Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
147 PM akdt Friday Oct 24 2014
Analysis and upper levels...
an elongated upper level low over eastern Russia into northern
Alaska is bringing zonal flow aloft over southern Alaska from the
Bering Sea through the Gulf of Alaska. An upper level disturbance
is moving into southcentral Alaska from southwest Alaska. This
wave is dissipating as it moves to the east.
This pattern will begin to shift on Sunday and Sunday night as
the low in eastern Russia digs southward into the Bering Sea which
will also amplify an upper level ridge over the Copper River basin
near the alcan border.
At the surface there is a large and complex low over the northwest
Bering Sea through eastern Russia. A front associated with this
low complex is keeping a fairly tight pressure gradient over the
Bering Sea as it pushes into the ridge over southwest Alaska. A
low near the north Gulf Coast will remain in the area through
Saturday and is bringing some moisture into the coastal area and
Copper River basin.
model initialization was good on the 12z runs for all models.
Models continue to show good consensus until Saturday night when
the solution for the low strengthening in the northwest Bering
Sea begins to diverge. The European model (ecmwf) model is showing the low stronger
and farther east on Sunday and then is move northward faster than
do the GFS or NAM models. By Sunday night there is nearly 250
miles difference in location of the low with the European model (ecmwf) moving it
almost to the Bering Strait while the NAM and GFS have is
southwest of St Lawrence Island. While the center of the low is
far enough north to mitigate the effect it will have on the southwest
Alaska Mainland it is strong enough that the track will be
important. In short...there will be a strong low in the Bering
Sea through the weekend but the details related to the track of
the low may change some as the storm develops.
Short term forecast...
the upper level wave that is moving across the Alaska Range this
afternoon is rapidly weakening as it moves eastward. This is
diminishing the chance for snow showers across the Cook Inlet to
Susitna Valley regions. The low in the northern Gulf is producing
some rain and snow showers near the coastal locations. This low is
also pushing some moisture into the Copper River basin which will
cause some periods of snow throughout the basin into tomorrow
morning. Skies should begin to clear out over southcentral again
as the surface low in southwest Alaska moves over southcentral
the ridge over southwest Alaska will give way to a weather front
which will start to bring in snow to the Kuskokwim Delta tomorrow
morning which will spread eastward throughout the day. Coastal
areas of the Delta will also see some gusty winds with this front.
the mostly clear skies in the eastern Bering Sea will way to
stormy weather as the weather front moves into the area. A low
will develop near Kamchatka Saturday and move rapidly eastward and
strengthen by Sunday. This will bring some storm force winds into
some of the Bering Sea marine areas. As the upper level low digs
southward over the bring sea early next week it will keep the
storm track over the area through the middle of next week.
Long term forecast...
while model agreement beyond early next week remains quite
poor...there have been some small improvement in the models since
yesterday. There is now good agreement that remain the remnants of
tropical storm and move onshore south of the Panhandle...well
south and east of our aor. The weak low that will form behind this
system will also quickly dive southward into the North Pacific
Tuesday- Wednesday...keeping precipitation confided to the Gulf
Coast and western Bering through Wednesday.
Because of the poor model agreement with low location...the long
term forecast once again heavily used wpc guidance today (which
used mostly ensembles and the 00z ec through tuesday).