Scientific Forecaster Discussion
fxak69 pafg 282156
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
156 PM akdt Wed Jun 28 2017
the 12z model suite initialized with few differences between model
families however the model suite continues to play catch up with
the observations. The 06z model suite initialized with a 2 to 4 mb
gradient deficit between the surface high pressure near Banks
Island and the thermal trough over the interior as well as the low
in the Gulf of Alaska. The 12z models suite also initialized with
few differences between model families however the 2 to 4 mb
gradient deficit has diminished to 1 to 2 mbs between modeled and
observed slp's. The expected and observed impacts of the models
initializing with weaker gradients will be that observed winds
will likely be slightly stronger than modeled winds. Model spread
remains minimal in the the short range but has increased spread in
the mid range as compared to yesterdays 12z model suite especially
past Saturday. Considerable spread has crept into the model suite
in the long range.
Aloft at 500 hpa, the longwave trough over the southern Chukchi
Sea extends south through the Bering Strait and through the
central Aleutians. An upper level ridge remains over northern
Alaska and extends southeast into the southern Yukon and will
slowly move east over the Yukon and northwest territories through
Friday. A series of shortwaves will rotate north along the West
Coast around an upper level low over the central Bering Sea
through the weekend.
On the surface a 1018 mb high pressure system located 200 nm west
of Banks Island will drift to the east and be located over Banks
Island Friday. East winds will continue along the eastern North
Slope and will bring periods of low clouds and fog especially
along the the coastal areas to the east of Barrow.
Over the central and eastern interior isolated thunderstorms are
expected along and to the north and east of the thermal trough
which currently extends along a Ambler to Bettles to Eagle line.
Weak downslope flow will limit thunderstorm activity south and
east of the trough over the central and eastern interior however
an isolated thunderstorm is possible this evening. Red flag
temperature criteria will likely be met over much of the central
and eastern interior Thursday and Friday as temperatures reach
into the mid 70s. Red flag minimum relative humidity criteria will
likely be met over much of the central and eastern interior as
relative humidities drop into the mid 20s in over the eastern
interior and into the 20s and 30s over the central interior. Red
flag criteria for winds are not expected to be met over the
central and eastern interior however localized areas along and
near Alaska Range passes and foothills will approach criteria
this evening as well as Thursday and Friday.
Over the West Coast and western interior a series of shortwaves
will move north through the area and will be the focus for periods
of rain and for scattered rain showers.
Coastal hazard potential days 3 and 4...none.
near red flag conditions are expected this evening and again
Thursday afternoon and evening over the Yukon Flats as temperature
and minimum relative humidity criteria will be met lacking only
wind criteria. Red flag conditions for minimum relative humidity
will likely be met this evening and again on Thursday afternoon
and evening along and near the Alaska Range passes. Winds will
come close to meeting red flag criteria in these areas this
evening and again on Thursday afternoon and evening.
expect glacial rivers will be rising through the weekend as
temperatures and freezing levels remain above normal.
brisk Wind Advisory for pkz235-pkz240-pkz245.