Scientific Forecaster Discussion
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
437 PM akst Tuesday Nov 24 2015
the winter weather event previously advertised is well underway
across much of northern Alaska. The main concerns this forecast
package were involving the near-term weather and the ongoing
winter weather hazards across the West Coast...interior Alaska...and
northeastern Brooks range.
Also...there is the potential for some impacts within the
Thanksgiving day through Friday time frame for the southern
Models are in fair agreement through the first 54 hours/early Thursday
period before differences in the large scale pattern become more
apparent. Deterministic models then begin to diverge with respect
to timing and strength of features as a strong low aloft moves
eastward across the Aleutian Islands within the Wednesday to early Friday
Aloft...currently a longwave 500 hpa ridge spans north across the
North Pacific into the eastern third of Alaska and the Yukon
territory. Elsewhere...a longwave trough is positioned across the
Bering Sea with a 495 dam low near wrangel island. The ridge will
continue to slowly drift eastward to be over Southeast Alaska-Yukon by Wednesday as
a low south of the Kamchatka peninsula in the North Pacific moves
to the western Aleutian Islands. The low will continue to drift
east and be over the eastern Aleutian Islands by Thanksgiving day
as the ridge gets farther displaced east from the Queen Charlotte
islands to the northwest territories. The 500 hpa low begins
lifting north and will be over Bristol Bay by Friday.
Surface...a 982 mb low sits near over St Lawrence Island with an
occluded front this positioned roughly from near Kivalina to
Huslia with a broad surface high at 1038 mb spanning from the North
Pacific near 50n 140w...to Southeast Alaska...to British Columbia. The surface
low will move north through the Bering Strait over the next 12 hours
and weaken to 992 mb just west of Point Hope. A still developing
low in the North Pacific will move into the western Aleutian
Islands by Wednesday at 966 mb as the aforementioned weakening low fills
into 996 mb. The strong low will continue to move east and be near
Umnak Island by Thanksgiving day at 970 mb with a trough extending
northeast into south central Alaska and eastern interior Alaska.
Winter storm warnings and winter weather advisories continue for
a large portion of zones across northern Alaska in the West Coast and
interior. The synoptic setup has been very supportive for this
winter weather event with a southwest flow ushering moist air
inland. Both McGrath and Fairbanks upper air soundings showed precipitable water
values that were 152 and 181 percent of normal for this time of
year. In general...the winter weather event will start winding
down across the West Coast tonight as winds and snow decrease
with the surface low lifting north to be near Point Hope.
Elsewhere...interior Alaska will continue to see periods of snow and
scattered showers tonight and going forward into tomorrow night.
Looking ahead...there is concern for the potential of freezing
rain that will have to be further monitored. The period spans from
Thanksgiving night/Thursday night to Friday and is expected to be limited
to portions of the southern interior...mainly along and south of
the Tanana Valley. Maximum warm-layer aloft is sufficient for
partial melting...however...p-type will be difficult to determine
this far out given the complexity of the thermodynamic profiles
and model consistency lately.
Coastal hazard potential days 3 and 4...none.
high surf advisory for akz211-akz212-akz213-akz214.
Winter Storm Warning for akz207-akz208-akz210-akz211-akz216-
Blizzard Warning for akz209.
Winter Weather Advisory for akz206-akz222-akz227.
Heavy freezing spray warning for pkz200-pkz210-pkz220-pkz225.
Small Craft Advisory for pkz210-pkz220-pkz225.
Brisk Wind Advisory for pkz215-pkz230-pkz235.
Gale Warning for pkz200.
Et Nov 15