Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
637 PM EDT Wed Jun 17 2020
Valid 12Z Sun Jun 21 2020 - 12Z Thu Jun 25 2020
...Overview and Guidance/Predictability Assessment...
Guidance offers a reasonably similar larger scale medium range
pattern evolution for next week, but individual models offer less
than stellar forecast spread with especially the timing and
emphasis of offshore lows days 4-8. The 12 UTC GEFS/ECMWF
ensembles are more consistent and better clustered. A blend of
these ensembles and 19 UTC National Blend of Models along with the
model with the best fit, the 12 UTC ECMWF, seems to produce a good
starting point for the Alaskan medium range forecast package valid
Sunday-next Thursday. The blend maintains reasonable WPC product
continuity, low strengths consistent with favorable upper support
and acts to mitigate less predictable smaller scale variances.
...Weather/Threats Highlights...
Energy rotating around a persistent Arctic Ocean upper low will
force a surface front and some periods of precipitation underneath
across the North Slope/Brooks Range. Lingering instability to the
south should also favor a pattern with scattered Interior
convection.
Lead closed low energy should support a deepened low set to lift
slowly northward across the central Gulf of Alaska early next week
that will slowly weaken over the northern Gulf into next midweek.
This low should be a maritime winds/waves hazard and enhanced
rainfall potential should increase across the Alaskan southern
tier with lead wrapping moisture.
A second Pacific low with seemingly favorable upper support may
track eastward to the south of the Aleutians behind the main lead
low. This should wrap some rainfall into the Aleutians and
possibly more in earnest into the Alaskan Peninsula mid-later next
week.
Schichtel
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
Hazards: 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