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000
FXAK02 KWNH 230002
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
801 PM EDT Mon Apr 22 2024

Valid 12Z Sat Apr 27 2024 - 12Z Wed May 01 2024

...Overview...

An upper/surface low is forecast to track across the eastern
Aleutians and the Alaska Peninsula at the start of the period
Friday, and then east across the Northeast Pacific over the
weekend into early next week before pushing into British Columbia.
North and east of this feature, upper ridging will stretch from
Southeast Alaska northwest into the northern part of the state
late week but erode with time. Then upstream a round or two of
energy and troughing could move across the Bering Sea toward the
western coast next week, but with ample uncertainty.


...Guidance Evaluation and Preferences...

Guidance is in reasonably good agreement with the pattern through
late week as the aforementioned low undercuts an upper ridge over
portions of eastern to northern Alaska. Recent guidance has
maintained its trend of a steadier progression of the low eastward
that began with the 12Z Sunday models. Thus for the early part of
the forecast period, used a blend of the deterministic guidance
favoring the 12Z ECMWF and GFS.

Model spread increases rapidly into next week. First, by Sunday
there is some uncertainty with how much energy may remain/come in
near Bristol Bay. This makes the ECMWF (which has a ridge) out of
phase with the CMC that lingers a small upper low there and the
GFS runs that push additional energy in. Then a larger scale
trough may push into the Bering and the Aleutians and western
Alaska, but the timing is quite variable. GFS runs are faster to
bring the trough east than the ECMWF and CMC and leads to more out
of phase issues. There is certainly low confidence in the forecast
for Sunday-Tuesday. Quickly ramped up the proportion of the EC and
GEFS ensemble means in the blend to over half by Monday and 80
percent by Tuesday. The means are pretty zonal due to the
differences across the ensemble members but hopefully models will
converge with time.


...Weather/Hazards Highlights...

The upper and surface lows late this week will promote some
precipitation cross the Aleutians to Alaska Peninsula into the
southwest Mainland toward Kodiak Island and the Kenai Peninsula,
with moderate amounts Friday lowering on Saturday. Some gusty
winds are possible late in the workweek for the Aleutians to
Alaska Peninsula and maritime areas, but are likely to stay below
hazards criteria. Some precipitation is likely over the weekend
for Southeast Alaska as moist inflow increases ahead of the low
moving east. Generally light amounts are forecast in northern
parts of the Panhandle with more moderate amounts in southern
parts. By next week, precipitation chances may get renewed in the
Aleutians toward southwestern and south-central Alaska, but will
be dependent on the eventual flow. Meanwhile the northern half of
the Mainland can expect generally dry conditions.

Most of the state should see above normal temperatures during the
period, with the highest anomalies tending to be over the
Interior. To the north of a front settling over the north-central
mainland, cold high pressure over the Arctic may keep temperatures
near to somewhat below normal, especially across the North Slope.
Locations near the Southcentral coast and northern Panhandle may
also see near or slightly below normal readings.


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

$$