Storm Warning 158, NWS Anchorage, AK

063 
FZAK62 PAFC 301243
OFFALU

Offshore Waters Forecast
National Weather Service Anchorage AK
343 AM AKST Sun Dec 30 2018

Offshore Waters Forecast for the Bering Sea

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent an average of the highest
one-third of the combined wind wave and swell height.

PKZ499-310200-
343 AM AKST Sun Dec 30 2018
.SYNOPSIS FOR CENTRAL BERING SEA...

A 980 mb low at 45N 169W moves to 58N 162W at 957 mb and continues
to 68N 167W at 980 mb Tue morning. A 947 mb low near 51N 176E Sun
morning and a 981 mb low at 45N 166W Mon morning merge to form a 
947 mb low near 58N 159W Tue morning. Its front moves across the 
Aleutians into Western Alaska by Tue morning.

$$

PKZ411-310200-
Bering Sea Offshore West of 180 and East of the International
Dateline-
343 AM AKST Sun Dec 30 2018

...GALE WARNING THROUGH TONIGHT...

.TODAY...NE wind 30 to 45 kt. Seas 22 to 31 ft. Snow.
.TONIGHT...N wind 25 to 35 kt. Seas 18 to 23 ft. Freezing spray.
Snow.
.MON...NW wind 15 to 30 kt. Seas 12 to 17 ft. Freezing spray.
Snow.
.MON NIGHT...N wind 10 to 20 kt. Seas 10 to 18 ft.
.TUE THROUGH WED...W wind up to 20 kt. Seas 7 to 12 ft.
.THU...E wind up to 15 kt. Seas 5 to 9 ft.

$$

PKZ412-310200-
Bering Sea Offshore 171W to 180 and North of 56N-
343 AM AKST Sun Dec 30 2018

...GALE WARNING TODAY...

.TODAY...W of 174W, NE wind 25 to 40 kt becoming N 15 to 30 kt in 
the afternoon. E of 174W, S wind 30 to 45 kt diminishing to 20 to 30 
kt. Seas 15 to 28 ft. Snow.
.TONIGHT...NW wind 15 to 30 kt. Seas 11 to 19 ft.
.MON...NW wind 10 to 25 kt. Seas 8 to 16 ft.
.MON NIGHT...N wind 20 kt. Seas 9 to 13 ft.
.TUE THROUGH WED...NW wind 15 to 30 kt. Seas 8 to 13 ft.
.THU...E wind up to 15 kt. Seas 5 to 8 ft.

$$

PKZ413-310200-
Bering Sea Offshore 171W to 180 and South of 56N-
343 AM AKST Sun Dec 30 2018

.TODAY...S wind 10 to 25 kt. Seas 12 to 20 ft.
.TONIGHT...NE wind 15 to 30 kt. Seas 11 to 18 ft. Rain showers.
.MON...NW wind 15 to 30 kt. Seas 10 to 16 ft. Rain showers.
.MON NIGHT...NW wind 15 to 25 kt. Seas 11 to 16 ft.
.TUE THROUGH WED...W wind 10 to 25 kt. Seas 9 to 16 ft.
.THU...E wind up to 15 kt. Seas 7 ft.

$$

PKZ414-310200-
Bering Sea Offshore East of 171W-
343 AM AKST Sun Dec 30 2018

...GALE WARNING THROUGH TONIGHT...

.TODAY...S wind 25 to 40 kt becoming SE 15 to 30 kt in the
afternoon. Seas 11 to 19 ft.
.TONIGHT...SW wind 25 to 40 kt. Seas 9 to 14 ft.
.MON...S wind 10 to 25 kt. Seas 7 to 12 ft.
.MON NIGHT...S wind 10 to 25 kt. Seas 8 to 13 ft.
.TUE THROUGH WED...W wind 15 to 30 kt. Seas 9 to 17 ft.
.THU...SE wind up to 15 kt. Seas 4 to 9 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
617 AM AKST Sat Dec 29 2018

.ANALYSIS AND UPPER LEVELS...

A deep, negatively tilted trough extends from Norton Sound
through the southern Gulf. This trough continues to shift
eastward, becoming more negatively tilted with time. Cold, polar
air is moving over the eastern and central Bering around the
trough with the coldest air advecting over the western mainland.
At 300 mb, the jet stream is in a zonal flow pattern with a slight
ridge in the jet occurring over the western mainland. The jet
position and the thermal packing on the western edge of the Alaska
Range, marks the area of a polar front that extends from east of
Sleetmute south into the northern Gulf. With convective support,
moisture from the Bering and cold air driving the front, snow is
falling throughout western mainland. Gusty conditions persist
through the AK-Pen, Bristol Bay and lower Kuskokwim Valley behind
the front. Shifting eastward, a meso low over the northwestern
Gulf is creating southeasterly flow into Southcentral. The influx
of moisture around this low combined with a column of cold air is
causing showers to occur throughout Southcentral and the northern
Gulf.

