Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Prognostic Meteorological Discussion (PMD)

Issued by National Weather Service (NWS)

                            
000
FXAK02 KWNH 181941
PMDAK 

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
340 PM EDT Tue Jun 18 2019

Valid 12Z Sat Jun 22 2019 - 12Z Wed Jun 26 2019

An upper level low in the Gulf of Alaska to start the medium range
period (Saturday) will shift south and eastward towards the
Western U.S. coast as upper level ridging builds across the
Peninsula into the Bering Sea and western mainland Alaska.
Meanwhile, multiple shortwave perturbations will rotate around a
broad upper level low anchored across the Kamchatka Peninsula of
Russia to the far western Aleutians. A general consensus continues
that this pattern will be slow to change through the medium range
period as ensemble means hint at a developing omega block. There
is good enough agreement between the deterministic runs of the 12z
GFS/00z ECMWF/00z CMC to warrant a majority deterministic blend
days 4 and 5. After this, increasing weighting of the ensemble
means (GEFS/ECENS) was used to mitigate the smaller less
predictable timing and detail differences. This resulted in a
forecast close to yesterdays continuity.

In terms of the sensible weather, most places across the Mainland
should be fairly warm and dry, with the best chance for showers
across the elevated terrain of southern Alaska. Increased rain
chances will be possible across parts of the central and western
Aleutians as southerly flow ahead of the broad upper level trough
advects moisture into the region and a series of surface lows move
nearby.

Santorelli


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

$$