High Wind in Alaska, September 5 to 6, 2017

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
321 PM AKDT Mon Sep 4 2017

.DISCUSSION...
The models are in good agreement that an active weather pattern
is expected for the Interior Tuesday night into Wednesday with a
combination of gusty winds and rain. After Wednesday the models
start to diverge some on the placement and strength of the main
synoptic scale features.

Aloft, at 500 mb, a 532 dam low currently just south of Sand Point
will slide south a bit tonight and tomorrow. Tuesday night this
low will start to move northward in response to a much stronger
low moving eastward just south of the Aleutian Islands. By early
Wednesday morning this upper low will be situated near McGrath and
by Wednesday evening it will be situated near Huslia and by
Thursday morning the low will be situated near Nuiqsut. A upper
level ridge along the Canadian Border will persist through
Tuesday before pushed into Canada Tuesday night as the
aforementioned low starts to move north. An upper level ridge
will build east over the west coast of Alaska tonight. This ridge
will be pushed northward Tuesday night by a combination of the
low starting to move north in through the Interior combined with
the strong eastward moving low in the Aleutians.

At the surface, a 988 mb low south of Sand Point will drift south
and weaken through Tuesday afternoon. A low moving north in the
Pacific will intensify during the day on Tuesday. At 4 AM Tuesday
the this 1000 mb low will be around 675 SE of Anchorage. By
Tuesday evening it will be a 992 mb low just south of Anchorage.
By early Wednesday morning this low will be over McGrath at 990 mb
and by Wednesday evening it will be just north of Galena at 992
mb. A 994 mb low will form south of Deadhorse Wednesday evening
and will move north to be over Deadhorse by Thursday morning.

Central and Eastern Interior: The main issue for this evening is
southerly gap winds in the Alaska Range. Winds will likely reach
speeds just under advisory levels early this evening before
diminishing after 6 PM. A weather system will move through the
Interior Tuesday afternoon into Wednesday night bringing rainfall
and gusty winds. Rainfall associated with the low mentioned above
will start to move into the southeastern Interior during the day
on Tuesday pushing north and east through Wednesday evening. The
band of heaviest precipitation will be situated from Circle to
Fairbanks to Mcgrath 10 PM Tuesday. By 4 AM Wednesday the band of
heaviest rainfall will be situated from Fort Yukon to Tanana To
McGrath. Areas north and west of Fairbanks will see 0.25 to 0.75
inches of rainfall total as this system passes through. Areas from
Fairbanks south will see a bit less due to downslope effects. As
the low moves northward winds are expected to pick up. From
Fairbanks north and west wind gusts of 20 to 40 mph are possible
with the strongest winds expected on summits. Initially the winds
from Fairbanks north will be easterly but will become more
southerly as the low moves north. Strong southerly winds are
expected to develop in the Alaska Range Tuesday night into
Wednesday. In the eastern Alaska Range southerly winds with gusts
up to 70 mph are possible. I have issued a High Wind Watch for the
eastern Alaska Range (zone 226). Winds in zones 225 and 223 will
approach advisory criteria on Wednesday, but will hold off on
issuing any products on this shift.

West Coast and Western Interior: A weather front will push into
the Western Interior late Tuesday night and early Wednesday
morning. This will bring rainfall and gusty winds. Wind gusts of
20 to 40 mph are possible along with 0.25 to 0.7 inches of
rainfall through Thursday morning. Some localized areas could see
up to 1 inch of rain, particularly in areas enhanced by an upslope
component of the wind. The low will stall and weaken on Thursday,
this will keep the potential for showers over the western
Interior through Friday.

North Slope and Brooks Range: Some fog and low stratus along the
coast tonight and tomorrow morning along the coast, particularly
from Barrow east. Rainfall will push into the eastern Brooks range
Wednesday morning and make it to the coast (Barrow east) by
Wednesday afternoon. Current thinking is that snow levels should
be high enough that most of the precipitation will fall as rain.
0.5 to 0.75 inch rainfall amounts will be common on the south side
of the range with around 0.25 inches of rainfall north of the
range. Gusty north to northeasterly winds are expected as the low
moves north towards the Brooks Range. The low will move north of
the Brooks Range Thursday causing winds pick up along the coast
and adjacent offshore waters. .

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

&&

.HYDROLOGY...
A weather system will bring 0.25 to 0.75 across much of the
central and Western Interior and the eastern Brooks Range Tuesday
night through Thursday morning. A few locations could see
localized rainfall amounts in excess of one inch. This will cause
rises some in rivers and streams; however, at this point we
aren't anticipating any flooding.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
None.
&&

SEP 17