Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
310 PM EDT Thu May 02 2019

Valid 12Z Mon May 06 2019 - 12Z Fri May 10 2019

A triad of upper ridging (positive height anomaly) centers will
meander around Mongolia/southern East Siberian area of Russia,
northern Greenland, and the northeastern Pacific near Haida Gwaii
next week. This favors troughing to anchor over the Bering Sea and
central Aleutians with impulses generally lifting northward while
making very slow progress eastward. The 12Z GFS and 00Z ECMWF
clustered near enough to their ensemble means to utilize a blend
of that guidance through the period. One area of contention lied
over the western Aleutians next Thu/Fri with an incoming
system--the ECMWF ensembles were farther north than the
GFS/GEFS/ECMWF but at that lead time confidence was low in
favoring one over the other. A small/compact upper low over
northern Yukon may likely stay over Canada but some
models/ensembles took either a part of most of the vorticity
westward over the North Slope and weak troughing is favored into
early next week before ridging noses northward.

With increased and sustained southerly flow next week,
precipitation and temperatures will increase over Southcentral to
the Alaska Range, focused over the the western side of Cook Inlet,
the Kenai, and into Prince William Sound. Ensembles indicate
precipitable water values to rise to 1-2 sigma above average
Mon-Tue over Southcentral and then potentially 2-3 sigma above
average Wed-Thu over southeastern Alaska and QPF values in the 2-5
inch range over favored coastal areas. Orientation of the
lower/mid-level flow and track of surface waves along the
stationary or slowly moving cold fronts will affect how much rain
(elevation snow) accumulates.


Fracasso


Bullet points from the WPC Days 3-7 Hazards chart can be found at:
<a href="https://www.wpc.ncep.noaa.gov/threats/threats.php"><u>https://www.wpc.ncep.noaa.gov/threats/threats.php</u></a>

- Heavy precipitation across portions of mainland Alaska, Tue-Wed,
May 7-May 8.


WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:

<a href="https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif"><u>https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif</u></a>
<a href="https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml"><u>https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml</u></a>
<a href="https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html"><u>https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html</u></a>