Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
526 am akdt Wednesday may 22 2013
Analysis and upper levels...
the ridge over the Gulf continues to slowly retreat into the North
Pacific due to a developing weak wave currently south of Kodiak
Island. This is allowing continued cloudiness...as well as a few
areas of light rain or drizzle over southcentral and southwest
Mainland. Weak low over the northwest Bering is clipping the extreme
northwest edge of the aor. This system will continue to only impact
the offshore marine areas as it weakens this evening.
Model discussion...
the main disagreement between the models continue to be differences
in where they paint areas of light rain over the Mainland. The GFS is
initializing the best with regards to the light rain falling around
southcentral...while the NAM is preferred out west with an area of
light rain stretching from the southwest Mainland to Alaska
Peninsula. Otherwise there is good synoptic agreement through the
weekend. The models have come into much better agreement with the
next Aleutian low for Friday...especially with regards to the low
track. There are however some minor discrepancies with low intensity
that should have little impact to the forecast.
Short term forecast...
southcentral...with the exception of lingering showers along the
mountains...the isolated light rain showers from the northern
Kenai...Anchorage bowl...Gulf Coast will diminish this morning as
instability departs the area. The clouds however will likely linger
through this evening...since there will be very little forcing to
help scour them out until the ridge rebuilds along the Gulf Coast
overnight tonight. Once this occurs...expect diurnal convective
showers to develop along the thermal trough starting Friday afternoon
along the mountains from Anchorage into the Copper River basin.
Convective showers should then increase in coverage and intensity for
the Memorial Day weekend...and could lead for the first lightning
strikes of the season...most likely in the northern Copper River
basin.
Southwest/akpenn...the light rain over the southwest Mainland will
finally diminish this afternoon as weak upper level ridging moves
into the area. This will be start of a pattern where more seasonably
warmer and drier weather will be present for most of the area through
Saturday. The exception to this will be the Alaska Peninsula...where
rain and gusty southerly winds will return Friday afternoon with the
next Aleutian low. A few showers from this Aleutian low may clip
Bristol Bay late Sunday into Monday...but is not expected to be a
widespread rain at this point.
Bering Sea/Aleutians...widespread stratus clouds...with areas of fog
over the water will continue through the weekend for much of the
Bering Sea. This will likely continue into next week due to low level
moisture from the next Aleutian low. Inland areas of the Aleutian and
Pribilof Islands may see some diurnal patchy fog during the overnight
and early morning hours.
Long term forecast...
the ridge that will build over the Gulf this weekend will push north
onto the southern Mainland for the first half of next week. An upper
level trough will also develop over the southern Gulf...which will
cause the diurnal convective showers along the thermal trough to
continue into middle week. Out west...the Aleutian low will become
nearly stationary over the central and western Bering next
week...which will help keep most of the active weather to the west or
south of the Mainland.
Aer/alu...watch/warning summary
public...Flood Warning 152
marine...Gale Warning 170
fire weather...Fire Weather Watch 141 for low relative humidity
Dek may 13
