Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
709 PM EDT Tue May 11 2021
Valid 12Z Sat May 15 2021 - 12Z Wed May 19 2021
...Overview...
Upper ridging will build across the Arctic/North Pole and the
mid-latitude western and eastern Pacific during the period as
blocky flow tends to unwind a bit over Alaska. The pattern next
week favors low pressure mostly over the northern Pacific into the
Gulf, with a storm track suppressed around 50N. Appreciable
precipitation will be limited to the Panhandle.
...Guidance/Predictability Assessment...
The models and ensembles were in fair agreement overall but
differed starting mostly by Sunday. The 12Z ECMWF paired best with
the ensemble means, varying between its own mean and the 12Z
GEFS/Canadian ensemble means. The UKMET and Canadian offered
varying amounts of agreement as well with the smaller embedded
features, followed by the GFS. The GFS failed to carry a small
closed low (currently over Siberia) across northern Kamchatka and
maintain its identity as it slips southeastward, eventually
merging with an incoming Pacific system early next week. Though
the GFS may not be wrong, its lack of this feature modifies the
timing of the pattern downstream and became out of phase at times
with the consensus. Used a majority ECMWF weighting for details
along with a blend of the ensemble means which differed on timing
of the Mon-Wed system.
...Weather/Threats Highlights...
Lead system on Saturday will feature waning precipitation over the
Aleutians and southwestern areas as the old parent low dissipates,
with a focus into the Panhandle near the new triple point.
Progressive pace will limit amounts to mostly light to moderate in
some areas. Surface trough over the interior next week may help
instigate afternoon showers in an otherwise dry pattern. Next
system over the Pacific may be far enough offshore to limit any
significant precipitation to the middle of next week, depending on
its track/speed. 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