Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
649 PM EDT Wed Mar 17 2021
Valid 12Z Sun Mar 21 2021 - 12Z Thu Mar 25 2021
...Overview and Guidance/Uncertainty Assessment...
Models and ensembles still offer better than average agreement for
the pattern evolution and significant features. A 12 UTC
GFS/ECMWF/UKMET/Canadian model blend seems to provide a good
representation of the most likely scenario into next midweek, with
an ensemble focus day 8. The composites tend to mitigate the less
predictable smaller scale differences still inherent with most
systems embedded within the larger scale flow. WPC continuity is
well maintained.
Guidance continues to show a progressive and active pattern across
the Bering Sea/North Pacific into the Gulf of Alaska. Expect a
lead weekend storm over the Gulf of Alaska, with a subsequent
North Pacific storm likely to turn northeastward into the Gulf by
early next week. Meanwhile, expect several Bering Sea systems with
active weather will work into an unsettled mainland.
...Weather/Hazards Highlights...
Lead Bering Sea upper troughing and surface low/frontal system
development and onshore track seems likely to spread some
organized snows eastward across the Interior and into the Brooks
Range/North Slope early next week. Subsequent system energies
slated to track across the Bering Sea would bring a front across
the southern Bering and Aleutians into midweek, accompanied by
precipitation and brisk to strong winds. Less defined late period
progression into the western mainland and the Gulf of Alaska would
also spread moderate activity across the broad region.
A lead and deepened Gulf of Alaska system will focus moderate to
terrain enhanced precipitation over the Southeast Panhandle Sunday
before exiting the region. Upstream, the Aleutians and Peninsula
may see a period of precipitation and enhanced winds early next
week on the northwest side of the trailing North Pacific system,
but this will be sensitive to the exact track of the surface low.
This storm will then quickly bring increasing moisture to the
southern coast and especially the Panhandle Tuesday-Wednesday
where there is the highest potential for terrain enhancing heavy
precipitation given the lower-latitude origin of the moisture.
Expect a majority of the state to see below normal temperatures
this period with anomalies tending to be colder for daytime highs
relative to morning lows (with some pockets of slightly above
normal anomalies possible for the latter). Extreme northern areas
may see moderately above normal readings. The upper trough
arriving into the mainland during the first half of next week
should push temperatures somewhat farther below normal compared to
the weekend.
Schichtel
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle,
Tue, Mar 23.
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards 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