Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
605 PM EST Fri Jan 24 2020
Valid 12Z Tue Jan 28 2020 - 12Z Sat Feb 01 2020
...Well below average temperatures for most of mainland Alaska...
...Active pattern with two deep Gulf of Alaska storms bring heavy
precipitation to portions of Alaska Panhandle and mainland next
week...
Through next week, the latest models and ensemble guidance
continues to show average to above average consensus featuring an
upper level ridge building to the west of Alaska and only
gradually weakening/shifting west through the forecast period.
Forecast confidence is high for a cold surface airmass settling
across much of Alaska well into next week.
An active North Pacific jet will send various shortwaves/surface
lows across the North Pacific into the Gulf of Alaska, one such
wave will deepen considerably over the northern Gulf Tuesday into
Wednesday. Low depth has trended deeper than yesterday and that
seems reasonable considering support. A second deep low then lifts
quickly towards Southeast Alaska, keeping relatively high
precipitation chances in the forecast through much of the forecast
period. Low depth has trended deeper than yesterday and that seems
reasonable considering support and much better guidance support.
Lingering deep layered cold air and proximity to the surface low
in place will support locally heavy snows through lower elevations
of southern Alaska and the northern Panhandle.
The 12Z deterministic guidance showed fairly high agreement
through Day 4-5 with slowly increasing model spread seen beyond
through the end of the forecast period. The WPC blend incorporated
primarily the 12Z GFS/ECMWF with higher weights of the 12Z
GEFS/NAEFS for Day 6-8. This approach accounted for changes seen
in the evolution of the Southeast Alaska low by the middle/latter
portions of the forecast period while maintaining some aspect of
continuity given the model spread/uncertainty.
Taylor/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-Fri, Jan 30-Jan 31.
- Heavy snow across portions of the Alaska Panhandle and mainland
Alaska, Mon-Wed, Jan 27-Jan 29.
- High winds across portions of the Alaska Panhandle, mainland
Alaska, and the Aleutians, Mon-Fri, Jan 27-Jan 31.
- Much below normal temperatures across portions of mainland
Alaska, Mon-Wed, Jan 27-Jan 29.
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