446
FXAK69 PAFG 121404
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
604 AM AKDT Wed Jun 12 2024

.SYNOPSIS...
A continued regime of scattered showers and isolated thunderstorms
over the S Interior, with heavier rainfall over the Alaska Range. Some
thunderstorms North winds over the Bering Strait will switch to south
on Thursday, and this will also bring in much cooler temps out west.
Slow warming trend begins over the Interior Friday as a ridge builds
in. More showers and thunderstorms are likely over the eastern
Interior on Friday.

&&

.DISCUSSION...

Upper Levels and Analysis...
There is a strong closed blocking high over the Chukchi
Sea. There are a pair of undercutting shortwave troughs moving
west at the base of this trough, with one over the Chukotsk, and
the other over the Noatak Valley. A remnant thermal trough
persists over the S Interior, with the main low center over the
Tanana Valley. There is a weak shortwave trough over the
Fortymile, slowly moving southwest.

Model Discussion...
Models are in good agreement with the large scale pattern. They
are overall in better agreement with the convective pattern as
well, over the next few days. The NAM nest was preferred for wind
details. A general model blend was preferred for precipitation.

Central and Eastern Interior...
Showers and thunderstorms occurred yesterday evening and overnight
and are still likely on Wed, although instability will be a bit less on
Wednesday. Slowly, ridging builds in Thu with general drying weather.
Friday will be warmer with chances for thunderstorms, especially over the
E Interior, where instability parameters look best, with the possibility of a
shortwave trough dropping south over the E periphery of the ridge
axis. Scattered to numerous showers and thunderstorms are, once again,
possible on Friday for the region with chances being more likely over the
Eastern Interior as model forecast CAPE values are around 800 J/kg, and
LI values are around -2. So, that has been put in the forecast. Good upper
level vorticity support will also be in place.

West Coast and Western Interior...
For today, isolated thunder chances will be over the Interior and into
the W Brooks Range. A low with cooler air will be moving into the W
Coast with winds switching around to west-southwest Thu and Fri,
which will quickly reduce temps back to more seasonal normal
levels.

North Slope and Brooks Range...
Northeast winds and high pressure over the Arctic continues, with more
stratus for the Arctic E of Point Lay and up to the slopes of the
Brooks Range. There is very little change in weather the next few
days, with persistent 15 to 30 mph northeast winds, strongest
over the W Arctic.

Extended Forecast Days 3-6...
A moderate strength ridge will be building into the E Interior
this weekend and into the next week, which will promote warmer
temps and more chances for thunderstorms over most of the
Interior. Meanwhile, a strong arctic low will be meandering over
the NW Arctic, which will bring in west winds to the West Coast
and cooler temps to the western half of the Mainland.

Scattered to numerous showers and thunderstorms are, once again,
possible on Friday for the for the Central and Eastern Interior with
chances being more likely over the Eastern Interior as model forecast
CAPE values are around  800 J/kg, and LI values are around -2. So,
that has been put in the forecast. Good upper level vorticity support
will also be in place.

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

&&

.FIRE WEATHER...
The thermal trough is still in place over the S Interior and stretching
to the northwest coast. This will promote areas of scattered showers and
isolated to widely scattered thunderstorms, and given the
instability, some storms may be strong and may produce a decent
amount of lightning. However, these will continue to be  wet, with
a decent likelihood of heavy wetting rains from about Salcha east
to the headwaters of the Tanana Valley, with heavy rains possible
through Wed night. Storms will be even more isolated after today
as the thermal trough weakens. It will remain drier north of the
thermal trough across the Yukon Flats. Wed and Thu will be near
red flag criteria, with min RH in the low 20s and highs near the
mid 70s, but winds look to be around 6 to 11 mph and just below
criteria.

We are monitoring the chance for high based thunderstorms
over the E Interior on Friday, as a ridge aloft builds in and
a disturbance passes over the E side of this ridge. Overall
though, a warming trend is expected over the eastern half of the
Interior this weekend, while it cools out west.

&&

.HYDROLOGY...
High water from snowmelt will make its way down rivers on the
Central North Slope over the next several days, and minor flooding
remains possible. Water levels will remain high through at least
Thursday, then fall slowly through the weekend. The high water
caused by warm temperatures and snow melt in the Brooks Range. It
is expected that high water will remain through at least Thursday,
and that water levels will fall slowly through the weekend. Water
levels will fall more significantly next week as temperatures
cool in the Brooks Range.

The Sagavanirktok River near Pump Station 3 crested on Saturday,
but remains high today. That high water is expected to reach the
coast today and to remain high for several days. Water will be
near bankfull, with minor flooding possible in low lying areas
downstream of Pump Station 3 over the next several days. Water
levels are expected fall slowly late this, then fall more next
week.

The Colville River at Umiat crested Monday and remains high.
That high water will reach the coast today and remain high for
several days. Minor flooding of low lying areas along the
Colville River downstream of Nuiqsut is possible.

On the Kuparuk River at the Bridge, flooding is occuring. The
low-water crossings approaching the bridges are inundated with
water, with up to 8 inches of water over the road. Water will
remain high through Thursday, and then is expected to fall slowly
through the weekend.

Continued heavy showers today will result in the potential for  up
to a couple inches of rainfall across parts of the Alaska Range,
which will likely result in fast stream rises and overall rises along
all rivers draining the Alaska Range. Some storms will be strong
and will drop copious rainfall in a short period of time. Residents
should be aware of the possibility of rapid stream rises with heavy
rainfalls generally lasting into this evening.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ812-858.
     Brisk Wind Advisory for PKZ814.
&&

$$