Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
733 PM EDT Tue Jun 08 2021
Valid 12Z Sat Jun 12 2021 - 12Z Wed Jun 16 2021
...Overview and Guidance Evaluation...
Since yesterday, model guidance has come into relatively good
agreement among each other. The main storm of interest will be an
occluded cyclone moving toward the Aleutians that will likely be
re-energized as an upstream upper-level trough merges with the
system over the Bering Sea during the weekend. The merger should
reach peak intensity on Monday as it edges into the Alaska
Peninsula before sliding off just to the south toward the Gulf of
Alaska by midweek.
A general model compromise trending toward the ensemble means for
Days 7-8 should work fine as a starting point. The 12Z ECMWF
tracked the low a bit faster to the east than the 12Z CMC and the
GFS by Days 7-8, as were their ensemble means. This general model
blend yielded a solution that did not stray too far from WPC
continuity. Elsewhere, a stationary front should remain draped
across the northern portion of Alaska through the medium-range
period.
...Weather/Threats Highlights...
The upper shortwave edging in from Siberia during the weekend
should promote periods of precipitation that should be best
organized over about the northwest half of the mainland. Recent
guidance has generally trended weaker with this shortwave. Expect
precipitation to become lighter and more scattered by late weekend
and early next week as the shortwave departs and an upper ridge
builds into the mainland from Canada. The strengthening system
that tracks into the Aleutians/Bering Sea will spread a broad area
of moisture across the Aleutians and into much of the Alaska
Peninsula early next week. The Aleutians may see a period of
enhanced rain/winds during the weekend and the Alaska
Peninsula/Kodiak Island could see a couple days or so of focused
rainfall as the occluded cyclone is forecast to reach peak
intensity on Monday.
Cool high temperatures over a majority of the state should
gradually moderate with time as shortwave energy lifts to the
north of the state by late weekend/early next week and then upper
ridging builds. By late in the period the Panhandle and parts of
Southcentral as well as portions of the northwestern mainland may
still be somewhat below normal for highs. For lows, expect
moderately below normal readings over parts of the Interior and
western mainland as well as the Panhandle plus far southeast
corner of the mainland, while remaining areas should be above
normal. The coverage of above normal lows should increase toward
midweek.
Kong/Rausch
No significant hazards are expected over Alaska during this
forecast period.
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