Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
311 PM EDT Sun Jul 28 2019
Valid 12Z Thu Aug 01 2019 - 12Z Mon Aug 05 2019
The flow pattern over Alaska during the medium range (Thurs-Mon)
continues to look fairly progressive. This features an upper level
low skirting the northern coast on Thursday before lifting north
into the Arctic, which drives a front through northern and central
interior Alaska. Meanwhile, one shortwave should be moving into
the Gulf/North Pacific at that time, while better defined
troughing moves into the western Bering. Models seem to be coming
into better agreement on the idea of the Bering Sea system lifting
towards the vicinity of the Bering Straight/northwestern Alaska by
day 7-8. Upper level ridging dominates most of the period across
southern Alaska and the Panhandle. This supports rain (and maybe
higher elevation snows) across northern Alaska/north slope region,
with the best chance for moderate to heavier activity along the
favorable terrain. A couple of rounds of rain are likely across
the Aleutians/Peninsula region as well as shortwave energy passes
through on Thursday, and more amplified troughing takes shape
across the Bering Sea next weekend. Expect additional rains across
northern Alaska next weekend as the Bering Sea system moves
towards the Bering Straight.
In general, the 12z GFS/00z ECMWF show fairly good agreement days
4-5 (albeit some minor timing and amplitude differences) to
warrant a majority deterministic blend for the first part of the
period. After this, detail differences in the deterministic runs
begin to emerge, especially with respect to the deep low across
northern Alaska/the Arctic and the evolution of the second
shortwave nearing the Bering Straight days 7-8. The ensemble means
show good agreement through day 7, with some timing differences
beginning to creep in by day 8. A blend of the GEFS mean with the
ECENS mean seemed to provide a good starting point days 6-8, with
smaller contributions from their respective deterministic models
as well. The resulting forecast fits well with the previous WPC
forecast, as well as with continuity downstream across the CONUS.
Santorelli
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