Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
335 PM EDT Wed Mar 27 2019
Valid 12Z Sun Mar 31 2019 - 12Z Thu Apr 04 2019
There remains very good agreement in models and ensembles for a
strong ridge/upper high building over the mainland through the
weekend and into next week which would keep temperatures above
average for this time of the year, with a handful of daily record
highs possible. There is some question towards the end of the
period on if/how much undercutting of the ridge happens which
could bring in southerly flow and an increase in precipitation
chances by the end of the period to parts of the Peninsula and
Southern Coast. The predominant storm track through the period
will be through a region of persistent negative 500 hPa height
anomalies well south of mainland Alaska, and mostly south of the
Aleutians. Some recent model runs have shown potential for a deep
low to enter the western Bering Sea by early next week, but
solutions have shown high run-to-run variability and thus
confidence is low in this specific scenario. An upper ridge across
Alaska in a more weakened state would likely be needed to allow a
stronger system to enter the Bering, and right now the general
consensus is to keep a strong ridge in place through early next
week, with perhaps even a slight westward modulation in position.
Model consensus was sufficient during the first half of the
extended period to base the forecast on a multi-model
deterministic blend (ECMWF/GFS/CMC) during days 4-6 (Sun-Tue).
After that time, increasing weight was placed toward the ECENS and
NAEFS ensemble means to account for increasing uncertainty and
spread during days 7-8 (Wed-Thu).
Ryan
Bullet points from the WPC Days 3-7 Hazards chart can be found 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