Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
609 PM EDT Mon Oct 12 2020
Valid 12Z Fri Oct 16 2020 - 12Z Tue Oct 20 2020
...Guidance/Predictability Assessment...
The 12 UTC models seemed compatible day4/Friday and used a blend
of the 12 UTC GFS/ECMWF. Despite a reasonably similar larger scale
pattern aloft through much of rest of the medium range period,
differences with offshore surface systems grow quite rapidly over
time, lowering forecast confidence. The WPC Alaskan medium range
product suite was accordingly derived from a more compatible
composite blend of the 12 UTC GEFS/ECMWF ensemble means and the 19
UTC National Blend of Models days 5-8. This strategy maintained
good WPC product continuity.
...Weather/Threats Highlights..
An amplified upper ridge over the Bering Sea will shift eastward
to the Interior Friday/weekend to stabilize/moderate. Lead Arctic
system energy digs through the Southeast Panhandle Thursday/Friday
and produce a swath of heavy precipitation.
Meanwhile, forecast spread is relatively low and guidance supports
unsettled conditions for the Aleutians heading into the weekend
and into early next week as amplified upper trough energies work
frontal systems over the area. Forecast confidence decreases over
time downstream with subsequent interactions with lead flow/system
details into the Gulf of Alaska and toward southern/southeastern
coastal areas in an overall wet pattern as the aforementioned and
amplified Interior upper ridge continues to shift eastward into
western Canada.
Schichtel
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
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle,
Thu, Oct 15.
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