Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
303 PM EST Wed Nov 13 2019
Valid 12Z Sun Nov 17 2019 - 12Z Thu Nov 21 2019
...Aleutians to Gulf of Alaska Stormy Pattern...
...Guidance/Uncertainty Assessment and Weather
Highlights/Threats...
Ensemble model guidance seems fairly well clustered this weekend
with the overall pattern evolution and for the most part a number
of potentially well-organized weather focusing systems. Unsettling
mid-upper level troughing will hover from Southwest Alaska
northeastward through the Interior/North Slope to the Arctic.
Limited moisture and lift will support periods of snow for the
region this weekend in gradually easing low level easterly flow.
Lead multi-stream low/jet energies are meanwhile slated to work
underneath toward southern/southeastern Alaska from the Gulf of
Alaska. These systems pose a maritime threat, and the circulation
is expected to wrap moisture onshore to sustain some threat of
locally heavy precipitation for coastal areas and especially
favored terrain early next week. A preferred composite solution of
the latest models and ensembles seems to offer a reasonable basis
for the effects associated with these systems.
The main weather focus will then shift westward toward the
Aleutians and southern Bering Sea by early next week and spread
steadily toward southwestern and south-central Alaska into next
midweek with advance of a series of deep lows. These systems
should have closed upper low/trough support and may deepen enough
to entrain some deeper lower latitude moisture. Expect a maritime
and coastal threat for high winds/waves and heavy precipitation in
a pattern with near average predictability. WPC progs used a blend
of the GEFS/ECMWF ensemble means amid growing model forecast
spread, but manually deepened the surface lows given favorable
upper support and continuity.
Schichtel/Tate
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-Wed, Nov 19-Nov 20.
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Sat-Sun, Nov 16-Nov 17.
- High significant wave heights for coastal portions of the
Aleutians, Mon-Tue, Nov 18-Nov 19.
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