Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
500 PM EST Fri Dec 18 2020
Valid 12Z Tue Dec 22 2020 - 12Z Sat Dec 26 2020
...Guidance and Uncertainty Assessment...
Upper troughing across the Aleutians and the Bering Sea on Tuesday
will extend southeastward by late next week across the Gulf
region, and upper ridging across western Canada will gradually be
shunted eastward. The models and ensembles generally agree on
this, but vary on the details for much of the period. The 12Z
guidance was close enough on the synoptic scale such that a
blended solution worked out well along with the ensemble means.
More noteworthy differences were noted with the 12Z CMC across the
North Pacific, so it was considered less during this forecast
period. Perhaps surprisingly, there is better model agreement
with a strong storm system that will be on the horizon by the end
of the forecast period next weekend.
...Weather/Hazards Highlights...
Areas along the southern coast and to the Panhandle could have
moderate to perhaps locally heavy precipitation early in the week
as the frontal system and developing triple point low move across
the Gulf of Alaska region. Several inches of QPF snow are likely
over the multi-day period, focused mainly over the southeastern
Kenai peninsula. Lighter precipitation is likely over the
Aleutians and southwestern areas of the state under the upper low.
Temperatures are forecast to moderate for the middle and end of
the week as southerly flow overspreads the area, eventually
leading to readings above average for many areas.
Hamrick
Hazards:
- Heavy precipitation across the Alaska Peninsula into southern
Alaska, Mon-Wed, Dec 21-Dec 23.
- Heavy precipitation across portions of the Alaska Panhandle into
southern Alaska, Wed, Dec 23.
- High winds across the Alaska Peninsula into southern Alaska,
Mon-Tue, Dec 21-Dec 22.
- Much below normal temperatures across much of the lower
elevations of eastern Alaska, Mon-Tue,
Dec 21-Dec 22.
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