Heavy Freezing Spray Warning 234, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
449 PM AKST Tue Dec 28 2021

.ANALYSIS AND UPPER LEVELS...

An expansive upper level ridge is over almost all of Southcentral
this afternoon, with its axis aligned right up Cook Inlet into the
Susitna Valley. A potent shortwave at the leading end of a 160-170
kt southwesterly jet streak over the Bering is causing the rain
that had been moving over Southwest Alaska and is now approaching
Southcentral. A large area of subtropical high pressure (591 dm)
is over the central Pacific, helping drive the unusually warm air
northward into Alaska.

A cold front associated with the aforementioned shortwave is
driving into the Alaska Range this afternoon. Most of the
associated precipitation is plain rain, as temperatures are in the
mid 30s to low 40s across Southwest Alaska.
For Southcentral, we continue to have an inversion sounding set up
over the area, with temperatures well into the 40s at higher
elevations of the Hillside, while temperatures in the Bowl are in
the mid to upper 20s. Thus, the atmosphere is set up for
additional freezing rain for the Bowl when the precipitation gets
here later this afternoon/this evening.

&&

.MODEL DISCUSSION...

The models are in excellent agreement through Thursday afternoon
on the large scale weather pattern. Overall we are finally seeing
a breakdown of this warmer pattern that is keeping freezing rain
in the forecast for portions of Southcentral, and we'll be moving
back towards a snowy and colder pattern. The main concerns for the
very short term will be precipitation type and final ice
accumulations for Anchorage and points north this evening. The
models are also in good agreement, but changed from previous runs
regarding when snow (and it's a high likelihood it will be all
snow away from the coast) Thursday night into Friday, delaying the
start time of the precipitation until later into Thursday night.
On the other end of the event however, the models are hinting at
snow persisting well into Friday night or even Saturday morning,
which is quite a bit longer than previous runs. Overall forecast
confidence is a bit above normal, as things look set for tonight's
event, and an all or mostly snow event away from the coast come
Friday is somewhat easier to forecast than the mixed precipitation
events we have seen this past Sunday through tonight.

&&

.AVIATION...
PANC... Pockets of freezing rain are expected late this afternoon
through this evening as a fast moving wave overspreads a highly
stratified layer, with temperatures currently in the 20s in the
Bowl, but in the 40s along the Hillside. During the freezing rain
conditions will fall to MVFR to briefly IFR at times if any
heavier showers move through. Fortunately, because the wave is
fast-moving, the precipitation should be mostly over by mid-
evening, with colder air moving in potentially making for a period
of either freezing drizzle or snow as the colder air squeezes out
additional moisture from the atmosphere. A period of wind shear is
expected overnight into Wednesday morning as southerly winds out
of Turnagain Arm are overspread by gusty northwesterly wind aloft.
All the winds diminish Wednesday morning with VFR conditions
returning along with somewhat colder temperatures.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through
3; Tonight through Thursday night)...

The latest forecast remains on track for Southcentral this
evening. An upper low located over the northern Bering, which
brought a warm front through the region earlier this morning, will
keep upper-level temperatures more than warm enough for
precipitation to fall as freezing rain into tonight. In fact the
greater question now concerns whether some locations may warm to
above freezing and stay above freezing before a cold front sweeps
across the region early Wednesday. Many areas across Anchorage are
sitting just above freezing due to southerly winds making it into
town this evening, but will likely drop to at or below freezing
with any northerly pushes of wind. Latest radar shows scattered
showers are already ongoing over Southcentral from Talkeetna
through the Anchorage Bowl into Prince William Sound. Additional
showers will move into Southcentral through the evening hours.
Potential ice accumulations will range from a trace to a tenth of
an inch, with locally higher amounts of up to two- tenths of an
inch also possible. This will promote icy roads and hazardous
driving conditions. A cold front will quickly pass through
Southcentral early Wednesday morning with any lingering
precipitation to transition to all snow. Minimal snow
accumulations are anticipated for the Mat-Su southward as
precipitation should already be waning during that time period.
Instead, any meaningful snow accumulations will be confined to the
higher elevations of the Talkeetnas and Chugach Mountains.

