Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
717 PM EDT Mon Apr 18 2022
Valid 12Z Fri Apr 22 2022 - 12Z Tue Apr 26 2022
...Guidance/Predictability Assessment...
The latest guidance seems to continue to have a decent handle on
the overall upper level flow pattern over Alaska during the medium
range period. This features a deep upper closed low/surface low
initially south of the Aleutians on Friday, which should drift
slowly eastward into the Gulf and weaken somewhat as it lingers
through early next week with a building and blocky ridge to it's
north and east. The guidance seems to handle this feature better
today, with only some insignificant differences in placement. A
general deterministic model blend worked well for this system.
Meanwhile, upstream, a couple of systems should cross the
Kamchatka Peninsula and dissipate into the western Bering Sea.
There are some lingering uncertainties on timing each of the
systems, but most notably the 12z GFS is much farther north to
redevelop the first low bringing it into the Arctic, while both
the ECMWF and CMC (with support from the ensembles) suggest the
low will drift into the western Bering Sea and dissipate. As such,
the emphasis for todays forecast was placed more on the ECMWF with
smaller contributions from the CMC (which shows issues in the
Arctic early on as well) and the GFS. The second half of the
forecast period featured increased usage of the ensemble means
which helped to mitigate the uncertainties. At least half of the
deterministic models were used even through day 8 though due to
better than average agreement and for some added system definition.
...Overview Weather/Hazard Highlights...
The low pressures system into the Gulf will continue to bring
gusty winds and rough seas to parts of the Aleutians and Alaska
Peninsula at the end of the week, with some lingering
precipitation as well. Ahead of the low, moisture should direct
northward along the attendant cold front to support enhanced and
locally heavy precipitation (lower elevation rain/mountain snow)
across parts of the Southern Coast and eventually eastward into
the Panhandle this weekend and early next week as the system
weakens but the general low circulation lingers. The western
Aleutians may see some precipitation as well as a weakening cold
front approaches early next week. Elsewhere, much of the Interior
and North Slope regions should remain dry, with temperatures
mostly above normal and trending warmer through the period.
Southern regions, from the Aleutians to the Panhandle, should
remain near or below average owing to increased clouds and
precipitation.
Santorelli
Hazards:
- Heavy precipitation across portions of the Alaska and Kenai
Peninsulas, Sat, Apr 23.
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