A deepening vertically stacked low is positioned over the western
Aleutians this morning. This low is producing a front that is
extending over the western and central Aleutians. Behind the
front an area of strong winds, referred to as a sting jet, has
formed on the convergent side of the flow around the low. Within
the sting jet, scatterometer passes detected storm force winds
over the western Aleutians including Shemya and Adak over night.
Hurricane force winds are possible with this system. Satellite
imagery shows the low well as a textbook cyclonic rotation over
the western Aleutians, while the front is displayed as a swath of
northwesterly oriented cloud cover over the central Aleutians.

&&

.MODEL DISCUSSION...

Models are in good agreement early on in the period, especially
regarding the location and strength of the low in the west. Models
have started to take this low on a more westerly track but remain
consistent through Sunday. On the other hand, the models struggle
with a North Pacific low moving over the central Aleutians
Saturday night. The EC is the fastest and more northerly
progressing solution while the GFS remains the model with the
strongest winds. This low is also quite deep but there is
discrepancy on the placement and the overall strength of the
system through Sunday. Sunday afternoon, yet another low moves
over the eastern Aleutians, and models continue to lock onto a
definitive progression as it tracks northward. Given the model
variability, confidence at this point is low with this system.

&&

.AVIATION...
PANC...Snow this morning will keep conditions bouncing between
MVFR and IFR as the heavier snow showers move through. Snow will
start tapering off this afternoon with light wind and VFR conditions
prevailing this evening through tonight. The next frontal system
will approach from the southwest Sunday morning with some brief
light snow possible. Increasing southeasterly flow will likely
downslope out precipitation and keep conditions VFR through Sunday
afternoon, though introduced the concern of low level wind shear and
increasing Turnagain Arm winds.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Monday night)...

The upper trough approaching Southcentral this morning is moving a
little slower than models had indicated, so snowfall will persist
longer over Southcentral today. With several forcing mechanisms,
an elongated short-wave and the much stronger negatively tilted
upper trough chiefly among them. Thus, there are bands of snow
and the snowfall won't necessarily be continuous. Expect snow to
taper to a few showers by midday from the Kenai Peninsula to
Anchorage, then diminishing across the remainder of Southcentral
during the afternoon hours. A blizzard warning remains in effect
from Homer to Anchor Point until 9 am. Winds were slow to develop
while snowfall has been mostly light and intermittent. There is
still a chance for steadier snow this morning as the upper trough
moves through and colder air advects in (possibly leading to some
"lake- effect" type snow showers). In any case, snow accumulation
across the region will generally be light with 1 to 4 inches
covering most of Southcentral.

Next up in this fast moving pattern, a front extending from an
Aleutian low will move into the western Gulf/Kodiak Island tonight
then northward to Southcentral on Sunday. While warmer air will
change snow to rain for Kodiak Island, the arctic air mass in
place over Southcentral will ensure precipitation stays mostly
snow (with the exception being the Gulf coastline). Despite
strengthening southeast low level flow ahead of the front, flow
will veer with height to south to southwest above 850 mb. Thus,
may see a quick shot of light snow from the western Kenai to
Anchorage and the Matanuska Valley before southeast flow and
downslope drying strengthens ahead of the next storm system
moving up from the Pacific. There is also potential for severely
reduced visibilities in snow and blowing snow beginning Sunday
morning for Portage, eastern Turnagain Arm and portions of the
Seward Highway corridor. With recent large fluctuations in model
guidance, confidence in the details of these storm systems has
been low, so will wait one more model cycle to make a final
decision on whether to issue a Winter Weather Advisory or
Blizzard Warning for this.

All eyes will then turn to what could be the most impactful storm
system of the bunch. It is looking more and more likely that a
deep low will track up from the Pacific Sunday and continue
northward across Southwest Alaska Sunday night into Monday
morning. This track screams "chinook" and potential windstorm,
especially for Anchorage and the Matanuska Valley. Once again,
confidence in track and depth of this system is low, but based
on some of the latest solutions there is good potential for high
winds in Turnagain Arm and higher elevations of Anchorage, with
some potential for strong and damaging winds moving into town.
These winds will also result in significant warming across the
entire region. The latest forecast has trended significantly
stronger with the wind and temperature forecast. With such strong
southeast winds, expect downslope drying for most of the western
Kenai Peninsula, Anchorage, Matanuska Valley, and eastern Susitna
Valley Sunday night through Monday morning. Meanwhile, heavy
precipitation is expect along the Gulf coast and Prince William
Sound along with the west side of Cook Inlet and the western
Susitna Valley.

