Flood in Alaska, June 22 to 24, 2020

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
242 PM AKDT Sun Jun 21 2020

.SYNOPSIS...
A wet and cool day is ongoing this Father's Day for much of the
Interior, as it resembles September more than late June. Many
locations from Fairbanks south received over an inch of rainfall
last evening through this morning as yet another strong "easterly"
wave passed through. Cooler and damper weather will continue into
the next week with more heavy rain in store for the Fortymile
Uplands as another 1-2.5" is expected. Elsewhere, the warmest
temps will remain relegated to the northwest Interior and Southern
Brooks Range where the final remnant of the thermal trough
resides.

&&

.DISCUSSION...

Upper Levels and Analysis...
The upper level pattern is going to sound eerily similar to the
past week, with a low in the Gulf of Alaska and "easterly waves"
moving west into the Interior from the Yukon. The latest easterly
wave is now propagating southwest from the Central Interior to the
Lower Yukon. This low was responsible for the heavy overnight rain
across the Tanana Valley and White Mountains. A skinny upper ridge
persists over the Brooks Range to the Yukon Flats to Kotzebue
Sound. An anomalous upper low is moving south toward the Arctic
Slope with the center of the low around 520 dm. A shortwave trough
which is leading the height falls south is moving east across the
eastern Arctic Slope this afternoon. The thermal trough remains in
place underneath the ridge axis aloft, and this is the only warm
area in the state of Alaska.

West Coast and Western Interior...
Another easterly wave will bring showers and isolated
thunderstorms to the southern Interior and Yukon Delta as well as
the Nulato Hills this afternoon. Otherwise, northwest onshore flow
will gradually strengthen as a front moves into the West Coast.
Rain along the front will move into the region Monday
afternoon/evening and shift eastward Tuesday and Tuesday night,
bringing widespread clouds, cooler weather, and rain through
Wednesday.

North Slope and Brooks Range...
Active weather is in store for the North Slope and Brooks Range as
a series of fronts moves onshore. The first comes onshore tonight
and stalls out over the Eastern Brooks Range and Slope on Monday.
This will bring rain along with mixed snow, along with good snow
accumulations possible from Umiat to Anaktuvuk Pass, possibly
clipping parts of the Dalton Highway. In addition, this same front
will spark off a cluster of thunderstorms  The cold front will
retreat west on Wednesday, with any snow switching back to rain
across the region except over the Northwest Arctic where a mix
will still be possible.

Eastern and Central Interior...
Showery and cool weather will become the dominant mode the next
few days. The one last refuge for possible thunderstorms will be
the far reaches of the of the Interior around the Upper Koyukuk
Valley. Otherwise, cool and damp with more heavy rain for parts of
the Fortymile Uplands as yet another easterly wave encroaches on
the area. Heavy rain will move in late this evening and will
spread as far west as the Upper Tanana Valley and Eastern White
Mountains Monday with lighter rain likely into Fairbanks NSB.
Heavy rain persists into Tuesday morning with a gradual tapering
to showers thereafter. Expect 1-2.5" additonal rainfall for the
Fortymile Uplands along with sharp rises along the Salcha, Chena,
Goodpaster, Fortymile, and Charley Rivers into midweek.

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

&&

.FIRE WEATHER...
Fire weather activity will continue to dwindle into midweek, but
there does remain a narrow thermal trough across the North Slope
and into the northern INterior which will be good for isolated wet
thunderstorms today. The axis of instability becomes compressed
along the southeastern Brooks Range into the Yukon Flats tomorrow,
but there will be a good lee low and strong compressional heating
along with upper forcing. Expect a cluster of strong storms to
develop late tomorrow afternoon with heavy rain and quite a bit of
localized lightning strokes. Thereafter, cool and damp weather
will reign supreme as troughing develops region wide for the
remainder of the week with below normal temps.

&&

.HYDROLOGY...
Multiple days of significant rainfall accumulations in the
Interior will result in continued rising streams and rivers. Due
to continuing potential for significant rainfall through Tuesday,
the Chena, Salcha, Tanana, Charley, and Fortymile River basins
should see rapid rises and then remain elevated going into later
portions of the week.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Small Craft Advisory 210 220 225.

&&

AHSENMACHER JUN 20

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FAIRBANKS AK
937 PM AKDT SUN JUN 21 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0900 PM     HEAVY RAIN       2 W TWO RIVERS          64.87N 147.17W
06/21/2020  M2.32 INCH       FAIRBANKS NORTH STAAK   TRAINED SPOTTER

            2.32 INCHES STORM TOTAL (SINCE FRIDAY
            AFTERNOON). 1.01 IN LAST 24 HOURS.

&&

LC