Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 252152
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
152 PM AKDT SUN SEP 25 2016
.SHORT TERM...Satellite imagery shows mid and high level clouds
spreading N across the central and northern panhandle this
afternoon as a low pressure system approaches Haida Gwaii from the
SW. Light rain has spread into the southern panhandle this attm
and will continue to expand NWD this evening. Meanwhile, another
low is evident spinning S of Kenai peninsula. The cool upper low,
combined with warm SSTs continues to destabilize the atmosphere
with fairly persistent lightning detected over the N central gulf
and into AKZ017, mainly W of Icy Bay.
Models in fairly good agreement through the period with the low
approaching Haida Gwaii moving across Dixon Entrance and across SE
portions of CWA overnight. Satellite continues to indicate high
PWAT values, 150-200% of normal, so continued mention of heavy
rain overnight E of the low as it tracks NE. Meanwhile the low
over the N central gulf is progged to drift E and fill as another
low drops out of the Bering and moves S of Kodiak by Mon night.
Instability will slowly push E and kept mention of ISOLD TSTMS
over the gulf overnight and pushing E into the outer coast Mon
afternoon. Stream and rivers in the area are running at normal
levels or lower, and with only 1 to 3 inches of rain expected over
SE zones, do not expect any hydrologic impacts.
Pressure gradient will tighten over the southern panhandle as the
surface low moves inland and expect a brief period of advisory
level winds in Clarence Strait late Mon morning. Seas will be a
concern over PKZ041 as they build to 8-10 feet tonight and persist
through Mon afternoon before subsiding.
Other impacts will be potential for fog development over the
northern and central panhandle overnight. Weak pressure gradient
will result in light winds across the area. Shower coverage will
be scattered resulting in breaks in cloud cover overnight and
could be enough to aid in fog development late Sun night into Mon
morning, so kept mention of patchy fog through late Mon morning
over the north central panhandle.
.LONG TERM...Midlevel temperatures near -28C are forecast to
persist over the gulf through midweek as an upper trough
gradually slides EWD. This will yield steep lapse rates/sufficient
CAPE for isolated thunderstorms over the outside waters, and
showery precipitation over the panhandle. Previously mentioned
trough then evolves into a broad closed low over the NERN PAC by
Thursday. As this takes place, an offshore oriented surface
pressure gradient will develop over SERN AK, which will favor
clearing skies/a drier airmass, and larger diurnal temperature
swings. Morning temperatures near freezing still appear possible
for wind sheltered locations at sea level due to enhanced
radiational cooling beneath clear skies. This pattern is forecast
to last through at least Saturday, with clouds/moisture possibly
increasing Sunday into early next week.
MARINE...Small Craft Advisory for PKZ036.
Small Craft Advisory due to Seas for PKZ041.
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