134
FXAK02 KWNH 022240
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
640 PM EDT Wed Apr 2 2025

Valid 12Z Sun 06 Apr 2025 - 12Z Thu 10 Apr 2025

...Heavy coastal rain and mountain snow threats across the
southern tier of Alaska this weekend into early next week...


...Guidance/Predictability Assessment...

Models, ensembles and machine learning tools offer a quite
similar, amplified and blocky upper flow pattern evolution valid
for well into next week. Predictability on this scenario is well
above normal. This pattern should favor multi-day coastal heavy
rain and terrain heavy snow threats across the southern to
southeast tier of the state. There is also some uncertainty on
any more localized snow potential underneath a western mainland
upper trough/closed low position. Embedded system differences and
run to run variances grow rapidly over time, especially for the
offshore surface lows that may vary local focus details to monitor
into shorter time frames. With this in mind and with the intent
to try to mitigate forecast spread consistent with uncertainties,
the WPC medium range product suite was primarily derived from a
composite blend of the 12 UTC GFS/ECMWF/UKMET/Canadian this
weekend and Monday before transitioning to a blend of the less
detailed, but compatible with each other GEFS/ECMWF/NAEFS/Canadian
ensemble means. This also acts to maintain reasonable continuity.

...Weather/Hazards Highlights...

An upper ridge extending from western Canada through most of the
mainland into the weekend should steadily give way to upper
trough and embedded closed low amplification over the western
half of the mainland into early-mid next week. At the same time a
larger mean upper low should wobble to the south/southeast of the
Alaska Peninsula/Kodiak Island through the period. The initial
surface system associated with the Pacific upper low will bring
strong winds to the eastern Aleutians heading into this weekend
and heavy precipitation to the southern coast and Panhandle
through the weekend into early next week, with some rain/snow
likely continuing into mid next week as another offshore lw
pressure system rotates into the mean low position and ultimately
reach closer to the southern coast. A broad area of lighter
precipitation should extend farther north across the mainland,
especially during the weekend, as some moisture advects inland.

The weekend should start with above normal temperatures over most
areas, with near to slightly below normal readings along the
western coast. Warmest anomalies should be over eastern locations.
The upper trough developing over the western mainland and leading
frontal boundary starting to push eastward will promote an
eastward expansion of near to below normal temperatures next week,
ultimately confining most of the above normal anomalies to the
southeastern part of the state by the middle of next week.

Schichtel


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

$$