Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
628 PM EDT Sat Jul 20 2024

Valid 12Z Wed Jul 24 2024 - 12Z Sun Jul 28 2024

...Hazardous heat possible for parts of Interior Alaska into mid
next week with increasing heavy rain threat late week...


...Overview...

A strong upper ridge over the mainland as the period begins
Wednesday will continue to promote well above normal temperatures
for much of interior and northern Alaska through about mid next
week. South of the ridge, a deep upper low will bring a period of
moderate to locally heavy rains to parts of the Panhandle before
it shifts inland on Wednesday. Another deep upper low in the
Bering will shift eastward with time bringing heavy rainfall and
significantly cooler temperatures into parts of the western to
central/southern Mainland by next weekend.


...Guidance Evaluation/Preferences...

The latest guidance continues to have a good handle on the overall
synoptic pattern for the first half of the period as the upper low
in the Bering lifts northeastward, but there are some mainly minor
timing and detail differences that will take time to resolve.
Another strong trough will drop southward from eastern Russia late
week, and the models continue to show a lot of uncertainty on how
this interacts with the Bering low. The better consensus
(including AI/ML guidance) suggests this system should push the
Bering low more south and east eventually resulting in some sort
of triple point redevelopment in the Gulf. The GFS aligns with
this general track, but was notably faster than the ECMWF. The CMC
is stronger and faster with the northern trough and thus pushes
the Bering low more eastward into northern Alaska. The WPC blend
for today used a general operational model blend the first half of
the period, but with greater weighting towards the ECMWF. Late in
the period, leaned heavily on the ensemble means, with some
operational ECMWF to help add some detail where feasible.


...Weather/Hazards Highlights...

Rain, locally heavy, will be ongoing across the Panhandle region
on Wednesday as an initial surface low pressure system moves
through. The Bering Sea low will initially spread rain west to
east across the Aleutians through about mid week, but as the cold
front reaches the West Coast around Thursday or Friday next week,
the threat for more widespread rains progressing steadily eastward
with time increases across the Mainland into next weekend. Some of
the rainfall could be heavy in spots, especially along/near the
favored terrain and the southern coast as another surface low
develops in the Gulf. Gusty winds may accompany this system,
depending on exact strength, but should remain below hazards
thresholds.

Well above normal temperatures will continue through Wednesday,
with parts of the Mainland/Interior seeing some of the hottest
temperatures of the season so far, bringing daytime highs into the
80s to near 90 degrees, with an increased wildfire threat as well.
The ridge breaks down by Thursday and the next cold front will
usher in cooler temperatures. By next Friday, much of Western and
Central/Northern Alaska could be 10 to 20 degrees below normal
lasting through the weekend. The exception to the heat will be
across Southeast Alaska, where temperatures may be near or below
normal for much of next week.

Santorelli


Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:
https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html