Small Craft Advisory 419, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
343 PM AKDT THU JUN 9 2016

.SHORT TERM...Rather quiet 24 hour period on tap for Southeast
Alaska. There is quite a temperature contrast this afternoon with
mid to upper 70s across the northern panhandle and low to mid 50s
across the south. The south is much cooler due to an upper low
situated off the Pacific Northwest coast which has brought clouds
and a band of rain into the southern panhandle early this morning.
A northerly pressure gradient over the north resulted in downslope
warming with temperatures hitting the 80 degree mark in Skagway by
11am. The upper low will continue to slowly drift to the
southeast through Friday afternoon with a weak ridge of high
pressure building over the eastern gulf. Under this weak ridge of
high pressure a band of marine stratus will expand along the
outer coast and extend northward to the vicinity of Yakutat by
late tonight. Current indications are this layer will remain
elevated (1000-1500 ft ceiling) and not reduce visibility at the
surface. There is lower confidence in this portion of the
forecast, but it will continue to be monitored by the next shift.

With the ridge building over the panhandle through the day, winds
have shifted to the south. The far northern panhandle remains
northerly as of early afternoon but expect winds to switch to the
south by late afternoon and increase to 20-25 kt in Lynn Canal. By
late tonight, the pressure gradient relaxes across the area with
winds becoming light. Strongest winds on Friday will be across the
northern Inner Channels with southerlies increasing to 15-20 kt in
the afternoon. The lack of northerly wind component and more cloud
cover on Friday will result in cooler high temperatures with many
locations in the 60s. Expect high temperatures to be 5 to 10
degrees cooler than today across the northern panhandle.

Relied on Hi-Res model guidance for updates to the short term
forecast.

.LONG TERM...Progressive upper level pattern will produce large
scale changes in the weather over the coming week with shifts from
offshore flow to onshore, and then back to offshore flow. mid
level circulations are a bit more subtle with these changes but
still apparent. At the surface, a weak surface trough will be
working its way across the top of the surface ridge situated over
the gulf and a threat of rain re-enters the forecast for Yakutat
as early as Saturday morning. Meanwhile, scattered showers from
the east will still be present along the coast mountains, with
greater frequency and areal coverage over the southern half of the
panhandle. Saturday night, a low and associated front will move
into the central gulf with rain from this front arriving Sunday
morning. Details in the structure of the front differ from model
to model, but it does look like the highest probability of rain
and the largest rainfall totals will be over the southern half of
the panhandle. Look for 6-hourly totals of 0.25 inches or less, so
flooding and significant rises in streams not a concern at this
time. Precip is forecast to taper off through early next week and
by mid week, we may be back into an offshore regime at the surface
as another trough builds west from British Columbia across the
panhandle and into the Gulf of Alaska. Is this happens, look for a
patter similar to what we have going on right now with shower
activity concentrated along the coast mountains and fair
conditions west to the outer coast.

Northwesterly winds over the eastern gulf Friday night will give
way to southwesterlies on Saturday and the southeasterlies by
Saturday night in advance of the front. Winds speeds through this
time will be generally 15 kts of less, but increase to 20 kts out
of the southeast. Post-frontal, the low will track northwest into
the far northern gulf, resulting in southwesterlies at 15 kts or
so on the outer coast once again by early next week. On the
inside, winds generally 10 kts with pockets of 15 kts at times in
various locations. Notable exceptions will be Lynn Canal with
southerlies of 20 kt through Saturday evening and then again
Monday evening.

Overall forecast confidence is average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ012.
&&

TPS/Fritsch

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