Scientific Forecaster Discussion
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Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
223 PM akdt Mon Oct 23 2017
active weather pattern this week for northern Alaska.
The persistent long wave that has Sat over western Alaska will
retrograde to the west over the Bering Sea through the week. As
the long wave retrogrades over the Bering Sea a 993 mb surface low
pressure currently east of the kamchtka peninsula will undergo
dramatic cyclogenisis with an anticipated deepening of over 50 mb
in 24 hours to around 940 mb as the low moves east tonight into
the western Aleutians. The low will continue to move east along
the Aleutian Islands Tuesday and will weaken to around 955 mb by
Wednesday morning as the low passes near Atka and weakens further
to 975 mb as it moves just north of Dutch Harbor Thursday morning.
A strong front extending east of the low will push northeast into
southwest Alaska and will bring a round of strong winds, a period
of heavy snow over the yk Delta and Norton Sound and St Lawrence
Island. The snow will mix with freezing rain before turning to
rain Wednesday morning. The snow will mix with and change over to
freezing rain over the southern portions of the western interior.
2 to 4 inches of snow are expected in the lower yk Delta and
southern Seward Peninsula and 4 to 7 inches of snow are expected
in the western interior. Ice accumulations in the southern
portions of the western interior are expected to be less than one
tenth of an inch. Winter weather advisories have been issued for
these areas for a host of winter conditions including snow,
blowing snow, strong winds and ice accumulations.
As the Bering Sea low and moves east along the Aleutian chain the
mid level and upper level winds ahead of the storm will increase
dramatically and will become nearly perpendicular to the Alaska
Range beginning Tuesday evening and will continue through
Thursday. A Strong Mountain wave is expected to develop over the
central Alaska Range Tuesday afternoon or evening and over the
eastern Alaska Range Tuesday evening. The exact timing and
duration of the winds are hard to pin down as the mid and upper
level wind field will be alternating between southerly and
southwesterly which will impact the strength of the mountain wave
and how much the stronger winds aloft are force to the surface.
Expect the potential for very strong wind gusts in excess of 70
mph to alternately develop and diminish and develop again from
Tuesday afternoon to Thursday along the northern slopes, foothills
and passes of the Alaska Range. The strongest winds are expected
Wednesday morning. Computer guidance continues to indicate the
potential for the strong winds to impact the Healy and the Delta
Junction areas. High wind watches have been issued for the central
and eastern Alaska Range and the Delta Junction area beginning
Tuesday afternoon and evening.
The 12z model suite initialized well against the 12 analysis with
the exception of the low near Nunivak Island which models under
developed. The placement of features was overall good. Model
spread was minimal in the short range between model families as
well as from model run to model run. Model spread increases
significantly in both the mid range and long range.
Coastal hazard potential days 3 and 4...none.
high wind watch for akz223-akz225-akz226.
Winter Weather Advisory for akz210-akz211-akz212-akz213-akz214-
Small Craft Advisory for pkz210.