068 
fxak67 pajk 202123 
afdajk 
Southeast Alaska forecast discussion 
National Weather Service Juneau Alaska 
1225 PM akst Thursday Nov 20 2008 


Analysis... 
4-wave pattern for the northern hemisphere this morning with the 
anchor upper low over Scandinavia for the next week. Cold major upper low 
center just west of Kamchatka with -42c at 500 hpa which sets up an 
upper ridge along 180. Major up low over central Gulf -32c at 500 hpa with 
positive tiltd trough to SW and negative tilt off b.C. To California. 986 mb surface 
low 56n 146w at 18z with secondary wave over the charlottes. Old 
tropical system has become T-Bone shape 1002 mb around 38n 162w with lots 
of warm air and triple point low about 42n 150w. 250 hpa jet over 
150kt from Asia to exit over western Aleutians. South-southeast flow aloft over 
Panhandle and some cold air in negative tiltd trough. 


Short range...satellite imagery this morning is showing at least 
two low level circulations underneath the major upper level low in 
the Gulf. Also evident is the frontal zone which extends southeast 
from Cape Suckling to west of the Queen Charlottes. This front has 
made very little progress eastward this morning and will continue 
to be a slow mover this afternoon. Accordingly...the pop forecast 
for tonight and tomorrow keep the vast majority of the Panhandle 
at precipitation likely or better the entire time. A pair of upper level 
troughs will rotate around the primary upper low over the Gulf and 
bring in some significantly colder upper air...first tonight and 
then again Friday afternoon/evening. Cold air advection at the 
lower levels not nearly as evident...so do not anticipate and 
significant changes to over night lows...Friday highs...or to the 
snow forecast. 


Still have some breezy to windy conditions associated with the 
southeasterly low level flow in advance of the front in the 
southern half of the Panhandle this morning and several locations 
have had gusts close to advisory levels. Do not expect to see a 
significant increasing trend so do not anticipate any new wind 
advisories for the remainder of today. As for those wind 
advisories currently in effect for zones 17 and 18...the strong 
northerly pressure gradient remains in place but is beginning to 
weaken so will expire/cancel them at noon today. Am expecting to 
see northerly gales continue over Lynn Canal through the day today 
and strong small craft conditions elsewhere over the Inner 
Channels though...so mariners should remain vigilant. 


The strong pre-frontal southeasterly winds are also generating low 
level wind shear and this is reflected in the tafs today. Have 
already received an urgent pilot weather report from an aircraft at Wrangell and 
Ketchikan verifying this. 


For tonight and tomorrow...the front will slowly make its way east 
and then begin to re-Orient more east-west as a surface trough 
rotates inland and lifts north. Meanwhile...a developing storm 
force low currently well to the south will track rapidly to the 
northeast tonight while continuing to intensify. This low is 
projected to remain well south of Southeast Alaska and be an issue 
for locations from hecate Strait and points south...but some 
models are suggesting this low will reach hurricane force and even 
as currently forecast...the Dixon Entrance will likely see 
easterly winds 25 to 30 kts tomorrow afternoon. If the forecast 
track of this system moves north over the next one to two model 
runs...much stronger winds over the southern Panhandle and Inner 
Channels will be likely. 


Long term... 
again not comfortable with meridional flow and tropical system well S 
today. Good thing is that Ops models are starting to come together on 
forecasts for early next week as cold air aloft moves into Bering Sea. 
The HPC forecasts are used and preferred 12z Monday and beyond. Until 
then used the 12z Alaska-GFS-40 due to reasonable initialization and good 
agreement. Will tag a developing low to the SW that arrives over 
western Dixon Entrance on sun. This wind event should just miss 
southern southeast for below Wind Advisory. 


Ajk watches/warnings/advisories... 
public...none. 
Marine...gales pkz012-013. 
Smcr all other waters. 
$$ 


Fritsch/jcc 

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