Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
557 PM EST Sat Jan 30 2021
Valid 12Z Wed Feb 03 2021 - 12Z Sun Feb 07 2021
...Overview and Guidance/Uncertainty Assessment...
Positive height anomaly centers will meander over the Arctic north
of Siberia and south of the Gulf of Alaska, leaving an opening in
between for the northern branch of split flow across the Bering to
push eastward along 50-55N. The longwave setup lends itself to a
bit of uncertainty in embedded smaller-scale features that, with
today's deterministic model runs, escalated rather sharply after
about next Thursday. In addition, the 12Z ECMWF was different in
its handling of a Wednesday upper low supposedly forecast to dip
southward south of the Aleutians though it showed a rather robust
northern portion of that otherwise more southern (south of 45N)
upper low. In order to prevent large changes to the forecast,
opted to rely mostly on a blend of the ensemble means (GEFS and
ECMWF ensembles) as upstream surface low development into the
Bering was quite chaotic and without a clear trend. This would
allow ridging to build back across the Interior Thursday but allow
weaker shortwaves to still push inland, in between the deeper
upper ridge centers to the NW and SE. QPF differences also
remained for areas north of the Alaska Range -- wetter GFS
earlier, and wetter ECMWF later.
...Weather/Hazards Highlights...
Precipitation across the northern Gulf/southern mainland next week
will generally be on the light to perhaps modest side, enhanced by
weaker areas of low pressure into the Panhandle. Generally do not
prefer any solution that shows a stronger low/precip area (GFS)
into the Gulf at this point. By next Thu-Fri, system into the
eastern Bering will spread snow across the Interior as its old
triple point weakens but carries moisture eastward. Another system
late Fri will spread its moisture eastward as well, but perhaps
over southwestern areas (Y-K Delta). Temperatures will trend
milder than normal through the period, limiting the below normal
temperatures to the Panhandle and far northeastern areas Wed-Fri.
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