Gale Warning 187, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
547 AM AKST Sun Feb 20 2022

.ANALYSIS AND UPPER LEVELS...

A large low pressure system that is currently near 52N 172E is
moving northeastward. A large upper level ridge of high pressure
is currently building across the North Pacific and is extending
into the Gulf of Alaska. Another low pressure system is currently
developing near 47N 175W and is moving northeastward. The
jetstream currently extends from the subtropical central Pacific
to over the Kuskokwim Delta and then southeastward to over the
Pacific Northwest.

Closer to the surface, radar imagery shows precipitation moving
northeastward across the Kuskokwim Delta and Bristol Bay.
Observations show the precipitation-type to be rain along the
immediate coast with snow across the inland locations. Nighttime
Microphysics IR and observations show dense fog across the
Anchorage Bowl early this morning.

&&

.MODEL DISCUSSION...

Forecast confidence remains moderate at this time. Models remain
in good synoptic agreement, though there is less agreement on
smaller scale features. One major example is the strength of the
cross-barrier flow across the Chugach Mountains into the Anchorage
Bowl. The NAM shows much stronger cross-barrier flow Monday night
and Tuesday compared to the GFS which means the NAM favors warmer
temperatures and less precipitation due to stronger downsloping
on the leeward side.

&&

.AVIATION...
PANC...VLIFR conditions are expected to continue through 20th/19z
as dense fog will reduce visibility to 1/4SM or less at times.
Conditions will then improve to VFR after 19z when the fog clears.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Today through Tuesday
Night)...

Upper level ridging is quickly building into Southcentral this
morning. A weakening front on the leading edge of the ridge is
going to try to squeeze out a flurry around Homer, but the vast
majority of the radar reflectivities are virga (precipitation
sublimating before it reaches the ground). Otherwise, expect
filtered sunshine for much of the day as the predominately high
cloud cover moves overhead. Expect that temperatures will be a
fair bit cooler today than yesterday owing to the 10 degree colder
start to the day. Only Homer, Kodiak and Seward are starting the
day above freezing.

Precipitation associated with the main storm system will begin
early Monday morning in Kodiak, quickly spreading north to the
Kenai Peninsula later Monday morning. Any precipitation that
starts out as snow should quickly change over to rain with daytime
heating. A quick hit of snow or a rain snow mix is possible with
the onset of precipitation around lunchtime Monday for Anchorage
and the Valley. Meanwhile snow will begin up in the Susitna Valley
Monday morning and quickly intensify during the day. With the
front causing the main forcing for precipitation expected to drape
itself from the Susitna Valley south along Cook Inlet, the Western
Kenai Peninsula, Anchorage and the Mat Valley should largely dry
out as intensifying southeasterly winds downslope out most of the
precipitation Monday afternoon. There is some disagreement as to
how effective the downsloping will be at drying the area out, but
the south to southeasterly winds aloft will also transport another
round of warmer air over the area, making rain the dominant
precipitation type after any initial hit of snow.

Continued southerly flow overnight Monday night will intensify the
snowfall rates over the Susitna Valley. With the southerly flow
also transporting somewhat warmer air over the area, think the
snow will be a low-ratio heavy, wet consistency. Thus, lowered
snow totals a bit despite similar amounts of snow-water equivalent
precipitation as previous forecasts. Heavy snow is also expected
overnight Monday night into Tuesday morning for many of the area
mountains, including through Thompson, Turnagain, and Hatcher
Passes. For most areas, the heaviest precipitation will be Monday
night.

Towards the Cook Inlet Region, unfortunately with all of the
strongest forcing remaining west of the area for almost all of
the event, we will continue to see strengthening winds through
Turnagain Arm and the Knik River Valley. Issued a High Wind Watch
for Turnagain Arm and higher elevations for gusts to 75 mph,
highlighting Monday night into Tuesday morning. These strong
southeasterly winds will keep temperatures safely above freezing
in most areas, so chinook downsloping winds will once again take a
bite out of our dwindling snowpack. For the Valdez and Thompson
Pass area, think that the warm air should stay out of the area due
to strong southeasterly flow largely keeping that air out over
Prince William Sound. While the heaviest snow will be early
Tuesday morning, expect over a foot of wet snow. Downsloping
starting in earnest further north along the Richardson Highway
will warm things up there as well, with temperatures quickly
rising above freezing Monday night as gusty southeasterly winds
move into the Glennallen area. Warmed temperatures significantly
(more than 10 degrees) from the previous forecast Monday night
through Tuesday in Anchorage, the Valley, and into the Copper
River Basin.

