Gale Warning 144, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
257 PM AKDT Mon Apr 27 2020

.SHORT TERM.../Monday through Wednesday/ Active weather continues
across the Panhandle over the next few days as another impactful
low pressure system is expected to move into the region. As of
late Monday afternoon, a 986 mb low in the east central gulf was
slowly moving north and weakening. This low will continue to
weaken into tomorrow before being taken over by a more potent low
moving in from the south. This next system is expected to bring
another round of heavy rain to the Panhandle and potentially high
winds across the south.

For Monday evening and into Tuesday morning, widespread rain
showers will continue over much of the Panhandle with Yakutat
being the exception. There will not be much of a break, if any, in
the rain as the next system will be right on the heals of the one
today. By Tuesday morning, a 987mb low near 51 N 141 W will
continue northward pushing a front into the Southern Panhandle.
Heavy rain will spread northward throughout the day as the low
treks northward along longitudinal line 139 W. With southeasterly
flow aloft over the region, expect heaviest rainfall amounts over
the south with lesser amounts across the north. Through Tuesday
night expect one to two inches of rain in the Southern Panhandle
with locally higher amounts possible. Across the Central and
Northern Panhandle expect a half inch to one and a half inches of
rain. Lesser amounts expected across the Upper Lynn Canal area and
Yakutat.

Potentially impactful winds expected in the Southern Panhandle
Tuesday afternoon through early Wednesday morning. As the gale
force low heads northward, the pressure gradient will tighten and
southeasterly flow will increase aloft. Winds at 850 mb will
increase to 65 kt through the day on Tuesday then die down to 35
to 45 kt as the low heads northward on Wednesday. The surface
pressure gradient on Tuesday is not optimal for a high wind event
at the surface for the south as there is more of an E or ENE
component to the gradient between a ridge over BC and the low
moving north in the gulf. The gradient becomes conducive for high
winds late Tuesday afternoon and evening; however at this time the
low will be weakening and winds aloft will be diminishing as
well. The best timeframe for potentially high winds in the
Ketchikan area and on Prince of Wales should be Tuesday afternoon
through early Wednesday morning. With this thinking in mind, have
condensed the timing for the High Wind Watch to 00z Wed through
12z Wed. Confidence is only marginal in this high wind event
materializing as the best dynamics do not quite all line up.

No major changes were made to the forecast for today. Used a blend
of the NAM/GFS and hires models for minor tweaks.

.LONG TERM.../Wednesday through Monday as of 10 pm Sunday/ Active
weather pattern in the long range is starting to trend more toward
being less active. Overall pattern keeps a broad upper trough
over, and upstream of the region through the period with the
Pacific storm track continuing to send storms East across the
northern Pacific. The improving trend comes for next weekend when
guidance pushes the eastern end of the jet stream a little
farther south delaying the next storm into the panhandle.

Mid range changes were minor with a lingering low in the gulf that
gradually moves northwest into the north central gulf and
gradually weakens away. Generally wet conditions expected into Thu
night for the panhandle remains mostly unchanged.

Overall forecast changes were more focused on the extended range
tonight as with the farther south trend of storm tracks the
weekend is looking drier particularly for the north on Sat. A low
that had rather large spread on where it was going for the
weekend yesterday has clustered up a bit more in the guidance
today. Most guidance is suggesting that the low will struggle to
get into the southern gulf and its front will likely mainly affect
the southern panhandle. Chance pops are kept for the southern
panhandle, but the north has been lowered to slight chance or
lower on Sat.

Favored GFS and ECMWF for guidance in the mid range and WPC and
NBM for extended range shifts.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Watch from Tuesday evening through late Tuesday
night      for AKZ027-028.
     Strong Wind Tuesday afternoon for AKZ027-028.
     Strong Wind until 7 PM AKDT this evening for AKZ021.
     Strong Wind from Tuesday morning through Tuesday afternoon for
     AKZ021.
MARINE...Gale Warning for PKZ036-041.
     Small Craft Advisory for PKZ022-031>035-042-043-051>053.

&&

CM/EAL

Visit us at http://www.weather.gov/Juneau