Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
357 PM EDT Tue Mar 19 2019
Valid 12Z Sat Mar 23 2019 - 12Z Wed Mar 27 2019
Upper ridging over northwestern Canada at the end of the week will
only briefly relax next Monday before again building over the
eastern interior into the Yukon. This favors continued/renewed
troughing in the Bering Sea with a split flow south of the Gulf of
Alaska. The models/ensembles were in good agreement through much
of the period but showed a large shift in the forecast for next
Mon/Tue near the central Aleutians. Instead of maintaining a
singular frontal passage, the models/ensembles now forecast a
significant surface wave to develop off Asia and deepen into the
Bering Sea, potentially into the 950s mb. The ensemble means were
closer to 980mb and opted to depict a 970s mb low for now given
the large change in continuity, lead time (6 days), and the spread
among the models in location/timing (and even depth per the 12Z
Canadian). Such a deep system (winds at least 30-40kts) would
bring a wind/wave threat to the open Bering Sea waters and western
coastal areas. This system is forecast to lift
north-northeastward, blocked from moving inland too much from the
ridge downstream, focusing precipitation west of 155W (multi-inch
totals). Southerly flow would bring in well above average
temperatures, possibly near record highs, to much of the interior
and especially North Slope. By next Tue/Wed, ensembles show no
discernible system behind that front but troughing would maintain
cold air aloft over the Aleutians/Bering and eventually into
western Alaska.
Fracasso
Bullet points from the WPC Days 3-7 Hazards chart can be found at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
- Heavy precipitation across portions of the Alaska Panhandle and
mainland Alaska, Fri-Mon, Mar 22-Mar 25.
- Heavy precipitation across portions of mainland Alaska and the
Aleutians, Mon-Tue, Mar 25-Mar 26.
- High winds across portions of mainland Alaska and the Aleutians,
Fri, Mar 22.
- High winds across portions of the Aleutians, Mon, Mar 25.
- High significant wave heights for coastal portions of mainland
Alaska, Fri, Mar 22.
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