Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 301343
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
543 AM AKDT MON MAY 30 2016
.SHORT TERM...Narrow high pressure ridge builds over the
panhandle through the day with increasing southerly gradient. A
front, associated with a low moving into the western gulf from the
N Pacific, will track into the eastern gulf this afternoon and
into the night. As the front advances over the panhandle from
south to north the high pressure ridge will move east into
British Columbia with gradient switching to the north.
Cloudy skies and shower activity over the panhandle through the
morning will begin to subside as weak short wave is moves northward
ahead of the building ridge. Shower activity has been scattered
but will have a brief increase over the central and northern
panhandle as the vort max moves overhead. Not much total qpf from
these showers but not ruling out a few short bursts of moderate
rainfall. There will be a brief break in precipitation and
possible clearing tonight between the advancing front and exiting
vort max. Saturated air and clearing skies would provide set up
for fog development but think and clearing will be very short
lived. Low marine stratus deck along the gulf coast this morning will
rise as the front advances. Showers will transition to stratiform
rain as stable air along the front advances.
Southerly winds over the central and northern inner channels will
increase through the afternoon with the building ridge, then
diminish and shift to the north as the gradient flips. Southerly
winds over the southern panhandle will increase later tonight due
to the advancing front. As of now do not expect any inner channel
winds to reach small craft levels, but both N Lynn Canal and
Clarence Strait have the best chance. Small craft winds over the
eastern gulf will develop with the advancing front wind llj along
with rising seas.
Synoptic scale models are in good agreement for general pattern
with high res NMM producing better solution for winds over the
panhandle. Use of the high res resulted in some increased wind speeds
under the two main features (short wave for today and front for
tonight.) Otherwise little change was made to other forecast
elements. Confidence is above average.
.LONG TERM...The front that arrives along the outer coast by the
end of the short term will spread north and inland through Tuesday
night. Latest model data indicating that the proximal end of the
front will be sheared from the remainder and move west across the
northern gulf. This would favor drier conditions over the northern
half of the panhandle, but is not currently depicted in the
extended range forecast. Is this trend continues, an update to the
POP fields will become necessary. By Wednesday evening, the next
low and associated front will be moving east across the southern
gulf, with rain from this system arriving Wednesday night and
spreading north through Thursday night. Long range models
indicating that a third front will arrive over the southeastern
gulf and southern outer coast Sunday evening and also work its way
north over the panhandle. In summary, an extended wet weather
pattern has returned to Southeast Alaska. Supporting this pattern
is a long wave upper level trough that has taken up a position
over the gulf and northern Pacific Ocean. Numerous short wave
impulses of varying strength will keep deep layer moist onshore
flow going for the foreseeable future. Blended TPW imagery
indicating above normal levels for at least two plumes, with one
extending due south of the GOA and the other extending WSW from a
point south of the Aleutians.
Each of the three lows that enter the gulf are expected to bring
with them small craft winds over the Gulf of Alaska. In addition,
seas over the gulf will be at or above 8 feet for most of the
upcoming week. Winds on the inside expected to remain at 20 kts or
less with the possible exception of Cross Sound and the ocean
entrance areas near Cape Decision.
Warmer than normal daytime highs from this past week will give
way to cooler temps in the upper 50s by mid week, which is much
closer to normal for this time of the year.
For the past few years, Southeast Alaska has enjoyed an early
round of summer weather in May. In some cases, this early summer
weather has been the finest of the season. Hopefully, we will see
a return of Summer after this period of wet weather.
No significant changes made to the existing forecast. Overall
confidence is average.
MARINE...Small Craft Advisory for PKZ041>043.
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