Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
641 PM EST Sun Nov 07 2021
Valid 12Z Thu Nov 11 2021 - 12Z Mon Nov 15 2021
...Overview and Model Guidance...
Model guidance today shows rather good agreement on the synoptic
evolution for Alaska through the medium-range period, especially
with respect to the ensemble means. The most significant system
of concern will be a sizable occluded cyclone forecast to move
into the Gulf of Alaska late this week and then slowly weaken by
the weekend. By early next week, models are indicating a
negatively-tilted trough to move into the western Aleutians, with
some spread on how far southeast the upper-level energy will dig.
A higher percentage of the ensemble means from the 12Z GEFS, 00Z
EC mean, and 12Z CMC was included to handle the uncertainty
associated with this system on Days 7-8. This yielded an
elongated occluded cyclone edging slowly into the western
Aleutians for early next week. For Days 4-6, a blend of the
deterministic and ensemble means from the 12Z GFS/ECMWF/CMC
provided very compatible results with yesterday's forecasts.
...Weather/Hazard Highlights...
The majority of Alaska will remain relatively quiet weatherwise
through much of the medium-range period. Dry conditions will
likely continue for the interior sections northward to the North
Slope. Meanwhile, an occluded cyclone is forecast to move into
the Gulf of Alaska late this week, bringing an increasing chance
of precipitation to the Panhandle. The precipitation along the
Panhandle may become heavy by Friday and will likely linger into
the weekend. Some of the heavier precipitation could spread
further north into the southern coastal sections of Mainland as
the system slowly weakens. Farther west, the next occluded
cyclone is forecast to bring an increasing chance of rain and
gusty winds into the western Aleutians early next week.
For temperatures, colder than normal conditions are expected to
persist for the central and southern portions of Alaska, with
sub-zero temperatures over the interior section. The coldest
anomaly will be found across southwestern mainland. The Alaska
Peninsula, the Panhandle, and the Aleutians will also see below
normal temperatures. Meanwhile, the North Slope will likely
experience above normal temperatures into early next week. Light
winds will prevail across much of Mainland as a weak surface high
pressure system remains in place.
Kong
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook 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