Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
644 PM EST Sun Jan 02 2022
Valid 12Z Thu Jan 06 2022 - 12Z Mon Jan 10 2022
...Overview...
A blocky pattern will continue through much of the medium range
period over the high latitudes as an upper high over northeastern
Russia/Chukchi Sea meanders in place while reorienting itself
before finally shifting west by early next week. This favors cold
high pressure over most of the region south of the Brooks Range,
while a storm track near the Aleutians and the southern part of
the state leads to periods of generally light precipitation and
brisk winds for the Aleutians late this week, before moisture is
likely to increase for Southcentral Alaska and the Panhandle by
the weekend into early next week.
...Guidance Evaluation and Preferences...
Model guidance particularly in terms of the ensemble means
continues to show good consensus with the overall pattern, though
with some typical model differences in the details. The upper high
centered over northeastern Russia and the Chukchi Sea should be
reorienting itself more north-south by Friday and then becomes
more west-east oriented by early next week as it shifts west, with
reasonably good model agreement. A more active storm track will
occur for southern Alaska due to a combination of energy tracking
into the northern Pacific well south of the high as well as
shortwave energy dropping initially southward to the east of the
high around Friday and then retrograding across the southern half
of the state, serving to push the high northwestward away from
Alaska. At the surface, this likely will result in a cold front
pushing through eastern parts of Alaska late in the week, while
possibly multiple surface lows spin in the northern Pacific and
bring precipitation chances to southern Alaska. These features
show more variability among guidance in timing, strength, and
position, but at this point no clear outliers stand out. Most
recent (12Z) guidance keeps surface lows south of the Aleutians
and out of the Bering Sea, unlike some GFS guidance from the last
couple of days.
For the initial part of the medium range period, went with a
deterministic model blend of the 12Z guidance somewhat favoring
the ECMWF. Ended up with a 60% deterministic/40% ensemble mean
blend by the end of the period after gradually increasing the
components of the GEFS and EC ensemble means, which served to
maintain some strength of features but blend out particular model
variations. This provided good continuity from the previous
forecast.
...Weather/Hazard Highlights...
Precipitation during the latter half of next week will be
generally limited to light to locally moderate rain/snow over the
Aleutians to Kodiak Island, while much of the mainland should see
dry conditions given periods of high pressure encroaching from the
north. One exception over the mainland could be light snow showers
for far northeastern Alaska as a weak surface cold front slips
through northwest Canada Thursday-Friday. Then by next weekend, a
warm front is currently forecast to push toward or into the Gulf
stemming from a low over the northern Pacific, increasing moisture
and potentially spreading rain/snow into Southcentral Alaska. The
increase in moisture should also interact with the temperature
gradient/stationary front along the Panhandle and bring possibly
heavy precipitation there by the weekend into next Monday.
Given the cold surface high pressure encroaching into Alaska,
below normal temperatures remain forecast for the mainland south
of the Brooks Range, gradually trending less extreme with time and
moderating to slightly above normal by early next week as the high
retreats. After a chilly period during the short range for the
Panhandle, potentially setting daily records for cold
temperatures, below average temperatures should continue there
with offshore flow until early next week. Meanwhile, North Slope
will see well above average temperatures on Thursday before
moderating closer to normal by the weekend.
Tate
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