Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
705 PM EDT Fri May 14 2021
Valid 12Z Tue May 18 2021 - 12Z Sat May 22 2021
...Overview...
Storm track will largely stay west-to-east along ~50N during the
period, with weak flow over the Interior. This will maintain a
fairly quiet pattern over much of the state with showers over the
Alaska Range to the Brooks Range with daytime heating (50s and 60s
in the valleys) and still cool air aloft. More organized rainfall
will be along parts of the Aleutians and eventually to the
Panhandle late next week.
...Guidance/Predictability Assessment...
Models and ensembles have been trying to capture the Pacific flow
from the northern and southern sources, and waver on how to
interact each of them near the Aleutians before progressing
eastward. The 12Z GFS stood out apart from the ECMWF/Canadian in
showing a quicker and stronger upper feature east of Kamchatka
next Tue that overtakes and downstream system, but also shifting
it northward into the Bering Sea. The ensembles still generally
show this secondary shortwave/upper low to merge into the lead
upper system and track it eastward just south of the Aleutians.
This has been the preference the past few days and saw no reason
to deviate with the GFS solution. Therefore, used a blend of the
12Z ECMWF/Canadian and 12Z GEFS mean/00Z ECMWF ensemble mean as a
starting point. Trended toward just the ECMWF for some details by
late in the period but with low confidence. This at least
maintained a reasonable system progression albeit slightly
different than the forecast 24 hrs ago.
...Weather/Threats Highlights...
Weak troughing over the mainland will promote scattered showers
(snow over higher elevations) across the Interior/North Slope
through much of the week. Areas of the Panhandle may see some
showers early in the week and perhaps by next weekend. A more
defined system may organize around the Aleutians on the heels of a
leading weakening system ~Wednesday with generally light to
perhaps modest rain for the island chain. Temperatures will be
within several degrees of normal over much of the state, warming
into next weekend, but near to below normal over the Panhandle.
Fracasso
Hazards:
No significant hazards are expected over Alaska during this
forecast period.
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards 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