Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
546 PM EDT Thu May 14 2020
Valid 12Z Mon May 18 2020 - 12Z Fri May 22 2020
...Guidance/Predictability Assessment...
The WPC medium range Alaskan product suite was mainly derived from
a composite of reasonably well-clustered guidance from the 12Z
ECMWF/UKMET/Canadian Mon-Wed in a pattern with above average
forecast predictability. The 12Z GFS was notably quicker against a
slower trend in the rest of the guidance with the Pacific system
moving along the Aleutians next Tue-Fri. For next Thu-Fri, the 12Z
ECMWF/Canadian offered reasonable details to the 12Z GEFS/00Z
ECMWF ensemble means as the system slowly moves eastward. Over the
rest of Alaska, weak troughing over the interior will gradually
give way to rising heights as the Bering/Aleutian system passes
east of 170W. The Panhandle will have a lead system push through
the region around Tue where the 12Z GFS was a bit closer to the
larger ECMWF-led consensus but still just a bit quicker.
Thereafter, northern edge of high pressure will move into the
area.
...Weather/Hazard Highlights...
Lead and subsequent system over the Aleutians will bring rounds of
precipitation to the island chain into the AKPen and southwestern
areas, where heavy rain is possible during the week. Breezy
conditions will surround the low, which could be as strong as the
low 980s mb or so. Southerly flow later in the week along with the
triple point over the AKPen may enhance rainfall over Kodiak and
south-southeastward facing terrain.
Temperatures may stay just below average along the North Slope
with an easterly fetch over the water. Areas south of the Brooks
Range may be above average with less cloudiness and slightly above
average 850mb temperatures (>0C). Coastal areas may see below
average temperatures on cloudier/rainier days, especially over the
AKPen and Southcentral nearer to the coast.
Fracasso
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:
- Heavy precipitation across portions of southern coastal areas of
Alaska, Tue, May 19 and Thu, May 21.
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