Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
757 PM EDT Wed Mar 30 2022
Valid 12Z Sun Apr 03 2022 - 12Z Thu Apr 07 2022
...Overview...
Alaska will begin next week with an overall pattern of upper
troughing/lows over the state, which should persist particularly
over western Alaska through the medium range period. At the
surface, low systems are expected to track across the northern
Pacific/Gulf of Alaska while additional low pressure may linger
near the southwestern mainland. This will promote a wet pattern
for southern Alaska, particularly over the Panhandle, though
amounts do not look to be terribly heavy. Meanwhile a reasonably
tight surface pressure gradient with an arctic high and southern
Alaska lows could lead to some moderate to strong winds over the
North Slope during the early part of the week, along with some
breezy conditions possible along other low tracks as well.
...Guidance/Predictability Assessment...
Recent model guidance shows fairly good clustering with the
initial pattern Sunday-Monday over Alaska, with upper low centers
over the Bering, northern mainland, and the northern Pacific/Gulf.
Most models also seem to capture two surface lows in the northern
Pacific/Gulf reasonably well, with one in place early Sunday and
another south of the Alaska Peninsula moving east by Monday. With
the second low, the 12Z UKMET appeared to be a bit of an outlier
by day 5/Mon with its position farther south of consensus, but the
GFS/ECMWF/CMC all seem within reasonable spread for a medium range
forecast. It also still appears that separate, likely weaker low
pressure will hover near the southwest mainland. Ensemble means
seem to capture this better in recent model cycles compared to
previous ones that showed (probably erroneously, given the
deterministic guidance) a mean position for more combined low
pressure. Given the fairly good initial agreement, utilized a
blend of the GFS, ECMWF, and CMC deterministic runs for the early
part of the forecast period.
Flow upstream shows more significant differences beginning Monday
and through midweek. Energy across Siberia should move eastward
toward Kamchatka and the Bering Sea Monday into Tuesday, but with
notable timing issues, as the ECMWF remains a slower solution.
This causes models to be out of phase by Tuesday and beyond. While
yesterday it was just one run of the ECMWF that was different from
consensus, the EC runs have stayed consistent with their ridge
pattern in the western Bering Tuesday and the UKMET is pretty
similar, as opposed to the GFS runs carryingÂan upper low that
tracks over the Aleutians by Tue-Wed and a separate upper low
nearer the Panhandle by midweek. On the other hand, the EC shows
one trough axis across western Alaska Wednesday-Thursday stemming
from the upstream differences. The ensemble means are flatter of
course but generally follow the deterministic models' pattern. The
12Z CMC may be the best compromise, but this is all quite
uncertain given the flow's origin. These upper-level differences
affect the timing/positioning of a relatively strong surface low
coming from the southwest toward the Panhandle midweek. For the
latter part of the WPC forecast, leaned slightly away from the
ECMWF/UKMET cluster partly due to continuity, but with low
confidence. Had the greatest weight on the GEFS mean by days 7-8.
...Weather/Hazard Highlights...
Precipitation is possible over southern parts of Alaska from the
Aleutians and Alaska Peninsula east into Southcentral Alaska and
the Panhandle through much of next week near low pressure systems.
Precipitation amounts should vary from day to day and place to
place. Some rain/snow amounts could be enhanced at times, but the
heaviest totals through the period will be dependent on exact low
tracks that are uncertain at this point. The current forecast
indicates southern portions of the Panhandle may receive the most
precipitation overall, with local enhancements elsewhere. Interior
Alaska should see generally dry conditions as the storm track
stays to the south. Periods of gusty winds are also possible along
low tracks, and the gradient south of Arctic high pressure may
support a period of strong winds across the North Slope.
Near average to below average highs are forecast over much of the
state early in the week, with the greatest anomalies across the
North Slope and lower elevations of the interior. The cold
anomalies could ease by the middle of next week, but troughing
over the southwest mainland could shift highs from above normal
Sunday closer to normal as the week progresses. Low temperatures
should be closer to normal over the North Slope and Interior
compared to the cool highs, while milder than average lows are
predicted in the southern mainland and the Brooks Range. The
Panhandle can expect to see below normal highs and around average
lows through the period.
Tate
Hazards:
- High winds across portions of northern Alaska, Sun-Mon, Apr
3-Apr 4.
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