Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
200 PM akdt Sat may 25 2013
Model discussion...
model initializations in general were reasonable. The most glaring
issue is that a low 990's low center near Nikolski is a little
further north at 18z then the 12z model projections. Overall synoptic
forecast trends and general placement of ridges and troughs are
somewhat similar and reasonable. The timing of the easterly wave is
fairly similar between the GFS/ECMWF/UKMET. The NAM has a slower
movement and is putting more emphasis on a secondary wave moving out
of western Canada. However the quantitative precipitation forecast patterns are in fair agreement
though the NAM brings a little more quantitative precipitation forecast into the Copper River basin
sun.
Upper levels...
a cut-off low center over the southern Gulf of Alaska moves north and
west across the Gulf sun and across southwest Alaska as an open wave
Monday. A broad long wave trough extends from a low near the eastern
Aleutians to a secondary center over the southern Gulf through Monday.
The thermal trough over the interior strengthens over the next couple
of days as warm air spreads west from Canada.
Surface...
a broad ridge extends across the northern Gulf of Alaska. Satellite
imagery shows a extensive area of low clouds and fog associated with
this feature. This ridge will drift to near the north Gulf Coast sun
and Monday as a weak frontal boundary skirts the northern Gulf. Out
west...a low center near Nikolski weakens and drifts SW of the
pribilofs sun and Monday. The trailing frontal system extending across
the Alaska Peninsula is expected to weaken Monday.
Short term forecast...
southcentral Alaska...
ridging across the north Gulf will help push some low level moisture
in the form of low stratus and fog into Cook Inlet tonight. The
stratus some break up some during the afternoon. A easterly wave
moves across the Gulf sun and brings increasing chances of
rain...probably more showery inland. A secondary surge of moisture
associated with a frontal system moving from the Gulf will bring a
little more extensive area of rain/showers to southcentral Sun
night...though the north Gulf and Kodiak will likely see the brunt of
it. Ridging builds back in on Monday. Conditions become somewhat more
unstable across the Copper River/Alaska Range as the thermal trough
intensifies.
Southwest Alaska...
clouds and some light rain...associated with a frontal zone over the
eastern Gulf will brush the southwest coast this afternoon and
evening. Drying is expected overnight as the front moves east and
offshore flow develops. Weak instability along with weak upper wave
could kick off a few afternoon and evening showers over interior SW
Alaska sun. Chances look even better for afternoon and evening
convection Monday as the thermal trough intensifies.
Alaska Peninsula...
rain...though a little lighter will continue across the Alaska
Peninsula through Monday as the nearly stationary front weakens.
Bering Sea/Aleutians...
unsettled weather with showers/rain will continue over the eastern
half. Ridge over the western half will create more stable conditions
with low clouds and fog.
Long term forecast...
the west will be dry...but SW Alaska will have showers by middle week as the
thermal trough drops south into the area. These will also affect
southcentral.
Aer/alu...watch/warning summary
public...Flood Watch zone 141.
Marine...gales...150 160.
Fire weather...red flag warning 141.
Rmc may 13
