Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
330 PM EDT Wed Jul 24 2019
Valid 12Z Sun Jul 28 2019 - 12Z Thu Aug 01 2019
The 00Z ECWMF and GFS have more amplitude than previous runs and
are fairly clustered with there means; however, in general, the
latest guidance still has an appreciable amount of variability and
spread. The CMC is nearly 180 degrees out of phase by Monday and
remains so through the rest of the forecast. Again, the shortwave
tracking from the Alaska Peninsula across the Gulf to the
Southeast and a westward drifting Arctic ridge near the beginning
of the extended is the most agreeable aspect of the forecast. From
Monday onward the means maintain the eastern Siberia upper low
west of the spread.
To maintain continuity in this below average confidence forecast,
this issuance began with 00Z ECWMF/GFS at 70 percent with 30
percent using the EC/GEFS means, 50/50 split by Monday and 100
percent means by the end. This approach maintains the forecast of
a North Pacific warm front lifting toward/to the western Aleutians
while a modest surface ridge covers the Bering. Meanwhile there is
a hint of a weak trough aloft settling over the Gulf of Alaska
with modest low pressure over the northern Gulf.
A brief period of enhanced rainfall is expected across the
southern Coast and across the Southeast as the shortwave/surface
low crosses the Gulf of Alaska this weekend. Otherwise a fairly
broad area will see some precipitation potential for one or more
days during the period but with low confidence in location/timing
specifics due to the uncertainty in flow details aloft and
corresponding surface evolution.
Rausch/Campbell
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