Weather Service Report


594 
FXAK69 PAFG 271352
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
552 AM AKDT WED JUL 27 2016

.DISCUSSION...

UPPER AIR...
A deep upper low centered 500 nm northwest of Wrangel Island will
move to 200 nm northwest of Barrow by late Friday night and to 400
nm north of Barrow by Saturday afternoon. A weak short wave trough
over the western Beaufort Sea and northwest Alaska mainland will
exit northeastward into the eastern Arctic Ocean by this evening.
A second weak short wave trough rotating around the low center
will move eastward to the Chukchi Sea by late tonight then exit
into the eastern Arctic Ocean by Friday morning. The third short
wave trough in the series will be the strongest, moving
southeastward to the northwest Alaska coast, Chukchi Sea and the
northern Bering Sea by Friday morning. By Sunday afternoon the
trough will continue to move eastward and intensify, extending
from the central Beaufort Sea to near Galena to near Cape
Newenham. Weak ridging poking out of the Yukon Territory into the
eastern Alaska interior will give way to a westerly flow pattern
by late Thursday night as the expansive circulation around the
Arctic low center expands southward and eastward across the
northern half of the Alaska mainland.

SURFACE...
A weak 1001 mb low near Barrow will move to 600 nm north of
Nuiqsut by late tonight, deepening to 997 mb. A weak 1000 mb low
200 nm southwest of Wrangel Island will move to near Prudhoe Bay
by Thursday afternoon and to 100 nm north of the Mackenzie River
Delta by late Thursday night. An elongated 1004 mb low will
develop by Friday evening extending from southwest of St Lawrence
Island to the eastern Brooks Range. A high pressure ridge along
the along the eastern North Gulf coast will gradually weaken, and
dissipate by Friday evening.

Rain or showers will develop over the northwest coast this
morning and will spread south and east to the Chukchi Sea
Coast, Kobuk and Noatak Valleys, Baldwin Peninsula, Selawik
Valley, Seward Peninsula, and most of the Brooks Range and Arctic
Slope by late tonight. Rain or showers is expected over most of
the Arctic Slope, Brooks Range, parts of the west coast south and
east of Nome, and most of the interior Thursday. A most westerly
flow pattern aloft is expected to develop over the west coast and
interior Friday and become southwest Saturday in advance of the
eastward moving and deepening third short wave trough aloft in the
current series. This will cause widespread significant synoptic
scale lift and potential for significant rainfall over the west
coast from the Seward Peninsula south and over much of the
interior. Significant rainfall will be possible over and near the
southern parts of the Seward Peninsula, eastern Norton Sound, and
the Nulato Hills Friday, with widespread rain over the interior
from the Middle Tanana Valley south and west. Rain will continue
over the southern west coast areas tonight while spreading to
almost all of the interior except the extreme southeast parts.
Rain will continue Saturday over the west coast south and east of
Nome and over almost all of the interior except the extreme
southeast parts. Rain will continue over most of the interior
Saturday night and over most of the central and eastern interior
Sunday.

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

&&

.FIRE WEATHER...
Minimum RH values today are expected to be 28 to 38 percent
in the northeastern interior, 35 to 45 percent over the remainder
of the eastern interior and the central interior, and from 40 to
above 50 percent in the western interior. Minimum RH Values
Thursday and Friday are expected to be 50 percent or above in
almost all interior areas. Parts of the western interior will
see minimum RH values of 60 percent or higher Friday. RH
values at night will recover to 80 percent or higher. South
winds gusting to 40 mph are expected to continue through Thursday
in eastern Alaska Range passes west of the Tok cutoff, with
somewhat lower gusts speeds expected in passes near the railbelt
area in Denali Park. Gusty east to southeast winds in the Delta
Junction area are expected to diminish by this evening. Elsewhere
in the interior, winds are expected to be mainly 10 mph or less
through Thursday. Isolated thunderstorms will be possible in parts
of the southern and eastern interior during the afternoon and
evening hours today and Thursday. Widespread wetting rains
are expected over most of the western and central interior
Friday, and over much of the interior except the extreme 
south parts Friday night through Saturday night.

&&

.HYDROLOGY...
The Chena River near Chena Lakes remains stationary at a stage of
about 25.0 feet, which is 0.5 foot above minor flood stage.
Little change is expected in the water level near Chena Lakes
today, with the water level expected to begin falling tonight.
Flow on the Chena River through Fairbanks is continuing to be
controlled to less than 12,000 cfs by the Moose Creek Dam. The
stage of the Chena River at Fairbanks is expected to remain
steady near 8.8 feet today then start falling slowly. Minor flood
stage on the Chena River at Fairbanks is 12.0 feet. Some other
river stages as of 1 am this morning: The Chena River near Two
rivers is at 17.9 feet and falling. The Salcha River at the
Richardson Highway Bridge is at 10.7 feet and falling. The Tanana
River at Fairbanks is at 23.3 feet and falling slowly. The Tanana
River at Nenana is at 10.7 feet and falling slowly. Stages on
other rivers in the eastern interior will continue to fall slowly.

Significant rainfall is expected over much of the interior and
southern west coast areas, beginning over the southern west coast
areas Friday and spreading eastward through the weekend. Storm
total rainfall totals over the southern west coast areas, western
interior from the middle Yukon Valley south, the central interior
from the upper Koyukuk Valley south, and the middle Tanana Valley
are expected to be 1 to 1.5 inches, with some areas seeing amounts
in excess of 2 inches. Widespread significant rainfall will
cause significant rises in the levels of the smaller rivers
and streams.

In the middle Tanana Valley, significant rainfall is expected to
begin Friday morning and continue through most of Sunday. GFS time
cross section indicates deep moist flow with west to southwest
winds 35 to 45 kt aloft, along with deep vertical motion. There
will likely be significant orographic enhancement of rainfall in
the upper reaches of the Chena and Chatanika river basins, and
rainfall amounts in these areas will likely be significantly more
than the larger scale model QPF forecasts. There is a high
probability of another flood event on the upper Chena River should
the forecast pattern be correct. Subsequent model runs will need
to be monitored for the area coverage and amounts of rainfall
expected.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Flood Advisory remains in effect for the Chena River above
Nordale Road.

&&

$$

RF JUL 16

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Western Regional Climate Center, wrcc@dri.edu