240 
fxak67 pajk 222309 
afdajk 


Southeast Alaska forecast discussion 
National Weather Service Juneau Alaska 
209 PM akst sun Nov 22 2009 


Short term...strong storm in the works out in the southwestern 
Gulf today. As it moves north through the western Gulf it will 
send a strong front into the Panhandle for late tonight and 
Monday. Resent model runs have been shifting the low track just a 
bit west of previous forecasts. Currently the GFS is the farthest 
east with most of the rest of the models clustered about 200 to 
300 miles further west. In our neck of the Woods, timing of the 
front is rather good between the various models with the first of 
the frontal bands hitting the southwest outer coast late tonight. 
The front will be kicking up higher winds ahead of it so have 
kept the wind advisories that were posted by the middle shift the 
same except that the advection for 23 now starts at midnight instead of 
3 am. 


As the front pushes through the Panhandle late tonight and 
Monday, it will spread some moderate precipitation across the area. Type 
will mainly be liquid south of a line from Juneau to Hoonah to 
Cross Sound, with all snow along and north of that line late 
tonight and into tomorrow. Believe that snow levels will be low 
enough and qpfs high enough for advisory level snow accumulations 
for the northern Inner Channels starting early tomorrow morning. 
Have posted winter weather advisories for Gustavus, Hoonah, 
Juneau, Haines and Skagway for most of the day tomorrow. Snow 
levels should rise high enough by Monday afternoon for the snow 
to begin to mix with rain in Gustavus, Hoonah, and Juneau. 


One sticky point is a developing wave on the front before it 
makes it into the Panhandle. This could cause a brief increase in 
winds for the southern zones. Did not have enough confidence in 
this to issue a wind warning however. 


Short term forecast was updated using a blend of the UKMET and 
NAM today. With relatively good initial placement and a scenario 
that was supported by the GFS ensemble mean, felt that the UKMET 
was the model of choice today. The exception was that I used the 
higher wind magnitudes of the GFS in the wind forecast. Forecast 
confidence is a little above average today due to uncertainty 
with how the developing wave on the front will affect the system. 


Long term...it was a very tricky day on the long term desk as the 
overnights models did not have good run to run continuity. The ec 
flip flop on the weather system lifting into the Gulf on Tuesday and 
there are other issues through the week with the track and 
strength of the series low pressure systems moving into the Gulf. 
Also there has been a large increase in ensemble member spread 
overnight so with that said there was not many changes made to the 
previous forecast. Where changes were made used a blend of the 
inherited grids with the GFS through Tuesday night as it has been 
consistent with the elongated low over the western Gulf with a 
front extending over the eastern Gulf. Then for the extend 
portions used HPC guidance. Overall there is low forecaster 
confidence in any individual system that will move into the Gulf 
this week. There is fair forecaster confidence that there will be 
3 to 4 weather front that will move over the Panhandle this week 
along with warming temperatures. 


At the start of the long term a surface trough with a front will be 
lifting over the Panhandle Monday night. This front will continue to 
spread rain over the southern half of the area with a mix over the 
central areas that will change to all rain over night. Further 
north it will be snowing but as the front moves through and the 
surface ridge begin to build over the Panhandle the southerly flow 
will increase and mix out the cold air. It may stay all snow along 
the highways longer with significant accumulation. As the ridge 
builds over the area the winds will increase to small craft over 
the northern Inner Channels and it will become breezy to windy 
near pagy and pahn. 


Showers will continue into Tuesday morning but a upper ridge will move 
over the Panhandle ahead of a low moving out of the North Pacific 
and into the western Gulf through Wednesday. The associated weather 
front will spread rain from south to north through Tuesday and the 
winds along the Gulf will increase to gales along with small 
crafts over inside waters. The winds over the coastal areas may 
need Wind Advisory but there is low confidence at this time as with the low 
center over in the western Gulf think the strongest winds will 
remain over the Gulf. 


Ajk watches/warnings/advisories... 
public...Wind Advisory from midnight tonight to 9 am akst Monday for 
akz027. 
Winter Weather Advisory from 3 am to 3 PM akst Monday for akz020- 
021-025. 
Wind Advisory from midnight tonight to noon akst Monday for 
akz023-028. 
Wind Advisory from 3 am to noon akst Monday for akz029. 
Winter Weather Advisory from 6 am to 6 PM akst Monday for akz018- 
019. 
Marine...Storm Warning for pkz043-051-052. 
Gale Warning for pkz021-022-033>036-041-042. 
Small Craft Advisory for pkz011>013-031-032. 


&& 


$$ 


Eal/abj 

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