Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 311354
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
554 AM AKDT TUE MAY 31 2016
.SHORT TERM...Broad surface low over the AK Gulf with a secondary
circulation in the southeast gulf moves northward. Weak frontal
boundary just moving into the southern panhandle this morning will
track over the central panhandle through the day then begin to
stall. with only weak forcing mechanisms expect the front to shear
apart as it moves northward. Due to this, dropped QPF amounts
slightly using the NAM12 as base guidance. Still some uncertainty
with how far north the front will progress and still produce any
precip so have only chance pop for the northern panhandle.
Northerly flow for the north and central regions flips south as
the shortwaves advances. Weak gradient keeps overland winds
generally less than 15 kts with the exception of areas under the
front were winds will near 20 to possibly 25 kts. Small craft
winds over coastal waters advance east as the front progresses
through the day. 925 mb winds indicate some potential 25 kt winds
for Clarence strait this afternoon so will need to keep an eye
Synoptic scale models still in good agreement with the exception
of of far north precip advances. Only some cosmetic changes to
the forecast. Did use high-res NMM to bump up inner channel winds
under the front. Smoothed out pop field and used periodic wording
to indicate the weakening front. Forecast confidence is average.
.LONG TERM...The front referenced in the short term discussion
will still be producing rain over southeast Alaska by the time the
next front arrives over the southern outer coast Wednesday
evening. This second front is also looking like it will mainly
impact the southern panhandle. With a surface ridge over the
panhandle, the gradient will tighten up as the low approaches, but
it still looks like winds will not get above small craft
intensity over the marine zones. Low level jet may possibly result
in some low level wind shear, so will have to keep an eye on that.
After this second front, a third low and associated front is still
being forecast to approach the southern panhandle from the
southwest Thursday night into Friday. This low looks like it will
be the strongest of the three and may result in marginal gale
force winds over the eastern gulf with high end small craft winds
over the ocean entrances near Cape Decision and Cross Sound. Model
differences are still considered significant due to the close
proximity with the outer coast, so have not committed to any one
particular solution at this point. Suffice to say that this aspect
of the forecast will change in the days to come. Apart from the
differences in track and intensity, models are in good agreement
on POP and QPF. Much higher confidence here, so have updated the
forecast to include heavy precipitation, which will begin over the
southern zones late Thursday night and spread north through Friday
night, possibly Saturday morning.
Moist onshore flow continues through Sunday night, but a surface
ridge forecast to develop over the southeastern gulf early next
week may provide us with some dry weather going into next week.
.AVIATION...Minimal visibility reduction expected due to precip
from the weak front but lower ceilings resulting in MVFR to
occasional IFR flight categories. Wind shear for southern coast
as front tracks over.
MARINE...Small Craft Advisory for PKZ041>043-051-052.
Small Craft Advisory due to Seas for PKZ022.
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