Scientific Forecaster Discussion
fxak69 pafg 161224
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
424 am akdt Mon Sep 16 2019
Synopsis...broad low pressure will persist over the state. Winter
weather warning remains in effect for the Brooks range south of
sag river dot with additional snowfall today of 2 to 6 inches.
Isolated showers to the east and south of Fairbanks this morning
will taper off this afternoon, but more showers will move into the
interior later today. Snow mixing with rain north of the Yukon
river tonight with no accumulation. A low moving into the Chukchi
Sea later this week will bring elevated surf to areas from Wales
to Point Hope.
Models...not seeing many differences in the solutions from run to
run, and the 16/00z solutions are in good agreement through about
48 hours. Beyond that there is disagreement on position and
strength of the low that will be sweeping over the state, but the
primary low over the Chukchi Sea is being handled similarly by all
the solutions as it loops around over the area. Big picture in
the extended periods the solutions are in pretty good agreement
with this latest run. Precipitation in the solutions still seems a
bit overdone in the GFS for the near term, but overall they are
all pretty similar in the 36 to 72 hour time frame, so will use a
blend for location and the sref to increase the probabilities.
Aloft...at 500 hpa...a 543 dam low that was over St Matthew
island yesterday has moved over the Gulf of Alaska and will
continue to move southeast. Weak ridging over the interior and the
eastern Bering Sea will move south today. Over the Arctic a 537
dam low that was north of Point Barrow yesterday has moved Over
Point Barrow this morning and will dig south over the upper Kobuk
valley by this evening, then swing around to be over Coldfoot by
Tuesday afternoon at 532 dam. A 534 dam low that was over the
Canadian archipelago is moving west over the northern Beaufort
this morning and will be 200 nm northwest of Point Lay by Tuesday
afternoon, and over the central Chukchi Sea by Wednesday
afternoon. The ridging over the eastern Bering Sea will slide east
and be pushed south by the lows to the north. A 552 dam low will
move over the central Aleutians this morning and near the
pribilofs by Tuesday afternoon at 537 dam, then moves over the
southwest Mainland and merges with the low over the Chukchi Sea
Wednesday. The low over Coldfoot will continue to swing around to
be over Demarcation Point Wednesday morning, then over the
offshore waters before merging with the low over the Chukchi Sea.
At 850 hpa...0c isotherm has moved to lie along the crest of the
Brooks range and will move south to lie from Eagle to Delta
Junction to Denali to McGrath to Emmonak and south of St Lawrence
Island Tuesday morning. The is a pool of -10c over the Northwest
Arctic coast that will linger over the area into early Wednesday
then spin of over chukotka. The 0c isotherm will slide back north
a bit by Wednesday morning and will lie from Chalkyitsik to Tanana
to Emmonak to St Matthew island.
Surface...broad area of low pressure around a 982 mb low that has
moved to the Gulf of Alaska extend north and west over the
remainder of the state and the near shore waters. High pressure
extends south over the western Arctic and chukotka from a 1036 mb
high near the North Pole. A 1016 mb low that was in the Canadian
archipelago has moved to 500 nm north of Barter Island and will
move southwest to be over Wainwright at 1015 mb this evening. The
low continues SW and merges with a 985 mb low in Kuskokwim Bay. A
994 mb low will move into the southern Bering Sea near Adak
tonight, to the Pribilof Islands by Tuesday evening as it deepens
to 988 mb, and to the western Alaska Range by Wednesday afternoon
at 992 mb as it absorbs the low over the Northwest Arctic coast. A
1007 mb low will develop over MacKenzie Bay Tue afternoon and
moves northwest to Point Barrow by Wed afternoon at 999 mb pushing the
high pressure west.
Arctic coast and Brooks range...snow began at Anaktuvuk Pass
around 10 PM Sunday evening and will continue through a good
portion of the day. Snowfall south of The Sag river dot facility
along the Dalton Highway will continue and the winter weather
warning remains in effect with 4 to 8 inches of snow south to
Atigun Pass before it ends. Expect a mix of rain and snow
depending on the time of day over the remainder of the area but no
significant accumulations as most of it will melt as it falls or
soon after. North to east winds 10 to 20 mph for most areas.
Temperatures will continue to trend down with lows in most areas
West Coast and western interior...rain showers tapering off as
the low that brought them to the area moves to the southeast and
some clearing will occur. Winds north to northeast at 5 to 15 mph.
Temperatures cooling as high pressure to the west builds south
then moves over the West Coast by midweek.
Central and eastern interior...some isolated showers to the east
and south of Fairbanks to start the day, then showers developing
over most of the area later in the afternoon as an upper level low
moves to the north of the area. Rainfall amounts will generally
be less than 0.25 inch. Some mixed rain and snow possible tonight
north of the Yukon river with no accumulation expected. Winds west
to north at 5 to 15 mph for most of the area. Some gusty gap
winds to 50 mph in the Alaska Range Tuesday night into Wednesday
Coastal hazard potential days 3 and 4...a low pressure system
north of the Chukchi Sea will produce elevated surf from Wales to
Point Hope Wednesday night through Friday night as seas offshore
build to 7 to 10 ft with wave runup above the normal high tide
Fire weather...temperatures mid week warm a few degrees with
highs in the mid 60s for some interior locations. Elsewhere cooler
temperatures to the west and north of Fairbanks through the week
that will slowly cool even more late in the week. Periods of
clouds and showers with some snow possible during the overnight
hours west of Tanana. Relative humidity values above 40 percent
with excellent overnight recovery. Winds generally north to
northeast 5 to 15 mph. Some gusty gap winds near Alaska Range
passes Tuesday night into Wednesday to 50 mph.
Hydrology...rivers continue to slowly fall or have leveled off.
No areas of concern at this time.
Extended forecast for days 4 to 7...a pretty active, cloudy and
showery pattern set up with an upper level low anchored over the
Chukchi Sea and zonal flow over the Aleutians and northeast
Pacific. Expect a mix of rain and snow in the Arctic and west of
Tanana as highs during the day will still be warming into the
upper 30s in the Arctic, and 40s west of Tanana. Some higher
elevation areas in the interior may also see some mixed rain and
snow during the overnight hours, but primarily it will be rain.
Temperatures will be cooling with lows west of Fairbanks and in
the Arctic falling into the 20s, while in the middle Tanana Valley
they will fall into the 30s.
Winter Storm Warning for akz206.
Small Craft Advisory for pkz210-pkz220-pkz225.