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Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
134 PM akdt sun Sep 22 2019

Discussion...

Synopsis...mostly clear skies under weak high pressure will bring
a hard frost to areas south of the Yukon river in the interior
tonight. Temperatures around Fairbanks will fall to the upper 20s,
with temperatures possibly in the teens in the cold spots. Low
pressure over the West Coast and western interior with weak high
pressure over the interior. Cloudy with showers will continue to
the west with partly to mostly cloudy conditions to the east. The
Arctic will remain cloudy with light rain/snow along the coast,
while some clearing will occur in the Brooks range.

Models...run to run continuity is good, even into the extended
periods. 23/12z solutions are in pretty good agreement through
the early extended periods. Location and strength of the major
features are similar and they handle the building ridge and
decaying tropical system well. No significant differences in
precipitation solutions so will lean on an equal blend for
location and amounts. Late in the extended periods solutions
diverge on location and amounts, so will lean more on the
ensemble mean.

Aloft...at 500 hpa...broad area of low heights remains over most
of the state anchored by a 518 dam low over chukotka north of the
Gulf of Anadyr. A 550 dam high persists 200 nm southwest of the
North Pole with ridging extending southeast over the Beaufort Sea.
Weak ridging is pushing north over Prince William Sound and the
southeastern interior. Troughing extends from the chukotka low
over the Arctic coast to a 536 dam low over MacKenzie Bay to a 540
dam low over Skagway and will continue to lift out of the area to
the northeast. The 524 dam low that was over Cape Romanzof
yesterday is drifting over Norton Sound and a shortwave will
extend from Wales to Fairbanks to Tok this evening, continuing
north and east tonight. By Monday morning it will lie from
Kivalina to Barter Island and east with a 533 dam low developing
near Barter Island overnight. A 525 am low in the North Pacific
has moved to just south of Sand Point and will move 300 nm south
of Prince William Sound by Monday morning, then over the southeast
Panhandle late Monday evening. Ridging develops between the
chukotka low and the North Pacific low over Bristol Bay tonight
and a 538 dam high will develop over the southwest Mainland and
move over southcentral Alaska by Monday evening at 543 dam. The
high will move east across the Copper River basin Monday night as
ridging that extends north over the eastern Brooks range moves
east over the alcan border by Tuesday morning. A strong shortwave
associated with the chukotka low will develop behind the high and
move over the eastern Bering Sea Monday evening, and by Tuesday
morning the low will move over the Bering Strait at 524 dam with
the shortwave extending southeast over Marshall to Dillingham to
Unalaska. At 850 hpa...0c isotherm lies from Eagle to Nenana to
Togiak and will lie from Eagle to Livengood to Bethel by Monday
morning and remain stationary into Monday evening, then gets
pushed slowly south and east of the alcan by Wednesday morning.
The 0c isotherm will surge north as a front associated with the
remnants of Tropical Storm Tapah move to the West Coast Wednesday
night.

Surface...weak high pressure over the central and eastern interior
with a 1003 mb high over Fairbanks this afternoon. Broad area of
cyclonic flow to the west with a 997 mb low near wrangel Island, A
994 mb low in Norton Sound, and a 977 mb low near Sand Point. A
1025 mb high remains near the North Pole with high pressure
extending southeast to MacKenzie Bay. Monday morning the the high
will be over Anaktuvuk Pass with high pressure extending north,
then northwest to the high southwest of the North Pole. Low
pressure will extend from 996 mb low in the Chukchi Sea southeast
to 980 mb low 300 nm south of Prince William Sound. A 999 mb low
will develop in MacKenzie Bay and merge into leeside troughing
north of the Brooks range by Tuesday morning. The low will persist
in the Chukchi Sea as it weakens. The low south of Prince William
Sound will continue east and move into the southeast Panhandle.
Weak trough will develop in the upper Yukon Flats with a 1007 mb
low near Beaver. Weak high pressure will also push in north of the
Alaska Range.

Arctic coast and Brooks range...some clearing on the Northwest
Arctic coast, elsewhere generally cloudy with rain, snow, or a
mix of rain and snow. Snow in the eastern Brooks range with up to
1 inch of additional accumulation tonight. No significant
accumulation expected otherwise. Front remains over the coast, so
winds to the south of it will be southeast to southwest to 10 mph,
while north of the front winds will be northeast to north 5 to 15
mph.

West Coast and western interior...low moving into Norton Sound
will continue to spin showers over the region as it moves to the
Seward Peninsula. Inland areas may get a shower, but will
generally be partly to mostly cloudy. Winds northwest to north at
5 to 15 mph offshore, with light winds over the coast, and
northeast to southeast winds to 10 mph inland. Low temperatures
will be near 30 inland, and in the upper 30s along the coast.
Highs will be in the 40s.

Central and eastern interior...some lingering snow and rain
northeast of Fort Yukon this evening will be ending. Otherwise
mostly clear to partly cloudy. Temperatures falling sharply
tonight will bring a hard frost to most locations that have not
seen one yet. Lows tonight falling to the 20s for most areas and
possibly into the teens for the cold spots. Highs Monday will be
in the 40s and 50s, with cooler temperatures the remainder of the
week. Winds generally light and variable.

&&

Coastal hazard potential days 3 and 4...remnants of Tropical Storm
Tapah will move into the western Bering Sea and will produce some
elevated surf along the West Coast Thursday and Friday.

&&

Hydrology...rivers and streams in the central and eastern
interior will rise through tonight, but remain below bankfull,
then slowly fall the remainder of the week. There are no areas of
concern at this time.

&&

Extended forecast for days 4 to 7...West Coast generally cloudy
and showery as remnants of Tropical Storm Tapah, which is
currently near hiroshima Japan, move into the western Bering Sea
and spin a weather front over the West Coast. High pressure will
build over the central and eastern interior with just some periods
of clouds, but generally partly cloudy. The Arctic coast will see
a little of both as initially high pressure will bring some
clearing to the inland locations, but leeside troughing develops
and will bring clouds. Along the Arctic coast expect stratus to
prevail with areas of fog. Temperatures cool a bit mid week, then
warm.

&&

Afg watches/warnings/advisories...

None.

&&

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