Small Craft Advisory 92, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
221 PM AKDT Tue Aug 14 2018

.DISCUSSION...
Main forecast concerns include the potential for high surf
conditions from Utqiagvik west and strong west to southwest winds
along the Arctic Coast as well as ongoing rainfall in parts of the
Interior. 24-hour rainfall totals over the Interior ranged from
0.25" to 1.25" with the heaviest totals in an area from the Upper
Koyukuk River to Fortymile Country including the Middle Tanana
Valley. High Surf Advisories for the Western Arctic Coast from
Utqiagvik (Barrow) west starting Wednesday morning. Strong wind
headlines are up for the Arctic Coast for Wednesday and Wednesday
night. Latest suite of model solutions are in fair agreement
during the first 24 hours but quickly show differences in respect
to the individual features strength and track beyond 24 hours.

Aloft...At 500 mb, a broad upper level trough extending from the
high Arctic south over Alaska and Gulf of Alaska will persist over
the next couple of days. A 547 dam low over Nunivak Island will
dig southward towards Port Moller and Sand Point through Thursday
morning with a piece of energy breaking off to travel northeast
into the Gulf of Alaska. A ridge of high pressure over Siberian
Russia will build east over the Chukchi Sea, Bering Strait, and
into the western Bering Sea through Wednesday night, but will then
be pushed south over Kamchatka Peninsula and the far western
Bering Sea by Thursday morning. A shortwave over the Seward
Peninsula will move south and weaken this evening. A 520 dam low
over Banks Island will move east into the Canadian Arctic
Archipelago through Thursday morning with several trailing
shortwaves in the west to northwest flow moving over the North
Slope. Another low will move southeast from 80N 165E to be 200 to
300 miles north of Utqiagvik by Thursday morning; however the trio
of GFS/ECMWF/NAM all have different solutions regarding this low
with the ECMWF being the more progressive of the three solutions.

North Slope and Brooks Range...Primary concerns include strong
west to southwest winds Wednesday into Thursday along the Arctic
Coast with high surf possible from Point Barrow west. West winds
will steadily increase from Point Barrow west after midnight
tonight and into tomorrow as a low moves southeast from 78N 170W
to Banks Island by tomorrow evening. Winds will peak around 20 to
30 mph sustained with gusts to around 45 mph. Latest surge
guidance continues to indicate elevated seas around one-half to
one foot thus significant coastal flooding will not be an issue
as high surf remains likely. Will keep the High Surf Advisories
the same as timing seems to be good with the uptick in wind
speeds. As the low moves east tomorrow, the gradient along the
Beaufort Sea Coast will tighten resulting in strong southwest
winds gusting up to 55 mph. Wind speeds are going to be close to
high wind warning criteria, current thinking is that the winds
will approach, but not exceeded the threshold. A front associated
with the eastward moving low will bring a chance for
precipitation to the North Slope as it initially passes with
additional precipitation likely through Thursday evening. At this
time, it looks like the warm atmospheric profile will support
rain, but could see some snow mixing in during the overnight
periods with diurnal trends.

Eastern and Central Interior...24-hour rainfall totals up to 1.00"
has been observed across the Eastern Interior through earlier
this morning. Rainfall amounts around between 0.50" to 1.5" have
been reported in Denali National Park. Periods of rain will
continue across the area into tonight for the Eastern Interior and
will taper off towards morning from west to east. Additional
rainfall amounts of up to 0.50" are possible. The exception will
be the Upper Tanana Valley where weak downslope conditions kept
rainfall amounts light. Will see river levels increase in response
to this latest round of rain over the next couple of days, but
are expected to remain below action stage. Areas of fog are likely
to develop in areas with breaks in overcast conditions tonight
and early Wednesday morning. High temperatures will remain below
normal, but will slowly warm by a couple degrees each day through
Friday returning near normal values by the weekend.

West Coast and Western Interior...Upper level ridge will nudge
into the Bering and Chukchi Seas over the next couple of days,
bringing a brief break to cloud and wet conditions. Strong north
winds have weakened over the Chukchi Sea and Bering Strait, but
remain gusty to around 35 mph over St Lawrence Island. Will
continue see to a downward trend through the evening. Temperatures
will remain near to slightly above normal through the rest of the
week.

Coastal Hazard Potential Days 3 and 4...None, but see North Slope
Section above for issues in the shorter term.

&&

.FIRE WEATHER...No issues anticipated. Periods of rain will
continue across the Eastern Interior and Alaska Range, except for
the Upper Tanana Valley where weak downslope conditions exist.
Minimum RH values will remain above 40 percent across most of the
area for Wednesday and Thursday as well (with the main exception
being the upper Tanana Valley, which will drop into the mid 30
percent range).

&&

.HYDROLOGY...Rises are expected on Interior rivers over the next few
days due to recent rainfall. Current thinking is that rivers will
remain below action stage.
&&

.AFG WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory for AKZ201-AKZ202.

Small Craft Advisory for PKZ210-PKZ220-PKZ225-PKZ230-PKZ235.

Brisk Wind Advisory for PKZ240-PKZ245.
&&

LTH AUG 18