Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
547 PM EDT Mon Jul 19 2021
Valid 12Z Fri Jul 23 2021 - 12Z Tue Jul 27 2021
...Guidance/Predictability Evaluation...
Today's WPC Alaskan medium range product suite was primarily
derived from a composite blend of reasonably well clustered
guidance of the 12 UTC GFS/ECMWF/Canadian/UKMET and the 19 UTC
National Blend of Models for days 4/5 (Friday-Saturday). Overall
predictability seems above normal for this period, but increasing
forecast spread into early next week seems best addressed by the
still compatible 12 UTC GEFS/NAEFS/ECMWF ensemble means. WPC
continuity is well maintained with this strategy in conjunction
with manual adjustments to ensure low depth consistent with
favorable upper support and predictability over the Gulf of Alaska.
...Weather/Threats Highlights...
A fairly stagnant high latitude pattern will feature a Bering
Strait closed low/trough that would support lingering
precipitation chances with ejecting impulses over northwest Alaska
and into the Brooks Range as a shielding/warming upper ridge
settles over eastern portions of the Interior/North Slope. A less
certain system track emerges by the weekend into the north-central
Bering Sea and lead affects may reach western Alaska early next
week.
A modest undercutting system track offers some timing/focus
variance, but should keep the southern Bering Sea, Aleutians,
Southwest AK and the Alaskan Peninsula/Kodiak Island unsettled.
This flow works into a lead Gulf of Alaska closed low/trough
position. Main surface low positions there hold offshore and
associated frontal systems will present an extended maritime
weather focus. Less defined impulses rotating around the larger
main circulation should periodically enhanced precipitation inland
over southeastern and south-central Alaska, as well as farther
inland into the southeast Interior underneath the ridge.
Schichtel
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 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