Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
730 PM EDT Wed Jun 02 2021
Valid 12Z Sun Jun 06 2021 - 12Z Thu Jun 10 2021
...Overview and Guidance Evaluation...
A deep upper-level low is forecast to be located between
northwestern Alaska and Siberia at the start of the medium-range
period later this weekend. The ECMWF and CMC led the trend
yesterday to dig this upper low southeastward down the West Coast
early next week toward the Gulf of Alaska. There has been
increasing support from the ensemble means for this scenario since
yesterday. The GFS has also joined this camp but with
considerable run-to-run variability with the forward speed of this
upper low. A general model compromise was used to derive the WPC
Alaska medium-range grids. This blend included the 12Z GFS/GEFS,
12Z CMC/CMC mean, and the 12Z ECMWF/00Z & 12Z EC mean, trending
toward the ensemble means for Days 7-8. With a general model
compromise, the upper low is allowed to slide southeastward across
western and southwestern Alaska into the Gulf of Alaska through
early next week. Elsewhere, upper troughing and a surface front
appear to linger south of the western Aleutians as weakening
impulses push northward toward the area from the northern Pacific.
...Weather/Threats Highlights...
Lingering precipitation across the Alaska Panhandle and in the
vicinity of the Tanana River Valley in southeastern Alaska is
forecast to gradually taper off this Sunday. Meanwhile,
increasing chance of rain can be expected to reach western Alaska
on Sunday before overspreading southwestern Alaska and the Alaska
Peninsula on Monday and Tuesday due to the passage of the upper
low. Some diurnal rain showers could linger across the interior
mountain ranges into midweek. Across the Aleutians, rain chances
should increase gradually through the middle of next week as
moisture from the south arrives ahead of a lingering frontal
system across the far northern Pacific. Temperatures are expected
to be cooler than normal for southwestern Alaska on Sunday due to
clouds and precipitation but they should return to slightly above
normal level early to middle next week. Temperatures for the
remainder of Alaska should not stray too far from normal while a
slow warming trend sets in. Much of the interior sections should
see highs reaching into the 70s but only into the 40s near the
coast of the North Slope.
Kong
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