Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
225 PM EDT Wed Jul 17 2019
Valid 12Z Sun Jul 21 2019 - 12Z Thu Jul 25 2019
Flat flow aloft will transition into a more amplified pattern with
time across the region which evolves into a Rex Block pattern
extending from Alaska/Yukon (closed deep layer high) into the
northeast Pacific (closed deep layer low). Broadly, the guidance
is agreeable but detail issues continue to cloud the picture. In
order to deal with the system crossing Alaska Saturday night, and
maintain as good of continuity as possible, used the 06z GFS
outright Thereafter, a blend of the 00z Canadian/06z GFS/00z
ECMWF/00z UKMET/00z ECMWF ensemble mean/00z NAEFS mean was used,
with increasing percentages of the ensemble means with time as the
UKMET and Canadian percentages dropped off. This led to a
quicker/weaker eastern AK system early on and a slower progression
with the system moving through western and central Alaska early to
mid next week. Confidence is no better than average in the
forecast by mid next week.
Mild to warm temperatures are forecast for the state this period
-- temperatures remain on pace for record warmth for the month of
July across south-central AK. North and Northwest AK have the
highest rain chances this weekend (where moderate to heavy
rainfall is expected) before the low moving eastward through the
northeast Pacific increases rain chances for southeast AK and the
AK panhandle early to mid next week.
Roth
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
No significant hazards are expected over Alaska during this
forecast period.
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