Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
530 PM EDT Sat Aug 08 2020
Valid 12Z Wed Aug 12 2020 - 12Z Sun Aug 16 2020
...Guidance Evaluation and Preferences...
A Bering/Aleutian system on Wednesday will move eastward into the
Gulf and eventually the Panhandle by next weekend. The 12Z models
and ensembles offered a reasonable clustering with this system
with the exception of the Canadian. Embedded waves along the front
may ripple through and perhaps slow the system a bit, but the
overall pattern will be quasi-progressive. To the north, the 12Z
GFS/GEFS (and somewhat the Canadian) handled an upper low north of
Wrangel Island differently (meandering north/northwestward) than
the ECMWF/UKMET (which continued eastward). Preferred the eastward
consensus with the support of the ECMWF ensembles. By later in the
period, GFS/ECMWF offered similar enough solutions with the
then-Gulf system to include with their ensemble means as the
upper/sfc lows progress eastward. Next system may enter the
western Bering by then and a consensus between the quicker GFS and
slower ECMWF sufficed as it was near the ensemble means.
...Weather Highlights/Threats...
Bering/Aleutian system will bring showers/rain initially to the
eastern Aleutians with breezy conditions as well as the modest
parent low scrapes the islands. Expect light to modest rainfall
into the AKPen as the warm front and triple point approach early
Wed. Some locally heavier rainfall is possible on southeast-facing
and terrain-enhanced areas over Kodiak, but overall rainfall will
be modest. Rain will spread eastward across Southcentral and
especially the southern/southeastern Kenai as the triple point
takes over in the Gulf. Some modest to heavier rain could push
into the Panhandle assuming the system continues eastward, though
the higher precipitable water values (>1.25") may stay near/south
of the new triple point and warm front. Daytime temperatures will
be cooler than normal along southern coastal areas but warmer than
normal over the Interior and especially western areas as upper
ridging attempts to hold. Overnight mins will trend a bit milder
than normal into next weekend.
Fracasso
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