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Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
230 PM akdt sun Aug 25 2019

Synopsis...
an Arctic cold front that stretches from Barter Island to
Wainwright, will remain quasi-stationary through 4am Tue, then
push south along the Brooks range Tue PM, and over the northern
interior on Wed. There will be rain along the front, that will
change to rain and snow north of the front. Expect 1.00 inch of
rain in the areas from Wainwright to Sagwon to deadhorse tonight
through Mon night. Most precip with this will be rain, with snow
above 4500 ft and could see several inches of snow above 4500
feet tonight through Mon night. Could see heavier snow of 4+
inches Tue into Tue night above 4000 ft in the Brooks range, with
snow level dropping Tue night, as the front pushes in the Brooks
range.



Aloft...
the long wave pattern consists of a deep trough stretching from
the high Arctic south over Alaska into the western Gulf of Alaska
with a ridge over the Bering Sea and NE Russia. The pattern is
progressive with the trough moving to the alcan border by 4pm Tue
with the ridge building over the West Coast and western interior,
the the trough moving over northwest Canada by 4pm Tue with the ridge
building over the West Coast and interior of Alaska and then the
ridge flattening slightly on Wed. This will cause northwest flow
aloft to turn westerly on Mon, and then increase on Tue and Wed.
This will server to keep most of the weather from the Brooks range
north through Tue, and possibly drop into the northern interior
on Wed.

A series of short wave troughs will move east across the North
Slope through Tue in this westerly flow. Due to timing
uncertainties between models, we can only say that it will be very
wet on the North Slope through Tue with little skill on timing,
and with heaviest precip in the upslope areas of northwest facing slopes
of the eastern Brooks range. Snow level in the Brooks will be
4500 ft from today through Mon, then falling to 4000 ft on Tue
and then lower Tue night. Expect isolated light showers over the
interior tonight through Tue occuring with the short waves.



Surface...
a 987 mb low 500 nm north of Barter Island will remain stationary
tonight, then move east Mon and Tue. A cold front stretching from
this low to Banks Island to Barter Island to Wainwright then west will
remain stationary through 4am Tue, then move south to the crest of
the Brooks range by 4pm Tue, and then over the northern interior
Tue night and Wed. There will be rain along the front, with mixed
rain and snow north of the front. Will see snow level 4500 feet
or higher south of the front, dropping to 4000 ft along the front,
and to 2000 feet north of the front over the North Slope Tue into
Wed.

A wave along the front that is now west of wrangel island will
move to 100 nm northwest of Point Hope by 4pm Mon, to near Point
Lay as a 1005 mb low by 4am Tue, to near Arctic Village as a 1003
mb low by 4pm Tue, and then moving east of the alcan border.
Expect rain to be enhanced just ahead of this wave, and then
changing to snow at elevation just after the frontal wave as low
level flow turns north and upslope of the north slopes of zones
206.

Also expect SW winds 15-25kt to developing over the northern
Bering and the Chukchi Sea south of this low late tonight through
Mon, then turning west 10-20kt along the West Coast Mon night into
Tue. These west to SW winds will push stratus and fog into the West
Coast from late tonight through Tue.

Over the interior expect west winds 10-20kt to spread over the
interior on Tue as the low moves east and tightens the gradient.

High pressure over the southern Bering Sea will build over the
southern interior through Tue and then persist into Wed. This
will help to tighten the gradient and keep the west winds going
Mon PM into Tue. This will also keep clouds scattered to broken over
the southern interior Mon and Tue.

&&

Discussion...
models initialize well aloft at 00z and show similar solutions
through 4am Tue. After that time, models differ significantly in
timing and strength of short waves moves east across the Arctic
coast, with the GFS taking a stronger short wave east across the
North Slope on Tue, with the NAM and Canadian about 12 hrs slower
taking it east on Tue night, and the ecmf moving the feature east
on Wed and Wed night. Models show better agreement on movement of
the surface Arctic front, while the movement of waves along the
front and precipitation timing with each wave is much more
variable. With significant differences in precip timing and
amounts, will use a blend of the ecmf, NAM and GFS for precip
timing and amounts.

At 15z at the surface, models verify well and show similar
solutions through 4pm Mon. After that time the ecmf differs
significantly from the NAM and GFS by having the Arctic front
along or north of the Arctic coast while the GFS and NAM keep the
front inland. At this time will use the GFS to locate the front
and surface lows from Mon through Wed as it is fairly close tot he
NAM solution.

What we can say is that the Arctic front will cause light rain
and snow across the North Slope tonight, and then rain and snow
likely Mon into Tue, with a chance Tue night and Wed. Expect
several inches of snow above 4000 ft in zone 206 tonight through
Mon night with rain below that elevation, and then the potential
for significant snow above 4000 ft Tue and Tue night.




Coastal hazard potential days 3 and 4...
southwest winds 15-20 kt over the northern Bering Sea will Mon
through Wed will cause slightly elevated sea levels and waves
along the West Coast from the Bering Strait south Mon-Wed night.
Main concern will be that waves will wash above the normal high
tide line and could wash belongings off of the beaches from the
Bering Strait to the Yukon Delta.

&&

Fire weather...
highs will be in the upper 50s and lower 60s the next several
days, with min relative humidity 25-45%, driest in the central and eastern
interior. Temps will cool and relative humidity rise on Wed. Will see west winds
10-15 mph Mon into Tue.

&&

Hydrology...
expect 1.00 inch of rain in the areas from Wainwright to Sagwon
to deadhorse tonight through Mon night. This will cause sharp
rises on North Slope rivers Mon through Wed.

Interior rivers remain high, but are falling slowly and will
continue to fall slowly this week.

&&

Afg watches/warnings/advisories...
Small Craft Advisory for pkz210-pkz220-pkz225-pkz230.
&&

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