Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
636 PM EDT Sun Jul 18 2021
Valid 12Z Thu Jul 22 2021 - 12Z Mon Jul 26 2021
...Guidance/Predictability Evaluation...
The WPC Alaskan medium range product suite was primarily derived
from a composite blend of well clustered guidance of the 12 UTC
GFS/ECMWF/Canadian and the 19 UTC National Blend of Models days
4-6 (Thursday-Saturday). Overall predictability seems above normal
through the period for much of the domain, but does increase
enough into days 7/8 to be addressed by introduction of majority
weighting of the more compatible 12 UTC GEFS/NAEFS/ECMWF ensemble
means. WPC continuity is well maintained in this manner along with
manual adjustments to ensure offshore low depth consistent with
favorable upper support and predictability.
...Weather/Threats Highlights...
A stagnant high latitude pattern will feature a Bering Strait
closed low and upper trough that will support lingering
precipitation chances for northwest Alaska and the Brooks Range
through this period as a warming upper ridge settles over the
eastern Interior/North Slope.
An undercutting system track will keep the Bering Sea and
Aleutians periodically unsettled and lead into a significant
closed low and trough to anchor over the Gulf of Alaska. Main
surface low positions offshore and associated frontal systems will
offer a prolonged maritime weather focus while less defined
impulses rotating around the larger circulation offers
periodically enhanced precipitation inland for southeastern and
south-central Alaska.
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