Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
639 PM EDT Fri Mar 19 2021
Valid 12Z Tue Mar 23 2021 - 12Z Sat Mar 27 2021
...Stormy pattern for Alaska next week...
...Guidance/Uncertainty Assessment...
Guidance offers much better than average agreement for the pattern
evolution and significant features for much of the next week's
expected stormy pattern. The Day 4-6 (Tuesday-Thursday) forecast
was primarily derived from a composite blend of well clustered
guidance of the 12 UTC GFS/ECMWF/Canadian/UKMET models and 19 UTC
National Blend of Models. Forecast spread increases gradually into
days 7/8 when a composite of the best compatible 12 UTC GFS/ECMWF
and GEFS/ECMWF ensemble means was mainly used along with the NBM.
Composites tend to mitigate the less predictable smaller scale
differences. WPC continuity is well maintained with this forecast
methodology in a pattern with above normal predictability overall.
...Weather/Hazards Highlights...
A lead northern Gulf of Alaskan storm will bring increasing
moisture to the southern coast and especially the Panhandle next
Tuesday into Wednesday where there is the highest potential for
terrain enhancing heavy precipitation given the lower-latitude
origin of the moisture.
A main storm track out from northeast Russia will bring a series
of deepened lows and frontal systems across the Bering Sea/Strait
that are expected to take aim on the mainland next midweek and
possibly again later next week into next weekend. These storms
will be accompanied by organized wrapping precipitation and strong
winds. Activity is slated to create unsettled maritime conditions
over the Bering Sea before reaching mainland coastal areas and
inland across the northwestern and western mainland along with
periods of enhanced snow and winds. Downstream energy transfers
underneath across Southwest Alaska and the Alaskan Peninsula next
midweek and later next week with these systems will meanwhile
favor northern Gulf of Alaskan cyclogenesis with renewed chances
for organized southern and southeast Alaska precipitation.
Schichtel
Hazards:
- No significant hazards are expected over Alaska during this
forecast period.
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
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