Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 041518
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
618 AM AKST Sun Dec 4 2016
.SHORT TERM...A low over the northern gulf has begun to move
southeast. High pressure over the northern interior of the state
has begun to build south and east. Snow showers continue over the
southern half of the panhandle. Temperatures aloft are very cold
and support a vigorous convective environment once again today.
Apart from including isolated thunderstorms in the forecast,
believe snow showers will continue to produce advisory level
snowfall rates a little longer than originally anticipated for the
central outer coast and southern zones. Thus, the advisory for
zone 26 will expire on time, but have extended the advisory for
zones 23 ans 27 till noon and till 3 pm for zone 28. To the
north, snowfall rates have diminished or ended and this trend will
spread south by this afternoon. As precipitation exits the
forecast area entirely tonight, offshore winds resulting from the
Canadian high building south will begin clearing out clouds.
Daytime highs have already occurred for most locations and temperatures
will fall significantly over the next 24 hours. Look for overnight
lows in the single digits over the far northern zones and the
teens as far south as Hoonah and Juneau as well as in Hyder.
Elsewhere, lows will range from the lowers 20s to the very low 30s
Strong northerly winds - to gale force over some of the marine
zones - will result in freezing spray over the northern inner
channels. Am also expecting some freezing spray associated with
outflow winds vicinity Cross Sound and Dry Bay. Strong winds in
Skagway and along the Klondike Highway will cause blowing snow.
Not expecting gusts to 40 mph along the Haines Highway, but
reports of blowing snow yesterday and similar conditions forecast
today prompted the inclusion of blowing snow there as well. Wind
chill will be getting down to -20 or -25 degrees along the
highways tonight as well, so travelers will need to exercise
caution today and tonight.
Updated pressure and wind over the gulf for the today period using
NAM. Forecast from yesterday for Sunday night still looks right on
the money, so no changes there. PoP, QPF, and snow for the today
period scrutinized very closely as they relate to the winter
weather advisories currently in place. Did not want to end the
advisory too soon, nor extend it unnecessarily long. Used early
morning observed temperatures for today`s highs. Min temps from
yesterday`s forecast still looked good, but did adjust temps over
the gulf a bit. Overall forecast confidence is average.
.LONG TERM...Long range forecast continues to gradually change as
successive models runs come in. The general trend for the last
few days has been toward the cold strong Yukon high having a
greater influence on the weather over the panhandle into mid to
late week. The general result is a drier and colder forecast
compared to the solutions presented a day or two ago. The
persistence of the cold air also means that outflow winds will
continue for much of the long range and any precip will likely
remain snow. Mainly used NAM and some GFS for forecast guidance.
A few other trends are also apparent. The weak low and front that
is forecast to move across the gulf and northern gulf coast Tue
into Wed is spreading precip much further east than was suggested
yesterday before it starts moving back west again. Models are now
suggesting an eastern edge all the way to Wrangell and Klawock
rather then the Hoonah area that they were yesterday. This would
result in more light snow for many areas of the panhandle and also
the possibility of advisory level snow amounts for the northern
gulf coast as well. Successive shifts will continue to monitor
this developing scenario.
The other trend is for the mid to late week low that was expected
to appear in the southern gulf and spread a front across the
panhandle. That scenario has fallen apart with the low track
trending southward over the last few days due to the increased
presents of the Yukon high. Current track is toward the BC coast
south of Haida Gwaii with the front now barely even making it into
the southern panhandle. Result is the late week and weekend
periods are looking rather dry with colder temps.
PUBLIC...Winter Weather Advisory until 9 AM AKST this morning for AKZ026.
Winter Weather Advisory until noon AKST today for AKZ023-027.
Strong Wind through late tonight for AKZ018.
Winter Weather Advisory until 3 PM AKST this afternoon for
MARINE...Gale Warning for PKZ012-013-022-031-043-051.
Small Craft Advisory for PKZ011-021-032>034-052.
Small Craft Advisory due to Seas for PKZ041-042.
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