Flooding in Alaska, June 10 to 13, 2023

Northern Alaska Forecast Discussion...UPDATED
National Weather Service Fairbanks AK
303 PM AKDT Fri Jun 9 2023

.SYNOPSIS...
Cooler conditions with increasing moisture expected through
Saturday. Some warming and drying expected Sunday, as a southerly
flow increases over the Alaska Range. Cool and moist conditions
return Monday and persist through the middle of next week.

&&

.DISCUSSION...
Upper Levels and Analysis...
Upper low continues to spin over the central and eastern
Aleutians, while a ridge axis lingers across northern Alaska. A
deformation zone between the two features is providing widespread
rainfall across the central and eastern Brooks Range, while
isolated convection can be seen bubbling up on satellite imagery
across the Fortymile Highlands and the central and western
Interior. A lot of cloud cover across the Fairbanks area is
holding temps back and keeping things more stable. At the sfc, a
trough lingers across the center of the state from the YK border
to the Seward Peninsula. High pressure persists across the Arctic.

Rainfall totals across the south slopes of the Brooks Range look
on track, with a little over 0.5" measured near the Anaktuvuk
Pass. Additional 0.5" or so is expected tonight into Saturday for
the Brooks Range. A piece of energy is expected lift north out of
the Alaska Panhandle into southwestern Yukon, then stall along the
AL/YK border Saturday. Models agree on an area of enhance rainfall
with this feature, but disagree on the exact placement. The 12z
ECMWF/Canadian have trended east, more on the YK side, while the
NAM has trended west, with rain all the way to the Salcha/Chena
headwaters. The GFS is in the middle and closer to our current
thinking. Rainfall amounts of 1-1.5" is possible with this. There
est of the area will see just isolated to widely scattered
showers, with isolated thunderstorms across the southern parts of
the Western Interior. Meanwhile, numerous showers will continue
across the Brooks Range until tapering Saturday night.

As the low over the Aleutians begins to lift north into Bristol
Bay Sunday, an increasing southerly pressure gradient will cause
a pronounced downslope off the Alaska Range into the Interior.
These areas are not expected to get much rain tonight thru
Saturday. So there may be some elevated fire weather concerns, as
RH values drop and winds expected to be above Red Flag criteria.
More cloud cover and cooler temps should result in less fire risk
on Monday, but gusty southerly winds will continue.

Central and Eastern Interior...
Less thunderstorm coverage today than last couple days, with
mainly isolated storms across northern and extreme eastern
Interior. Cooler conditions expected Saturday, with an area of
moderate to heavy rain across the Fortymile area, isolated to
widely scattered showers elsewhere. Slightly warmer temps expected
Sunday, with good downslope southerly flow off the Alaska Range.
Only isolated showers expected. Cooler and wetter conditions
gradually return Monday thru midweek.

North Slope and Brooks Range...
High pressure over the Arctic Ocean will keep a northeasterly
flow over the North Slope. This flow pattern will bring periods
of low stratus and some fog along much of the Arctic Coast thru
the weekend.

Western Interior and West Coast...
Southeasterly flow around the Bering Sea low will bring increased
moisture and PoPs across the West Coast, while the western
Interior will see a chance for isolated thunderstorms thru this
evening. Temperatures will be above normal with a general
offshore flow for much of the West Coast, cooling to near normal
on Saturday.

Days 4 through 7...
The ridge over the northern Interior will break down as a low
forms near Bristol Bay. A continued cool down to slightly below
normal temps is expected with generally unsettled weather,
continuing into early next week. Overall, chance to likely PoPs
across the area thru the period.

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

&&

.FIRE WEATHER...
The main concern today is thunderstorms. Expect isolated storms
across the northern and extreme eastern Interior. On Saturday, only
isolated storms expected across mainly southern portions of the
Western Interior, while generally cooler/wetter conditions
expected across most of the state.

Elevated fire weather conditions possible Sunday on the north side
of the Alaska Range from Delta Junction to the Denali National
Park area, with gusty southerly winds and RH values dipping into
the mid to upper 20s. High temperatures are expected to be mainly
in the 60s to lower 70s. From there, temperatures will gradually
decrease and moisture will gradually increase Monday thru
Wednesday.

&&

.HYDROLOGY...
The Sag River is running out of its banks, and eroding parts of
the Dalton Hwy between Mileposts 401 and 407, and this may
continue for a few days. A Flood Warning was issued for the
impacts to Dalton Highway. Rises on rivers can be expected across
the Brooks Range thru Saturday due to rainfall and snowmelt.
Heavy rain will be possible across the extreme eastern Interior,
mainly in the Fortymile Highlands Saturday into Saturday night,
which may cause rapid rises and isolated flooding on area rivers.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ812.
     Brisk Wind Advisory for PKZ813-859.
     Brisk Wind Advisory for PKZ814-815-858-860-861.
&&

ARK

Special Weather Statement
National Weather Service Fairbanks AK
819 PM AKDT Fri Jun 9 2023

AKZ219-110030-
Upper Koyukuk Valley-
Including Allakaket, Hughes, Bettles, Caribou Mountain,
and Gobblers Knob
819 PM AKDT Fri Jun 9 2023

...High Water Levels Through the Weekend...

Runoff from rainfall and remaining snowmelt will cause rivers
draining the Brooks Range to rise to bankfull and possibly
overbank in some low lying areas into the weekend. The high water
will cover gravel bars and push water up to the brush line. Those
living or recreating along rivers draining the Brooks Range are
encouraged to monitor river levels this weekend.