Scientific Forecaster Discussion
Southeast Alaska forecast discussion
National Weather Service Juneau Alaska
336 PM akdt Wednesday Sep 17 2014
Short term...a complex gale force low will move NE into the
central Gulf Thursday. Complex frontal system will move into the eastern
Gulf Thursday. Used blend of the 12z GFS/ECMWF/Gem to handle the
Main forecast concerns will be winds...precipitation potential...and
whether any fog hangs around tonight. Right now...the most wind is
over the central Gulf northward to near buoy 46082. Winds around 25 knots
are occurring there at this time. These winds should increase to gales
tonight as low and stronger part of complex front moves closer to
the area. The gales should spread to much of the remainder of the
Gulf by late tonight or early Thursday morning. The stronger winds
should reach the outer coast early Thursday morning...and think wind
gusts to 40-45 miles per hour will be occurring along the central and southern
coast and far southern Inner Channels by late Thursday morning. Will be
headlining strong winds for zones 23...27...and 28. Most inner
channel marine areas will reach 25-30 knots Thursday as front moves to the
outer coast by late afternoon...but the far northern Inner Channels
will stay somewhat lighter due to slight northerly pressure gradient
As for precipitation...there may be spotty light showers over the Inner
Channels early this evening as shallow convection will be
occurring (cape values 50-80 j/kg). This should rapidly diminish
due to loss of daytime heating. Then...precipitation from the complex
frontal system will reach the southern and much of the central
Panhandle by late tonight...then overspread remainder of Panhandle
Thursday morning. The NE Gulf Coast has some precipitation at this time associated
with weaker part of complex front...but this should diminish
tonight as lower level flow backs to a more Ely direction due to
approach of low and stronger part of front from the S. Think some
rain should move back into the paya area Thursday afternoon as front
gets close enough to veer some of the flow just off the surface to a
more southeasterly direction.
As far as the fog GOES...combination of the shallow convection
this evening and thickening middle-level clouds tonight should
dissipate any fog by early this evening and not allow more to
develop later tonight. Will not mention the fog for this package
due to the rapid dissipation expected very early in the period.
Long term...wet weather continuing through the weekend.
Temperatures should remain slightly above normal through the long
term forecast period.
The start of the long term forecast period will feature a 975-mb
low in the north central Gulf, with its associated front making
landfall across the Panhandle late Thursday afternoon. Do expect
gusty winds across the Panhandle. Most areas should see
southeasterly winds around 15 to 25 miles per hour with higher gusts in
exposed areas. Gale force winds are expected along the outer
coast, in the north central Gulf, and along Clarence Strait. Small
craft level winds will prevail over the Inside Passage. The gusty
conditions should persist through Thursday night as the secondary
wrap enhance wind speeds behind the weather front. Once the
weather front pushes through, pressure rise will induce another
push of strong southerly winds across the Inside Passage on
Friday. For northern Lynn Canal, do expect gale force winds for
Friday. Winds in Skagway will be gusting to 40 miles per hour. Besides gusty
winds, do expect moderate rain to fall across the Panhandle. Some
areas will see locally heavy rainfall due to enhancements from
There will be a brief break before a short wave brings in
another round of gusty winds and rain to the Panhandle starting
early Saturday. Right now, models are struggling in pinpointing
the storm track and intensity. By Sunday, model uncertainties
continue to increase. Thus, keep likely probability of precipitation for the County Warning Area.
With the storm track remaining mainly west of the Panhandle, do
expect wet and slightly above normal temperatures. Highs will
typically be in the middle to upper 50s, while lows will be in the
middle to upper 40s.
Area streams and lakes should see rising water levels. However,
due to forecast uncertainties, it is tough to pinpoint where the
heavy rain is going to hit at this point.
Forecast confidence is about average through Friday night, then
drop to below average beyond Saturday. Utilize a blend of
European model (ecmwf)/Gem/GFS/official for day 2 to day 4, then transition to wpc
guidance beyond day 4.
public...strong wind from Thursday morning through Thursday afternoon for
Strong wind from Thursday morning through Thursday evening for
Marine...Gale Warning for pkz022-033-036-041>043-051-052.
Small Craft Advisory for pkz021-031-032-034-035-053.
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