Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
509 PM EST Tue Jan 28 2020
Valid 12Z Sat Feb 01 2020 - 12Z Wed Feb 05 2020
...Some moderation in temperatures next week...
...Low pressure system to bring windy/rainy conditions to the
Aleutians...
A well-defined system (sub-960mb) will move into the Bering next
week and unravel to the east. The models have showed this
evolution with increasing heights to the mainland for several
days. However, uncertainty in the forecast ramps up after Sunday
due in part to how much northern stream energy either slips
westward/ southwestward near the Bering Strait or splits eastward
or northward atop upper ridging. The ECMWF fell in the former camp
while the GFS in the latter, but the ensembles mostly clustered
near their parent model. Opted to favor the ECMWF a bit over the
GFS as the Canadian/UKMET were closer to the ECMWF. Nevertheless,
could not rule out any scenario as upper ridging could be
underestimated as it surges northward. This would affect the
possible sfc low into western areas that may be overdone in the
ECMWF guidance, and as such showed a weaker version of this.
Favored upper pattern suggests triple point development into the
Gulf around Monday as the front continues eastward. Could see
shortwaves develop around the decaying Bering upper low that may
or may not help to slow the front via sfc wave development, which
was a scenario showed by all the deterministic runs though at
various points in time. Ensembles show weakening troughing in the
Bering by the end of the period as another system may enter from
the west.
Temperatures will moderate from 15-25 below average to within
several degrees of average over much of the interior, from south
to north, as southerly flow strengthens. Models may be too quick
to erode the cold air mass in place so trended a bit slower to
raise temperatures than the NBM.
Precipitation will be favored along the coast from the Aleutians
across to the Panhandle where several inches of rain (some onset
snow) are possible along the coast and southeastward-facing areas
(Kodiak, Kenai peninsula) but much more favored for the Panhandle
by later in the period.
Fracasso
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
Hazards:
- Heavy precipitation across portions of the Alaska Panhandle,
mainland Alaska, and the Aleutians, Fri-Mon, Jan 31-Feb 3.
- High winds across portions of mainland Alaska and the Aleutians,
Sat-Sun, Feb 1-Feb 2.
- Much below normal temperatures across portions of mainland
Alaska, Fri-Mon, Jan 31-Feb 3.
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