 5 1 1 or visit
511.alaska.gov.