297
FXAK68 PAFC 151330
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
530 AM AKDT Sun Sep 15 2024

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

Precipitation across Southcentral is on track to continue through
this morning. Any threat for flooding concerns in the Anchorage
area however, will be coming to an end later this morning as
rainfall becomes more scattered and showery. Gusty southeast
winds is gradually shift southwesterly as a surface low tracks
eastward skirting along the Gulf of Alaska coast through tomorrow
morning. Winds are expected to remain gusty for the Anchorage
area and as southwest flow strengthens up Cook Inlet, communities
along the western Kenai coast and Anchorage could expect gusts of
25 to 35 mph likely through Monday morning. Multiple weak
shortwaves will allow for upslope precipitation enhancement for
showers most likely along the mountains. Increasing instability
into this afternoon will raise the potential for a lightning
strike or two in the Susitna Valley and perhaps in the Copper
River Basin for a short period of time this afternoon. As the low
over western Alaska moves inland, models are struggling to
capture how far south the trough will dip into the Copper River
Basin. This has led to lower confidence in the probability of
precipitation forecast for Monday afternoon for the Copper River
Basin.

As that trough passes east though, a ridge will briefly
build across Southcentral allowing for some clearing skies Monday
night and Tuesday morning. Temperatures look to trend cooler with
many locations forecasted for lows into the 30s and perhaps near
freezing in the coolest spots that also manage to clear out
Monday night into Tuesday morning. Temperatures are expected to
remain on the cooler side for much of the week ahead. Clouds will
fill in on Tuesday afternoon as the next front moves across
Southcentral and the sogginess returns Tuesday afternoon through
Wednesday.

rux

&&


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

Key Points:

* A Coastal Flood Advisory for the Kuskokwim Delta coastal
  communities and a River Flood Advisory for the Lower Kuskokwim
  River communities remain in effect through today. Water levels
  have peaked for most communities, but a higher peak in water
  levels is expected with high tide today.

* An even stronger storm system will track across the Aleutians
  into the Southern Bering Sea Monday afternoon then track toward
  Southwest AK through Tuesday. There remains high uncertainty in
  the exact track of this storm and locations most at risk of
  coastal storm surge flooding.

Discussion:

Winds across Southwest Alaska are expected to gradually diminish
through tonight as the low tracks inland across Western Alaska.
Light rain will continue into Monday morning, followed by a brief
drier period ahead of the next front.

Attention will then shift to the west, as a deep upper level low
and short-wave trough drop out of Russia and interact with a
surface low crossing the Northwest Pacific, causing the surface
low to deepen and curve northward toward the Aleutians tonight
into Monday.

Models continue to struggle with this as it approaches Southwest
Alaska through mid-week. Most recent runs (00Z) has most of the
models pushing into the Bristol Bay area by Tuesday night, though
at different times and at different strengths. The 00Z NAM was
the biggest outlier, pushing to push into the Y-K Delta. The 06Z
NAM has trended further south, choosing to align closer to the
GFS. This allows for some increased confidence on the low track.

Ultimately, expect a deep low somewhere along the Southwest coast
by late Tuesday, leading to another round of rain and wind and a
threat of coastal storm surge flooding. Stay tuned for updates as
we gain a better idea of the track of this storm and location of
greatest impacts.


&&


.LONG TERM FORECAST (Days 4 through 7: Wednesday through
Saturday)...

Operational models are in surprisingly good agreement with the
progression of a deep Bering low into Southwest Alaska next week
on Wednesday. Gusty winds will accompany the low`s movement
through the Aleutians with guidance suggesting the strongest winds
will be directed into Bristol Bay. There has been some variation
amongst previous models runs with the exact track of the low.
However, the differences in the low`s track have yielded minimum
differences in where the strongest winds are forecast to occur. In
addition to winds, widespread showers are anticipated as the low
and its associated front track from the Bering into interior
Alaska. The progressive nature of the low should see it shift
eastward and into Canada by Thursday, allowing precipitation
chances to diminish. A broad troughing pattern looks to resume
thereafter, which will keep shower chances in play for both
Southwest and Southcentral Alaska through the remainder of the
long term period.

BL

&&

.AVIATION...

PANC...VFR conditions could lower to MVFR for a few hours in the
morning. As winds turn southerly and rain lightens, conditions
should improve to VFR. Winds will remain gusty over the course of
the TAF period with gusts to around 30 kts.

&&


$$