Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
656 PM EDT Tue May 05 2020
Valid 12Z Sat May 09 2020 - 12Z Wed May 13 2020
...Significant Bering Sea Weekend Storm...
...Guidance/Predictability Assessment and Weather/Hazard
Highlights...
There is a good guidance signal in support of deep storm genesis
this weekend as an anomalously deep closed low/trough aloft lifts
northward over the western Bering Sea on the western periphery of
a building/warming upper ridge over the mainland. Favorable upper
support should help ensure a deep low/system underneath and the 12
UTC models have trended WPC continuity strongly in that direction.
Surface low pressure may fall into the upper 960 mb range by 12
UTC Saturday before slowly filling over the subsequent several
days. Tight pressure gradients around the low will offer a threat
of high winds/seas over the Aleutians and much of the Bering Sea
in addition to wrapping areas of heavy rain that could work into
western and southwestern Alaska. A second developing low/frontal
system may threaten the Aleutians and southern Bering Sea next
Tuesday/Wednesday. This storm should also be well organized, but
does not seem to have as potent support as the powerful lead
system.
Meanwhile, rising heights across mainland Alaska as the upper
ridge builds will promote warming temperatures. High temperatures
are forecast to upwards of 20 degrees above average across much of
mainland Alaska through much of the forecast period, with
temperatures forecast to rise into the 60s and 70s for portions up
through the Interior. Underneath, low energies held down over the
Gulf of Alaska and the northeast Pacific should offer limited
influence on Alaska weather into next week, but flow should
support periodic rainfall over the southern Alaskan tier.
Overall of all the models, the 12 UTC GFS seems most in line with
GEFS/ECMWF ensembles and was favored through the weekend. A
composite blend of the GFS and ensembles offers a solution with
system details consistent with a pattern with above normal
predictability next week.
Schichtel
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
Hazards:
- Heavy precipitation across portions of mainland Alaska, Fri, May
8.
- High winds across portions of mainland Alaska, Fri, May 8.
- Much above normal temperatures across portions of mainland
Alaska, Fri-Tue, May 8-May 12.
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