Yet another strong storm looks like it will move up from the
Pacific into the Gulf sometime Monday or Monday night. With a
completely different storm track than the prior system, observed
weather will be significantly different. The commonality will be
another system with strong winds and heavy precipitation.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Monday)...

Beneath clear skies, much of Southwest is currently enjoying the
calm before the storms, though temperatures are definitely on the
cold side with interior portions of the Kuskokwim Valley and
Bristol Bay seeing temperatures around 10 below so far. Along the
coasts, temperatures are around zero. This cold air will prove
pivotal to helping keep the precipitation mostly snow for this
first of two systems. High clouds are approaching the coast
already this morning in association with a strong front tracking
northeastward across the Bering towards Southwest Alaska. The
clouds will thicken through the day as the front approaches. The
first snow from this front will take until this evening to arrive
at the coasts, and longer to spread inland. Once the front
reaches the area, snow will become increasingly heavy as the
winds ramp up at the same time. With the expectation of
potentially heavy snow and strong winds, Blizzard Warnings have
been issued for both the Kuskokwim Delta and the Bristol Bay
areas. The worst conditions are expected along the coast of the
Kuskokwim Delta and Nunivak Island. Further south, the worst
conditions are expected along the western Capes west of
Dillingham. That being said, since the front will survive some
ways inland, most everywhere away from the Alaska Range is
expected to get at least some snow and gusty winds are also
expected to make it well inland. Thus, blowing snow resulting in
reduced visibilities can be expected even outside of the Blizzard
Warning areas. Due to upslope and proximity to the low, the most
snow is expected from Koliganek west in the Bristol Bay zone, and
west of Bethel in the Kuskokwim Delta zone. Once the front moves
inland Sunday morning, conditions will rapidly improve over all of
Southwest Alaska from south to north. The winds will also weaken
a bit behind the front, but gusty southerly winds will persist
over all of the area through the day on Sunday. As is typical with
southerly winds, the front will also be transporting much warmer
air into Southwest Alaska, so high temperatures area-wide will
recover at least to the freezing mark. Southeasterly downslope
winds through the Alaska and Aleutian Ranges should lead to more
40s for highs in King Salmon and points south.

Leading forecast models are coming into much better agreement on
the development and intensification of another strong low on
Sunday south of the Alaska Peninsula that is expected to track
straight northward towards the Western Capes of Bristol Bay Sunday
afternoon and evening. This time with little to no cold air left,
as the low tracks north, a good bit of the Bristol Bay area in
particular will see plain rain as the low moves into the area.
While the models are improving, there remains a significant amount
of uncertainty as to the exact track of the low, how warm it will
get, and where the worst impacts from the storm will be.
Nevertheless, this storm too may be capable of near warning
criteria wind gusts once the low center passes. Thus, many areas
will see a blowing rain, and more gap winds will enhance strong
winds through the Kamishak Gap. The models are in general
agreement that the center will track right into the Kuskokwim
Delta late Sunday night, which, if the track persists, should mean
the only land on the cold side of the storm may be the coast of
the Kuskokwim Delta and Nunivak Island. Thus, there is potential
for blizzard conditions to return to those same areas again Sunday
night. Model uncertainty rapidly increases in the wake of this
storm, with the possibilities for New Year's Day weather ranging
from a third strong low tracking near Shelikof strait putting
Bristol Bay and the Lower Kuskokwim Delta on the cold side of the
low, to relatively quiet weather with rain and snow showers taking
over until another Bering low approaches on Tuesday followed by
the return of cold air.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Today
through Monday)...

In the western Bering, a very strong low over the western
Aleutians remains the primary weather maker over the region this
morning. It is producing hurricane force winds across the islands
and the waters on both sides of the Aleutians. Over the Bering,
the hurricane force winds and gusts are out of the northeast,
gusting down into Shemya, while on the Pacific side, the "sting
jet" winds are gusting to hurricane force out of the southwest.
The low is nearing peak intensity now as it stalls out over the
area. With the center approaching Shemya now, the hurricane force
winds will subside through the morning, with the High Wind Warning
expiring at 9am. Meanwhile, snow associated with the leading front
have moved into the Pribilof Islands, which in addition to the
strong winds are causing near-blizzard conditions. With more
precipitation and winds to come, a Blizzard Warning remains in
effect through the day.

