Scientific Forecaster Discussion
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
607 am akst Sat Feb 28 2015
Ridge aloft along the alcan border and southward will be pushed
eastward and flattened as a vigorous short wave trough cuts
eastward through the ridge. The short wave trough is now over the
Bering Sea along 175w...and will move east to the alcan border by
midnight tonight. After the passage of the short wave trough...ridging
will rebuild sun and Monday...then weaken as it moves into the Yukon
territory Tuesday. Another short wave trough will move to the northern
Bering Sea and chukchi by Tuesday morning...and move eastward across
the Arctic slope slope and Beaufort Sea through Wednesday morning. The
short wave trough will bring colder air aloft...especially over
the North Slope and Beaufort Sea...but temperatures aloft will
rebound sun into Monday as upper ridging rebuilds. The second short
wave will impact areas mainly from the Brooks range northward.
06z GFS/NAM model runs initialize well on the 1004 mb low center
just west of Gambell. The low will track across northwest Alaska
and northeastward into the Beaufort Sea. GFS/NAM prognosticated position
for 9 PM Sat is about 200 miles north of Demarcation Point...central
pressure around 993 mb. GFS forecast agrees well with the 00z gefs
ensemble mean. By 9 am sun...the low will move eastward to Banks
Island weakening to around 996 mb. A strong cold front associated
with the low center will sweep eastward across northern Alaska
today into this evening. High pressure will rapidly rebuild
eastward following the cold frontal passage. The very tight
pressure gradient following the cold front passage...along with
rapid pressure rises and sharp cold advection will bring a period
of colder temperatures and gusty winds to much of northern Alaska.
strong winds...snow...and blowing snow will develop over the
northwest Alaska coast this morning...spreading rapidly eastward
this afternoon into this evening as the cold front moves eastward.
Several inches of snow are expected. Blizzard conditions will
develop on the central Arctic coast this afternoon and over the
eastern Arctic coast early this evening. Severe blizzard
conditions will develop on the eastern Arctic coast early
this evening and continue overnight. Blizzard conditions will
continue through around noon sun on the central Arctic coast...
and through around 6 PM sun on the eastern Arctic coast. The cold
advection and pressure rises behind the front are very strong. On
the eastern Arctic coast...a pressure rise of almost 25 mb is
expected between 6 PM this evening and 3 am sun...with another 10
mb rise between 3 am sun and 9 am sun. Temperatures at the surface
and at lower levels aloft will fall by 22-23 degrees celsius
between 6 PM this evening and 3 am sun. Winds at lower elevations
aloft will maximum out at 60-65 knots. These factors along with the tight
pressure gradient are expected to generate west winds to around
65 miles per hour with gusts to 80 miles per hour on the eastern Arctic coast tonight.
West winds gusting to 50-60 miles per hour are expected on the central Arctic
coast. A period of strong winds is expected elsewhere on the
Arctic coast...but not as strong as winds expected on the central
and eastern Arctic coast. Winds will become light over the
northwest coast by Sun afternoon...then become east 15-25 miles per hour by
late Sun night. Winds will become light over the northern Arctic
coast by sun evening...and on the central and eastern Arctic
coasts by late Sun night.
The next surface low center is prognosticated to move eastward across
the coast Tuesday into Tuesday night. Since the projected track of
this low is along the Arctic coast instead of farther to
the north...surface winds will be substantially less than
those produced by the current system...and redevelopment
of blizzard conditions is not anticipated.
the eastward moving cold front and short wave trough aloft...along
with the associated tight pressure gradient...cold advection...and
strong pressure rises...will bring a period of gusty winds and
snow to the western interior today...and to the central and
eastern interior later this afternoon and tonight. Snow amounts
are expected to be 1 to 3 inches in most areas. Winds are expected
to gust to as high as 40-45 miles per hour at valley levels in the central
and eastern interior. Higher summits will likely experience winds
of 30 to 50 miles per hour and near blizzard conditions in snow and blowing
Over the middle Tanana Valley...winds are expected to increase
late this afternoon with snow and blowing snow developing. The
strongest winds...along with more snow...are expected to be
between 6 PM this evening and midnight tonight...coincident with
the period of strongest pressure rises and cold advection. Winds
at lower levels of aloft are expected to maximum out at around 40 knots.
These factors...along with the strong pressure gradient behind the
frontal passage...will result in blustery conditions with winds
gusting to as high as 45 miles per hour. Winds will diminish during the late
night hours and become light by Sun morning.
On the West Coast...snow is expected to end in almost all areas
by early this evening. Winter storm warnings continue in effect
for zones 207-208-213-217...but are scheduled to end today or
this evening. GOES infrared loop currently shows the back edge of the
coldest cloud tops and snow currently extends from Point Hope
to Nome and Emmonak...and is moving slowly eastward.
Additional snow amounts expected on the West Coast...
zone 207...6 inches.
Zone 208...6 to 10 inches.
Zone 209...4 inches.
Zone 210...4 inches.
Zone 211...up to 4 inches.
Zone 212...4 inches.
Zone 213...3 inches.
Zone 216...up to 4 inches.
Zone 217...6 to 10 inches.
Winter Storm Warning for akz207-akz208-akz213-akz217.
Blizzard Warning for akz203-akz204-akz206.
Winter Weather Advisory for akz201-akz202-akz205-akz209-akz210-
Brisk Wind Advisory for pkz200-pkz210-pkz215-pkz220-pkz225-
Gale Warning for pkz240.
Hurricane force wind warning for pkz245.
Rf Feb 15