Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
646 PM EDT Mon May 11 2020
Valid 12Z Fri May 15 2020 - 12Z Tue May 19 2020
Pattern Overview
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Through the period /Fri May 15 to Tue May 19/ there has been
relatively stable continuity with the synoptic pattern evolution
across the Alaska domain and adjacent maritime regions. An
anomalously strong Arctic high will remain in place initially with
some retrogression expected to the west. This will funnel cooler
mainland temperatures for much of the Interior and Arctic Coast
region. A pair of strong surface lows are expected to track
through the domain, the first passing through the Gulf of Alaska
but well south of the Mainland. The second system is expected to
pass south of the Aleutians this upcoming weekend.
Guidance/Predictability Assessment
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The 12Z model guidance showed average to slightly above average
synoptic scale through most of the period. Aloft, the 500 mb
pattern exhibited fairly good agreement and at the surface,
through about day 6, the ECMWF/GFS/CMC showed good clustering with
the initial low track across the Gulf of Alaska. After that, the
CMC lags the low back while the ECMWF/GFS carry it eastward early
next week. The faster solutions from the ECMWF and GFS were
favored. With the second area of low pressure passing south of the
Aleutians late in the weekend and early next week, there is
greater model spread and the CMC was largely discounted as it
develops the low too deep and large compared to the more compact
GFS and ECMWF. Finally, toward the end of the period and in the
far western part of the domain, another area of low pressure is
possible. Here, the ECMWF rapidly deepens this feature, much more
than the GFS and CMC. While the ECMWF solution may be a bit of an
outlier, the WPC blend favored heavily the ECENS which dampened it
a bit, given the uncertainty and model spread.
Weather/Hazard Highlights
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There is reasonable confidence in the general trend toward cooler
temperatures over a majority of the mainland over the upcoming
week. Above normal readings should decrease in coverage and
become more confined to southern/western areas of the state while
the pattern will gradually become more favorable for below normal
temperatures over northern and eastern areas. Expect significant
precipitation to be fairly limited in coverage during the period
owing to the southern extent of the oceanic lows and the surface
high governing the overall weather pattern for central and
northern sections. The front settling across the southern
mainland may focus some activity at times while light
precipitation may reach northeastern areas next weekend with the
arrival of upper troughing. As the Gulf of Alaska system moves
eastward, expect its track to remain far enough south for at most
a little moisture to reach the southeast Alaska Panhandle. The
system tracking over the western Pacific may bring some moisture
into the Aleutians late in the weekend but with limited confidence
on placement and intensity.
Taylor
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