Area Forecast Discussion
Issued by NWS Anchorage, AK

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000
FXAK68 PAFC 111206
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
406 AM AKDT Tue Jun 11 2019

.ANALYSIS AND UPPER LEVELS...

Early this morning, a pair of lows dominated the weather picture,
with one weak low entering the Gulf south of Kodiak Island, and a
stronger and more organized system just south of Shemya. The Gulf
low is helping to swing some showers up towards portions of the
Prince William Sound coast, as seen in various satellite imagery
and Doppler radar loops, with a few instability showers developing
across interior portions of Southcentral.

&&

.MODEL DISCUSSION...

In general, the models remain in very good agreement at the
surface and aloft, with just some minimal convective instability
differences in terms of amount and location. Some differences do
begin to crop up as we head through the weekend, as the GFS is
faster with a front approaching the southcentral coast as compared
to its European (ECMWF) counterpart, with the Canadian Global
supporting the GFS timing and positioning. In general, all models
indicate an active pattern continuing for much of southwest and
southcentral Alaska.

&&

.AVIATION...
PANC...Look for VFR conditions with light winds to persist through
the afternoon. Afternoon heating will once again foster shower
development. At this time, we expect any thunderstorms to remain
just beyond the field vicinity up towards Eagle River, thus it
wasn`t included in the TAFs for now. By evening, southerly winds
gusting to just shy of 20 knots will likely develop.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2/Today
through Wednesday night)...
A weakening warm front oriented from northeast to southwest across
the Gulf of Alaska will slowly makes its way onshore along the
northeastern Gulf coast, rotating northwestward across the
southeast Copper River Basin and eastern Prince William Sound.
Expect steady light rain with some embedded heavier showers for
these areas. The front will fall apart tonight with precipitation
becoming more showery, though a series of upper level waves will
track to the northeastern Gulf. This may bring additional periods
of rain to the Cordova area as well as the southeastern Copper
River Basin. The parent low will drift into the southern Gulf
today and dissipate through Wednesday.

The arrival of this synoptic scale system will push the thermal
trough north and west as we head through the next couple days as
cloudier more stable air pushes inland across Prince William Sound
and the southern Copper River Basin. The best locations for
afternoon showers and thunderstorms will be from the northern
Copper Rover Basin westward to the Mat-Su. Expect less activity
as you head south to Anchorage and the western Kenai Peninsula.
Storm motion will cause convection in the southern Mat-Su to drift
southward late in the day which may be the best chance for a few
showers in Anchorage. The remnant clouds from convection today
combined with clouds moving in off the Gulf will lead to
considerable cloudiness most places on Wednesday. Thus, expect
cooler temperatures, but still around normal for this time of
year. Things will quiet down Wednesday night as high pressure
builds back overhead of Southcentral.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
High pressure and warm conditions will continue today and
Wednesday over Southwest. Expect daytime highs to reach the low
70s in low lying areas. Showers and isolated thunderstorms are
possible this evening, and the greatest instability looks to be in
the middle Kuskokwim Valley and greater Bristol Bay area, though
convection can`t be ruled out in the lower Kuskokwim Valley/Delta.
The thermal trough will shift northward Wednesday, and the
Kuskokwim Valley/Delta will see an increased chance over Tuesday
for thunderstorms. As has been the case over the last week,
convection will be driven primarily by daytime heating and
isolated in nature. A low skirting south of the Aleutians will
approach Thursday, shifting the general flow to southerly. Expect
a cooling trend from south to north beginning Thursday, and this
should kill any thunderstorm chances in the greater Bristol Bay
area Thursday. Farther north in the Kuskokwim Valley,
thunderstorms can`t be completely ruled out but in general
forecast instability is not impressive.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
A gale force low southwest of Attu will continue its slow trek
eastward, with gales likely only observed western Aleutians before
weakening today. The leading front will bring rain to the
Aleutians from west to east through Thursday, with cloudy skies
and broad cyclonic flow in the Bering.

&&

.MARINE (Days 3 through 5)...
Thursday through Saturday a low pressure system meanders near the
eastern Aleutians bringing gusty small craft winds around its
core. Gale strength winds are possible...however, models slightly
differ on solutions late Thursday. Rain overspreads the eastern
Aleutians and Alaska Peninsula Thursday into Friday. Meanwhile, a
ridge holds across the Gulf through Friday night. The front to the
west of the Gulf is expected to break the ridge down by
Saturday...pushing the frontal boundary across Kodiak Island
early saturday morning with northward progress to Prince William
Sound Saturday afternoon.

&&

.LONG TERM FORECAST (Days 3 through 7)...

The long range forecast starting on Wednesday is expected to be
relatively active to the west around a organized low near the
Alaska Peninsula. Higher chances for rain across the southern
mainland enters the forecast at the end of the week as the upper
low actively sends shortwaves toward the interior forcing its
front inland. The advertised forecast was kept intact for the
afternoon package as model run to run consistency continues to
support the frontal progression through Saturday. Models begin to
diverge on solutions for Sunday with the ECMWF taking the low near
the Alaska Peninsula on an eastward track across the Gulf. The
operational GFS keeps the low nearly stationary...sending
shortwave energy eastward. A blend of both the GFS and ECMWF
ensembles was used for creating grids to start the next week which
keeps the most active weather pattern along the Alaska Peninsula
and western Gulf.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MM
MARINE/LONG TERM...KH


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