A strong upper level shortwave will act as a broom of sorts,
sweeping away the precipitation from southwest to northeast
during the day Tuesday. Ahead of this shortwave, expect the
heavier precipitation rates to overcome the gusty southeasterly
winds through Anchorage and the Valley. Thus, a gusty driving rain
is expected for the Tuesday morning commute. Once the shortwave
passes through Tuesday morning, everything including the winds
will quickly dissipate and end. Ridging will build in right behind
it, strengthening over Southcentral through Tuesday night. Another
front will move into Kodiak Tuesday night causing a gusty driving
rain there through much of the night. The ridge likely holds
strong, preventing much northward progress of that front, but
guidance disagrees on how far north it gets. For now just a
chance of precipitation is forecast for Homer and along the Gulf
Coast.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3 - Today
through Wednesday morning)...

A weak front is pushing north over Southwest Alaska this morning
with a broad transition of snow to rain occurring over most
areas. Brief periods of freezing rain or a rain and snow mix have
been observed but have transitioned to all rain as warm southerly
winds increase behind the front. Warm temperatures will persist
as a deepening low moves over the Aleutian Chain this morning,
with its front reaching the Southwest coast this afternoon. With
strong southerly flow along the front and plentiful warm air
advection, rain is expected to be the main precipitation type for
the region. The Lower Kuskokwim Valley will be the last area to
hold on to it's cold air at the surface, so a brief period of
freezing rain is possible before the temperatures warm above
freezing this evening.

Cold air aloft will begin to wrap around the backside
of the low Monday afternoon, as another round precipitation moves
in from the south. The lift for this precipitation is enhanced by
the right entrance region of the jet as it moves overhead. Most of
the precipitation will fall as rain close to the Alaska and
Aleutian Ranges, with snow expected farther to the west. The
exact transition location remains uncertain but it does look like
most areas will receive some snow as cold air moves back in from
the west Monday afternoon into Tuesday morning. With an abundance
of moisture and residual warm air, this snow could be heavy. On
Wednesday, yet another north Pacific low moves over the Aleutians
and into the Bering, bringing another likely round of mixed
precipitation.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3 -
Today through Wednesday morning)...

The High Wind Warning for the Central Aleutians has been cancelled
as a result of a significant shift in the storm track to the
east. It remains in effect for the Eastern Aleutians with the
strongest winds expected in Nikolski and Akutan. This storm will
be a quick hitter, with the strongest winds expected between 11am
and 2pm. Gusts to 75 mph are possible in Unalaska, mainly as a
result of the isallobaric winds and some cold air advection on
the backside of the low and moderate jet support. Any strong winds
that do occur will be short lived. The other area that will
receive strong winds today is Cold Bay, where channeling has
resulted in sustained winds of 45 mph this morning. These are
expected to increase to 60 mph as the low passes through to the
west. As the storm travels to the north, winds will also increase
over the Pribilof Islands this afternoon, but are not expected to
be stronger than 50 to 60 mph. Monday should be mostly calm and
well above average for temperatures as the low slowly occludes and
moves north. On Tuesday a front extending east from a Kamchatka
low will moves east across the Chain bringing another round of
rain and gale force winds from Atka West.

&&

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

Gulf of Alaska:
A barrier jet along the Gulf coast is expected on Tuesday and
will weaken Tuesday night. Predominantly south to southeasterly
flow is expected in the Gulf through midweek as a ridge shifts
east and a North Pacific low approaches the Gulf. A front moving
through the Gulf on Wednesday will bring the potential for gales
through the western Gulf with the possibility for enhancement to
storm force winds through the Barren Islands. Winds may also bend
into Shelikof Strait. Another coastal barrier jet could return
Thursday evening. Precipitation is also expected with these
frontal passages. Seas about 10 feet on Tuesday will build through
Wednesday evening with the highest seas to around 17 feet,
associated with this front. Higher seas will be aimed towards the
western Gulf, south of Kodiak Island to the Kenai Peninsula.

Bering Sea/Aleutians:
Predominantly southerly flow is expected midweek as a front
enters the Western Bering Tuesday. Storm force winds will reach
the Western to Central Aleutians and gales stretching north into
the Bering on Tuesday. This front will track eastward through
Thursday with the passage of a northward moving low. Gales are
expected through midweek with some enhancement through bays and
gaps. Plenty of warm, southerly moisture will wrap into this low
and bring widespread precipitation through midweek. By Thursday
afternoon, another, less vigorous low follows into the Bering.
Seas up to 18 feet with the strongest winds near the front through
Wednesday in the Bering. On the Pacific side, seas will be
widespread 15 to 20 feet for the Western and Central Aleutians.

