Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
610 PM EDT Sun Aug 09 2020
Valid 12Z Thu Aug 13 2020 - 12Z Mon Aug 17 2020
...Guidance Evaluation and Preferences...
A mostly progressive pattern will continue across the northern
Pacific later this week into next week with a storm track along
50-55N. Models have been wavering on how to evolve the Aleutian
system Thursday into the Gulf (either in a couple pieces or with
embedded waves) which has slowed or quickened the frontal
progression. The parent low progression (and then the triple point
progression) have been a bit more stable. The 12Z
ECMWF/Canadian/UKMET were close to the 00Z ECMWF ensemble mean and
not too far from the 12Z GEFS mean but the GFS was quicker into
the Gulf (not implausible but at least noticeable). Opted to rely
mostly on the 00Z ECMWF ensemble mean rather than keep wavering
quicker/slower due to the hard-to-predict smaller-scale features
that will modulate the frontal evolution. This still maintained
the front on an eastward trajectory into the Panhandle Saturday.
Another system is still progged to enter the Bering at that time,
moving eastward next Sun-Mon. To the north, guidance has trended a
bit stronger with an upper trough through the Arctic/Beafort with
a weak front at the surface scraping the North Slope.
...Weather Highlights/Threats...
Main system Thu/Fri will bring showers/rain and breezy conditions
to the AKPen initially then to the east thereafter. Expect light
to modest rainfall into the AKPen as the triple point redevelops
late Thu into Fri. Some locally heavier rainfall is possible on
southeast-facing and terrain-enhanced areas over Kodiak, but
overall rainfall will be modest. Some showers will spread across
Southcentral but the system will be pretty far to the south. Some
modest to heavier rain could push into the Panhandle, though the
higher precipitable water values (>1.25") may stay near/south of
the new triple point and warm front, mainly over the southern
Panhandle. Daytime temperatures will be cooler than normal along
southern/southeastern coastal areas but warmer than normal over
the Interior and especially western/southwestern areas as upper
ridging noses in atop the Gulf system. Cooler than normal
temperatures are forecast for the North Slope/Brooks Range.
Overnight mins will generally be a bit milder than normal.
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