Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
231 PM EDT Sat May 25 2019
Valid 12Z Wed May 29 2019 - 12Z Sun Jun 02 2019
Deterministic and ensemble model guidance continues to have a good
handle on the overall synoptic evolution over Alaska through the
medium range period. The upper level pattern favors a blocking
ridge in place over mainland Alaska during the beginning to middle
of next week which allows for a meandering main cyclone near the
central to eastern Aleutians where it gradually weakens and
dissipates. This supports unsettled weather across much of the
Aleutians through most of the period, with rounds of locally heavy
precipitation along the immediate coast. By the middle to end of
next week the ridge should begin to break down allowing troughing
to expand northward and the low near the Aleutians to nudge
eastward. Farther inland across central to northern Alaska, mainly
showery activity and near normal to just above normal temperatures
are expected. A blend of the 00z ECMWF/12z GFS/06 FV3-GFS with
ensemble mean guidance (ECENS/GEFS) provided a good starting point
for today for days 4-6. The deterministic runs get increasingly
chaotic by days 7 and 8 mainly with respect to the details of
individual shortwaves/surface lows rounding the base of the mean
trough. For this reason, the blend consisted of majority ensemble
mean guidance for days 7 and 8. This maintains good continuity
both with yesterday's WPC Alaska forecast and with the downstream
forecast over the East Pacific/CONUS.
Santorelli
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