Scientific Forecaster Discussion
Southeast Alaska forecast discussion
National Weather Service Juneau Alaska
245 PM akdt Thursday may 28 2015
Short term...upper low just southeast of Misty Fjords will drift very
slowly southeast just inland of the central British Columbia coast through Friday. Upper
ridge will build some over the Gulf and Yukon areas through
tonight...then remain there Friday. Surface high over the Gulf will
remain there through Friday...with a slight weakening trend beginning Friday.
Models were very close on the main features and close to current
pressure forecast in grids...so did not change pressures. Did make
other tweaks though...which will be described below.
Main forecast concerns will be precipitation potential...marine layer
issues...winds...and temperatures. Right now...a band of precipitation is
moving across Misty Fjords from the NE with a minor shortwave
rotating into that area around the upper low. Precipitation in this band
is more convective than it was in previous bands moving in. Kept
highest probability of precipitation in the Misty Fjords area through Friday...although do
indicate a gradual decrease in probability of precipitation as upper low shifts away from
the area and shortwaves coming around it stay more to the S of
there. Left in mention of isolated thunderstorms this evening near Hyder
The marine layer clouds are covering most of the eastern Gulf
at this time...with mainly small holes in it near the coast. These holes
will likely fill in this evening. Expect the marine clouds to push
to the outer coast by late this evening...but burn off from much
of the coast Friday. Some fog may also be in the marine layer
airmass...especially over the more northern parts of it. There may also
be patchy radiation fog over mainly the central Inner Channels
late tonight and early Friday morning.
Winds are strongest over the eastern Gulf and adjacent coastal areas.
Generally 20 knots west-northwest winds are going on over the eastern Gulf...with
localized Small Craft Advisory level winds around Cape Spencer and Cape Decision.
Think the winds over the Gulf will generally stay around 20 knots for
most areas...although some diminishing trend may develop over the
far northern Gulf near the coast later tonight and Friday. Inner channel
winds will generally be west to north up to 20 knots through Friday...although
local effects may cause some spots to become more S-SW both this
afternoon and Friday afternoon.
Warming trend should continue into Friday as northerly flow brings in
warmer air. Many places over the north will get well into the 70s
Friday...with a few lower 80s possible well away from the water. The
southern area will also be warmer although they will have more clouds
around. Most places over the southern area will be in the 60s to near
70 Friday. The outer coast will remain somewhat cooler as they will
have less sunshine and cooler marine air coming ashore...so they
will be in the upper 50s to lower 60s Friday.
Long term...models remain in general agreement through the
weekend for the weakening upper level low over British Columbia
continues filling and upper ridge dominates Southeast Alaska.. an
upper level shortwave trough across the Yukon will tilt and spill
upper dynamics westward over Alaska interior. This upper trough
may bring a slight chance of showers over the northernmost
Panhandle Saturday and Saturday night. Surface high pressure will
continue to dominate across the Gulf with an inverted trough of
low pressure persisting over the Panhandle. The high pressure will
slowly move south as the inverted trough expands a little farther
Refreshed the inherited forecast with the European model (ecmwf) for its
good consistency through Sunday evening. Marine stratus will be
confined over the outer waters and slowly move southward as the
area of subsidence drifts southward. No significant winds/seas are
expected due to relaxed pressure gradient. Dry and seasonably warm
weather will continue over Southeast Alaska through early next
week. Used the wpc ensemble guidance for next week and new model
runs depict an upper level low moves over the central Gulf by
Wednesday...slowly fills and drifts northeastward toward the
weekend. Increased clouds by middle week with elevated rain chance
for the second half of the week.
Marine...Small Craft Advisory for pkz022.
Small Craft Advisory due to seas for pkz041.
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