Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
758 PM EDT Sun Apr 14 2024

Valid 12Z Thu Apr 18 2024 - 12Z Mon Apr 22 2024

...Synoptic Overview, Guidance Evaluation, & Preferences...

An amplified upper level flow pattern is forecast to be in place
across the Alaska domain for the middle of the week, with a strong
ridge axis extending northward to the Yukon Territory, and a broad
upper low situated south of the Alaska Peninsula.  Strong onshore
flow directed towards the coast will produce heavy precipitation
for southern coastal areas, and lighter rain farther inland.  A
second area of low pressure will likely develop over the same
general area by the weekend as a shortwave approaches from the
west. 

The 12Z model guidance suite features decent overall synoptic
scale agreement across the Alaska domain for the beginning of the
forecast period Thursday.  Going into late Friday and the weekend,
the CMC and the UKMET take the Gulf low farther to the south than
the model and ensemble consensus.  By Sunday and Monday, models
diverge considerably across the North Pacific with subsequent
surface low evolution, and forecast confidence is limited outside
of the mainland by this time.  The fronts/pressures forecast was
based on mainly a CMC/GFS/ECMWF blend as a starting point on
Thursday, and then tapering off the CMC for Friday and beyond. 
Increasing percentages of the GEFS and EC means were used going
into next weekend and next Monday.


...Weather/Hazards Highlights...

Coastal rain and mountain snow is expected to be locally heavy
going into the second half of the work week from the southern
AKpen to the Prince William Sound region as moist onshore flow
increases ahead of the Pacific low off the coast.  Strong winds
over this region is expected to produce high waves and gusts over
40 mph at times, especially through coastal inlets.  Light showers
are possible farther inland across southern mainland Alaska. 
Temperatures are generally expected to be mild with readings in
the mid 40s to upper 50s for highs across most Interior locations
south of the Brooks Range, and generally 40-45 degrees near the
southern coastal areas.  A cooling trend is likely by next weekend
as the upper ridge axis breaks down.  The Brooks Range will be the
demarcation for much colder conditions across the North Slope and
extending to the Arctic Coast. 

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