Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
723 PM EDT Sat Mar 21 2020
Valid 12Z Wed Mar 25 2020 - 12Z Sun Mar 29 2020
...Turning colder for much of the Interior late next week...
...Overview and Guidance/Predictability Assessment...
Upper ridging initially over the northeast Pacific and Aleutians
Wed-Fri will shift back to the northwestern Pacific to the south
of Kamchatka as troughing digs through the Interior from the
north. The models and ensembles were in good agreement to start
but diverge rapidly after Thursday west of 170W. This is related
to a splitting upper low near 45N/153E that translates
northeastward on Thursday. The 12Z GFS and most GEFS members favor
the lead (initially southern) portion of the splitting upper low
whereas the other guidance favor the trailing/northern upper low.
The GFS takes this stronger lead low through the Bering into
Bristol Bay but the other guidance push the upper low southward
once the jet upstream strengthens, favoring split flow. While all
guidance show lower heights west of 170W next weekend (GFS from
the west, others from the north) preference continues to be with
the ECMWF-led consensus which maintains some ridging into
northeastern Russia, allowing heights to dig south-southeastward
through the mainland on cold NW flow. Trended strongly toward the
00Z ECMWF ensemble mean which has been a tempered version of the
deterministic ECMWF (and 12Z Canadian, today) with greater
stability.
...Weather Highlights/Threats...
Above average temperatures across the North Slope on Wednesday
will give way to near average or below average temperatures
through the week along and north of the Brooks Range, but turning
much colder over the central/eastern Interior as a lead and
secondary cold front push through. Another modest snow event is
possible later in the week around Friday as the Bering system
unravels into western areas coincident with the arctic frontal
progression from the north. This will all move into the Gulf next
weekend with increase rain/snow for the Panhandle but much drier
for the mainland and even Aleutians.
Fracasso
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