Late Wednesday into Thursday a fast moving shortwave trough is
forecast to track across Kodiak Island with a quick shot of a
snow/rain mix. No accumulations are expected at this time and
winds should be subdued. Attention then turns to Thursday as a
pattern change finally comes to fruition. The stubborn subtropical
ridge previously over the Eastern Aleutians and Alaska Peninsula
will be in the process of sliding southeastward and into the North
Pacific. This, as a new low pressure system amplifies over the
Bering. This next low is forecast to bring an occluded front into
Southcentral Thursday into Friday with a triple point low forming
over the northwest Gulf. Our previously warm temperatures will
exit the Gulf to the east with a colder airmass in place to take
advantage of increasing precipitation across Southcentral Thursday
night into Friday. Snow showers are forecast across most areas,
perhaps excluding Kodiak further to the south. Several inches of
snow will be possible but confidence in snow amounts remains low
at this time. There are still some uncertainties in the forecast
with regard to exact timing and intensity of snow; however,
precipitation type is not one of those concerns and any
precipitation should fall entirely as snow.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Ton
through Fri)...

A frontal boundary over Southwest will continue to dump steady
light rain across the eastern parts of Kuskokwim Delta, and from
Bristol Bay through the lower Kuskokwim Valley this evening. Dry
air trailing behind the front will invite clear to partly cloudy
skies from west to east tonight through Wed morning. A lot of
moisture seen on the satellite extends across the lower Kuskokwim
Valley this afternoon and the bulk of it could likely erode as it
shifts over the Alaska Range this evening. Temperatures will
fluctuate in the 20s to mid 30s the next couple days, as warm
airmass continues to push through the area through Thu night
followed by the onset of cold polar air advection between Fri
morning and Fri night.

The next frontal system from the eastern Bering may enter
Southwest Alaska as early as Thu afternoon if not sooner, which
could bring increasing cloudiness, steady rain over parts of
Southwest Coast and potentially rain/snow mix along the northern
Kuskokwim Delta and wintry weather through the lower Kuskokwim
Valleys between Thu and Fri. Light rain could likely spread more
inland but with the cold air quickly filling the Kuskokwim Delta
Fri afternoon through Fri night may reduce the chance for rain
leading to mostly snow for areas from Kuskokwim Delta through
lower Kuskokwim Valleys on Fri.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Tonight through Friday)...

The expected big event for the short term is the onset of the
North Pacific low Wed night. This next system will provide gales
for the Bering/Aleutians starting Wed night through Fri night,
reaching Pribilofs potentially by Thu night and Fri morning.
Large seas of 20 ft or more associated with the low will remain
south of the Aleutian Chain and along the southern Bering through
at least Fri afternoon. Warm tropical moisture and southwest winds
will aid to bringing a wet spell over much of the Aleutians with
rain/snow mix as cold air advection spills southward past Pribilof
Islands Thu night into Fri morning. Meanwhile, another front
pushes through the western Aleutians and could bring gales there
into Fri evening. Overall, an active weather pattern is expected
to maintain multiple headlines for the Bering/Aleutians, including
freezing spray.

&&

.MARINE (Days 3 through 5: Friday through Sunday)...

Bering...A low in the Eastern Bering tracks across the AKPEN
Friday. Winds will be northerly across the Central and Eastern Bering,
peaking at high-end gales on the backside of the low. As the low
exits into the Gulf, storm-force gap winds and heavy freezing
spray are possible south of the AKPEN late Friday through early
Sunday. In the Western Bering, a strong front will bring southerly
gales and areas of storm-force winds Friday through Sunday. Seas
will be mostly 8-15 ft except 15-25 ft where gales are expected.

