Scientific Forecaster Discussion
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Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
505 am akdt Mon Apr 23 2018
broad low pressure over the central Bering Sea containing two
distinct height minima are exhibiting a fujiwara-type interaction
as they begin the merging process. The first of several
shortwaves associated with this system has already begun its trek
up the Alaska West Coast, thus ending the relative calm of the last
several days. Main impacts from this system will include rain and
snow along much of the West Coast and Brooks range, as well as an
amplified Chinook pattern for the interior, especially as the
occluded front will be accompanied by a strong southerly low-mid
level jet. Mid level ridging over the northwestern Chukchi Sea
continues to support stable conditions across the North Slope,
though the impact of the aforementioned shortwaves will gradually
erode its effect over this area.
stable conditions persist across the North Slope, though areas of
low, thin stratus associated with weak northeasterly onshore flow
exist from Point Barrow eastward. Sfc high pressure situated
approx 200nm north of Point Barrow will retreat east towards Banks
Island by late Monday in advance of a series of shortwaves moving
through the Brooks range. The first of these waves will reach the
southern Chukchi Sea early Tuesday and progress northward to
roughly parallel the Arctic coastline by early Wednesday. Snow and
rain can be expected along the chukchi coast south of Cape
Lisburne, with snow lvls generally in the 500-1000' range
Tuesday. Southerly flow across the Brooks range will be amplified
by the arrival of the short wave and will act to enhance the
formation of a Lee-side low which will deepen over Barter Island
Wednesday evening. Mixed wintry precip across the eastern Arctic
coast Wednesday may be enhanced as the low will facilitate
northeasterly onshore flow and increased convergence in the
region. By Thursday, a ridge is expected to build across the
northern Arctic, forcing the low eastward and permitting the
return of stable conditions for the latter half of the week.
West Coast and western interior...
the first shortwave trough has reached the Yukon Delta and will
continue northward producing a rain which will mix with snow in
the higher elevations. The band of precip mixed precip will reach
Nome by this afternoon then the Kotzebue Sound by Tuesday morning.
Subsequent waves will draw in additional moisture content and
warmer air, producing a gradual increase in snow levels precip
accumulation through Tuesday. Additionally, a strong occlusion
emanating from the low centered in the central Bering will spawn a
new surface low which will rapidly deepen over Nunivak Island
early Tuesday and proceed to St. Lawrence Island Tuesday evening
as a 968 mb low. The surge of southeasterly moisture associated
with this cyclogenesis will inflict heavy precip along parts of
the Nulato Hills and Kuskokwim Mountains Tuesday morning and
afternoon and will affect the southern Seward Peninsula and St.
Lawrence Island later in the afternoon. By early Thursday, the
weakening low will track north into the Chukchi Sea as ridging
builds across the central Bering. Cooler SW winds will infiltrate
the West Coast and interior, producing widespread rain and snow
showers west of the Kuskokwim Mountains.
Central and eastern interior...
Chinook winds continue to keep much of the Tanana Valley warm and
dry. Snow will increase in the higher terrain of the Alaska Range
Monday as the shortwaves progress northward. By Monday evening,
winds will begin to increase as the low level jet and frontal
occlusion reach the Alaska Range. By Tuesday, a very strong Chinook
pattern will include winds up to 70 mph throughout the Alaska Range
with gusts possibly exceeding 100 mph over Mt. Denali. Heavy snow
in the higher terrain of the Alaska Range will combine to form
dangerous conditions through early Wednesday. Strong winds through
Isabel Pass may reach as far north as Delta Junction, producing
erratic gusty winds up to 60 mph at times. Additionally, snow can
be expected late Tuesday in the eastern Brooks range as moisture-
laden SW winds impact the higher terrain. Weak Chinook conditions
will persist throughout the latter half of the week, shielding
much of the eastern interior from the influx of marine
southwesterly flow that will inundate much of the west with
good initialization and tight agreement in track through Thursday.
The European model (ecmwf) again remains the outlier regarding intensity as it
keeps the Bering sfc low around 6 mb higher than its Peers.
Coastal hazard potential days 3 and 4...none.
Chinook conditions persist for the Tanana Valley and will continue
through the latter part of the week. Strong, erratic winds can be
expected as far north as Delta Junction Tuesday. Red flag
conditions may be met Tuesday through Thursday in this area.
Wind Advisory for akz223-akz227.
High Wind Warning for akz225-akz226.
Small Craft Advisory for pkz200-pkz225-pkz230.
Heavy freezing spray warning for pkz210.
Brisk Wind Advisory for pkz240-pkz245.
Gale Warning for pkz210.