Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
604 PM EST Sun Feb 09 2020
Valid 12Z Thu Feb 13 2020 - 12Z Mon Feb 17 2020
...Guidance and Uncertainty Assessment...
The 12 UTC ECMWF has trended toward the 12 UTC GFS and 12 UTC
GEFS/ECMWF ensemble means Thursday-Saturday, albeit with some
lingering timing differences. The 12 UTC GFS though offers a more
consistent solution that is better clustered with the ensemble
means. Accordingly and after collaboration with the local WFO
offices, the forecast starting point for the WPC Alaskan product
suite was primarily derived from a blend of the reasonably
compatable guidance from the 12 UTC GFS and GEFS/ECMWF ensemble
means along with the 19 UTC National Blend of Models. Forecaster
adjustments were applied to add increased detail consistent with
individual weather feature predictability and support, especially
as per the deepening of offshore lows that were artificially
weakened by the blend process. This acts to maintain good WPC
continuity as compared to yesterday.
...Weather Pattern and Hazards Highlights...
The mid-upper flow pattern later this week will feature a mean
trough/low over the Aleutians/Bering Sea. This will support a
series of potentially deep storms to focus a threat of heavy
precipitation/winds/seas across the Aleutians/Bering Sea. This is
especiallty the case with a very deep/threatening low Thu-Fri. A
weakening downstream ridge will shift from Southwest Alaska to
southern Alaska Thu/Fri as an amplified and quite wet lead upper
trough/low works over the Southeast Panhandle. Frigid air settled
over the Interior now moderates in guidance more gradually late
week into next week as guidance now rebuilds Arctic stream upper
troughing back over the region. Pattern de-amplification with time
over the Gulf of Alaska will allow periods of precipitation spread
into the Alaska Peninsula/Southwest Alaska and southern Alaska.
Active flow over the Gulf of Alaska will support several organzied
low pressure systems that especially offer the threat for periods
of heavy precipitation over the Southeast Panhandle.
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
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