Scientific Forecaster Discussion
fxak67 pajk 272249
Southeast Alaska forecast discussion
National Weather Service Juneau Alaska
249 PM akdt Sat may 27 2017
Short term...mid and upper level flow remains S-SW onshore
through the short term period with the large scale ridge axis over
b.C.. this is evident looking at satellite imagery, showing high
clouds streaming in from the Gulf. At the surface however, the
pressure pattern shows a high centered over the NE Gulf with a
weak northerly gradient. Since this will be countering the upper
level flow, think that predominant winds will be sea breeze driven
in the afternoons then become light and variable (mostly north)
tonight. Sunday night into Monday the surface high pressure
weakens due to a weak disturbance passing by to the west, then a
high pressure ridge re-orients along the Panhandle forcing a
predominantly southerly flow through the Inner Channels (although
remaining relatively light).
Overall the high pressure will keep the Panhandle dry, but the weak
disturbance/front over the central Gulf, mentioned above could
introduce some light rain to the Yakutat area late tonight into
Sunday morning, so have left in the slight chance pops for that.
Otherwise think that it will just make for some more clouds. Cloud
cover was increased some on Monday as well, which resulted in
slightly cooler temperatures (low to mid 60s) compared to those
for Sunday (mid 60s to around 70).
Preferred the European model (ecmwf) and GFS for updates to pressure and resulting
wind field. Made local adjustments to wind for sea breezes etc as
mentioned above. This was the biggest change to the forecast, both
to lower speeds and adjust some directions through Monday.
Forecast confidence is average.
Long term.../Sunday night through Saturday/ upper ridge just east of
the area will shift slowly east through the end of the week. Upper
trof/low will shift gradually east into the epac through the end of
the week as well. This should increase threat for precip over the
area with time, but models differ in individual shortwave features
which makes timing them difficult at this point. Left in previous
forecast which has a gradual eastward shift of systems toward the
area. Forecast confidence is on low side day to day though due to
the differences mentioned. That being said, does not look like any
strong systems will affect the area through the end of the week,
so impacts will not be significant except for possible Small Craft Advisory level
winds from time to time.
public...frost advisory from 9 PM this evening to 6 am akdt Sunday for
Frost advisory from 10 PM this evening to 7 am akdt Sunday for
Marine...Small Craft Advisory for pkz052.