Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
627 PM EDT Fri Jul 2 2021
Valid 12Z Tue Jul 6 2021 - 12Z Sat Jul 10 2021
...Overview and Guidance/Predictability Evaluation...
The deterministic models and the ensemble means are in generally
above average agreement on the synoptic scale pattern. North
Pacific and western Aleutians shortwave energy will likely merge
with a northern Bering Sea upper level low early in the forecast
period, followed by the upper low eventually dropping over the
Gulf of Alaska. Meanwhile, low-mid level flow around the
periphery of a deep Arctic low should begin to lower heights aloft
over the northern/western mainland later in the week. This
overall pattern evolution will favor a broad coverage of scattered
showers next week, with typical model differences regarding
placement of heaviest rainfall totals.
In terms of model preference, the WPC forecast was primarily
derived from a deterministic model blend through Thursday, and
then less of the GFS and more of the ensemble means for Friday and
Saturday. The GFS becomes more amplified and farther south with
the core of the upper low over the Gulf of Alaska compared to the
model/ensemble consensus, so less weighting was applied to the GFS
for the end of the forecast period.
...Weather/Threats Highlights...
The general pattern will support a broad area of moisture
overspreading the state with many locations seeing multiple days
of scattered to numerous showers. The initial Aleutians/Bering
Sea system could also produce some gusty winds, especially over
marine and coastal areas. Upstream flow could bring another
surface system and precip area into the western mainland late in
the week. At this time, the best potential for highest five-day
totals would likely be over portions of the southern
coast/mainland into the southeast Panhandle. The clouds and
rainfall will keep high temperatures below normal over most of the
state with the coolest anomalies tending to be over the southern
mainland.
Hamrick/Rausch
Hazards:
- Much below normal temperatures across portions of southern
mainland Alaska, Mon-Thu, Jul 5-Jul 8.
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