Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
651 PM EDT Sun Mar 21 2021
Valid 12Z Thu Mar 25 2021 - 12Z Mon Mar 29 2021
...Stormy pattern for Alaska next week...
...Guidance/Uncertainty Assessment...
This forecast cycle the model guidance showed above average
agreement and clustering through about day 6. The upper level flow
will initially be quasi-zonal but then the approach of digging
shortwave energy will carve out a more amplified pattern toward
next weekend and early next week. At 500 mb, the deterministic
ECMWF/CMC/UKMET were well clustered and even the typical faster
GFS showed some utility. The GFSP favored better than the current
operational version, and the GFSP was included in the blend over
the GFS. At the surface, several waves of low pressure will track
through the region, mainly impacting the southern mainland and
southeastern areas the most. The most active storm system looks to
come day 6-8 with back to back lows. Aside from the typical model
spread noise, there was decent agreement. However to mitigate the
less predictable smaller scale differences during that time frame,
the WPC blend utilized the ECENS/GEFS means and this resulted in a
forecast blend that maintains forecast continuity.
...Weather/Hazards Highlights...
A few storm systems are expected to bring unsettled to active
weather to the area, particularly later in the forecast period.
The first system at the start of the period will bring
precipitation mainly to the western mainland before
weakening/dissipating. This will be followed a stronger low
impacting the southern mainland by late in the upcoming work week
or early next weekend. A final system at the end of the period is
likely to track across the Bering Sea into the western mainland
early next week. The highest QPF amounts are forecast for the
southern mainland and the southeastern areas. Temperatures are
expected to at or above normal for nighttime lows for much of the
upcoming period while highs generally range below normal for the
southern mainland and southeastern areas with some above normal
departures for the northern mainland.
Taylor
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