Zephyrs, or soft gentle breezes, will be non-existent over the
Bering as a developing low forms along the front over the
Aleutians between Unalaska and Atka this afternoon. This will
intensify the snow ongoing across the Pribilofs this evening. The
low will also bring much warmer air across the islands, which may
lead to the snow mixing with rain as the front goes by this
evening, especially in Saint George. The winds and snowfall rates
will rapidly diminish as the front crosses the islands between 9pm
and 3am tomorrow morning. Behind it, the winds will intensify once
again this time out of the southwest to similar levels as ahead of
the front. While any precipitation behind the front may mix with
or be all rain, the strong winds may re-suspend the already
fallen snow over the area into the morning. Thus, the Blizzard
Warning has been extended until 6am to include this dramatic shift
in winds. Yet another low develops south of the Alaska Peninsula
Sunday morning and will cross the Peninsula Sunday afternoon.
While precipitation with the low should be mostly rain at sea-
level, this low will also be strong and near-hurricane force winds
will be possible. Especially as the low over the Pacific and
Bering tracks northward past Cold Bay this afternoon and into
Southwest Alaska Sunday evening. Meanwhile, the first low, the one
currently over the western Aleutians will begin to slowly track
eastward along the Aleutians Sunday night into Monday. Behind the
low, much colder air returns to the Bering, sweeping from west to
east across the Bering, which should return most of the Bering to a
cold, snow showery pattern going into midweek.

&&

.LONG TERM FORECAST (Days 3 through 7)...

The run to run consistency with the global models has been poor.
Generally speaking, anticipate a wet pattern for this forecast
period for the southern tier of Alaska with the possibility of a
rain/snow/freezing rain mix for Southwest Alaska. The forecast
period commences Monday Dec 31st with a broad trough over the
Bering and Aleutians and a high amplitude ridge from the Eastern
Pacific to British Columbia. Meanwhile at the surface at 12z
Monday, both the GFS and the ECMWF have a potent low now north of
the chain between Unalaska and Adak. And the GFS has a specious
cyclone near St Matthew Island that the ECMWF doesn't have at all.
South of the chain the models have an additional low but the
position of the GFS feature is more than 100 NM from the ECMWF's
position. Both models show this feature moving towards the Gulf of
Alaska. The lack of consensus is echoed at 500 mb at 12z Monday,
which compounds with time. The timing of the precipitation shield
and the gusty winds is dependent the placement of the lows that
develop and on the ensuing track. There was a hefty amount of
blending and hedging this forecast period as a result of the models
poor performance record.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning: 121 155 161 195.
         High Wind Warning: 191.
MARINE...Hurricane Force Winds: 178 411.
         Storms: 130 155 172 177 180 181 185 412 413 414.
         Gales: 119 120 131 132 136 137 138 139 141 150 160 165
                170 171 173 174 175 176 179 351 352.
         Heavy Freezing Spray: 130 138 160 179 180 185 412 414.

&&

SYNOPSIS AND MODEL DISCUSSION...RA
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JPW
LONG TERM...PS

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
1144 AM AKST SAT DEC 29 2018

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

1114 AM     SNOW             16 S KNIK               61.22N 149.78W
12/29/2018  E3.0 INCH        ANCHORAGE          AK   TRAINED SPOTTER

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1200 PM AKST SAT DEC 29 2018

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

1159 AM     SNOW             5 NE FRITZ CREEK        59.78N 151.17W
12/29/2018  E4.0 INCH        KENAI PENINSULA    AK   TRAINED SPOTTER

            BLOWING SNOW WITH LOW VISIBILITY.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1246 PM AKST SAT DEC 29 2018

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

1150 AM     NON-TSTM WND GST 2 SSE COLD BAY          55.20N 162.72W
12/29/2018  M79 MPH          ALEUTIANS EAST     AK   ASOS

            64 MPH SUSTAINED GUSTING TO 79 MPH. 1/4SM
            VISIBILITY WITH HEAVY SNOW. WINDS OUT OF THE
            SE (150).

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
356 PM AKST SAT DEC 29 2018

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

0354 PM     SNOW             LAKE OTIS & HUFFMAN     61.11N 149.83W
12/29/2018  E5.0 INCH        ANCHORAGE          AK   PUBLIC

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
357 PM AKST SAT DEC 29 2018

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

0356 PM     SNOW             WASILLA                 61.58N 149.46W
12/29/2018  E3.0 INCH        MATANUSKA-SUSITNA  AK   PUBLIC

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
409 PM AKST SAT DEC 29 2018

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

0408 PM     SNOW             6 SSE EAGLE RIVER       61.27N 149.48W
12/29/2018  E2.0 INCH        ANCHORAGE          AK   PUBLIC

&&