Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
200 PM akst Sat Mar 8 2014
Analysis and upper levels...
a 970s low over the eastern Gulf is moving slowly north. The occluded
frontal system is pushing west and weakening...but is bringing some
light snow over the southeast Copper River basin and along the north Gulf
Coast. Strong outflow winds are evident along the north Gulf Coast
and eastern Kenai Peninsula with increased pressure gradients caused by The
Squeeze between this Gulf low and higher pressure over the Mainland.
Water vapor imagery showed a fairly pronounced dry slow associated
with subsidence dropping south across Cook Inlet/Kenai Peninsula.
Out west...generally offshore flow continues across the SW Mainland
with some snow showers over the Bering Sea and mixed showers across
the Aleutians associated with a weakening frontal boundary.
model initializations overall were OK. The GFS still is the fastest
of the solutions with the developing storm over the North Pacific.
The other global models as well as the NAM were much slower. The
European model (ecmwf)...which as one of the slower models...has been fairly
consistent over the last couple of runs. So since grids currently
have a ec look and the model looks reasonable...few changes are
expected in this forecast package.
Short term forecast...
pressure gradients will likely remain fairly tight along the north
Gulf through tonight and support continued gap flows. Winds should
diminish sun as gradients weaken. Onshore flow rapidly increases late
Sunday as a pattern change towards much more active weather
commences. With the onset of onshore flow moisture transport will
increase dramatically with a weather front moving into the
southwestern Gulf Sunday night and reaching the Gulf Coast late
Monday. Temperatures appear to be warm enough for all
rain toward Kodiak after a brief period of snow...but precipitation
will likely be all snow at least in the beginning for the Gulf Coast.
Potential hazards for Monday into Tuesday will include the potential
for heavy snow and blowing snow for the eastern Kenai Peninsula as
well as blizzard possible Snow Advisory conditions over the western
Susitna Valley. We will continue to evaluate the threat through the
mostly clear skies and brisk northerly winds will continue through
the weekend as weak high pressure remains overhead. Precipitation
will then return to the southwest Mainland early Monday as a North
Pacific low and associated front track into the western Gulf of
Alaska. Precipitation will likely be snow...south will probably mix
with rain over the Alaska Peninsula.
Showery weather will linger over the southern half of the Bering
through the weekend as an elongated upper trough and a weak frontal
boundary remain over the area. The pattern will become more active
over the eastern Bering by Monday as the aforementioned North Pacific
low tracks south of the chain to the vicinity of Kodiak Island and
spreads snow and strong winds over the eastern Aleutians and Alaska
Peninsula. Blowing snow potential will have to be watched closely
over these areas...as the most intense snowfall could remain east of
Dutch Harbor and temperatures may be a little too warm across the
akpen depending on the exact evolution of the system over the coming
Long term forecast...
The southern Mainland will transition to a more active pattern marked
by increased precipitation and occasional strong winds by the
beginning of the week as the first in a series of North Pacific lows
tracks into the western Gulf of Alaska and pushes an associated front
over the norther Gulf Coast. The next system will then follow closely
on its heels in the Wednesday night/Thursday time frame as it takes a
very similar track. Temperatures should remain cold enough for all
snow over inland locations...with rain possibly mixing in at times
along the coast.
public...Winter Storm Watch...125
marine...gales...132 352 150 155 165 170 172 174 176 179 185.
Heavy freezing spray...179 185.
Rmc Mar 14