Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
653 PM EST Thu Feb 03 2022
Valid 12Z Mon Feb 07 2022 - 12Z Fri Feb 11 2022
...Overview...
The majority of guidance shows an upper-level evolution that
appears to share some traits with an episode from a couple weeks
ago, with elongated mainland trough energy pulling off an upper
low that tracks into the Bering Sea while a building eastern
Pacific ridge extends into northwestern North America. The flow
between these features will carry two or maybe three systems, the
first into the Gulf of Alaska and the latter one(s) likely
somewhat farther west. These systems will bring periods of
enhanced precipitation to the Panhandle and parts of the southern
coast, and possibly farther north into the mainland depending on
exact storm track. Heaviest precipitation should extend from the
Kenai Peninsula into the Panhandle.
...Guidance/Predictability Assessment...
As was the case in the previous episode involving this type of
evolution, the operational ECMWF is the misfit relative to most
other solutions by bringing its upper low farther east
into/through the mainland by the latter half of the period--in
contrast to the majority that keeps it farther west over the
Bering Sea or at least begins to eject it on a farther northwest
track. The 12Z ECMWF run adjusted somewhat westward of the prior
00Z run but still strays questionably far eastward by late next
week. ECMWF means have been somewhat east of the GEFS/CMCens but
are not nearly as extreme as the operational runs. Teleconnections
relative to the strong core of positive height anomalies
associated with the building East Pacific upper ridge also
recommend leaning toward higher heights over the mainland than
forecast by the ECMWF late in the week. Based on this large-scale
consideration, the forecast started with an even blend of the 12Z
GFS/ECMWF/CMC/UKMET for about the first half of the period and
then eventually trended to slightly more total weight of the 12Z
GEFS/CMCens and 00Z ECMWF mean relative to the GFS/CMC. This blend
maintained fairly good continuity from yesterday's forecast in
principle, with most changes involving greater strength/definition
or modest adjustments in other details.
There is good agreement that a leading storm should track into the
Gulf of Alaska by early day 5 Tuesday. However the models are
split over whether it will be the parent low from the previous day
or development of a triple point wave while the original low stays
back, either dissipating or somehow combining with the next
system. Differences with the upper low farther north begin to have
an influence on the track of this next surface low. ECMWF runs
have been tracking it into the Gulf, the ECMWF mean a little west
of the operational runs, and other solutions more into the Alaska
Peninsula/Bristol Bay. Uncertainty increases further with the
potential third system (around Friday) that could develop ahead of
a larger-scale system to the south of the Aleutians. It is not
reflected in the ensemble means but has been showing up in GFS
runs and 12Z CMC. Plus the 12Z ECMWF has a slower version of it.
The favored blend reflects this system, but in a conservative
fashion while awaiting a more coherent signal from ensembles. Note
that after the early part of the week there is still enough spread
among non-ECMWF solutions for exactly how the Bering Sea
trough/upper low will evolve to temper confidence in forecast
details.
...Weather/Hazard Highlights...
Southwesterly flow between the Bering Sea upper low/trough and the
East Pacific/far western Canada ridge will support wet weather
over southern Alaska during most of next week. Individual surface
lows will periodically help to focus heavier episodes of rain in
low/coastal areas and heavy snow in higher elevations. Highest
totals are likely to be from the southeastern coast through the
Panhandle while amounts over locations farther west will depend
more on exact storm track. Each storm may also produce brisk to
strong winds and rough seas between the Aleutians/Alaska Peninsula
and the Panhandle. Some snow may extend farther north into the
mainland mid-late week based on a most likely storm track into the
southwestern mainland. The majority of the state should see below
normal temperatures early next week, with Southcentral and the
Panhandle tending to be the exception with above normal readings.
The evolving upper pattern should promote a warmer trend by
mid-late week, ultimately confining most of the below normal
temperatures to the far western mainland.
Rausch
Hazards:
- Heavy precipitation across the Alaska Panhandle into the
southern coastal sections of Alaska, Sun-Thu, Feb 6-Feb 10.
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