412
FXAK69 PAFG 301404
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
604 AM AKDT Tue Apr 30 2024

.SYNOPSIS...
Temperatures along the North Slope will remain much cooler than
normal into the weekend. The North Slope will continue to have
periods of flurries and fog through Thu, and possibly into the
weekend. NE Winds increasing to 15 to 25 mph over the Western
Brooks Range and from Point Lay to Point Hope today will persist
into Thu.

The West Coast and Western Interior will be slightly cooler than
normal through Wed, then warm to near normal Thu, and above normal
Fri into the weekend. Areas of fog near Kotzebue and over the YK
Delta will thin by this afternoon. Scattered showers will develop
over the YK Delta and SW Interior tonight, becoming likely Wed
then diminishing Wed night then drying out on Thu. NE Winds
increasing to 15 to 25 mph over the Western Brooks Range
and from Point Hope to the Bering Strait and St Lawrence Is today
will persist into Thu.

The Eastern Interior will remain cooler than normal today, and
warm closer to normal on Wed and Thu, then warm to well above
normal by the end of the week. Conditions will become more cloudy
today and Wed, then decreasing on Thu. Expect increasing areal
coverage of showers over the Southern and Eastern Interior today
through Wed with showers likely from Denali and Tanana to Eagle
by Wed. Showers will diminish late Wed night as southerly Chinook
winds develop across the Alaska Range, and conditions will be
mainly dry on Thu. South winds 15 mph through AK Range Passes on
Wed, will increase to 15 mph gusting to 25 mph on Thu. Expect
south winds 25 mph gusting to 40 mph along the North Slopes of the
Alaska Range Fri into Sat, and possibly into Sun. This could
cause low RH values and Red Flag conditions along the North Slopes
of the AK Range Fri into Sat, and possibly into Sun.

Surface features...
A weather front stretching from Banks Island to Point Lay will
move to Inuvik to south of the Brooks Range by 4am Wed. This is
causing fog and flurries along the Arctic Coast. This will cause
NE winds of 15 to 25 mph over the Western Brooks Range and western
North Slope today into Wed.

Strong high pressure over the Chukchi Sea will build over the
Western North Slope tonight and continue into Wed. This will cause
decreasing clouds over the Western North Slope Wed.

A 1018 mb low near Kotzebue will move to near Koyuk by 4pm Tue
then weaken. An Arctic front that stretches from Circle to the
Kotzebue low to St Matthew Island will move to Eagle to Koyuk to
St Matthew Is by 4pm Tue, then remain stationary through Wed,
before moving north to Eagle to the Seward Peninsula on Thu.

A strong low west of Shemya will move to the southeast Bering Sea
by Wed, then move into the Gulf of AK Thu and weaken. This will
feed moisture north along the Arctic Front tonight and Wed. This
moisture will cause the isolated rain and snow showers along the
Arctic front today to become scattered tonight and numerous on
Wed. The moisture feed will be cut off Wed night and Thu as the
low moves east into the Gulf of AK.

A weak thermal trough just north of the Alaska Range will persist
into Wed. This will cause light south winds through the AK Range
passes into Wed with winds increasing to 15 to 25 mph on Thu.

A second strong low will move over the Western Aleutians on Thu
and to the Southeast Bering Sea on Fri. This is expected to
cause moderate strength southerly Chinook winds to develop across
the Alaska Range in Fri, which could last through the weekend.
This will cause dry and warm conditions over the SE Interior Fri
into the weekend, with windy conditions along the Alaska Range.

&&

.DISCUSSION...
At 00Z, most models initialize well on features aloft, except
that the GFS is 10-20 meters too low on 500 MB heights south of
the Arctic Circle compared to what RAOBs indicate. Models show
similar solutions aloft through Thu, with slight differences
becoming larger by the weekend. The ECMWF lingers a short wave
over NE AK longer on Wed than other models, while the GFS had
slightly lower 500 mb heights over Nrn AK than other on Wed. Sine
the NAM and Canadian models initialize well and show similar
solutions through Thu, we will use the NAM and Canadian for
features aloft. through Thu. From Fri into the weekend the GFS
moves the low aloft from the SE Bering Sea into the Gulf of AK
more quickly than other models, which weakens the southerly
chinook winds over the AK Range more quickly. At this time do not
favor the GFS so will use a blend of the ECMWF and Canadian for
features aloft for Fri into weekend, keeping the chinook winds
going into Sun.

