Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
402 PM EST Wed Jan 26 2022
Valid 12Z Sun Jan 30 2022 - 12Z Thu Feb 03 2022
...Overview and Guidance/Uncertainty Assessment...
Significant uncertainties in the upcoming medium range forecast
period pattern mainly result from embedded system
evolutions/interactions within a large scale Omega block settled
over Alaska and surrounding areas. This results in a highly
chaotic array of surface lows near the Aleutians and to a lesser
degree the Gulf of Alaska.
Guidance solutions diverge significantly with embedded system
evolutions from short through medium range time scales with
development and uncertain breakdown of Omega blocking over/near
Alaska, especially with lows rotating into the block position near
the Aleutians. The 12 UTC ECMWF has issues, but overall seems the
best overall fit with GEFS/ECMWF ensembles and WPC continuity days
4 into 6 (Sun into Tue). Accordingly added the ECMWF to a
composite with the ensemble means in this time frame to add some
detail consistent with the pattern. Used a composite of the
generally compatible ensemble means later Tue into next Thu (later
Day 6 to Day 8), shifting majority weighting to ECMWF ensembles
that flows a bit better from the day 4-6 embedded system locations
and depths. WPC product continuity is decently maintained with
this forecast plan.
...Weather/Hazard Highlights...
Arctic high pressure slowly weakens during the medium range
period, but keeps most of mainland Alaska dry. Meanwhile, storm
systems in the Gulf especially early in this forecast period will
translate to unsettled conditions along the Southeast coast and
Panhandle regions. Moderate to heavy precipitation there will
shift slowly southward this weekend with conditions tending to dry
out by early next week.
Meanwhile, a number of highly uncertain storm systems offer
potential to bring highly unsettled periods of wet and windy
weather to the Aleutians through this period, and potentially with
slow erosion of the Omega block with leading flow downstream into
mid-later next week with otherwise generally benign weather
conditions for the AKpen/Kodiak Island and the Alaskan southern
tier.
Schichtel
Hazards:
- Heavy precipitation across the Alaska Panhandle, Sat, Jan 29.
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