Scientific Forecaster Discussion
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
531 am akst Friday Dec 19 2014
quiet weather pattern to continue over northern Alaska
weak upper level ridge extending east-west across northern Alaska
will continue to drift slowly northward and weaken through
Sat...with a weak low pressure pattern taking over the southern
two thirds of the northern Alaska Mainland by late Sat night.
Current operational model runs are in good agreement in showing
By Monday afternoon...operational models indicating an upper trough
will move eastward out of Siberia to the Bering and chukchi seas
by Monday night...bringing a colder air mass to that area and to the
Alaska West Coast. Model solutions differ in the handling'of this
trough next week...GFS lifting the trough northeastward across the
Brooks range and Arctic slope through Wednesday while the exmwf holds
the trough in place. The GFS ensemble mean looks closer to the
European model (ecmwf) forecast...which appears to have good support from its
ensemble mean. A mean south to southwest flow aloft is likely to
be predominant over most if not all of northern Alaska during the
early part of next week...keeping temperatures above normal. This
is indicated in both the GFS and European model (ecmwf) ensemble mean 850 mb. Naefs
ensemble means also indicates somewhat above normal 850 mb
temperatures over the southeastern two thirds of the northern
Alaska Mainland early next week.
GOES infrared loop and polar satellite nighttime microphysics rgb
imaging show areas of stratus remaining over the northeast
quarter of the northern Alaska Mainland...stratus is much more
extensive in areas to the east over northwest Canada. We are
looking for gradual dissipation of the remaining stratus over the
northeast interior today with a small increase in the surface
pressure gradient providing some low level mixing.
Flurries and/or scattered snow showers continuing over most
of the Arctic coast today...and over the central and western
portions parts of the West Coast tonight.
The Tanana Valley jet continues in progress...models suggest
a gradual decrease in wind speeds as the small scale ridge
nosing eastward into the upper Tanana Valley gradually weakens.
Over the western marine areas...current GFS/European model (ecmwf) solutions
developing a strong low near 54n/178e by 18z Tuesday...European model (ecmwf)
central pressure of 948 mb is about 20 mb deeper than the GFS.
Beyond Tuesday...GFS/ECMWF solutions diverge rapidly...forecast
confidence beyond Tuesday is low. Operational GFS suggests development
of system over the Alaska Peninsula Wednesday which could generate
northeast gales over the northern Bering Sea by Thursday...but this
system as well as the Bering Sea low are lost in the GFS ensemble
mean solution. The European model (ecmwf) is much closer to its ensemble mean...
maintaining the strong low over the western Bering and at this
time the European model (ecmwf) solution is preferred.
Coastal hazard potential days 3 and 4...none
heavy freezing spray warning for pkz210.
Small Craft Advisory for pkz210.
Brisk Wind Advisory for pkz220-pkz225-pkz230-pkz240-pkz245.
Rf Dec 14