Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
312 PM EDT Wed May 29 2019
Valid 12Z Sun Jun 02 2019 - 12Z Thu Jun 06 2019
Flow over the high latitudes will feature a blocking pattern with
slowly moving features. On Sun 02 Jun a slowly moving upper low is
forecast to be centered south of the central Aleutians roughly
near 52N 161W. The 00Z-06z suite of guidance (ECMWF/Canadian)
clustered fairly well together and close to the ensemble means
(00Z ECMWF ensemble mean and 06z GEFS Mean/00z Canadian mean). The
consensus of these solutions stayed close to the prior forecast/
continuity through Sunday 02 June. As the low drifts south, an
upper ridge drifts south across mainland AK. The 12z GFS was a few
hours faster than the pack and given the least weighting in the
forecast.
The majority of models have kept yet another upper low north of
Wrangel Island and retrograde the circulation west with time. The
12z GFS becomes an outlier by strengthening the low and developing
a second sfc circulation. Consequently, more weighting was give to
the ECMWF/Canadian models and their ensemble means.
On next Tue 04 Jun the models mostly show a new cyclone developing
in the northern central Pacific to the southwest of the lower
Aleutians. There are latitude differences with the 06z-12z GFS
north of the low positions/track vs the further south 00z
ECMWF/ECMWF Ensemble Mean/Canadian . There is above average
agreement on the development of a low and increasing clustering,
minus the 12z GFS. Given the typical fast GFS bias in moving
closed lows too quickly, greater weighting to the 06z GEFS/00z
ECMWF Ensemble means should bias correct the forecast.
Temperatures will average above normal in northern AK and the warm
core spreads south in tandem with the upper ridge, reducing
coverage of cool areas as next week progresses. Rainfall will
generally be light but locally moderate in favored areas in
windward terrain and coastal areas of the Kenai down into the
Panhandle this weekend. Scattered showers are expected near a
residual low level boundary in interior southern AK each day.
Petersen
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