165
FXAK02 KWNH 082356
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
755 PM EDT Wed May 08 2024

Valid 12Z Sun May 12 2024 - 12Z Thu May 16 2024

...Overview...

A mean trough aloft atop Alaska will be persistent through the
weekend and lasting through at least the first part of next week.
A couple features of note should be present within the broad
trough pattern, including a weakening upper/surface low moving
into the Gulf over the weekend, and troughing extending into the
northern Pacific that has trended stronger over the past day that
supports another low in the Gulf Tuesday-Wednesday. Lingering
heavy precipitation is forecast across favored portions of the
Kenai Peninsula on Saturday, while the pattern will favor multiple
rounds of precipitation across Southeast Alaska next week.


...Guidance Evaluation and Preferences...

Model guidance is agreeable with the overall mid-upper trough
pattern atop the state into early next week, and show reasonable
agreement with the upper/surface lows coming into the Gulf while
weakening Sunday. Most model guidance also continues to show
reinforcing energy into the trough as additional energy drops
south into the northern Pacific, positively tilting the southern
portion of the trough Monday-Tuesday. For the most part, recent
models indicate that a potential upper low forming within the
trough could be stronger than models a day ago suggested, though
there remains some spread. The 12Z CMC was weaker and more
progressive with the troughing/energy, while the 06Z GFS was quite
strong with the upper low as it moved into the Gulf midweek and
also produced a stronger surface low that was an outlier. But the
12Z ECMWF and GFS runs seemed to be a good middle ground. Behind
these systems, rounds of troughing and energy emerging from
Siberia remain uncertain in timing and strength for
Tuesday-Thursday. The flat ensemble means and the spread in the
ensemble members themselves yield low confidence in these
features, so this will continue to be monitored as it could be
impactful to western Alaska later next week.

The WPC forecast was based on a blend of the deterministic 12Z
models favoring the GFS and ECMWF early in the period, and
increased the proportion of the GEFS and EC ensemble means to half
while maintaining some GFS/EC components late period. This yielded
deeper/sharper troughing in parts of southern Alaska than the
previous forecast, but otherwise maintained reasonable continuity.


...Weather/Hazards Highlights...

Into the weekend, upper and surface lows tracking into the Gulf of
Alaska will lead to lingering heavy precipitation across the
eastern Kenai Peninsula that continues to be shown on the Hazards
product for Saturday. Gusty winds are possible for the
northeastern Pacific ahead of the low. As the lows weaken over the
Gulf, moist flow will be directed into Southeast Alaska for some
generally moderate precipitation totals into Sunday-Monday. Then
by Tuesday-Wednesday, another low system shifting into the Gulf
should renew precipitation chances. Precipitation amounts could be
moderate to heavy and will be partially dependent on the eventual
strength of the surface low. Some lighter precipitation in the
form of rain showers and higher elevation snow showers could
extend into the Interior as well. The Aleutians and the western
Mainland may see precipitation chances and winds increase for the
middle of next week, but with considerable uncertainty.

The unsettled pattern will tend to keep diurnal temperature ranges
more narrow than climatology, with daytime highs most likely to be
below normal and morning lows averaging above normal. However,
some pockets of modestly above normal highs may be possible over
the Interior, while various locations depending on the day may see
slightly below normal lows.


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

$$