261 
fxak67 pajk 071231 
afdajk 


Southeast Alaska forecast discussion 
National Weather Service Juneau Alaska 
431 am akdt sun Sep 7 2008 


Short term...early morning satellite loop shows a progressive low 
in the western Gulf rapidly moving north towards Kodiak area with 
associated front and rain band stretching north and northeast with 
its triple point just northeast of Kodiak Island. Middleton Island 
radar shows an intense rain band invading onshore and expanding east 
to Yakutat area. Southern Panhandle reports less clouds at this 
time. However...middle clouds are consolidating rapidly over the 
adjacent coastal waters and Biorka radar shows an organizing rain 
band slowly drifting northeast towards the coast along the leading 
edge of the incoming front. This leading edge of the front has 
also generated 25 to 30 kts east wind and rough seas over 
northern most outside waters overnight. Buoy data indicate 
southeast wind slowly increasing across the outside waters from 
Cape Fairweather southeast. Pressure gradients across the inside 
passages remain pretty weak under weakening ridge of high pressure 
at this time. 


All models arrived on time and are in fair agreement with the 
weakening ridge drifting south as a frontal boundary moving into 
the north eastern Gulf through tonight. Behind the front...the 
ridge rebuilds and the 06z run NAM shows a bit flatting ridge top 
on Monday while the 00z and 06z GFS runs maintain a better ridge 
top over the Panhandle. Used the GFS solution primarily blending 
with the inherited grids through Monday and the NAM as a smoothing 
tool for today and tonight. With the incoming front...expect 
categorical probability of precipitation for northern coastal zones while more inland and 
southern areas expecting a delay through the afternoon hours with 
likely to categorical probability of precipitation. As the trailing edge of the front 
drifting northeast across central and southern Panhandle 
tonight...likely probability of precipitation will remain over the areas. Winds will 
slightly decrease behind the front across the water body but due 
to long periods of southwest swells generated by the progressive 
low in the western Gulf...seas will remain rough over the outside 
waters through Monday. 


&& 


Previous discussion... /issued 103 PM akdt Sat Sep 6 2008/ 


Long term...GFS this morning was a little more progressive in 
moving a ridge and upper low east across the Gulf middle week next 
week than the 00z European model (ecmwf). Likewise with a short wave in the upper 
levels late next week. At the surface...some differences regarding 
the placement of a low on Wednesday in the northern Gulf but have 
little impact on the eastern Gulf and Panhandle. At the end of the 
long range forecast period...GFS is placing a front in the central 
Gulf whereas European model (ecmwf) locates this same feature farther north in the 
northern and eastern Gulf. Overall...good agreement between GFS 
and 00z European model (ecmwf) through next Sunday. Even better agreement between 
GFS and the new 12z European model (ecmwf) so forecaster confidence in this long 
range forecast is above average. Used GFS for primary guidance. 


The extended range forecast begins with an occluded front over the 
coastal waters and rain over all of the Panhandle. A surface ridge 
will build in behind this front but the usual surface ridge 
precipitation will keep Panhandle probability of precipitation at chance or better through 
Monday night. The next developing system will spread rain into the 
western portions of zone 17 Tuesday morning Sep 09th and spread south 
down the Panhandle through Wednesday afternoon. Models have sped 
this front up since yesterday so have advanced this feature and 
the associated precipitation accordingly. A surface trough approaches the 
Panhandle Thursday night September 11th and looks like it will 
spread showers over the central and southern zones through the day 
Friday. Upper level support for this is not that strong nor is it 
phased well with this feature so confidence in this particular 
aspect of the extended range forecast is not as good as other 
portions. 


In terms of winds...nothing significant until the approach of the 
front on Tuesday 09 September. At that time...small craft 
southeasterly winds expected to build in from the west across zone 
310 and the coastal marine zones in advance of the surface front. 
May see marginal gales north of Cape Spencer by Wednesday morning 
10 September and also am expecting pre-frontal small craft winds 
over the southern Inner Channels by this time. Still far too early 
to issue a Wind Advisory...but indications are that this may be 
necessary for zone 27 for next Wednesday...so will watch this 
closely. Do not expect things to pick up over Lynn Canal until 
after frontal passage Wednesday night when a strong northerly 
pressure gradient will set up between the Panhandle and a surface 
low over the Yukon. The surface trough that approaches the outer 
coast Thursday night September 11th does not have a lot of wind 
associated with it and so marginal small craft winds are currently 
forecast over the northern Inner Channels. As indicated 
above...however...forecaster confidence in this particular feature 
is not that good so will have to monitor over the next several days. 


&& 


Ajk watches/warnings/advisories... 
public...none. 
Marine...Small Craft Advisory for pkz041>043-051-052. 


$$ 


Sja 

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