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FXAK02 KWNH 092355
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
754 PM EDT Thu May 09 2024

Valid 12Z Mon May 13 2024 - 12Z Fri May 17 2024

...Overview...

Upper troughing will generally prevail across Alaska next week in
a broad sense, as a trough stretching into the Aleutians/Alaska
Peninsula and the northern Pacific tracks energy into the Gulf
during the first half of the week, and then another upper
low/trough affects at least the western part of the state later
into next week. The pattern will favor multiple rounds of
precipitation across the Panhandle and light precipitation
stretching into the Interior, while there is more uncertainty in
precipitation and wind potential from the Aleutians to the western
Mainland.


...Guidance Evaluation and Preferences...

Model guidance continues to indicate broad troughing over Mainland
Alaska as the period begins Monday, with energy across the Alaska
Peninsula southwest into the northern Pacific creating a positive
tilt to that southern part of the trough. This energy and possible
upper low is forecast to pivot east and then northeast toward the
Gulf by midweek, though with some timing uncertainty--the CMC
seems to be a slow outlier as other guidance is faster, while the
ECMWF is faster than the GFS runs. Naturally the associated
surface low follows a similar pattern in the models. The depth of
the surface low varies a bit as well but recent models do not show
it to be very deep.

Farther west, models continue to advertise the likelihood of
energy tracking from Siberia across the Kamchatka Peninsula and
likely forming a closed low in the Bering Sea. While
Tuesday-Wednesday has become more agreeable for the timing of this
to move into the Bering, the placement varies where the sensible
weather across the western part of the state is affected. Into
Wednesday, the ECMWF shows the upper and surface lows moving east
toward and into the western Mainland, while the GFS and CMC runs
track farther south and cross the Aleutians into the northern
Pacific by Thursday. While the ensemble means are much flatter,
the GEFS mean is more like the GFS/CMC while the EC mean is more
like the ECMWF. The differences in the model suites yield low
confidence in which solution may play out.

A mainly deterministic model blend favoring the ECMWF and GFS was
used for the early medium range period. As the period progressed,
increased the proportion of the GEFS and EC ensemble means to over
half by Days 7-8 amid the increasing uncertainty. This seemed to
provide a reasonable middle ground, though changes to the forecast
could certainly be needed if models converge.


...Weather/Hazards Highlights...

A weakening surface low and shortwave aloft could help direct
moisture into the Panhandle early in the week, and by
Tuesday-Wednesday, another low system shifting into the Gulf
should renew precipitation chances. Precipitation amounts will
likely be on the moderate side but perhaps locally heavy. Some
lighter precipitation in the form of rain showers and higher
elevation snow showers should extend into the Interior as well.
Then there is considerable uncertainty with precipitation and
winds that may affect the western Mainland and/or Aleutians by
midweek depending on how the pattern evolves. Low confidence in
the sensible weather persists into the latter part of next week,
but generally some light to moderate precipitation seems possible
for the southern coast.

On average, temperatures should not be too far from average next
week. Highs look to be cooler than normal across the southern
coast to the Panhandle as well as Brooks Range, and near to
slightly above normal by late next week across portions of the
Interior and the North Slope. Meanwhile lows may be a bit above
average in many areas, for a smaller than normal diurnal range.


Tate


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

$$