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FXAK67 PAJK 132251
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
251 PM AKDT Sun Oct 13 2019

.SHORT TERM.../Through Tuesday night/ Main concern of the short
range period today is the gale force front that will be making its
way into the gulf and panhandle on Mon and Mon night. Structure of
the system is very complex with the main parent low meandering
around 50N and an occluded front wrapping through the southern
gulf most of Mon and Mon night. The main forecast uncertainty is
dealing with the various short waves that are embedded in the
frontal structure through guidance is getting better on that
issue.

In any case, rain will be starting up in the southern panhandle as
early as Mon morning and will spread N. Areas N of Angoon and
Tenakee Springs should remain dry through Monday before the rain
reaches them Mon night. Areas South of Frederick Sound will
receive the bulk of the rain as the system shows a decent
tropical connection that includes moisture pulled from former
tropical storm Ema near Hawaii. Current PW measurements in the
moisture plume are around 1.5 to 2 inches which is around 150 to
200 percent of normal. Total rainfall is expected to range
anywhere from 1 to 4 inches through Tuesday afternoon with the
highest rain rates expected Mon Afternoon into Tuesday.

Snow is also a possibility on the Haines and Klondike Highways Mon
Night and Tuesday. Not much qpf makes it up that far north
thought, so snow accumulation should only amount to around 2 to 3
inches at higher elevations Mon night and Tuesday. Some snow may
even mix in with the rain at sea level in Haines and Skagway late
Mon night, but no accumulation is expected there.

Also of concern is the gusty winds expected with this front. Wide
spread mid to high end gales are expected across the gulf Mon into
Mon night. There is the possibility of some min storm force winds
along this front Mon Afternoon in the gulf but confidence was not
high enough for its inclusion in the current forecast. Wide spread
gusts to 40 or 45 mph are likely for the southern panhandle and
southern outer coast at the same time. Farther north, winds will
have more of a northeasterly component as the front comes up.
Northerly pressure gradients will likely increase enough for small
craft northerlies in Lynn Canal on Mon. There is also the
possibility of some gusty winds in Downtown Juneau and Douglas due
to a synoptically driven mountain wave event Mon. I do not expect
gusts to exceed 35 mph at this time though. Those winds should
diminish as the first rain bands move in Mon Evening.

Forecast changes mainly limited to local effect changes with large
scale features still well represented in the current forecast.
Used mainly nam for guidance.


.LONG TERM.../Tuesday through Saturday as of 10 pm Saturday/...Long-
term forecast continues to pose a challenge.The fall pattern will
continue to impact the area. Ensembles are falling into more
agreement with the idea of multiple shortwaves developing around
the broad area of low pressure which will be in the Gulf of Alaska
throughout most of next week, especially from Tuesday onwards.
There are some indications of possible shortwave interaction with
the Panhandle on late Tuesday followed by another wave early
Thursday. However, timing and exact placement of the wave features
remains up in the air and guidance has yet to reach a firm
consensus, so have elected to hold off on sketching out any real
impacts from possible shortwaves at this time.

What is not in disagreement however is the continued chance of
precipitation for the Panhandle throughout the long term forecast
period. Moisture transport, though not ideal, will provide the
impetus for continued opportunities for rain throughout the area.
Any shortwave development could also elevate POP through the
Panhandle, and will continue to monitor as event approaches. Also
a chance of snow in some of the upper elevations and at White
Pass is not beyond the realm of possibility.

Still watching what might happen with the extratropical evolution
of Typhoon Hagibis into the middle of next week. The system being
driven by a very strong upper level jet is likely to move near
the Aleutians late Monday. The interaction with the previous low
will likely be complex, but additional tropical energy could
definitely increase POPS next week if it can make it into the
Gulf.

Relatively few changes made throughout the long term. POP was
generally elevated in some locations throughout parts of next
week, and wind speeds were increased in some locations for
Tuesday. Additionally, temperatures were moderated in some
northern forecast locations. Forecast confidence is average
through the long range.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind Monday afternoon for AKZ026-028.
     Strong Wind Monday afternoon for AKZ023-027.
MARINE...Gale Warning for PKZ022-036-041>043-051.
     Small Craft Advisory for PKZ012-013-021-031-033>035-052.

&&

$$

EAL/GFS

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