Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
645 PM EST Wed Feb 09 2022

Valid 12Z Sun Feb 13 2022 - 12Z Thu Feb 17 2022

...Overview...

The extended range over Alaska begins on Sunday with troughing
over the Mainland and a shortwave/frontal system moving quickly
through the Gulf of Alaska. Behind this, a strong ridge will build
in across the northeast Pacific increasing heights across much of
the Mainland which should hold until early next week. A large and
deep surface low will track towards the central/western Aleutians
on Monday, which eventually looks to weaken as it gets wrapped
into a second deep low approaching next Wednesday-Thursday. Given
the size of these lows, regardless of the exact track, they're
likely to affect the Aleutians with high winds, rough seas, and
precipitation. A couple of weaker shortwaves may eject from the
main Aleutians/Bering Sea trough sending a possible storm into the
Peninsula and southwest Alaska on Wednesday.

...Guidance/Predictability Assessment...

Recent model guidance continues to show reasonably good overall
agreement on the large scale pattern through most of the the
forecast period. Models continue to wobble with respect to timing
and details of individual systems, especially towards the latter
half of the period. The departing cyclone in the Gulf on Sunday
shows some disagreement in low placement, with the 12z CMC quite a
bit north of the consensus (closer to the southern coast), while
the 12z UKMET is south. The UKMET also has some additional
placement issues with the couple of deep lows into the western
Aleutians so it was excluded completely from the blend today.
Models all show an impressively deep system approaching the
Aleutians Sunday into Monday, with surface pressures near 950mb.
By the middle of next week, there is good agreement that a weak
shortwave rounding the base of the mean trough over the Aleutians
should send a possible storm system across the Peninsula and into
southwest Alaska. The GFS and ECMWF are much more aligned with the
low position while the CMC is farther to the east. Differences in
this shortwave and its strength also has implications for how
quickly the amplified northeast Pacific/Gulf of Alaska ridge gets
pushed east. For the second deep low towards the Aleutians next
Wednesday, the GFS and ECMWF continue to show good agreement right
now while the CMC is depicting a little more elongated/double
structure of a surface low.

Todays blend over Alaska used the deterministic 12z GFS and ECMWF
with their respective ensemble means. A majority deterministic
solutions was used for the early part of the period with
increasing mean percentages the second half to account for some of
the harder to resolve and smaller scale detail differences.
Smaller parts of the GFS and ECMWF were continued through day 8
though just for some added system definition.

...Weather/Hazard Highlights...

Southwesterly flow between the Bering Sea upper low/trough and the
East Pacific/far western Canada ridge will continue to support
some wet weather over southern Alaska on Sunday, although
precipitation amounts should be waning by that point.
Precipitation will be on the increase across the Peninsula to
southwest Alaska and Southern Coast regions as a possible storm
system moves in. Moderate to locally heavy snow (with rain closer
to the coast) is possible. As the associated upper shortwave moves
into the Gulf, another round of heavy precipitation is possible
for the Panhandle. Across the Aleutians, regardless of the exact
track of the Aleutians low pressure system, the pure massive size
is likely to bring high winds, rough seas, and modest
precipitation. Winds are most likely to be the worst near the
central and western islands on Sunday, with several pieces of
guidance indicating gusts near hurricane strength are possible.
The winds should relax early next week, but another round of gusty
winds and precip is possible with the approach of the second low
on Wednesday into Thursday.

Northwest Alaska and the North Slope region should start out
chilly and much below normal this weekend, but should moderate
closer to normal early next week. The southern half of the
Mainland should be in a warming trend through much of the period
as a strong upper level ridge builds into the region. Daytime
highs near 10-20 degrees above normal are possible, with overnight
low anomalies even greater.

Santorelli


Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at:
<a href="https://www.wpc.ncep.noaa.gov/threats/threats.php"><u>https://www.wpc.ncep.noaa.gov/threats/threats.php</u></a>

Hazards:
- High winds across the western portion of the Aleutians, Sun-Mon,
Feb 13-Feb 14.
- Much below normal temperatures across portions of western
Alaska, Sat-Tue, Feb 12-Feb 15.
- Heavy precipitation across southeastern Alaska into the
Panhandle, Wed, Feb 16.


WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:

<a href="https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif"><u>https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif</u></a>
<a href="https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml"><u>https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml</u></a>
<a href="https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html"><u>https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html</u></a>