Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
301 PM EDT Thu Mar 14 2019
Valid 12Z Mon Mar 18 2019 - 12Z Fri Mar 22 2019
Guidance still highlights a multi-day signal for several inches of
QPF along the southern coast of the Mainland and northern portions
of Southeast Alaska for each of a series of lows slated to lift
northward over the Gulf of Alaska. The airmass will quickly lose
moisture content farther inland however, with relatively dry
conditions expected to persist across the Interior and the North
Slope. The continuous track of storm systems across the Gulf into
southern Alaska, and the persistent deep and long fetch southerly
moisture inflow will make for a period of widespread and
occasionally heavy precipitation for many areas from southern
mainland Alaska to Southeast Alaska. Additionally, the weekend
system brings the threat of high winds to southern mainland
Alaska, particularly for coastal areas.
Confidence remains fairly high that multiples systems within the
atmospheric river will result in well above normal amounts of
precipition with daily totals averaging several inches and 5-day
totals of 10+ inches. The WPC Alaskan Days 4-8 product suite was
primarily derived from a guidance blend focusing on ensemble
means. This Alaskan WFO collaborated solution was used given the
run to run model inconsistency with the series of embedded
systems, albeit within a more predictable larger scale pattern
highlighted by aloft by a Bering Sea/Southwest Alaska mean
trough/low and an interior Alaska to western Canadian centered
ridge.
Schichtel
Bullet points from the WPC Days 3-7 Hazards chart:
https://www.wpc.ncep.noaa.gov/threats/threats.php
- Heavy precipitation across portions of the Alaska Panhandle and
southern mainland Alaska, Sun-Tue, Mar 17-Mar 19.
- High winds across portions of the Alaska Panhandle and southern
mainland Alaska, Sun-Mon, Mar 17-Mar 18.
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