Area Forecast Discussion
Issued by NWS Anchorage, AK
FXAK68 PAFC 310037
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
437 PM AKDT MON MAY 30 2016
.ANALYSIS AND UPPER LEVELS...
Near the southern mainland, two closed lows are visible in Water
Vapor satellite imagery. One is spinning along the southern gulf
and a second better organized system is over the Central Aleutians.
The Gulf low is moving an axis across the Western Alaska Range
with a line of rain stretched across eastern Bristol Bay to the
Kuskokwim Mountains. Both upper lows are nearly stationary and
pin-wheeling energy around their cores.
Models are generally in good agreement with the transitioning pattern
into Wednesday. Not many changes were needed with the afternoon
package; the main adjustments were made for winds along the front
associated with the Aleutian storm system and to refine
precipitation and thunderstorm coverage.
Diurnal convection will produce wet thunderstorms this evening as
low to mid level moisture increases along southeasterly flow. On
Tuesday, subsistence brings drier air down to the surface across
interior early in the day with the trend pushing south through
the afternoon. At the same time, an upper shortwave begins to lift
from the southern coastal areas. Thunderstorms are expected to be
wet, but if the air mass dries sooner than expected dry thunderstorms
could be possible across higher terrain surrounding the Kuskokwim
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Quieter weather is in store for the mainland with continued above
normal temperatures through midweek. Some lingering showers and
thunderstorms over the western Susitna Valley early this evening
should give way to clearing skies overnight. Tuesday will be
warmer and drier with Kodiak Island being the exception where a
front will bring steady wetting rain. Wednesday will continue the
warmer and drier trend with the chance for thunderstorm, mainly
along the Alaska Range, Talkeetna Mountains, and Copper River Basin.
The upper level disturbance that brought thunder to the area last
night is pushing into the southwest today. Lingering instability
and disturbances in the flow are helping showers early this
evening, however, the atmosphere is stabilizing quickly as upper
level heights build and subsidence increases. The next chance for
showers or thunderstorms comes on Wednesday as instability
increases and ridging aloft weakens.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The easterly wave moving over the area will bring showers and
thunderstorms through late this evening. The majority of the
thunderstorms should continue over the Kuskokwim Valley, Delta and
the higher elevations of northern Bristol Bay where the strongest
instability exists. On Tuesday, a frontal system currently moving
through the Aleutians will bring gusty winds to the Southwest
coast along with a chance of showers and thunderstorms primarily
for the Kuskokwim Delta and northern Bristol Bay, though a few
strikes over the Kuskokwim Valley can`t be ruled out. Showers and
Thunderstorms will then remain in the forecast into Wednesday as
a cold upper level trough dives southward from the interior,
especially for the Kuskokwim Valley and Alaska Range.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The low moving through the eastern Aleutians will spread Gale
force winds and rain into the eastern Bering and Pribilofs for
Tuesday before dissipating on Tuesday evening. This low will
however become nearly stationary as it dissipates near Dutch
Harbor, leaving widespread Small Craft winds and a chance of
rain for much of the area through mid-week.
.LONG TERM FORECAST (Days 3 through 7)...
Models are in agreement that Wed night into Thu a front will dive
south to the Alaska range where it slowly dissipates through Fri.
This front will be associated with showers and some thunderstorms
west and south of the Alaska Range Wed and Thu afternoons and
evenings. Otherwise showers can be expected over the rest of
mainland AK through this period. Persistent north flow across the
Bering will also bring some showers through Thu night. The day 3
forecast utilized the 12z NAM for continuity with the short term.
Beginning Thu evening the EC and Canadian hemispheric models dissipate
the front along the AK and Aleutian Ranges. A North Pacific low
begins to weaken as it approaches the Akpen. This feature
continues weakening into a separate low in the northern gulf,
which rapidly dissipates, and another near Cold Bay Sat morning.
The Cold Bay low weakens and is then reabsorbed by a third low
that remains south of the Eastern Aleutians beginning on Sunday.
This pattern will keep showers over mainland AK through the
weekend, with fairly dry conditions across the Aleutians and
Bering. When the low redevelops south of the chain on Sun, the
chance of precipitation will increase across the islands. The
forecast utilized the ensemble approach of WPC guidance which
also included the EC and Canadian models.
MARINE...Gale Warning 138 150 155 165 170 172 179 180.
SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK