081
FXAK68 PAFC 031250
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
450 AM AKDT Wed Jul 3 2024

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

An upper level ridge that has been sagging gradually south
from the Interior is beginning to move overhead this morning. This
is helping to keep just about everywhere precipitation free, but
a mid level cloud deck associated with moisture trapped under the
ridge has stubbornly held on across a good chunk of the Copper
Basin, as well as parts of the Mat-Su and Anchorage areas. It`s
unclear just how much this deck will erode as the day progresses
given the weak to nonexistent flow in place, and this uncertainty
will affect how far into the 60s we will manage to get over lower
elevations as the weakening ridge slowly drifts towards the Gulf
coast. A weak shortwave will also dive down past the Talkeetnas
and Alaska Range today, and this will help set off scattered
showers progressing from the far northern Susitna Valley into
parts of the Copper Basin by this evening.

Looking towards the July 4th holiday, the overall shift to a
wetter pattern we`ve been advertising still looks on track, but
confidence regarding the exact timing of rain moving in for
various locations is still in flux. Models have struggled to
ascertain how quickly a strong shortwave and trailing front over
Southwest will progress south across the Alaska Range, making it
difficult to say exactly when conditions will deteriorate towards
the latter half of the day on Thursday. Newer guidance has moved
back the timing of rainfall spreading in ahead of the trough just
a touch. Thus, have opted to update the forecast with this
package to reflect a slightly more optimistic outlook through
Thursday evening for all but the Susitna Valley where rain will
arrive first. In general, the farther south the later the arrival
of any rain threat will be, possibly holding off until after 10 pm
from Anchorage south to the Kenai Peninsula.

By Friday, an overall break in the rain is expected for all but
the Prince William Sound area as the shortwave continues southeast
into the northern Gulf and weak ridging momentarily tries to
rebound behind it. Unfortunately, the break doesn`t look like it
will last long. A much deeper upper level trough will begin to
dig into Southwest late on Friday, setting up a belt of
convergence and southwest flow extending from the mid to upper
levels between this next approaching system and the ridge sinking
into the Gulf. A more widespread and significant rainfall event
looks increasingly possible with this setup heading into the first
half of the upcoming weekend. Suffice to say, the endless stretch
of sunshine back in June is not coming back anytime soon.

-AS

&&


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

High pressure ridging extends over Southwest Alaska, promoting
dry conditions for the rest of today. A front extending off a
Kamchatka low stretches across the Central Aleutians and central
Bering sea that will eventually feed into a shortwave dropping
south into Southwest Alaska early Thursday morning. There is a
decent moisture feed that will pull into Southwest, bringing a
round of wetting rain showers on Thursday.


&&


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

The long range models are in more agreement today with the
pattern change mentioned in previous discussions. The areas of
high pressure that have been persistent over the Bering Sea and
the Gulf of Alaska in the early part of the period will start to
break down allowing a North Pacific low to track northward into
the Gulf. This combined with troughs of low pressure transiting
across the Bering Sea and Kuskokwim Delta will track eastward
across the region through the end of the period. As a result,
expect scattered precipitation and cooler temperatures across the
much of the forecast area. Additionally, gusty winds and possible
small craft conditions are expected in Cook Inlet and coastal
regions of the Kenai Peninsula Saturday afternoon and into Sunday.

-DD

.AVIATION...

PANC...VFR conditions and light winds persist through Wednesday
evening. Westerly winds this afternoon will shift southerly
overnight, before becoming westerly again tomorrow afternoon.

&&


$$