Scientific Forecaster Discussion
fxak67 pajk 272243
Southeast Alaska forecast discussion
National Weather Service Juneau Alaska
243 PM akdt Thu Jul 27 2017
Short term.../ Friday night to Sat night / a narrow ridge along
Southeast Alaska Panhandle tonight and Friday as low pressure
over the far southern Gulf of Alaska strengthens and moves
northeast closer to the southeast Panhandle Saturday and Saturday
night. Should see scattered showers around the Panhandle Friday
and Friday night. Late Friday with developing low approaching have
rain/showers spreading north through the Panhandle. With a little
tighter pressure gradient have increased winds slightly for
southern areas from southern Baranof Island to Prince of Wales for
later Saturday with 25 to 30 kt of winds or even briefly minimum
gale force. Should see gusts 40 to 45 for the marine waters, not
sure if it will catch the coast though.
Also as the upper level low gets closer to the coast, there looks
to be a pocket of good instability on the southeast to south side
of the the will approach the southern Panhandle. Put in mention of
small area of thunder potential.
Long term.../Sat through Thu/ as of 930pm Wednesday... little
change to inherited forecast as model solutions remain fairly
similar to the past couple of days with a series of perturbations
eject across Southeast Alaska from an upper low in the Gulf. Models in a
little better agreement with the first low moving north-northwest across the
southeast Gulf Sat into sun. Naefs and ecens show 1000mb and 850mb
windspeeds 2-3 std dev above normal into the S Panhandle during
this time so the main change to forecast was to increase winds.
Biggest increases were over the southeast Gulf where strong to near gales
expected. Otherwise, Clarence Strait along the the ocean
entrances to S Chatham and Sumner Strait will see advisory level
winds. Less confident in strength of winds in Cross Sound so kept
them in 15-20kt range attm, but could increase/decrease on how far
north the low moves before west in the Gulf.
Little change in model solutions with upper low persisting over
the Gulf with a series of minor short waves ejecting across the
region maintaining an active weather pattern through the extended.
Minimal spread in ensembles 500h lead to above average confidence
in the synoptic pattern, but surface features differ significantly
from run to run and between models leading to lowering confidence
in surface features by early next week. Minor changes to inherited
forecast through the weekend the trended towards latest wpc
guidance towards the middle of next week.