Area Forecast Discussion
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033
FXAK67 PAJK 161458
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
558 AM AKST Mon Jan 16 2017

.SHORT TERM...High wind event in progress for the southern outer
coast and southern inner channels will end later this morning. At
that time, strong southerly winds will increase to high wind
criteria for the Skagway and portions of the Klondike Highway,
where a Winter Storm warning is already in effect. Daylight and
webcams plus spotter information will confirm heavy snow falling
at higher elevations, but precipitation rates observed at the
Skagway airport suggesting that this is certainly the case. Across
Lynn Canal, rain is likely changing to snow somewhere along the
Haines Highway, but here too, will need to get verification from
spotters and webcams later this morning. Elsewhere, rain will be
heavy at times with strong wind gusts in many locations.

Post frontal low level airmass will advect in cooler airmass over
the course of the short term forecast period and high temps today
have likely already occurred for most, if not all locations. As a
result, rain will change to snow from north to south late today
and through monday night. Apart from the Klondike Highway, snow
accumulations expected to be less than advisory levels.

Marine winds on the inside and outside dominated by gales this
morning and storm force winds in Clarence Strait. Winds will
relax in the post frontal environment but southerly gales will
persist in Lynn Canal through midnight. Seas over the eastern gulf
quite high with buoys reporting 17 to 21 feet with portions of
the eastern gulf probably much higher. Conditions improving
through the day and night, but southwesterly swell will remain
high at 17 feet or so.

Used an ensemble approach to pressure updates. Used NAM12 as a
foundation for winds over the gulf. Minor adjustments to existing
winds grids over the inner channels and public zones. Temps
adjusted using current conditions as an expected daytime max with
GFS MOS for overnight lows. PoP and QPF from NAMDNG5, Canadian NH,
and SREF with some manual modifications. Overall forecast
confidence is average.

.LONG TERM...Forecast becoming much quieter for the rest of the
week as a strong westerly jet stream over the pacific forces the
main storm track south into the pacific northwest. The transition
period mid week will still feature a few systems impacting the
area from the south.

Low number one tracks north, just west of Haida Gwaii, on Tuesday
only to lose its upper level support and quickly fall apart west
of Dixon Entrance. This low will not bring much to the southern
panhandle except for an increased chance of rain and some breezy
conditions. Its the low behind it that will bring more interesting
impacts. Low number two follows almost the same path as the
first, but with better upper level support, it holds together for
much longer. This low looks to be making a bee line for Cape
Decision by early Wednesday spreading more wind and rain across
the inner channels. Possible concern for more strong wind gusts
for the southern inner channels Tuesday night into Wednesday if
this track holds as some models are suggesting low level jet
strength of around 35 to 45 kt on the eastern side.

Late week into next weekend is rather uncertain as the upper level
trough over western Alaska drifts to the east. A cold air mass in
the Alaskan interior will try to shift south and east over the
next week but long range models are at odds on how much of it gets
here. NCEP models are heading toward a colder scenario. The Ecmwf
on the other hand keeps the cold air farther west and north
allowing for more warm air to periodically push in from the south.
In any case, the general trend is toward cooler and drier weather
as we get into late week and next weekend.

&&

.AVIATION...MVMC will prevail with pockets of IMC at times. Main
limiting factor will be lower CIGS. LLWS and MOD turbulence will
persist through the daytime hours for most locations as a 60 kt
southwesterly low level jet pushes over the panhandle today.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until 9 AM AKST this morning for AKZ026.
     High Wind Warning until noon AKST today for AKZ027.
     Strong Wind until noon AKST today for AKZ019-025.
     Strong Wind until 6 AM AKST early this morning for AKZ020-022.
     Strong Wind until noon AKST today for AKZ023.
     High Wind Warning until 9 AM AKST this morning for AKZ028.
     High Wind Warning from noon today to midnight AKST tonight for
     AKZ018.
     Winter Storm Warning until 6 AM AKST Tuesday for AKZ018.
     Strong Wind from noon today to 3 PM AKST this afternoon for
     AKZ017.
MARINE...Storm Warning for PKZ036.
     Gale Warning for PKZ012-013-031>035-041>043-051-052.
     Small Craft Advisory for PKZ011-021-022-053.
&&

$$

Fritsch/EAL

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