Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
554 PM EST Fri Nov 22 2019
Valid 12Z Tue Nov 26 2019 - 12Z Sat Nov 30 2019
...Major Bering Sea Storm Early Next Week Threatens
West/Northwest/Interior Alaska...
...Guidance/Uncertainty Assessment...
The 12 UTC GFS/ECMWF offer excellent forecast clustering with each
other and the 12 UTC GEFS mean and 00 UTC ECMWF ensemble means
next Tuesday-Thursday. A blended deterministic model solution
offers a good forecast starting point with above normal
predictability.
The models are still generally in line with the larger flow
evolution, but offer a bit more variance days 7/8. Prefer an
ensemble based solution for these longer time frames. Applied
heavy weighting to ECMWF ensembles that better match with the 12
UTC GFS/ECMWF.
...Weather/Hazard Highlilghts...
A robust Bering Sea system will lift in energetic flow to the
Bering Strait/Arctic and northwest Alaska Tuesday-Thursday of next
week. Lead flow will slam inland with vigor through
western/northwest Alaska then the North Slope. Guidance is in good
agreement with this hazardous storm, bolstering forecast
confidence. The unusually well supported storm and organized
frontal system will bring a leading surge of strong southerly
winds to the west/northwest coast of Alaska, including areas where
near-offshore ice is still forming. This area was depicted on the
WPC day 3-7 hazards chart again for the wind/wave/precipitation
threat. There is an increasing guidance signal for another deep
low to work up into the Bering Sea again later next week, mainly
as a maritime risk this period.
Meanwhile, an uncertain Pacific evolution is slowly coming into
better agreement, with a closed low south of the Aleutians lifting
north-northeastward and gradually weakening, but still supporting
a weather focusing surface low/frontal system up into the Gulf of
Alaska. This complex system may tap anomalously deep moisture to
fuel some potentially heavy precipitation into the Alaskan
southern/southeast tier later next week.
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
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Wed-Fri, Nov 27-Nov 29.
- Heavy precipitation across portions of mainland Alaska, Tue-Thu,
Nov 26-Nov 28.
- Heavy snow across portions of mainland Alaska, Tue-Thu, Nov
26-Nov 28.
- High winds across portions of mainland Alaska, Tue-Wed, Nov
26-Nov 27.
- High significant wave heights for coastal portions of mainland
Alaska, Tue-Wed, Nov 26-Nov 27.
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