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FXAK67 PAJK 011407 CCA
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
528 AM AKDT Mon Jun 1 2020

.SHORT TERM...Remnants of the low pressure system from Sunday
weakened to an open wave trough that moved over the NE AK Gulf
late Sunday night with high pressure ridge over the AK Panhandle.
Bands of rain showers begin to subside slightly Monday morning as
the trough dissipated. Strong southerly winds from the
panhandle ridge overnight decreased, especially for north-south
oriented channels. Meanwhile south of the Aleutians a vertically
stacked low progresses eastward. Along the associated occluded
front a triple point low forms near Kodiak island. As the front
pushes northward into the southern AK gulf the panhandle will be
hit with another round of rain and winds Monday into Monday
evening. The southern regions will have biggest wind impacts with
gusts of 40 to 45 mph starting this afternoon and ending later in
the evening. Max small craft return for most inner channels as
the front advances today and will then drop off this evening.
While satellite scatterometer winds this morning were just below
gale force over the gulf decided to keep the 35 kts for the outside
waters considering model 925 mb winds. Rainfall amounts over next 24
hours of 0.50 to 1.00 inch over the south with 0.25 to 0.75 for the
central areas, and 0.25 to 0.50 for the north. Expect some river
rises with the precipitation however all stages should be below
bankful. Cool temps again with daytime highs only in the mid 50s. As
the front moves over the area and the triple point low weakens to a
trough, winds will diminish and rain transitions to showers again
with onshore flow and colder air aloft resulting in unstable
conditions. Another ridge builds over the panhandle Tuesday so
expect southerly winds over the northern inner channels to increase
again.

Model differences will mainly minor with position of the triple
point low. Any changes to current grids were minor with forecast
confidence bit above average.

.LONG TERM.../Wednesday through Monday night/...A vertically
stacked low just south of the eastern Aleutians as of this writing
will have shifted east to the western Gulf of Alaska by the start
of this extended range forecast period. The polar jet will lie to
the south and the upper low will be virtually cut off. With no
meaningful steering flow, it will drift slowly to the southeast
through Thursday morning. At that time, a descending branch of the
polar jet will pick it up and take it southeast out of the local
forecast area, becoming an issue for the Seattle office by
Saturday morning. As the shift to the southeast happens, upper level
onshore flow will back, becoming alongshore flow and then finally
offshore flow Friday night. At the surface, shower activity across
Southeast Alaska will taper off beginning late Thursday afternoon
with most locations, if not all, dry by Friday morning. As the
surface low departs the area to the southeast, a thermal trough will
set up over British Columbia, increasing the chance of showers
approach from east of the Coast Mountains. Currently, the PoP
gradient is still fairly large with likely showers over the coast
mountains becoming only scattered showers over the outer coast.

Overall confidence in the extended range forecast is average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from 1 PM AKDT this afternoon through this
afternoon      for AKZ026-027.
     Strong Wind from 10 AM AKDT this morning through this afternoon
     for AKZ023.
     Strong Wind from 4 PM AKDT this afternoon through this evening
     for AKZ028.
MARINE...Gale Warning for PKZ036-041>043-051-052.
     Small Craft Advisory for PKZ012-021-022-031>035.

&&

$$

PRB/Fritsch

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