Small Craft Advisory 465, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
451 PM AKDT MON JUN 6 2016

.ANALYSIS AND UPPER LEVELS...

An impressive upper level trough that stretches from northern
Alaska continues to dominate the weather pattern across mainland
Alaska. The trough is associated with anomalously cold air, with
the Anchorage morning sounding indicating a freezing level below
5000 ft. To the west, this cold air along with dynamic forcing has
already supported widespread convection across the Alaskan and
Aleutian ranges in the Bristol Bay area this afternoon. To the
east, widespread rain has been covering anchorage, southern
susitna valley, and kenai peninsula this morning. The heaviest
rainfall has been occurring across Anchorage where local
convergence has enhanced precipitation.

&&

.MODEL DISCUSSION...

Models have been in relatively poor agreement on rainfall totals
today, with all models under-estimating the rainfall that occurred
across especially the Anchorage Bowl. However, more recent model
runs are better capturing precipitation totals. In addition,
models are already capturing convective conditions correctly
across the alaska range in bristol bay, with ligthening strikes
already reported.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The widespread wetting rains that fell over southcentral this
morning will become more showery this evening as cold air aloft
associated the upper level through moves overhead. As this cold
air descends into Southcentral this evening, showers and
thunderstorms are expected to develop over this course of this
evening, especially along the eastern slopes of the Alaska Range.
With a westerly storm motion, any thunderstorms that do develop
along the Alaska Range will move over the waters of Cook Inlet
toward the Kenai Peninsula. Even though thunderstorms are not
expected over Anchorage this evening, the showers that develop are
expected to have moderate-heavy rain associated with them which
could cause continued ponding on roadways. As a result the Urban
and Small Stream Flood Advisory will continue until Tuesday
morning. Further to the south the potential for a rare
thunderstorm near Kodiak Island is much less certain. The models
do indicate some weak instability with a shortwave by late this
evening, which may allow for a strikes over inland areas, but this
is by no means certain.

On Tuesday the upper level trough will dive into the gulf and
allow for clearing skies and temperatures warming back into the
60's for most of interior Southcentral. By Tuesday afternoon,
showers and isolated thunderstorms will be limited to the higher
elevations of the Copper River Basin as a weak thermal trough
approaches from the interior. Temperatures will then continue to
warm to near or above normal by Wednesday with sunny skies as
stronger ridging begins to move in.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...

Scattered thunderstorms have developed this afternoon as expected
mainly across the Lake and Peninsula and Bristol Bay Boroughs. As
this system slides south and east away from the area
tonight...increasing northerly upper flow will help to clear and
dry things out rapidly, resulting in warming temperatures and low
humidity values. Upper ridging moves across the area Tuesday into
Wednesday, with increasing clouds and shower potential Wednesday
afternoon mainly toward the lower Yukon River Valley on the
northwest side of the ridge. However, some of this activity may
extend south to the Middle Kuskokwim Valley and northern Kuskokwim
Delta.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

Areas of low clouds and fog will continue to encompass a large
portion of the region through at least mid-week, save for some
drier air at times coming off the mainland. A gale-force front is
approaching the Central Aleutians, and will overspread the area
tonight. The low pressure system will affect the Western Aleutians
on Wednesday while the front to the east weakens. The eastern
Bering will see generally light winds.

&&

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

The EC and Canadian hemispheric are in the best agreement for Day
3, Wed night through Thu, with a large low south of Attu and its
associated front curving through the Bering, and a thermal trough
along the Ak range. The latter will be responsible for lingering
thunderstorms along the range, with the former bringing
Small Craft winds to the western Aleutians.

The EC and Canadian agreement continues into Sat. High pressure
develops over the northeastern Gulf, while the fronts associated
with the Aleutian low migrate first to the AkPen, and then are
shunted south of the Gulf on Sat. Models diverge and an EC
ensemble WPC solution brings the Aleutian low and occluded front
to the northern gulf on Sun and then southeast by early next
week. High pressure builds over the Bering after Sat.

The fronts and low will bring significant rainfall to the
Aleutians and Bering, as well as southwest Ak until drying begins
later Sat. South and east of the Ak range will have showery
conditions into Sat, when the possibility of easterly waves will
make rain more widespread into early next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warnings 175 176 177 178.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EN
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CC
LONG TERM...DS