Scientific Forecaster Discussion
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
129 PM akdt Monday Apr 20 2015
Models...initialized well against the 18z surface analysis. Good
run to run continuity for the short term at to around 60 hours.
Start showing quite a bit of spread in solutions beyond 90 hours.
Will lean on a blend of the GFS...NAM...and sref for the short
Aloft...at 500 hpa...503 dam closed low over Nunivak Island will
move north over St Lawrence Island by Tuesday afternoon...then
over the chukotsk peninsula by Wednesday afternoon. A weak
shortwave extending from the low will move north over the Alaska
Range this evening...and over the Brooks range by Tuesday morning
as a 524 dam low develops...the shortwave will continue to spin
north into the Arctic. A second shortwave will spin north over
the Alaska Range Tuesday night...then over the Brooks range
Wednesday morning. A 519 dam low will develop south of Kodiak
Island Tuesday evening and move east across the Gulf of Alaska
through Thursday. Broad cyclonic flow will continue over the state
around the low over the West Coast with ridging over the Canadian
Surface...broad area of low pressure will persist over the state
into Tuesday morning. A complex low system with several centers
over the eastern Bering Sea will persist into Wednesday before
being absorbed by a 974 mb low that moves into the western Bering
Sea Tuesday evening. A 1003 mb low 400 nm south of Adak will move
to 200nm south of Kodiak Island by Tuesday night at 985 mb...then
continue east to the Queen Charlotte islands by Thursday morning.
A 998 mb low is developing over the upper Yukon this afternoon and
will continue north to be over Barter Island by Tuesday morning at
997 mb. A ridge of high pressure over the northeast Pacific will
push north over the eastern interior by Tuesday morning and over
the eastern Arctic by Wednesday morning as a 1017 mb high develops
over the Yukon territory. Ridging will persist over the eastern
interior and eastern Arctic coast into the weekend.
Arctic coast and Brooks range...low developing over the upper
Yukon will make things interesting the next 24 hours on the
eastern coast. As the low pushes north over Barter Island by
Tuesday morning winds from Barrow east will snap around to
northwest for a time then southwest as the low continues to move
north in to the Arctic. Heaviest precipitation will be over
deadhorse and kuparuk areas with a couple inches as the low moves
just east of there. The Brooks range will see some upslope snow
that could pile up to several inches over the next couple days.
Some weak cold air advection over the next several days will push
temperatures down a few degrees...but no significant cool off
expected. GOES MVFR probability at 20/1730z correlates well with
the sport modis 24hr microphysics at 20/1529z. Band of stratus
over the northwest coast not moving much and not expecting it to.
West Coast and western interior...with the low complex remaining
over the area...expect bands of precipitation moving over the
coastal areas...but timing them will be difficult. Broad area of
MVFR on the GOES probability at 20/1730z can also be seen on the
sport modis 24hr microphysics at 20/1529z. With the low system
quasi stationary...do not expect significant change in the
coastal areas. Inland areas will see some clearing today as
surface ridging pushes north over the area. Winds generally
offshore at 5 to 15 miles per hour on the coast...except in the lower Yukon
Delta winds south at 5 to 15 miles per hour. Inland areas will see variable
winds to 10 miles per hour. Some cooling over the area will push temperatures
Downs a few degrees...but no significant cold air moving over the
Central and eastern interior...might get a little interesting this
afternoon with some unstable conditions aloft. The middle Yukon
valley had around 100 lighting strikes yesterday and that has
moved into the central interior. The difference is some
modification of that airmass could hinder the development of
convection. We will see some showers around the interior tonight
with most of that ending by Tuesday morning. Ridging building
north over the area tonight and Tuesday will bring clearing and
mostly sunny and drier conditions. Winds generally light.
No significant changes in temperatures next couple days.
Extended discussion for days 5 to 8...broad area of cyclonic flow
will persist over the state. Ridging over Canada will keep things
dry in the interior as predominant easterly flow continues.
Fire weather...weak instability this evening...then ridging over
the area the remainder of the week. Winds near the Alaska Range
have dropped off significantly from the last couple days. Expect
some winds near passes in the Alaska Range on Wednesday in the 20
to 35 miles per hour. Relative humidity values will but above 30 percent
Tuesday but expect them to fall into the 20 to 30 percent range
from Wednesday into the weekend.
Sdb Apr 15