Scientific Forecaster Discussion
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
138 PM akst Thursday Dec 25 2014
current GFS/NAM operational runs show similar solutions in the
handling of the upper trough moving eastward across northern
Alaska...followed by a building ridge. Two rapidly moving low
amplitude short waves will move up the back side of the ridge
sun through Sun night.
Upper level trough extending from the high Arctic southward along
180w to the northern Bering Sea will weaken slowly as it moves
eastward to the alcan border by midday Monday. Weak smooth top upper
ridge over western Aleutians will build rapidly...becoming a
strong high amplitude ridge extending from the central Beaufort
Sea to the eastern north Gulf Coast and south southeastward by Sat
night. The first of two short waves will move northward across the
eastern Bering Sea Sat night through Sun morning...and across
northwest Alaska Sun afternoon and evening. The second short wave
will move northward to the Yukon Delta region by Sun afternoon...then
move northeastward across the northern and western interior and
the Brooks range Sun night through middle day Monday...reaching the
northern alcan border by midday Monday. This short wave is also
prognosticated to dampen out some as it tracks northeastward. The two
short waves will put a temporary Dent in the ridge as the ridge
axis moves eastward into the Yukon territory Sun night. A new
ridge will rebuild sun tonight to extend from the northern Bering
Sea to the Panhandle and southeastward.
1017 mb high centered 50 miles northwest of wrangel island
will build to a 1036 mb high centered over the central Arctic
coast by Sat morning...then build to a 1044 mb high over the
Yukon territory by 12z sun. A low pressure trough extends from
Kuskokwim Bay to Demarcation Point. By Friday afternoon a 1011 mb low
will develop over the central interior...then weaken into a weak
trough over the northeast interior late Friday night.
Locally strong and gusty winds in zone 226 passes are expected
to diminish later this evening as pressures over the area
gradually rise and the pressure gradient decreases. Snow
over the western interior...western Arctic slope and western
Brooks range gradually spreading eastward through Sat night as the
first short wave moves east along with the development of the
surface low over the central interior.
974 mb low about 100 miles south of Shemya will deepen to a 960
mb center just north of Shemya by late tonight...then moving
a wobbly path to 150 miles north northwest of Shemya by late Friday
night...then filling to a 970 mb low centered about 300 miles
north northwest of Shemya by late Sat night. Ahead of the
associated weather front...winds over St Lawrence Island and
marine zone pkz210 will begin to increase Friday afternoon.
Easterly gales developing over southern and western areas of
marine zone pkz210 Friday afternoon...and to St Lawrence Island by
early Friday evening...and to the northern areas of pkz210 late Sat
night. The weather front will move northward to St Lawrence Island
by middle morning Sat and to the Bering Strait by middle afternoon.
Winds shifting to south or south and decreasing after the frontal
passage. A band of snow out ahead of the front will move northward
across the West Coast Friday night through Sat.
More snow possible over the West Coast and western interior
Sat and Sat night as another wave moves northward. Track...timing
and strength of a surface feature is uncertain at this time with
NAM/GFS differing substantially...but both models indicating
widespread precipitation. Future model runs will need to
be monitored since there is potential for an active system
producing strong winds and widespread precipitation.
Temperatures over southwest Alaska and southwest interior will
likely be warm enough for mixed precipitation with both
systems. BUFKIT GFS model soundings indicating freezing level
rising to around 3000 feet feet over the southern parts of the West
Coast and western interior Sat. A little cooling Sat night then
another surge of warm air sun with freezing level over the
southern areas rising to as high as 4000-5000 feet.
Strong Chinook winds expected to redevelop in Alaska Range
Coastal hazard potential days 3 and 4...none
Winter Weather Advisory for akz216-akz217-akz219.
Wind Advisory for akz226.
Heavy freezing spray warning for pkz210.
Small Craft Advisory for pkz210.
Brisk Wind Advisory for pkz220-pkz225.
Rf Dec 14