Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
631 PM EDT Wed Sep 18 2024

Valid 12Z Sun Sep 22 2024 - 12Z Thu Sep 26 2024

...Heavy rain for portions of the Panhandle early next week...

...Overview and Guidance Evaluation/Preferences...

An active pattern will continue over the high latitudes as fall
will be in full swing. Upper pattern favors strong
ridging/positive height anomalies in the mid-latitudes north of
Hawai'i and splitting ridging over the Bering, giving way to a
deep but progressive upper low early next week. This will scrape
the Aleutians on a path toward Kodiak Island and into the Gulf of
Alaska as the upper trough axis settles over the mainland. By
later next week, northern and southern stream energy should
support another system moving across the Pacific, but models
diverge on its eventual path toward the Gulf/Panhandle.

The latest 12Z/18 models offered reasonable clustering for the
Sun-Tue period with the ensemble means. Thus, was able to blend
the GFS/ECMWF/Canadian/UKMET and deepen the progs from yesterday,
now showing a sub-980mb low nearing Kodiak by late Sun/early Mon.
Thereafter, the deterministic models diverge on the handling of
the next upstream system, though the ensemble means were actually
in good agreement with the path of a low out of the North Pacific
and toward the southern Gulf of Alaska. However, individual
ensemble members were divergent across the entire northeast
Pacific. 12Z ECMWF was perhaps closest to the ensemble mean
consensus. Over the mainland/interior, troughing will maintain
itself through the week.

...Weather/Hazards Highlights...

Main focus will be on the North Pacific system grazing the
Aleutians and tracking near Kodiak and into the Gulf of Alaska
Sun-Mon. Deep low will create a large wind field around its
circulation, but perhaps gales and not quite storm force. Future
model runs will offer more insight. Ahead of the system, strong
influx of moisture tied back to the tropics will intersect the
coast, but likely focused over the southern Panhandle into
central/southern BC. WPC has outlined much of the Panhandle for
potential hazardous heavy rain next Mon/Tue as the low/front
approach. Several inches of rain are likely over the two-day
period, especially in favored/coastal/upslope locations. The next
system may bring in another surge of moisture but it may be just
beyond the Hazard Outlook period. Elsewhere, precipitation should
be light, though perhaps some more concentrated areas of rain/snow
over the northeastern portion of the interior.

Temperatures will generally be below normal for highs and slightly
above normal for lows, owing to abundant cloud cover. Much more of
the state will see lows below freezing, creeping closer to
Southcentral/Anchorage.

Fracasso

Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

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