659
FXAK68 PAFC 120030
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
430 PM AKDT Tue Jun 11 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

A large upper level low and associated surface low remain south
of Kodiak Island this afternoon, with a weak flattened ridge over
mainland Alaska. Multiple easterly shortwaves between these two
features continues to be the main driving factor in precipitation
across Southcentral Alaska. Steady showers across the Mat-Su
Valley, with lighter precipitation in Anchorage Bowl, will quickly
push through the area and end by early tonight. With another
approaching shortwave, widespread rain showers will fill in across
the Copper River Basin Wednesday morning, spreading westward into
the Mat-Su Valley and Anchorage by late afternoon. A few pop-up
rain showers are also possible across the western Kenai Peninsula.

On Thursday, much of the western Kenai northward through
Anchorage and the MatSu Valley will remain dry, but another
shortwave descending from interior Alaska will continue scattered
rain showers across the Copper River Basin. A few isolated
thunderstorms are also possible across the northern portions of
the Basin in the late afternoon/evening, however, instability is
very marginal. With more instability on Friday, the potential for
widely scattered thunderstorms exists for the entire Copper River
Basin and possibly in the Susitna Valley as well.

High temperatures on Wednesday will be in the 50s for most, with
upper 50s to lower 60s on Thursday. Friday will mark the beginning
of a warmer and generally drier period, albeit with thunderstorm
potential, for Southcentral Alaska with high temperatures in the
mid 60s near the immediate coast to mid 70s inland.

-ME

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3)...

Light winds persist across Bristol Bay as the pressure gradient
across Southwest Alaska weakens. Broad low pressures sits south of
the Alaska Peninsula, cycling weak shortwaves over Southwest and
south towards the Eastern Aleutians. Conditions will be mostly
dry, however, there will be light rain today as an easterly wave
pushes across the region tonight into Wednesday morning. A chance
for some wet thunderstorms in western Bristol Bay and along the
Western Alaska Range will be embedded in the wave that traverses
the Bristol Bay and the Lower Kuskokwim Valley. High pressure
builds in the over the western Bering Sea and will progress
eastward over the next several days. A low developing west of the
Western Aleutians will push south of the Aleutian Chain mid-to-
late week, eventually stalling in the North Pacific south of Adak.
This will bring rounds of rain showers and small craft winds to
the Western/Central Aleutians Wednesday through the end of the
week. In Southwest, a benign pattern will set-up by Wednesday
evening, with a break in active weather expected until the end of
the week. Through Thursday into Friday, northerly flow will drive
drier air down from the north into Southwest.

&&

.LONG TERM FORECAST (Days 4 through 7) Saturday through Tuesday...

High pressure looks to persist across the eastern Bering, the
Alaska Peninsula, and western mainland through most of the long-
term period. However, as with cases in the past, the GFS wants to
break the ridge down too quick on Sunday while the other guidance
has the ridge persisting. Therefore, the GFS seems to be an
outlier at this point. Additionally, the ensembles of the GFS also
have a similar solution to the deterministic GFS while the
ensembles of the other deterministic guidance do indeed have the
ridge persisting. All-in-all, odds favor warmer and drier weather
over southwest through the long-term with the occasional easterly
wave moving through to help induce diurnal scattered showers. Odds
favor cooler and unsettled weather over most of the Aleutian Chain
with low pressure dominating in the North Pacific.

The high pressure over the western mainland looks to nudge
eastward through Sunday and provide mostly dry and warm weather to
Southcentral for that time. Diurnal showers will be possible for
the interior locations of Southcentral and perhaps even
thunderstorms if enough instability builds with day-time heating.
Confidence then decreases dramatically for the Sunday night
through Tuesday timeframe as guidance has different solutions on
the orientation of the ridge and how fast or slow the ridge might
break down. Thus, forecast uncertainty remains on the high side
for Southcentral during the second half of the long-term.

&&

.AVIATION...

PANC...Light rain will continue through the evening hours.
Light northerly winds will gradually weaken late this evening,
being replaced by general up-inlet southerly flow. Rain chances
increase again on Wednesday, as well as a chance for MVFR CIGs.

&&

$$