Weather Service Report

FXAK67 PAJK 201415

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
515 AM AKST Mon Feb 20 2017

.SHORT TERM...Trough of low pressure along the coast of the
panhandle will persist through Monday night. A high pressure 
ridge is expected to build into the central Gulf of Alaska Monday 

Generally the inner waters will experience light winds with 15 kt
or less except for 15 to 20 for Lynn Canal. Out over the central 
gulf the advancing ridge against the trough near the coast will 
cause northwest winds to 20 kt for the eastern part of offshore 
and southern portion of the coastal waters. 

A low to mid level cloud deck is spreading to the northeast gulf
and northern portion of the panhandle, while a few clouds stream
north to the southern panhandle/Misty Fjords. Forecast to stay dry
although slight chance of snow or rain should approach the 
Yakutat to Sitka area late tonight from the west. 

.LONG TERM...Two systems will arrive in the eastern gulf Tuesday
and another Wednesday. Wednesday, the last exits leaving a
stronger ridge to develop over the gulf. Early this weekend, 
ensembles all point to a system flattening the ridge and sliding 
eastward from south-central AK or the northern gulf and likely 
bringing mixed precipitation for the Panhandle. For this edition,
our most substantial change to the forecast was to dry Thursday 
and Friday further and to decrease cloud cover by a category. 

Tuesday, scattered coastal snow and rain showers will make little
headway inland. High pressure will nose southward from the 
Canadian Yukon Tuesday night which will aid in clearing skies 
again from the north. Wednesday's system will then arrive in the 
eastern gulf a little late but start a southeastward turn earlier.
Despite being a stronger system than the Tuesday one, the
Wednesday system will limit precip chances even more than
Tuesday's. Overall, temperatures will remain very seasonable for
this time of year. However, we do expect a gradual warming into
later in the week as a ridge builds across the gulf. 

Forecast was left unchanged Friday night beyond as rain and snow 
develops with a quick moving system from the west. There are 
disagreements as to how much warm air is pumped into southern 
Alaska by the Thursday/Friday ridge. The GFS is far more 
conservative by preserving a cooler air mass over the Panhandle, 
and likewise producing a potentially snowier system. But at this 
point, the ECMWF looks a little more realistic, with any colder 
air arriving as the system exits. Therefore, rain/snow hedging is 
sound at this stage.

Forecast confidence is generally good with synoptic features in
the mid-range but falls on timing of the system this weekend, even
as it is positively represented in all solutions.


.AJK Watches/Warnings/Advisories...



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