Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
526 PM EDT Mon Apr 20 2020
Valid 12Z Fri Apr 24 2020 - 12Z Tue Apr 28 2020
...Guidance/Predictability Assessment...
A composite blend of reasonably well clustered guidance from the
12 UTC ECMWF/UKMET/Canadian models and GEFS/NAEFS/ECMWF ensemble
means along with the 19 UTC National Blend of Models seems to
produce a good forecast starting point Friday-Sunday in a pattern
with average predictability. The 12 UTC GFS does not seem as well
aligned with ensembles. Increased the ensemble mean weightings at
longer time frames consistent with growing forecast spread and
uncertainty. Manual adjustments were applied to produce
sufficiently deep offshore system consistent with favorable upper
support, but artificially weakened by the blend process. This
forecast maintains good WPC continuity.
...Weather/Threats Highlights...
A lead deepened low/frontal system along with an enhanced
winds/waves/precipitation remains slated for the Gulf of Alaska
into Friday, exiting over the Southeast Panhandle Saturday.
Meanwhile upstream, at least two additional emerging frontal
systems with deepening lows and enhanced winds/waves/precipitation
will dig through the Aleutians and rotate over the Gulf of Alaska
to off Southeast and Southern Alaska this weekend and early next
week on the heels of the lead system.
Farther inland over the state, several unsettling mid-upper level
troughs/impulses will work over the North Slope and the Interior
over the coming week, significantly cooling the recent warm spell.
In this pattern expect some locally/terrain enhanced snows will
focus in vicinity of the weaknesses/lows aloft and with a
persistent and wavy surface front.
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:
- Much below normal temperatures across portions of mainland
Alaska, Sat-Mon, Apr 25-Apr 27.
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