The long wave pattern consists of a trough from the Canadian
Archipelago southwest over northern AK and over NW Canada, with a
ridge over the Eastern Bering Sea and Chukchi Sea, and a second
trough over the Sea of Okhotsk, Western Bering Sea and the NW
Pacific. This pattern will retrograde over the next several days
as a strong short wave trough over the Eastern North Slope moves
southwest over the West Coast and Northern Interior today and
tonight, and another strong short wave moves from the NW Pacific
east undercutting the long wave ridge and forming a deep low aloft
over the southeast Bering Sea by Tue PM. By Tue night and Wed
there is a long wave trough from the Beaufort Sea SW across
Northern AK to the Bering Sea. On Thu the long wave pattern will
remain stable but the Bering Sea short wave will move east into
the Gulf of AK and cause south flow to increase slightly over the
Southern Interior. The long wave will deepen over the Bering Sea
on Fri causing southerly flow aloft to increase over the Interior
Fri. The long wave will shift over the Eastern Bering and Western
AK on the weekend, keeping moderate to strong southerly flow aloft
over the Eastern Interior over the weekend.

This will cause the flow aloft to turn northeast across NW AK
today and SW across the Interior today. Flow will become weak
south over the Southern Interior on Wed and weak northeast across
NW AK on Wed. Southerly flow will increase over the Interior from
Thu into Fri and possibly into Sat.

This upper level pattern means that temperatures along the North
Slope will remain much cooler than normal into the weekend, while
the West Coast and Western Interior is just cooler than normal
through Wed, then warms to near normal Thu, and above normal Fri
into the weekend. The Eastern Interior will remain cooler than
normal today, and warm closer to normal on Wed and Thu, then warm
to well above normal by the end of the week. This also means that
conditions will become more cloudy today and Wed with precipitation
areal coverage increasing over the Interior today into Wed, then
decreasing on Thu.

With precipitation, will use a blend of the NAM and Canadian
through Thu. Expect increasing areal coverage over the Southern
and Eastern Interior today through Wed with showers likely from
the YK Delta to Eagle by Wed, then precip ending on Thu.
Highlight include:
Chance of light snow over the Eastern North Slope today and
tonight. Isolated showers over the Eastern Interior becoming
scattered showers from McGrath to Fairbanks to Circle tonight,
with showers likely from the YK Delta to Fairbanks to Eagle by
early Wed morning and continuing into Wed afternoon. Showers will
diminish late Wed night as Chinook winds develop, and conditions
will be mainly dry on Thu. Could see wetting rain Wed in the
Southern Interior.

At the surface at 06Z, models verify well on most features over
AK. Will use a blend of the NAM and Canadian models for surface
features and winds since those are the preferred solutions aloft.
Highlights include:
NE Winds increasing to 15 to 25 mph over the Western Brooks Range
and from Point Lay to Point Hope to the Bering Strait and St
Lawrence Is today and persisting into Wed and likely into Thu.
South winds 15 mph through AK Range Passes on Wed, increasing to
15 mph gusting to 25 mph on Thu. Expect south winds 25 mph gusting
to 40 mph along the North Slopes of the Alaska Range Fri into Sat,
and possibly into Sun. This could cause low RH values and Red Flag
conditions along the North Slopes of the AK Range Fri into Sat and
possibly into Sun.

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

&&

.FIRE WEATHER...
RH values should rise slightly today compared to Mon, and more on
Wed. Will see RH values fall to 20-30% on Thu, but drier
conditions are possible Fri through the weekend.
Expect isolated light showers over the Eastern Interior today,
becoming scattered showers from McGrath to Fairbanks to Circle
tonight, with showers likely from the YK Delta to Fairbanks to
Eagle by early Wed morning and continuing into Wed afternoon.
Could see wetting rain Wed in the Southern Interior. Showers
will diminish late Wed night and conditions will be mainly dry on
Thu through Sat.

South winds 15 mph through AK Range Passes on Wed expected to
increase to 15 mph gusting to 25 mph on Thu with near Red Flag
conditions near Delta Junction Thu. Expect moderate Chinook winds
to develop Fri and continue into the weekend, causing south winds
25 mph gusting to 40 mph along the North Slopes of the Alaska
Range Fri into Sat, and possibly into Sun. This could cause low RH
values and Red Flag conditions along the North Slopes of the AK
Range including Delta Junction Fri into Sat and possibly into Sun.

&&

.HYDROLOGY...
Ice jam on the Yukon River just upstream of Eagle, combined with
ice remaining in place at Eagle, have lead to a Ice Jam Flood
Watch for Eagle. River watch team will fly area today and get more
information on this situation.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Flood Watch for AKZ835.
PK...Brisk Wind Advisory for PKZ806-807-811-854-856-857.
     Brisk Wind Advisory for PKZ810.
     Heavy Freezing Spray Warning for PKZ816.
     Small Craft Advisory for PKZ816.
     Brisk Wind Advisory for PKZ817.
     Brisk Wind Advisory for PKZ851.
&&

$$