Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
327 PM EDT Mon Jul 15 2019
Valid 12Z Fri Jul 19 2019 - 12Z Tue Jul 23 2019
Upper pattern will feature an upper low in the Arctic Ocean and
flat ridging over the Aleutians with lingering troughing just
south of the Gulf of Alaska. The models/ensembles show good
agreement along 50N with possible weak surface wave development
along a wavy stationary boundary. The GFS has been most aggressive
with such surface waves but has backed off over recent days. This
should stay south of the Panhandle but some runs do track the low
and lift the front northward.
Much more spread exists out of northeastern Russian into
northwestern/interior Alaska. The ensembles have been somewhat
split on timing of the breakdown/evolution of the flow near the
New Siberian Islands (~140E) and how quickly that moves eastward
through the Bering Strait. This influences the weather over the
North Slope as weaker surface waves may precede more significant
frontal passage. However, consensus does not exist at this point
and even it if did the lack of continuity yields lower than
average confidence. As such, a blend of the 12Z GFS and 00Z ECMWF
with the 00Z NAEFS mean and ECMWF ensemble mean proved to be a
good starting point for the first few days before a transition to
nearly all ensemble guidance was necessary. The 00Z ECMWF was off
in timing compared to most ensemble members out of the Bering and
through the interior to render it less useful (but not
implausible). 12Z GFS was a bit too deep given the uncertainty.
Cooler than average temperatures are forecast for much of the
northern half of the state due to the reinforced troughing. Near
to slightly above average temperatures are forecast for
Southcentral especially away from the higher PoPs. The Panhandle
may eventually see a drier pattern but the lingering upper trough
may maintain a daily chance of at least light rain. More
substantial rain is forecast for the Brooks Range westward toward
the Chukchi Sea over a multi-day period.
Fracasso
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
No significant hazards are expected over Alaska during this
forecast period.
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