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FXAK67 PAJK 181432

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
632 AM AKDT Sun Mar 18 2018

.SHORT TERM.../Sunday morning through Monday night/...A surface
ridge will build in across the gulf from the west today, resulting
in a slow backing of the winds over the gulf from northwest to
west over the next 24 hours. Farther west, a low is beginning to
develop over the central Aleutians as of early this morning, and
this will be the next meaningful source of precipitation for the
Panhandle. Look for precip to begin in the Yakutat area late
Sunday night, then spread east and south through Monday night.
Forecast overnight lows suggesting that there will be some snow,
but primary precip type expected to be rain. Stable air and light
winds in advance of the front is also expected to produce large
areas of low clouds and drizzle before precipitation starts in

Post-frontal westerly winds over the gulf will increase to small
craft intensity by Monday afternoon and reach Cross Sound by
Monday evening. Post-frontal southerly pressure gradient over the
far northern inner channels will produce small craft winds over
Lynn Canal Monday afternoon as well. otherwise and elsewhere,
winds 20 kt or less.

Temperatures have been above normal across southeast Alaska for
the past several days. Daytime highs for Sunday and Monday
expected to be closer to normal, ranging from the upper 30s to
mid 40s. Overnight lows still a bit warmer than normal owing to
the expected cloud cover and will range from the mid 20s to upper

Previous forecast remains on track, so little in the way of
adjustment made overnight. Overall forecast confidence is average
to above average.

.LONG TERM.../Tuesday through Sunday/ of 10 pm Saturday. The
long range forecast starts out with a strong upper trough/low
dropping S through the area while an upper ridge builds over
western Alaska. This pattern persists through late week for the
most part as the upper low stalls briefly W of Haida Gwaii. The
upper level pattern then appears to shift early next weekend as a
strong trough from Russia destroys the western Alaska ridge
establishing a broad trough over much of Alaska by next weekend.
The resulting trend is toward warmer SW flow over the Gulf and
Panhandle by that point.

Overall changes were rather minor especially in the Tue through
Thu period as current model guidance seems to be painting a
coherent picture with little difference noted between individual
models (ECMWF and WPC were the main choice for guidance). Strong
cold air advection behind the upper trough will cause outflow
winds to increase again shutting off showers across the northern
panhandle through Tue night due to combo of dry cold air intrusion
and downslope flow. Farther south, showers will persist as the
upper low lingers around Haida Gwaii. Temperatures should be warm
enough that most areas will see these showers as rain but some
snow could mix in during the cooler nighttime hours. Low to no
snow accumulation expected.

As for winds, Northerly outflow will be increasing Tue night into
Wed as a cold air mass drops into the area. Winds could reach gale
force in some areas (like Lynn Canal) during this time. Pressure
gradient forecasts are starting to suggest that even that might
be too weak for some areas so future forecasts may increase winds.
Surface temperatures will also be affected as 850 mb temps drop
to -8 to -10 C across much of the area through Fri. Overnight
lows will have the most noticeable drop with many areas dipping
into the mid to upper 20s during this time (this is a drop of 3
to 5 degrees over the previous forecast). High temps will not cool
down as much (if at all) as the lows will, as the Spring sun
should help warm temperatures up during daylight hours.


.AJK Watches/Warnings/Advisories...
MARINE...Small Craft Advisory due to Seas for PKZ041-042.




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