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Southcentral and southwest Alaska forecast discussion 
National Weather Service Anchorage Alaska
430 am akdt Thursday Jul 10 2014

Analysis and upper levels...
the main player in the flow pattern aloft is a large complex low
centered over the eastern Bering Sea. There appears to be a broad
center of circulation with many shortwave troughs propagating
through the periphery of the low. The focus for active
southcentral weather will be two stronger waves...one near Kodiak
Island this morning and a second further south in the Gulf. There
is a significant moisture plume with these systems with a
connection to the subtropics. Precipitable water values in the
moisture stream range from one to two inches which falls from 140%
to over 200% of climatological normals. The warm front associated
with the first Kodiak low pressure extends northeastward and is
spreading a large stratiform rain shield over the north Gulf Coast
and inland.

&&

Model discussion...
guidance has been struggling with the evolution of the two
shortwaves in and approaching the Gulf of Alaska. Previous model
runs had been developing the secondary frontal wave in the Gulf
and essentially merging the two systems with a negative tilt
aloft. The more recent runs take the secondary energy further to
the east with less of a negative tilt aloft resulting in a weaker
surface circulation near Kodiak...though the front will still be
very potent and strengthened by the second wave. All in all
guidance is in much better agreement with the system then
yesterday at this time. The consensus is the upper level low
pressure will shift from the eastern Bering Sea/Bristol Bay south
over the Alaska Peninsula keeping much of the southern Mainland
under the influence of the system or in the active southerly flow
ahead of it.

&&

Short term forecast...

Southcentral Alaska...the warm front will continue to shove into
the coastal mountains this morning the spread light to moderate
rain across most areas in the southcentral. Gap flow will continue
to increase as the front pushes mass through the mountains. The
Turnagain Arm wind will ratchet up through the day today into the
strong wind range then slacken a bit overnight before being
reinvigorated by the second system. The strong down inlet gradient
will keep the strong winds in The Arm and out of the Anchorage
bowl...likely until frontal passage on Friday morning/afternoon
when some gust into the 40s remains possible. Coastal areas will
continue to get slammed with moisture from the Gulf while inland
areas will be somewhat mitigated from the extreme moisture by the
mountains...but will still see precipitation due to the moist
nature of the system. The upper level low pressure hangs to the
southwest through the weekend keeping the threat for precipitation
around...though once the front passes on Friday...most areas will
only see spotty light precipitation.

Southwest Alaska...steady rain will continue to envelop the
Kuskokwim valley and interior Bristol Bay from east to west today.
Precipitation will be more spotty and showery over the Kuskokwim
Delta. The responsible system will hang around Bristol Bay and the
Alaska Peninsula through the weekend keeping rain in the forecast
for the Delta and more showery precipitation for the rest of the
Mainland.

Bering Sea/Aleutians...several weak disturbances will bring rain
showers to much of the chain while the Pribilof Islands will begin
to see steady rain later this morning from a weakening low
pressure system. High pressure begins to build in the western
Bering promoting fog and low cloud development through the
weekend.



&&

Long term forecast...
a large sprawling trough will remain across southcentral
Friday...with a well defined atmospheric river directed at
southcentral. Heavy rain will be impacting the coast...with
periods of lighter rain across much of the interior as deep
moisture pours over the lower coastal ranges. More showery
conditions will develop Friday afternoon as a dryslot aloft moves
overhead. The upper trough...however...will remain over the
region through Sunday...with periods of showers impacting
southcentral...with periods of rain along the coast.

&&

Afc watches/warnings/advisories...
public...none.
Marine...gale 119 120 125 128 129 130 131 139.
Fire weather...none. &&

$$

Mtl

Jul 14

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