Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
637 PM EDT Wed May 12 2021
Valid 12Z Sun May 16 2021 - 12Z Thu May 20 2021
...Overview...
Blocky flow will transition toward troughing centered over the
Bering Sea around the middle of next week, but with uncertainty in
how that evolves. With low pressure mostly over the northern
Pacific into the Gulf, appreciable precipitation will be limited
to the Panhandle and Aleutians.
...Guidance/Predictability Assessment...
The deterministic models were in mostly good agreement to start
the period, but then diverged by next Tuesday due to the multiple
weaker streams around Alaska. Trend has been for a bit less
merging of northern/southern shortwaves just south of the
Aleutians, and a slower pace overall. With so much uncertainty by
next Tue-Thu, used a majority ensemble mean blend (12Z GEFS and
00Z ECMWF ensemble mean) with some details from the 12Z GFS that
paired best with the ensemble consensus vs the ECMWF or Canadian.
Confidence was lower than average due to poorer-than-normal
run-to-run consistency even in the ensembles.
...Weather/Threats Highlights...
Weak troughing over the mainland into the Gulf will promote
scattered showers across the interior/North Slope into the
Panhandle early in the week. A more defined system may approach
the Aleutians around the middle of next week (lead system may
dissipate on Tuesday) with light rain for the island chain.
Temperatures will be within several degrees of normal over much of
the state, but near to below normal over the Panhandle.
Fracasso
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