Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
748 PM EDT Fri Jul 26 2024

Valid 12Z Tue Jul 30 2024 - 12Z Sat Aug 03 2024

...General Overview...

The beginning of the extended forecast period Tuesday will be
featured with an anomalous upper trough situated over southern
mainland Alaska, and then reaching the northeastern Gulf going
into Wednesday along with rather cool conditions and periods of
rain and high mountain snow.  An incoming shortwave to its west
will tend to fortify this trough across much of the Gulf going
into Thursday.  A hint of an upper ridge tries to briefly build
north across southwestern mainland Alaska Wednesday into Thursday
before upper level troughing likely returns to the region going
into Friday and next weekend.  Meanwhile, the slow moving upper
low north of eastern Siberia will likely move slowly eastward to a
position north of the Arctic Coast after idling in place for a few
days.

...Guidance Evaluation/Preferences...

The 12Z model guidance suite has a very good handle on the overall
synoptic scale pattern on Tuesday across the Alaska domain, and
with high confidence on the strong upper trough across southern
Alaska and into the Gulf region.  Going into Wednesday night and
Thursday, the GFS remains a more progressive solution in bringing
shortwave energy inland across northern British Columbia, and this
is similar to earlier runs, but is otherwise reasonably comparable
across the rest of the domain going through Thursday. The best
agreement in the guidance by this time is with the upper high
situated south of the Aleutians, and less confidence across
northwestern Alaska with timing of trough/upper low arrival. 
Looking ahead to Friday, the GFS becomes stronger with the next
trough approaching from Siberia, and also stronger with another
low over the Gulf by the end of the forecast period.  Model and
ensemble spread increases substantially by day 8 (Saturday), with
the ensemble means accounting for slightly more than half of the
forecast and toning down the GFS further.

...Weather/Hazards Highlights...

Scattered to numerous showers are likely to be ongoing across much
of southern Alaska and also parts of the Interior on Tuesday and
probably into Wednesday as well with steeper lapse rates in place
from the upper trough. This will also result in lower snow levels
for the major mountain ranges, especially the Alaska Range and
into the Chugach and St. Elias mountains.  The unsettled
conditions are also forecast to be in place across the Southeast
Panhandle region through the middle to end of the week with moist
onshore flow ahead of the incoming upper trough/front. 
Additionally, parts of the Brooks Range will likely multiple
rounds of showers, some of which could be locally heavy, but not
reaching hazardous level criteria.  Temperatures are generally
expected to be about 5-15 degrees below average for much of the
state through Wednesday, with some moderation closer to normal on
Thursday before another cooling trend in time for next weekend
across the northern 2/3rds of the state.  This will generally
equate to highs in the mid 50s to mid 60s for most of the
Interior, and lows in the 40s. 

Hamrick


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