Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
513 PM EST Thu Mar 03 2022
Valid 12Z Mon Mar 07 2022 - 12Z Fri Mar 11 2022
...Guidance/Predictability Assessment...
WPC Alaskan medium range products were primarily derived from a
blend of the 12 UTC ECMWF/UKMET versus the much more stream phased
12 UTC GFS/Canadian for Day 4/Mon. A tougher call today with
guidance, but this is consistent with WPC product continuity and
earlier AK ROC/WPC Hazards Outlook desk collaboration. Used the
whole forecast domain compatible ECMWF/UKMET into Day 6/Wed. This
blend does trend stronger with upper trough energy digging into
the North Slope/Interior Tue/Wed than WPC continuity, but in
retrospect this seems reasonable considering weekend system
organization up over the Bering Sea and coupled upper ridge
amplitude. Switched to a blend of the GEFS/NAEFS/ECMWF ensemble
means into days 7/8 that seem to best provide a broad forecast
consistent with an overall pattern sensitive to data input that is
leading to below normal predictability.
...Weather/Hazard Highlights...
Favored ECMWF/UKMET guidance indicates that a threat of moderate
to heavy precipitation over the Southeast Panhandle will diminish
Monday as high pressure filters into the region in the wake of
northern stream upper trough passage. The alternate solution of
the GFS/Canadian would allow for an extra day of activity. This
would be as southern stream low pressure/modest precipitation that
the ECMWF/UKMET lifts toward the AK peninsula is instead phased
northeastward into an eastern Gulf of Alaska northern stream
system.
The North Slope/Interior will be mostly dry into early next week
in a period with much above average temperatures, especially
overnight lows. Warmest anomalies are expected to generally range
from 20-30 degrees above normal, but locally higher values may
rival records. There is an increasing model signal for unsettling
and temperature moderating Bering Sea sourced upper troughing to
dig downstream into the North Slope/Interior into
Tuesday/Wednesday, and WPC products now more readily embrace this
temperature moderating and unsettling trend that could lead to
some periods of wintry precipitation as locally enhanced by
favored terrain.
Meanwhile, a series of main and triple point lows will work and
reform to keep conditions unsettled next week to include periods
of enhanced rains/winds for the Aleutians, with modest
precipitation spreading downstream into the Alaskan Peninsula and
eventually across the Alaskan southern tier with gradual system
progression undercutting the retrograded westward re-positioned
upper ridge within the generally blocky larger scale flow pattern.
Schichtel
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
southeast mainland Alaska, Sun, Mar 6.
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