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FXAK67 PAJK 242246

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
246 PM AKDT Wed May 24 2017

.SHORT TERM.../through Friday/ Quiet weather day across the area
as a surface ridge in the gulf is causing NW flow across the
panhandle. Northern panhandle and the northern gulf coast are
still seeing plenty of clouds due to onshore flow pushing marine
layer clouds into the area. Meanwhile the central and southern
panhandle have seen many breaks in the clouds due to the more
along shore flow there. Winds have calmed down along the outer
coast as the gulf ridge has flattened out a bit but we are still
seeing winds to 20 kt around Cross Sound and Cape Decision.

Main concerns for the short term is a weakening front that will be
trying its best to break through the ridge Thu and Fri. Yakutat
and areas westward will bear the brunt of the rain with
categorical pops expected tonight through Thu. For the rest of the
panhandle it will be a battle of how much of the front survives
going over the ridge axis to determine if any rain falls. The
northern panhandle I left as chance pops as there should still be
enough onshore flow combined with the remaining frontal dynamics
and terrain effects that at least the higher elevations will see
some precip through Thu night. Southern panhandle will likely stay
dry as flow stays more along shore and even a little offshore
down there through the period.

Winds expected to remain mostly low except in Lynn Canal and
along the outer coast. Tip jet effect may cause Cross Sound to
again rise to small craft conditions this evening and tomorrow
afternoon. As for Lynn Canal, the northerly pressure gradient is
the culprit that will keep winds around 20 to 25 kt for most of
the period.

Short range models were in decent agreement so not many changes
were made to the forecast overall. Used mainly Nam and GFS where

.LONG TERM.../Friday through Tuesday/ as of 10 pm Tuesday.
Generally a quiet weather pattern over the area for the weekend
into next week. Upper level pattern consists of a ridge parked
over BC and a trough over the Bering Sea. This overall pattern
remains largely unchanged through the period with some
fluctuations as short wave troughs move through the overall
pattern (particularly for the Bering Sea trough). These short
waves mainly serve to strengthen both large scale features by
early next week.

Meanwhile lower in the atmosphere, the surface ridge is setting up
further to the west then where the 500 mb ridge axis will be.
Stretching N to S across the eastern gulf, the ridge will be
another rather persistent feature for the long range even though
it will fluctuated in strength. Its persistence will mean NW flow
for the extreme eastern gulf and lighter winds for the inner
channels, generally dry conditions as gulf storms stay in the
western gulf, and mostly warmer weather.

One question mark remains, and that is how wide spread marine
layer clouds will be. High-res boundary layer RH model guidance at
the start of the long range reveals that there will be substantial
low level moisture in the gulf. So low clouds are likely to be
wide spread over the gulf at least, with the outer coast and
maybe areas farther inland seeing more low clouds during the
nights and mornings. Kept sky cover as mostly cloudy for many
areas of the gulf and outer coast for the extended period to
account for this and temperatures along the outer coast may need
to be lowered due to the persistent cloud cover.

Long range models in good agreement on the overall pattern but did
start to struggle with individual short waves that were rounding
the upstream trough into early next week. Model trends still
favoring a mostly dry and warmer long range period. Used mostly
WPC for updates where needed.


.AJK Watches/Warnings/Advisories...
MARINE...Small Craft Advisory for PKZ012-022-041-042.
     Small Craft Advisory due to Seas for PKZ051-052.




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