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Area Forecast Discussion (AFD)

Issued by Fairbanks, AK (AFG)

                            
064 
FXAK69 PAFG 132238
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
238 PM AKDT Mon Aug 13 2018

.SYNOPSIS...
An upper trough covers mainland Alaska and the northern Bering Sea
this afternoon. A strong surface low over the YK delta with a
surface boundary located from the low through Fairbanks to Dawson
City Yukon and point east remaining fairly stationary. Shower
activity will be located in the eastern section of the state with
more widespread rain for the west. An arctic boundary resides
along the Brooks range with areas of fog and stratus along with a
few light showers of rain and at times mixed snow.

Aloft...
The upper trough over the mainland of Alaska and northern Bering
Sea will continue over the region through Friday. A piece of the
upper trough cuts off on Wednesday afternoon and sinks into the
North Pacific by Friday. The upcoming weekend an arctic upper low
will push into the Russian far east with a strong upper low near
the end of the Alaskan Peninsula. This builds a ridge over the
eastern mainland of Alaska and the panhandle of Alaska. The
extended period the evolution of the upper low over the Alaska
Peninsula and the ridge over the Canadian Rockies battle of
dominance over the interior of Alaska.

Surface...
The strong 994 MB low over the YK Delta with surface front
stationary over the central and eastern interior extending into
the Yukon Territories will slowly weaken and remain fairly
stationary through Wednesday afternoon. On the North Slope a
surface ridge from the high pressure center located to the west of
Wrangel island will be pushed out of the way by a cold front
sweeping into the region from the northwest. That front then
remains over the region nearly stationary until the next wave
along the front moves into the region late on Friday. The weekend
will continue on the slope with weak waves along the stationary
boundary. The extended with strong low pressure to the south will
keep the polar easterlies going through most of the extended
period.

Models...
The big 3 (GFS EC CMC) all started out in fairly good agreement
with the analysis this morning. On Tuesday at the 18Z time stamp
all 3 have the upper trough extending from a strong arctic upper
low north of the McKenzie Delta to a developing upper low near the
Pribilof Islands. On the surface all 3 agree on the surface 
trough across the middle of the state with the weakening surface 
low near McGrath on average. Wednesday's 18Z time stamp still 
fairly good agreement on the models with the developing upper low 
now in the vicinity of Bristol Bay, a ridge building across the 
Russian far east and an upper trough for the rest of the area in 
the forecast. On the surface again very little movement or change 
in the interior frontal boundary. A surface front along the North 
Slope will bring some moderate wind to the region. Thursday at 18Z
the models remain in agreement with the upper level troughiness 
across the state and very little ensemble spread for moderate to 
high confidence. On the surface the interior front has weakened 
significantly, and the arctic front keeps a fairly brisk southwest
wind across the North Slope. The weekend the models have some 
differences with the North Slope, however in general expect fairly
seasonal arctic easterlies pattern with weak surface features 
moving through the flow. The interior will see a front being 
pushed up into the interior from a developing and strengthening 
low near the Alaska Peninsula. The extended shows the EC bullish 
on the development of a strong low in the northern Bering Sea 
whereas the GFS has the same feature just not as strong... the CMC
holds back the low south of the Alaska Peninsula. The extended 
confidence is fairly low at this time.

&&

.DISCUSSION...

North Slope and Brooks Range...
A cools start to the week up on the North Slope with temperatures
in the 30s. Ahead of the front by Wednesday temperatures will
increase into the 40s and 50s lasting through the weekend. Plenty
of surface systems moving through for precipitation chances
through the period with wintery types confined early then mostly
rain later in the period. The front will bring some wind to the
western coast to Barrow (Utqiagvik) Wednesday morning last through
Thursday for Prudhoe Bay east. Headlines will be possible for 
Wednesday and Thursday for the region. Will continue to monitor
the region for possible high surf conditions for the period.

West Coast and Western Interior...
The remnants of Shanshan will move northeast across the Y-K Delta
and into the Western Interior. Deep saturation with this system 
will bring rain to most areas south of the Brooks Range with total
amounts through Tuesday varying between 0.25 to 0.50 inches in 
the Valleys to over 1.00 inch possible in the higher terrain of 
the Kuskokwim mountains and middle Yukon Valley. Strong north 
winds across the Bering will cause high surf along north facing 
shores from St. Lawrence Island north to Diomede. Strong winds 
along the immediate Chukchi coast near Point Hope have prompted a 
strong wind headline for this area as well. By late Tuesday, weak 
ridging will build east across the Chukchi and force most of the 
shower activity south near a sfc boundary spanning Holy Cross to 
McGrath and east across the Alaska Range.

Central and Eastern Interior...
An increase in shower and thunderstorm activity is expected across
the lower Tanana Valley this evening. Rainfall will persist 
through Wednesday along a stationary boundary spanning much of 
southeastern Alaska from the Kuskokwim Valley across the Tanana 
Valley into Fortymile country. Rainfall amounts through Wednesday 
will generally fall between 0.25 to 0.50 inches with up to 1.00 
inch or more possible for favored upslope areas. Weak convergence 
along the boundary and modest daytime heating will support 
isolated thunderstorm development this afternoon. Cooler 
temperatures Tuesday should mitigate this effect. Weak Chinook 
conditions will remain steady for the upper Tanana Valley east of 
Tok through mid week, resulting reduced chances for rainfall in 
this area.

Coastal Hazard Potential Days 3 and 4...None.

&&

.FIRE WEATHER...
A large swathe of wetting rains is expected to inundate much of
the state, as fire weather remains suppressed by a broad troughing
pattern. However, some dry spots will remain somewhat immune to
this system over the next few days. Areas of the upper Tanana
Valley east of Tok will remain Chinooked out of much of the
incoming moisture, though chanced for wetting rain does increase
Tuesday as the low center nears and downsloping diminishes. 

&&

.HYDROLOGY...
High water will gradually decrease over the next couple
of days. An additional 0.50" to 1.00" of rainfall across much of 
the Interior over the next few days. Expect rises in river levels
across the Interior this week with the rainfall. The Chena river
basin is expected high water later this week that could impact the
Fairbanks area. For the latest information go to www.weather.gov/aprfc.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Advisory for AKZ217-AKZ224.

High Surf Advisory for AKZ213.

Small Craft Advisory for PKZ200-PKZ215-PKZ230.

Gale Warning for PKZ210-PKZ220-PKZ225.
&&

$$

PROTON AUG 18