Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
644 PM EDT Thu Apr 22 2021
Valid 12Z Mon Apr 26 2021 - 12Z Fri Apr 30 2021
...Overview and Guidance/Uncertainty Assessment...
A fairly benign weather pattern is forecast across Alaska during
the medium range day 4-8 period. The upper level flow pattern is
expected to feature slowly filling closed low over the Aleutians
while somewhat blockiness ridging to the west holds back any other
significant energy from lifting north/east into the area. This is
expected to keep the main storm tracks and significant sensible
weather to the south with perhaps brushing the southern coast. By
the end of the period, an increase in moisture could bring more
unsettled weather to the southeastern areas as low pressure
finally lifts northward in a bit more progressive upper level flow
pattern. The latest model guidance showed fairly good agreement
and predictability early on. The main issues noted were the faster
GFS bias with the progression/evolution of the upper level
shortwaves. By day 6, the differences between the faster GFS and
somewhat slower than consensus ECMWF were notable. The CMC offered
a reasonable consensus solution. Even the ECENS/GEFS means were
fairly separated by day 7/8, lowering confidence during that
period. The WPC blend leaned toward a slower solution with more
inclusion of the ECMWF/CMC and ECENS for the later periods. This
blended fairly well with continuity forecast.
...Weather/Hazards Highlights...
The majority of the state should remain dry through the first half
of the period with any precipitation chances confined to the
Aleutians/Alaska Peninsula areas early next week. By the middle to
latter portions of the period, low pressure lifting northward into
the Gulf of Alaska is expected to push higher moisture into the
area. With better forcing/dynamics, widespread precipitation is
expected for the southeastern areas. Some of this could be locally
heavy. No significant temperature anomalies are forecast during
the period.
Taylor
Hazards:
-Heavy precipitation across portions of the Alaska Panhandle,
Wed-Thu, Apr 28-Apr 29.
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