&&

.Long Term Discussion (Days 4 through 7: Wednesday through
Saturday)...

A couple of key features in the long term include a strong upper
level ridge along an axis that extends from the northern Gulf of
Alaska northward over the North Slope, and a broad upper level
trough over the western Bering. Several upper level waves in
between these two features will lift from south to north over the
central Bering, introducing widespread precipitation across the
Bering and Southwest Alaska. This pattern will also bring a surge
of warmer, southerly flow across much of the southern part of the
state as well as the Alaska Peninsula and Aleutians. By Friday,
the broad upper level trough that initially started out over the
Bering shifts eastward, laying down tracks for several North
Pacific lows to lift inland over Southcentral through next
weekend. Overall, an active pattern will continue through the next
week. By the weekend, a much colder airmass will settle in place
over the western Bering while a warmer airmass will remain parked
over the northern Gulf.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning 185.
High Wind Watch 101.
Dense Fog Advisory 101.
MARINE...Storm Warning 165 170 172 174 414.
Gale Warning 130 155 171 173 175 176 178 179 180 181 185 411 412 413.
Heavy Freezing Spray Warning 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...ED
SOUTHCENTRAL ALASKA...JW
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CJ
MARINE/LONG TERM...VR/KO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
121 PM AKST SUN FEB 20 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1139 AM     NON-TSTM WND GST 35 WSW AKUTAN           53.90N 166.54W
02/20/2022  M72 MPH          PKZ171             AK   ASOS

            SPECIAL REMARK IN METAR FOR OBS WIND AT
            UNALASKA AIRPORT: 130 DEG 72 KTS AT 2039Z.

&&

RUX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
122 PM AKST SUN FEB 20 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1139 AM     NON-TSTM WND GST 35 WSW AKUTAN           53.90N 166.54W
02/20/2022  M83 MPH          PKZ171             AK   ASOS

            CORRECTS PREVIOUS NON-TSTM WND GST REPORT
            FROM 35 WSW AKUTAN. SPECIAL REMARK IN METAR
            FOR OBS WIND AT UNALASKA AIRPORT: 130 DEG 72
            KTS AT 2039Z.

&&

RUX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
139 PM AKST SUN FEB 20 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1148 AM     NON-TSTM WND GST 35 WSW AKUTAN           53.89N 166.53W
02/20/2022  M92 MPH          ALEUTIANS WEST     AK   MESONET

            MESONET DUTCH HARBOR PORT OBSERVATION SSE
            WIND GUST MEASURED AT 79.6 KTS.

&&

RUX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
147 PM AKST SUN FEB 20 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1151 AM     NON-TSTM WND GST 35 WSW AKUTAN           53.89N 166.54W
02/20/2022  M79 MPH          ALEUTIANS WEST     AK   MESONET

            MESONET AT DUTCH HARBOR PILOT STATION
            RECORDED ESE WIND GUST OF 68.5 KTS.

&&

RUX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
158 PM AKST SUN FEB 20 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1139 AM     NON-TSTM WND GST 35 WSW AKUTAN           53.90N 166.54W
02/20/2022  M83 MPH          ALEUTIANS WEST     AK   ASOS

            CORRECTS PREVIOUS NON-TSTM WND GST REPORT
            FROM 35 WSW AKUTAN. SPECIAL REMARK IN METAR
            FOR OBS WIND AT UNALASKA AIRPORT: 130 DEG 72
            KTS AT 2039Z.

&&

RUX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
258 PM AKST SUN FEB 20 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0212 PM     NON-TSTM WND GST 2 WNW NIKOLSKI          52.97N 168.85W
02/20/2022  M87 MPH          ALEUTIANS WEST     AK   MESONET

            CORRECTS PREVIOUS NON-TSTM WND GST REPORT
            FROM 2 WNW NIKOLSKI. MESONET STATION NKLA2 1
            WNW NIKOLSKI. PEAK GUST REPORTED AT 1002.
            GUSTS OF 70 PLUS BEGAN AT 0922 AND THE FIRST
            GUST OF 80 PLUS BEGAN 0952. WIND GUST
            REPORTED AT 1152 WAS 82 MPH AND THE
            FOLLOWING 3 OBS HAD MISSING WIND DATA.
            SUSTAINED WINDS REGULARLY OCCURRING ABOVE 40
            MPH. SUSTAINED WINDS OF 60 PLUS FOR 20
            MINUTES 0942 TO 1002. NEW PEAK GUST 87 MPH
            AT 1412.

&&

RUX