Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
637 PM EDT Sun Jun 07 2020
Valid 12Z Thu Jun 11 2020 - 12Z Mon Jun 15 2020
...Overview and Weather Highlights/Threats...
A relatively progressive flow pattern is expected to persist
across the North Pacific and into the Gulf of Alaska through the
extended forecast period, while weak and broad upper ridging
persists from the Arctic Ocean into western Canada. Meanwhile, the
Interior of Alaska will lie within a region of chaotic and
relatively weak easterly upper-level flow. Onshore flow across
southern mainland Alaska as low pressure weakens in the Gulf of
Alaska will keep the potential for precipitation up through
midweek (especially across the higher terrain), while weak
easterly flow and occasional upper shortwave energy will also keep
isolated to occasionally scattered convective activity in the
picture across the Interior. A low pressure system expected to
pass near the Aleutians as it moves into the Gulf of Alaska later
this week and into the weekend will bring an increase in shower
and perhaps some gusty winds to the Aleutians, with precipitation
eventually increasing across the Alaska Peninsula as well.
Temperatures in this pattern are expected to be above average
through the forecast period, with highs ranging from 5 to 10 deg F
above average for many areas, especially across western mainland
Alaska. Meanwhile, more clouds and occasional precipitation will
keep temperatures several degrees below average closer to the
coast.
...Guidance/Predictability Assessment...
A blend of the 12Z ECMWF/GFS was used during days 4-5 (Thu-Fri),
with majority weight placed on ECENS/GEFS ensemble means from day
6 (Sat) onward. Despite some significant differences starting by
the weekend among the deterministic guidance across the North
Pacific, ensemble means showed relatively good agreement -
indicating that forecast confidence is likely near average through
the extended forecast period.
Ryan
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
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