Scientific Forecaster Discussion
Northern Alaska forecast discussion...corrected
National Weather Service Fairbanks Alaska
409 PM akdt Friday Oct 9 2015
Corrected wording in aloft section
aloft...broad upper low remains in the Gulf of Alaska near Sand
Point...with a downstream ridge that extends from the North Slope
southeastward through British Colombia and into the Pacific
northwest. A broad area over the Canadian archipelago completes
an Omega blocking pattern over the Alaska Mainland. A 513 dm low
was seen over the high Arctic at 85n 156 west with short wave
troughing over the chukotsk peninsula.
Surface...973 mb low remains vertically stacked below Gulf of
Alaska low 100 miles southeast of Sand Point...with a trough of
low pressure extending to the northwest into the central Bering
Sea. Meanwhile a 965 mb low around 100 miles west of Sitka
continues to move to the northwest...which is actually the
remnants Post tropical cyclone oho. Broad high pressure remains
over the chukchi and Beaufort seas with a 994 mb low north of the
ridge over the high Arctic near 85 north.
Model guidance...models remain in good agreement of overall Omega
blocking pattern persisting over Alaska through this weekend. A
series of shortwave troughs will weaken the ridge this
weekend...with the ridge expected to become briefly reestablished
on Sunday. Omega block will begin to break down later Sunday...as
strong short wave trough will round the broad Gulf of Alaska low
helping to flatten the downstream ridge. Short wave energy will
also eject out of east Siberia moving into western Alaska early
next week...further weakening the blocking pattern. At the
surface...high pressure of 1025 mb over Siberia will remain nearly
stationary and weaken to 1017 mb by Sun morning. The remnants of
oho will move northwest and merge with the broader 973 mb low near Sand
Point on Saturday. A second low will move into the eastern Gulf
and strengthen to around 967 mb near Sitka by sun evening...then
will move north and dissipate over the southern Yukon. High
pressure off the northern Arctic coast will shift east toward the
Canadian archipelago Saturday night...as lower pressure slides
down from the high Arctic.
North Slope...no major impacts are expected here through the
short and medium range. Gusty winds are expected over the Arctic
coast through the weekend due to pressure gradient that exists
over the northern two thirds of Mainland Alaska. Gale conditions
will exist off the Northwest Arctic coast through Saturday...then
will eventually shift to the east Arctic coast on Sunday. Onshore
flow will generate periods of sea induced fog and flurries through
tonight and possibly into Saturday.
West Coast...broad low pressure in the Gulf of Alaska will bring
scattered rain or snow showers to the West Coast of Alaska
through Sunday. This area will expand into the western interior
early next week as short wave troughing moves into west Alaska. A
fairly strong pressure gradient will exist over the Bering Sea
through this weekend...gradually weakening during the work week
next week as high pressure from east Siberia builds into the
Interior...gusty winds will continue under the northeasterly flow
regime through at least tonight...mainly focused over summits of
the eastern and central interior...as well as the foothills of
the eastern Brooks range. Wind advisories remain in effect mainly
for summits and channeled area for zones 218...219 and 220 until
early Saturday morning for wind gusts between 25 to 35 miles per hour. The
pressure gradient will gradually weaken on Saturday as high
pressure over the Beaufort Sea slides eastward and low pressure
over the Gulf of Alaska broadens. Meanwhile in the southeast
interior...the remnants of Post tropical cyclone oho will bring
snow for the southeast interior late this evening into Saturday.
Models consensus has increased the amount of precipitation with
this system over the past 24 hours...which is no surprise given
the storm having a tropical origin. Current thinking is a 2 to 4
inch snowfall east of a line from Eagle to Black Rapids. The snow
will mix with rain in the afternoon as temperatures warm.
Otherwise...looking for relatively quiet weather after
Saturday...persisting into early next week.
Coastal hazard potential days 3 and 4...none
Wind Advisory for akz218-akz219-akz220.
Small Craft Advisory for pkz200-pkz210-pkz215-pkz220-pkz235-
Gale Warning for pkz220-pkz225-pkz230.
Heavy freezing spray warning for pkz235-pkz240-pkz245.
Nova Scotia Oct 15