Gulf of Alaska...Winds increase to widespread small crafts Friday,
with a gale-force barrier jet along the northern Gulf Friday
morning. Gusty outflow winds intensify to gales early Saturday
and persist through Sunday, with storm-force winds likely through
Kamishak Gap. Heavy freezing spray is possible with these strong
and cold outflow winds. Seas 10 ft and lower Friday increase to
15-25 ft Saturday and Sunday.

&&

.LONG TERM FORECAST (Days 4 through 8: Saturday through
Tuesday)...

An upper-level ridge in the Bering moves eastward into Alaska
through Tuesday, transitioning the weather towards cold and mostly
dry conditions. On Saturday, an upper-level trough over Alaska
and a surface low in the Gulf will produce snow over Southcentral
and drive gusty gap winds. As the low moves out of the Gulf
through Saturday, snow will slowly taper off. Cold, northerly gap
winds out of the AKPEN and northern Gulf Coast will continue
through Monday due to high pressure over the interior and ridging
in the Eastern Bering. Cold air advection and clearer skies at
night will allow temperatures to drop below negative during the
weekend.

Behind the upper-level ridge, a strong warm front brings rain and
southerly winds as it tracks across the Aleutians through
Tuesday. Some uncertainty remains with how quickly the front will
move east. However, temperatures warm by Tuesday across Southwest
as the front approaches.

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC... Winter Weather Advisory 101 111 121 141 145.
MARINE...Gale Warning 119 120 129-131 139 141 173-178 181 185
					  351 411-414.
		 Heavy Freezing Spray Warning 181.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
MARINE/LONG TERM...KC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1041 PM AKST TUE DEC 28 2021

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

0200 PM     FREEZING RAIN    KENAI                   60.56N 151.21W
12/28/2021  U0.01 INCH       KENAI PENINSULA    AK   NWS EMPLOYEE

            NWS EMPLOYEE REPORTED DRIVING CONDITIONS
            WERE BAD FROM KENAI SPUR TO SOLDOTNA WITH
            FREEZING RAIN, LARGE DROPLETS. AIR TEMP 22
            DEG. TIME ESTIMATED AND RECEIVED A COUPLE
            CALLS.

&&

RUX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1042 PM AKST TUE DEC 28 2021

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

0435 PM     FREEZING RAIN    STERLING                60.52N 150.80W
12/28/2021  U0.01 INCH       KENAI PENINSULA    AK   PUBLIC

            PHONE CALL CAME IN ABOUT SOLID RAIN FROM
            KENAI TO SOLDOTNA TO STERLING WITH AIR TEMP
            31 DEG AND VERY SLICK ROADS. ALSO REPORTED
            THAT THE SPUR HWY WAS CLOSED ABOUT AN HOUR
            PRIOR AND ROADS SEEM TO ALSO BE SANDED. TIME
            ESTIMATED.

&&

RUX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1048 PM AKST TUE DEC 28 2021

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

0145 PM     FREEZING RAIN    1 SSE ANCHORAGE         61.20N 149.89W
12/28/2021  U0.01 INCH       ANCHORAGE          AK   PUBLIC

            PUBLIC PHONE CALL FROM SOMEONE IN THEIR
            VEHICLE DOWNTOWN MENTIONING RAIN FALLING.
            TEMPERATURES FROM OBS NEARBY ABOUT 31
            DEGREES. TIME ESTIMATED.

&&

RUX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1053 PM AKST TUE DEC 28 2021

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

0200 PM     FREEZING RAIN    5 SW ANCHORAGE          61.16N 149.99W
12/28/2021  U0.01 INCH       ANCHORAGE          AK   NWS EMPLOYEE

            RAIN WAS BEING HEARD ON THE ROOF AND RAIN
            WAS PARTIALLY FREEZING TO CAR SURFACES.
            NEARBY AIRPORT OBS ABOUT 31 DEGREES. TIME
            ESTIMATED.

&&

RUX