Scientific Forecaster Discussion
fxak69 pafg 051222
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
322 am akst Thu Dec 5 2019
a patchwork of clouds and flurries as well as clear skies and
cold temperatures are found over the central and eastern interior
today and these conditions are expected to continue through
Friday. A significant warmup is on tap for these areas as a strong
Chinook develops over the Alaska Range this weekend. Another
round of snow, mixed precipitation, strong winds and blowing snow
will impact areas of the West Coast and western interior south of
the Seward Peninsula Friday and Saturday and will impact the areas
from the Seward Peninsula north on Saturday and Sunday with snow,
blowing snow and strong winds.
Aloft 500 mb...
a highly progressive synoptic pattern continues with a prominent
ridge axis traversing east across the eastern Bering Sea with a
disorganized longwave trough over the interior. A deep low over
the North Pacific at the southward extent of the longwave trough
is tracking southeastward and will become cutoff from the longwave
pattern today. A more defined trough axis extends southwest from
a low centered north of Hudson Bay to the eastern North Slope.
This trough axis will drop southeast as the Bering Sea ridge
progresses east into the interior today. A deep longwave trough
west of a ridge currently located over southwest Alaska will push
into the eastern Bering Sea Friday, forcing the ridge to develop
into a very high amplitude ridge Friday and Saturday. By Saturday,
the ridge axis will extend from the central Pacific to near the
North Pole. Strong southerly flow will carry ample moisture
northward and result in a strong Chinook this weekend across the
Central and eastern interior...
cloud cover continues to produce large fluctuations in
temperature across the interior. Cloud cover over the Tanana
Valley continues to shift from mostly clear to mostly cloudy
allowing clear locations to drop into the 20s below while cloud
covered areas remain in the single digits below zero. Areas that
have remained consistently cloud free have dropped into the 30s
and 40s below especially north and east of Fairbanks with
Chalkyitsik winning the icebox award this morning with its
temperature holding at 44 below. Several other locations have
dropped into the 40s below this morning across the Yukon Flats and
fortymile country. The cold temperatures will persist through
Friday morning as winds turn southerly and increase through
Saturday. Chinook conditions will develop Saturday, facilitating a
return to above normal temperatures through next week. Valley
locations may remain locked in the colder airmass much of Saturday
while locations in the hills will enjoy temperatures in the teens
and 20s. The cold airmass is expected to mix out of the valleys
on Sunday in the middle Tanana Valley with temperatures climbing
into the 20s above in Fairbanks. Wind headlines will likely be
needed for the Alaska Range Friday afternoon and Saturday as a
Strong Mountain wave develops and brings stronger winds aloft down
to the surface in and near the Alaska Range passes and over the
northern foothills of the Alaska Range.
North Slope and Brooks range...
strong west winds supported by a tight gradient between deep low
pressure in the Canadian archipelago and high pressure to the
southwest will continue to taper off later this morning, with a
Winter Weather Advisory for blowing snow continuing through 9 am
for the eastern Beaufort coast. Temperatures will remain seasonable
cold today and Friday, then begin a warming trend as low pressure
moves north along the West Coast. Southerly flow will support
further warming into early next week.
West Coast and western interior...
a mix of clouds and flurries as well as areas of partly cloudy
skies continue over the West Coast and western interior today
before a front moving north and east out of the eastern Bering
Sea is expected to bring stronger winds and snow over the area
Friday and Saturday for areas south of the Seward Peninsula and
Saturday and Sunday for areas from the Seward Peninsula north.
Computer models continue to struggle with the track and strength
of this storm and minor differences in the track will impact where
the heaviest snow will fall. At this time the heaviest snow is
expected to fall in and near the Nulato Hills while the greatest
risk for freezing rain and sleet remains in the lower yk Delta. At
this time 4 to 8 inches of snow is expected in the Nulato Hills
with 2 to 4 inches expected elsewhere. Ice accumulations of a
glaze to 5 hundredths of an inch are expected in the lower yk
Delta Friday and Saturday.
South to southeast winds 25 to 35 mph with gusts to around 50 mph
are expected to develop along the Norton Sound coast and over St
Lawrence Island Friday and will continue into Saturday. Strong
winds will develop along the Seward Peninsula and points north
Saturday and continue into Sunday.
Coastal hazard potential days 3 and 4...at this time the track of
the storm is expected to produce mostly offshore winds or wind
directions over a relatively short fetch of open water which will
limit the threat for coastal flooding, high surf and sea ice
pushes onto shore. Coastal residents should however continue to
monitor this situation for the latest forecasts on the storm and
be prepared to take actions to protect property near the shore
should the track of the storm change.
For the latest warnings, advisories, and forecasts go to
Winter Weather Advisory for akz204.
Heavy freezing spray warning for pkz210-pkz220-pkz225-pkz230.
Gale Warning for pkz210.
Small Craft Advisory for pkz220-pkz225.
Brisk Wind Advisory for pkz200.