Small Craft Advisory 22, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
245 AM AKDT Sat Apr 28 2018

.DISCUSSION...
Active spring weather pattern continues over northern Alaska with
a strong late season low moving northeast out of the southern
Bering sea into Norton Sound late Sunday and Monday.

A 995 mb low near Nunivak Island will move onshore today and
weaken rapidly over the west coast and will bring another round of
rain showers at lower elevations and snow showers at higher
elevations today and tonight. The low will continue to weaken into
a trough as it enters the western and central interior and will
bring light snow at higher elevations and rain to the lower
elevations today and tonight. Gusty gap winds will develop today
through he Alaska Range passes and will continue tonight as the
trough moves into the central interior.

Focus turns to a 992 mb low currently located 250 nm south of
Shemya as it moves rapidly north and east and combines with a 976
mb low moving east over the western Bering Sea. The lows combine
as a 976 mb low over the central Bering Sea tonight and continues
to deepen to around 972 mb as the low passes 300 nm south of St
Lawrence Island Sunday. A strong front moves onshore over the
lower YK Delta Sunday morning and pushes north and east into the
western interior. Strong winds are expected to develop along the
west coast and St Lawrence Island Sunday morning. Rain and rain
snow mix are expected over the west coast as the front moves on
shore. South to southwest winds will increase ahead of the storm
and combined with low pressure will produce elevated tide levels
along the west coast. Wind direction and speed will be changing
rapidly ahead of the storm and will help limit the potential for
high surf Sunday along the west coast. As winds shift to the west
and northwest as the low moves on shore in Norton Sound, model
guidance continues to show increased potential for high surf and
minor coastal flooding especially along the lower YK Delta coast
as well as the northern shore of St Lawrence Island. There remains
considerable spread on track and strength of this late season
storm. Small changes in the track of this low will result in
significant differences as to where and when the highest surf and
tide values are expected. See Coastal Hazard Potential section for
additional details.

The low moving on shore today over the lower YK Delta will weaken
into a trough and will produce gusty winds through the passes in
the Alaska Range. The low pressure system currently south of the
Aleutians will push a strong front through the lower YK Delta and
over the Alaska Range Sunday. As the front moves north over the
Alaska Range expect the gusty gap winds through the Alaska Range
to strengthen to Advisory levels especially in the eastern Alaska
Range where a southwest flow aloft favors a weak mountain wave
developing and enhancing the gap winds. A Wind Advisory has been
issued for this area. Will need to monitor the northern foothills
of the western Alaska Range from Farewell Lake to Healy as a
barrier jet is expected to develop and may mix down and strengthen
surface winds in these areas late Sunday and into Monday.

Model spread on the tack and strength of the low developing in the
central Bering Sea is considerable with low center placement
varying several hundred miles on model initialization at 00z and
verification at 06z. Model tracks vary between models by several
hundred miles into Sunday morning however the ECMWF has come in
line better with track and strength depicted by the GFS, NAM and
Canadian model.

Coastal Hazard Potential Days 3 and 4...Potential continues to
increase for high surf and minor coastal flooding for Scammon Bay
and Cape Romanzof, the lower Yukon Delta as well as the northern
shore of St Lawrence Island late Sunday night and through the day
Monday. Current surf guidance indicates water levels rising to 5
to 6 feet above mean low low water levels or 3 to 4 feet above
High Astronomical Tide levels as gusty west to northwest winds
develop in these areas as a deep low moves into eastern Norton
Sound during the day Monday. There remains considerable
uncertainty on the track of the low at this time. Small deviations
in the track of the storm will produce significant differences in
where the highest surf conditions will occur. A track of a
hundred miles further north would significantly increase the
potential for high surf and minor coastal flooding to eastern
Norton Sound. Continue to monitor for additonal updates.

&&

.FIRE WEATHER...Near Red Flag conditions will continue today and
Sunday near the Alaska Range as Gap winds develop later today.
Expect winds gusting to around 55 mph with Relative Humidity
values in the 30s. Chances of rain and snow showers will increase
through the weekend as moisture moves northeast into the interior
around a low moving east out of the Bering Sea into Norton Sound.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Advisory for AKZ226.

Small Craft Advisory for PKZ210.
&&

CCC APR 18