High Wind in Alaska, March 24 to 25, 2019

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
729 PM AKDT Sun Mar 24 2019

.ANALYSIS AND UPPER LEVELS...
The big weather feature is the intensifying low that is south
of Kiska this afternoon and moving into the Bering Sea. The upper
level low is over the Kamchatka Peninsula and the trough extends
to the surface low putting the low in a good location for further
strengthening. A weakening front is moving through the Southwest
mainland today with the upper level ridge amplifying right behind
this front. This ridge will become a significant weather feature
for Southcentral Alaska the next few days. A weak low is just
southeast of Kodiak Island and drifting toward the island. The
weakness of this low can be seen by contrasting the way it looks
on the visible vs IR satellite. The visible satellite shows the
low spinning nicely with the clouds reflected well. The IR
satellite shows that these cloud tops are fairly warm and
therefore not very high. Neither is there any upper level support
to assist this low so it will just dissipate as it drifts toward
Kodiak. The front in the Prince William Sound region and central
Gulf will also weaken as it moves eastward overnight.

&&

.MODEL DISCUSSION...
Models have initialized well and are much tighter on the solution
for the Bering Sea low through Tuesday. Models consensus it that
the low will be a farther west and also a little stronger (lowest
pressure around 948 mb) as it treks though the western Bering sea
and just west of the Gulf of Anadyr on Tuesday. Other than that,
the models look to be in good shape into late in the week.

&&

.AVIATION...
PANC...VFR conditions will persist through Monday afternoon. Winds
will likely be gusty at times from the southeast through the
evening and the biggest question is when they will settle down.
Currently expecting the gusts to end around midnight but they
could persist longer than that though they should be done by
morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

The front stretched across the northern gulf pushes inland tonight
and dissipates by early Monday with a ridge building in its wake.
Drier conditions set up through mid week with offshore winds
returning late Monday night. Gusty flow increases for typical gap
locations along coasts as ridging slides from west to east across
the interior on Tuesday. Patchy fog will also be a challenge
Monday night and again on Tuesday night as skies begin to clear
and low level inversions steepen toward morning. Fog should clear
quickly shortly after sunrise.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
(Tonight through Wednesday evening)

Unseasonably warm temperatures look to return to Southwest Alaska
over the next 24 to 36 hours. A very strong Bering Sea Storm will
push a warm front northeastward across the area on Monday. Ahead
of this features, surface winds will be from the southeast while
just above the surface, 850 mb southwest winds will usher in a
warm and moist airmass, with temperatures here pushing 9 deg.
Some of this warm air should mix down to the surface, aided by
down- slope winds helping warm the temperatures via frictional
heating on the northern and western flanks of the mountains. In
fact, the latest guidance shows King Salmon in the 49 to 54 degree
range, with locations further inland a few degrees cooler than
this. Still, at least mid 40s seem to be a solid bet for many
locations.

This storm will also send a cold front towards the coast for
Monday evening, accompanied by some light precipitation. However,
this front will quickly begin its frontolysis phase, as it bumps
against a strong downstream ridge to its east, with this feature
falling apart by Tuesday over mid sections of the interior. This
will allow for dry conditions and seasonable temperatures to
continue for Tuesday into Wednesday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
(Tonight through Wednesday evening)

Deteriorating conditions will continue for the western Aleutians
and Bering over the next 24 hours, as a potent low moves into the
region while bottoming out around 948 mb. This low has been
rapidly deepening through the day, and the latest ASCAT pass
already shows sustained winds of 60 knots on its southeastern
through southwestern flank. Add into the mix favorable jet
dynamics, a very strong low-level tropical connection, and
seasonably cold air aloft, it wouldn't be surprising to see a few
lightning strikes accompany the low through the western central
Aleutians into the western Bering.

What's more interesting is just behind the associated surface cold
frontal passage. As this storm crosses the chain this evening, the
occlusion process will have commence, with the cold front racing
eastward, accompanied by widespread precipitation. Strong cold/dry
advection will advect from the backside of the storm into its
southern and southeastern flanks, accompanied by an unusually
strong PV anomaly (down to 770 mb in some instances). This
compression of the air from all of these processes will allow for
very strong downward mixing potential. As such, winds were
significantly increased for the area with the previous High Wind
Watch being upgraded to a warning. The worst winds over land look
to be between 1 and 7 AM AKDT just east of Adak to just east of
Amchitka, where sustained winds around 55 mph with gusts to 80 mph
likely.

The same holds true for the associated coastal waters here and
northward into marine zone 413, where sustained winds of 65 knots
with gusts to 80 knots appear likely, especially north of the
chain. Thus, Hurricane Force Conditions are expected. Seas will
also push/top 35 feet given the wind strength and long fetch
length. Conditions will gradually improve for your Tuesday into
Wednesday, as the system lifts away from the area.

&&

.MARINE (Days 3 through 5)...

Gulf of Alaska... Expect generally benign conditions, with winds
diminishing and seas subsiding as pressure builds.

Bering Sea...Gale force winds will diminish through Wednesday with
high pressure building across the eastern Bering Thursday.
Confidence is increasing with periods of southerly gale force
winds over the Bering Sea and Aleutians Thursday through Saturday.

&&

.LONG TERM FORECAST (Days 4 through 7)...

South Central: High pressure will be entrenched across the
mainland through the end of the week. Confidence that a shortwave
will traverse the Bering Strait Friday and work to flatten the
ridge is increasing. Weak southerly flow will help to promote
some showers along the Alaska Range and clouds locally. Much of
Southcentral will remain dry with temperatures remaining in the
mid/upper 40s and overnight lows flirting with freezing, keeping
the trend of well above normal temperatures well into the
weekend and beyond.

Southwest/Bering: High Pressure will dominate the weather pattern
through the end of the week. The aforementioned shortwave sliding
across Alaska will bring a mix of rain and snow to the King
Salmon/Dillingham to Rainy Pass corridor and along the Kuskokwim
mountains. A series of fronts will bring active weather across the
western and central Aleutians mid week and again leading into the
weekend.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Hurricane Force 175-177 413. Storms 173 178 185. Gales
155 165 170-172 174 179-181 414.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
MARINE/LONG TERM...SS