Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
625 am akdt Monday Sep 1 2014
Analysis and upper levels...
water vapor satellite imagery shows a trough over the Mainland
with the parent low spinning north of Barrow early this morning. A
trough axis extends from Barter Island to the northern Kenai and
is swinging east across the state. Skies are mostly clear for
south central as subsidence is drying the atmosphere along the
base of the trough. To the west...a ridge is building into the
Bering...streaming abundant moisture around to the northwest coast
where a front is a focus for rain developing along the Seward
Peninsula to lower Yukon valley.
models are in agreement with the synoptic pattern through Wednesday
afternoon and then begin to stray on the evolution of a long wave
trough with multiple closed centers developing Wednesday night
into Thursday. Model solutions shift the Arctic low near Barrow
eastward through the week...with its center moving northeast of
Kaktovik along the Beaufort Sea coast early Thursday. As the
Arctic low moves east nearly zonal flow sets up across the
southern Mainland into middle week. The Bering ridge shifts to the
Gulf and northeast Pacific through Wednesday. Weak shortwaves
move from the Arctic low...however the energy is shunted by the
ridge keeping most precipitation across the northern tier of the
Short term forecast...
the pressure gradient tightens along the western Gulf and along
the coast this morning as low pressure dives south from the
northwest pushing a front toward the Gulf Coast. Gusty winds develop
this morning through channeled terrain along the coast and across
the western Gulf of Alaska. The front loses momentum as it moves
along the Alaska Range and winds taper off as the gradient
relaxes tonight. Clouds will be on the increase today across the
southern Mainland as the front moves in from the northwest coast.
Rain chances increase late this afternoon along the Susitna and
coper river valleys. Downsloping along the Alaska Range and a
drier air mass to its south will keep most of the rain along the
a front moves across the southwest today bringing rain across the
region. Gusty winds associated with the front will continue
through tonight as the pressure gradient tightens along the
southwest. Quieter weather is on tap for Tuesday as ridging shifts east
from the Bering.
ridging keeps the southern Bering under weak flow through middle
week. Winds across the northern Bering increase out of the west as
the pressure gradient tightens between low pressure across the
Bering Strait and ridging along the Aleutian chain. Westerly flow
across the Bering brings a warmer air mass through middle week and
then a developing trough will slowly moderate temperatures back to
Long term forecast...
a long wave pattern sets up over the Bering at the end of the week
pushing the ridge into the northeast Pacific. The ridge should
hold its influence across the southern Mainland through the end of
the week. However...a cold front progresses south along the West
Coast at the end of the week on Friday. Models are struggling
with the longwave pattern and therefore confidence decreases into
the weekend on the evolution of the longwave pattern.
Kh Sep 14