Small Craft Advisory 1006, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
639 AM AKST Sat Dec 28 2019

.ANALYSIS AND UPPER LEVELS...

A vertically stacked low moving into the northern Gulf is
bringing widespread snow to much of Southcentral. With the upper
jet positioned well to the east, lifting is not overly
significant, though temperatures are still cold enough aloft to
increase snow-to-liquid ratios such that totals may be on the
higher end of the forecasted amounts through Saturday.

Wind Chill Advisories remain in effect for the Kuskokwim Delta and
Bristol Bay areas. Strong high pressure over Siberia combined
with low pressures over the North Pacific/Gulf are leading to
gusty northerly winds across much of western Alaska. Though winds
will slightly diminish over Bristol Bay today, they will remain an
issue for the Kuskokwim Delta through the weekend as this
aforementioned pattern will generally stay put.

Two deep upper level lows, centered over the Kuskokwim Delta and
North Pacific respectively, are continuing to drive an active
pattern over the Bering. A large, deep surface low will likely
track towards the eastern Aleutians by early next week.

&&

.MODEL DISCUSSION...

Though subtle differences remain, models have come into a better
consensus this morning showing the Gulf low tracking east of
Prince William Sound. Blizzard conditions remain likely for
Thompson Pass and significant snow accumulations continue to be
expected for the Whittier/Valdez areas. Near-term forecast
confidence has significantly improved since yesterday. Another low
will move over Kodiak Island on Sunday evening. The GFS is again
farther east, bringing the center up Shelikof Strait whereas other
models keep the center track more directly over Kodiak Island.
Based on the previous event, the latter appears to be the most
likely solution, though impacts could greatly differ depending on
the exact track and thus confidence for this system remains below
average at this point.

&&

.AVIATION...

PANC...Conditions will likely range from VFR to IFR this morning
as snow showers move across the terminal. The snow is expected to
slightly taper off in the afternoon, potentially briefly
improving conditions to prevailing VFR. Another round of snow is
likely this evening, though with light winds, MVFR is the most
probable category.

&&

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

A low moving into Prince William Sound this morning is bringing snow
to most of Southcentral this morning. This low will move inland this
afternoon, and the snow will taper off to scattered showers. Another
low over the southern Gulf this morning will move north into
Southcentral tonight, brining another round of snow.
Another stronger system will approach Kodiak Island from the
southwest on Sunday, and move into the mainland Sunday night. This
system will bring warmer air to the area. Many coastal areas will
see a switch from snow to rain, while inland areas will see snow
but with warming temperatures.

&&

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

Brutally cold temperatures expected across the region as arctic
air holds in place. Overnight -27F was observed at Sparrevohn and
-12F at King Salmon. Wind Chill Advisories were kept in place for
the Kuskokwim Delta and Bristol Bay. The bone chilling temperatures
will continue into next week. Storms moving over the North Pacific
will usher moisture into the AKPEN and displace the arctic trough
axis. However the vortex of polar air will circulate over the
Eastern Bering and it merits continuous monitoring.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

On satellite imagery (Himawari Air Mass RGB) there are
discernible lows south of Sand Point and Attu Island. The cloud
shields from the respective frontal boundaries connect between
lows south of the Aleutian Chain. The pressure gradient force with
the low south of Attu/Shemya is fierce and it retains much of
this tenacity through the weekend bringing gusty winds, enhanced
seas and freezing spray to the region. A dome of high pressure
will approach the Western Aleutians Monday but looking upstream
there is already another cyclone churning up over the Sea Of
Okhotsk.

&&

.MARINE (Days 3 through 5)...
(Monday through Wednesday)

...Bering Sea and Aleutian Coastal Waters...

It looks like a moderately strong low will be south of or over
the Alaska Peninsula Monday producing a broad area of northerly
gales across the majority of the Bering Sea. This low moves over
the southern mainland through Wednesday morning. The northerly gales
will be east of the dateline by Wednesday morning and weakening to
sub gale force through Wednesday. Weak ridging builds into the
central Bering Sea Tuesday behind the low over the mainland and in
advance of a front moving into the western Bering Sea. This front
may bring gale force wind to the western Aleutians and western
Bering Sea Wednesday.

...Gulf of Alaska...

Models continue to struggle to resolve the structure and track of
the storm moving into the southern mainland Tuesday. The storm
may remain a single low or it may split into two lows. This
results in either gales to minimal storm force winds across the
Gulf of Alaska Monday or much weaker wind and lower wave heights.
The current thinking is to maintain the single low solution that
supports low end gales across the entire Gulf of Alaska Monday and
early Tuesday.

&&

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

...Southcentral...

Active weather will continue into the New Year as we remain in a
pattern of storms tracking from the North Pacific into the southern
mainland. As is typical of model performance with such an active
pattern, solutions vary considerably, especially in the mid to long
term time frame, thus confidence in model solutions remains low.
Beginning the work week, a storm is expected to pass across the
Alaska Peninsula into the southern mainland. The models have now
converged on a solution that keeps the low farther south than
previous runs. This means the warmer marine air will most likely
remain along the coastal side of the mountains and not make much
headway inland through Thursday. The models are consistent about
keeping the low along the North Gulf Coast Thursday and Friday.

A front is expected to push into the western Aleutians Monday
night. Tuesday a weak low is likely to form along this front south
of or just along the central Aleutians then dissipate. At this
point the models are not in good agreement at all other than
generally weak wind and benign conditions for the central
Aleutians and central Bering Sea Wednesday through Friday. The
western Aleutians and Bering Sea will be influenced by a low
remaining in the Sea of Okhotsk supporting a front or weak lows
transiting through the western Bering Sea.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning: 131.
         Winter Weather Advisory: 141.
         Wind Chill Advisory: 155 161.
         Flood Advisory: 145.
MARINE...Gale Warning: 119-121 127 128 130-132 138 139 150 155
                       160 165 172-181 185
         Heavy Freezing Spray Warning: 160 175 179-181 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AP
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PJS
MARINE/LONG TERM...TM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1034 AM AKST SAT DEC 28 2019

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

1032 AM     SNOW             PAXSON                  63.07N 145.51W
12/28/2019  E2.0 INCH        VALDEZ-CORDOVA     AK   DEPT OF HIGHWAYS

            SPOTTER REPORTED 2 INCHES OF SNOW BETWEEN
            LAST NIGHT AND THIS MORNING.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1046 AM AKST SAT DEC 28 2019

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

1042 AM     SNOW             21 E VALDEZ             61.13N 145.73W
12/28/2019  E10.0 INCH       VALDEZ-CORDOVA     AK   DEPT OF HIGHWAYS

            SPOTTER REPORTED 10 INCHES OF SNOW SINCE 6AM
            ON THE 27TH. ALSO REPORTED NE WIND GUSTS TO
            40MPH AND ZERO VISIBILITY AT TIMES.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1109 AM AKST SAT DEC 28 2019

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

1108 AM     SNOW             KENNY LAKE              61.72N 144.96W
12/28/2019  E6.0 INCH        VALDEZ-CORDOVA     AK   PUBLIC

            SPOTTER REPORTED APPROXIMATELY 6 INCHES OF
            SNOWFALL LAST NIGHT.

&&

ED