Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
639 PM EST Fri Feb 14 2020
Valid 12Z Tue Feb 18 2020 - 12Z Sat Feb 22 2020
Strong positive height anomalies south of Kamchatka in the
subtropical Pacific (~25N/140E) will favor troughing in the Bering
Sea and western Alaska next week. The 12Z models were in good
agreement overall with fairly well-defined frontal systems moving
through the North Pacific and Gulf into the mainland/Panhandle.
This may bring a substantial system into Southwestern/Southcentral
areas from the short term into the medium range early in the week,
followed by another system Thursday-Friday. The active pattern may
continued into and beyond next weekend.
To start, models mostly agree on taking a parent low into Bristol
Bay toward Nunivak Island with its wavy front southward into the
Pacific. This may carry a sfc wave northward toward into the Kenai
Peninsula late Tue into early Wed before continuing eastward. Next
system showed a bit less agreement as it slides along or just
south of the Aleutians Wed-Thu. The 12Z (and prior) GFS took it to
the north of the eastern Aleutians but the majority kept it just
to the south, which was preferred. That low may shift into the far
NW Gulf near the Kenai Peninsula by early Fri with its front into
the Panhandle. Progressive pattern should keep these systems
moving and limit any sfc wave development. Last system may affect
the western Aleutians by next Saturday with better than average
agreement between the models and ensemble means.
Temperatures may briefly rise around the occlusion Tue before
trending back toward below average as colder air is dragged down
from the north behind the lead and second system. The Panhandle
should see nearer to average temperatures with mainly westerly
onshore flow, but a nearly daily chance of precipitation. Highest
rain/snow totals are likely over Southcentral, on the west side of
Cook Inlet and southeast side of the Kenai Peninsula across Prince
William Sound to Yakutat.
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
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
southern mainland Alaska, Tue-Fri, Feb 18-Feb 21.
- Heavy snow across portions of southern mainland Alaska, Mon-Thu,
Feb 17-Feb 20.
- Much below normal temperatures across portions of mainland
Alaska, Mon, Feb 17 and Thu-Fri, Feb 20-Feb 21.
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