Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
640 PM EST Sun Jan 30 2022
Valid 12Z Thu Feb 03 2022 - 12Z Mon Feb 07 2022
...Overview...
The large scale pattern over Alaska will be fairly stagnant late
this week into early next week, with a col generally in place over
Alaska, separating deep layer low pressure west of the Aleutians
and an upper high retreating well northwest of the state while an
upper low slowly drifts east over far northern Canada--these
features create some semblance of an omega block. The upper level
gyre just west of the Aleutians will produce shortwaves pivoting
around it, sending them eastward along the southern part of the
state. These shortwaves should produce rounds of surface low
pressure tracking across southern coastal Alaska along with
multiple rounds of precipitation, with the heaviest rain/snow from
the Kenai Peninsula to the southeast Panhandle.
...Guidance/Uncertainty Assessment...
The 12Z suite of model guidance remains in fair agreement with the
overall pattern described above, but with substantial timing and
track differences in smaller scale features such as the individual
shortwaves and associated surface lows tracking across the Bering
Sea, northern Pacific, and the Gulf of Alaska. Additionally, model
differences were noted with the timing of the high northwest of
the state retreating north with time. Per coordination with the
Alaska Weather Forecast Offices, models tend to be too fast to
erode a high/blocking pattern in this position near Siberia, so
favored holding onto the ridge axis into northwest Alaska through
the latter part of the week before a trough axis could dip into
northern Alaska by early next week. With deterministic guidance
generally quicker to erode this ridge than preferred, today's WPC
medium range forecast was based on a blend of half ensemble mean
guidance and half deterministic models (06Z/12Z GFS and 12Z ECMWF)
early in the period, increasing to about 70 percent ensemble means
by the end. This also worked given the uncertainty in individual
models with the shortwave features and surface lows, though some
deepening of the lows along coastal southern Alaska was drawn
manually to maintain some strength of those features.
...Weather/Hazard Highlights...
Several low pressure/frontal systems tracking near coastal
southern Alaska will draw moisture into the southern part of the
state and provide forcing for rounds of precipitation across the
Alaska Peninsula, Southcentral Alaska, and into the Panhandle late
this week into early next week. Gusty winds are also possible from
the Aleutians eastward across the coastal Alaska. Then farther
north, arctic high pressure will be in place across northern
Alaska, keeping the Interior dry through late week. Some snow
showers over the northern mainland may be possible early next week
as the high retreats. Below normal temperatures across much of the
Interior will gradually retreat to the North Slope by early next
week, while generally above average temperatures are forecast for
southern Alaska.
Tate
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