Gale Warning 63, NWS Juneau, AK

Southeast Alaska Forecast Discussion...Corrected
National Weather Service Juneau AK
1125 PM AKST Sun Feb 2 2020

.SHORT TERM...Last in a string of winter storms that has affected
SE AK over the past couple of weeks will impact the area Monday
through Tuesday morning.

Chilly arctic airmass has settled over SE AK as of Sunday
afternoon. Temperatures are in the mid 10s to mid 30s with
dewpoints into the single digits below zero over the far north.

Next front can be seen clearly on GOES 17 imagery this afternoon
pushing across the western Gulf. This front will be very slow to
move through SE AK due to the cold air in place and the parent low
located well to the west. Increasing isentropic ascent late
tonight will lead to precipitation breaking out before daybreak
for much of the northern Panhandle and this will be in the form of
snow. Isentropic ascent will increase throughout the day and by
evening, impressive low level flow of 40 to 60kt at 700 and 850mb
will lead to strong moisture transport over the cool dome near the
surface. Snow will likely be moderate to heavy at times Monday
night but will also be increasingly wet as snow to liquid ratios
decrease with the increased warming. By early Tuesday morning,
think a general 5 to 10 inches with locally higher amounts will
have fallen from Gustavus and Hoonah eastward to Juneau and
northward to Haines. Thus a Winter Storm Warning has been issued
for these areas from mid-morning Monday until early Tuesday
morning.

With the stable WAA regime, think the models are generally over-
doing the wind field over the inside waters on Monday and Monday
night, especially over the north. Thus have lowered winds there to
reflect more of the strong low level flow overrunning the low
level weaker wind fields. Further south, the cooler airmass has
sunk pretty far to the south and thus even with a SE wind
developing over the southern central channels Monday, think snow
will be able to hang on over the interior channels from Ketchikan
to Petersburg/Wrangell until Monday evening. A few areas will
likely pick up enough to warrant an advisory so went ahead with a
Winter Weather Advisory for areas just south and west of the
warning area.

Low level airmass will finally get mixed out Tuesday and temps
near sea level will warm above freezing over much of the area.
With the warming trend, anything that falls Tuesday onward will
likely be in the form of rain near sea level.

Overall the inherited forecast was in good shape. Only adjustments
were to decrease the winds on the inside and adjust temperatures
based on projected low level thickness values.

.LONG TERM.../Tuesday through Sunday/...As of 10pm Saturday. After
nearly a month of below normal temperatures and many rounds of
wintry weather, Mother Nature will finally give Southeast Alaska
a break with a mid winter thaw. The long term begins with a low
in the northern Gulf swinging a front through the Panhandle. Snow
will be changing to rain from south to north during the morning
hours on Tuesday as 1000-850 thickness values rise significantly
and deep southerly flow scours out low level cold air. Significant
accumulations are likely for the northern Panhandle before the
changeover to rain occurs.

The wet weather is expected to continue through the first half of
the week as another system will move into the northern Gulf on the
heals of the previous one. Guidance is coming into agreement with
another front swinging through the Panhandle Tuesday night
through Wednesday. With warmer maritime air already in place
across much of the region, the dominant precip type at sea level
with this next front should be mostly rain.

After Wednesday, model agreement dissolves, although the overall
pattern continues to look warmer than normal for February.
Southwesterly flow aloft will continue into Thursday keeping above
average temperatures and the chance for showers across the
Panhandle. Despite poor model agreement towards the end of the
week, guidance does hint at a ridge building over the gulf. The
axis of the ridge and where it sets up will be crucial for
determining the weather in Southeast Alaska. Relied heavily on WPC
for this time frame which shows a drying trend from Friday into
the weekend. Forecast confidence is above average for the system
on Tuesday then drops off through the week.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory from 9 AM Monday to 3 AM AKST
Tuesday      for AKZ017-018-022-024-026-028.
     Strong Wind Monday afternoon for AKZ027.
     Winter Storm Warning from 9 AM Monday to 3 AM AKST Tuesday for
     AKZ020-021-025.
     Strong Wind from Monday morning through Monday afternoon for
     AKZ023.
     Winter Storm Watch from Monday afternoon through Tuesday morning
     for AKZ029.
     Winter Storm Warning from 9 AM Monday to 9 AM AKST Tuesday for
     AKZ019.
MARINE...Gale Warning for PKZ036-041>043-051-052.
     Small Craft Advisory for PKZ012-021-022-031>035-053.

&&

DEL/CM

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