Scientific Forecaster Discussion
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
201 am akdt Tuesday Oct 13 2015
Models...reasonable agreement out to the Middle Range before it
falls apart. Run to run has also been good the last couple days.
Will lean mainly on the NAM for the short term.
Aloft...at 500 hpa...long wave trough over the West Coast with a
506 dam low 400 nm northwest of wrangel Island...A 520 dam low
over Cape Lisburne...and a 526 dam low just north of Unimak
Island. Weak ridge persists over the eastern half of the state.
By Wednesday morning the low north of wrangel moves west. The low
near Cape Lisburne moves to 250 nm northeast of Barrow at 524
dam...and the low near Unimak Island moves to the lower Yukon
Delta coast at 539 dam...and the ridge builds over the alcan
border with 537 dam heights pushing north to the Arctic coast.
Heights over the southeast interior will increase from 534 dam to
around 546 dam. As the low moves north into the Arctic a short
wave over the Bering Strait will move east across the Arctic coast
and Brooks range to lie from the low to kuparuk to Ambler to
Kipnuk to Unalaska. By late Thursday afternoon the shortwave
shears and the northern half moves east of the alcan border with
the southern portion remains over the southwest Mainland and
Bristol Bay. At 850 hpa...temperatures will remain below zero as
the zero isotherm remains south of the Alaska Range through Friday
before moving back to the north to lie roughly over the Yukon
Surface...relatively benign pattern over the forecast area with
weak troughing over the Arctic coast and Bering Strait...weak
troughing over the interior dissipating...and the low over the
northern Gulf dissipating. Through the day the ridging will build
north over the interior and troughing will extend east across the
Arctic and over the West Coast to the west of the Yukon river.
Benign pattern will persist with weak ridging remaining over
interior Alaska...ridging pushing north over the Brooks
range...and the Seward Peninsula. Weak troughing will remain over
the Arctic coast and the southwest Mainland. Troughing over the
southwest Mainland and western Alaska Range will slowly dissipate
by Thursday afternoon.
Arctic coast and Brooks range...shortwave will spread showers
over the northwest coast from Barrow west today and
tonight...then east of deadhorse on Wednesday. Some low stratus
over the coast and plains showing up on the modis nighttime
microphysics product at 13/0629z. Expect some patchy freezing
drizzle to be reported again today. There seems to be some
correlation between the occurrence of freezing drizzle and mixed
phase being reported on the GOES cloud phase product. Snow
amounts will not be very big with up to 2 inches possible. Winds
will be all over with some onshore over the northwest coast and
offshore over the eastern Arctic. Wind speeds will generally be
less than 15 miles per hour. No significant change in temperatures.
West Coast and western interior...pretty cloudy over most of the
coastal areas with mainly scattered showers. Mainly snow showers
in the Kotzebue Sound region and north of the Bering Strait. To
the south of the Bering Strait and from Norton Sound south
looking for a mix of snow and rain showers. No significant snow
accumulation is expected. North winds to the west of the Yukon
river with some gusts to around 35 miles per hour in the Bering Strait and St
Lawrence Island...otherwise winds generally less than 15 miles per hour.
Inland areas will generally be cloudy with light south to
southwest winds less than 10 miles per hour. No significant change in
Central and eastern interior...some lingering showers east of
Fairbanks this morning...otherwise showers ending with some
clearing through the day. Modis nighttime microphysics product at
13/0629z shows a pretty good patch of low stratus over the eastern
half of zone 221...most of zone 222...zone 223...and east of the
Parks Highway in 225. High clouds mask zones 224 and 226...but
observations indicate the low clouds extend over those areas.
Winds generally light. Not much change in temperatures today and
tonight...though in areas that clear out temperature will fall
Satellite...modis microphysics at 13/0629z clearly showing the
stratus over the Arctic coast and interior. GOES MVFR/IFR/LIFR
products at 13/0713z and observations in those areas verify the
low clouds. Using the GOES cloud phase product to try and find a
correlation between the freezing drizzle being reported on the
Arctic coast and cloud phase reported on the product. It appears
that the mixed cloud phase may indicate the potential for
freezing drizzle...but will continue to look into this.
Coastal hazard potential days 3 and 4...none.
Heavy freezing spray warning for pkz235-pkz240.
Small Craft Advisory for pkz235.
Sdb/rm Oct 15