Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
620 PM EST Thu Feb 13 2020
Valid 12Z Mon Feb 17 2020 - 12Z Fri Feb 21 2020
An active upper-level jet across the North Pacific will bring a
series of relatively deep low pressure systems across/near the
Aleutians and into the Gulf of Alaska or southern mainland Alaska
during the extended range period. The first of such lows moves
from just north of the Aleutians on Monday to the western/southern
Mainland by Tuesday. While the models agree that a significant
storm system is possible, there remains fairly substancial
disagreement on placement. The ECMWF/CMC remain the best clustered
with the ensemble means, while the GFS shows multiple triple point
lows, and a position well east/north of the better clustering of
ensembles. As this low weakens over the mainland on Wednesday,
models indicate a second potentially deep low to approach the
Aleutians. Significant timing and intensity differences remain,
but the ensemble means show good clustering on a track into the
northern Gulf or southern coast by Friday. For this system, prefer
a mostly ensemble mean blend by days 7 and 8.
Heavy snowfall is expected across the southern mainland Alaska and
perhaps into portions of the interior Monday and Tuesday with the
first deep low pressure system, with heavy precipitation also
working into the Panhandle region on Wednesday. The next low
pressure system towards the middle of next week will bring another
round of widespread precipitation from the Aleutians eastward into
the southern mainland and Panhandle. Heavy precipitation may be
possible for some locations. Additionally, an arctic air mass
across the interior and North Slope regions will hold through at
least the middle of next week, with high temperatures 10 to 20
degrees F below average to many. Some moderation of temperatures
is possible by the end of next week across interior locations, but
should remain below average across the North Slope.
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
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Tue-Thu, Feb 18-Feb 20.
- Heavy snow across portions of southern Alaska, Sun-Tue, Feb
16-Feb 18.
- Much below normal temperatures across portions of mainland
Alaska, Sun-Mon, Feb 16-Feb 17 and Wed-Thu, Feb 19-Feb 20.
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