Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
600 PM EDT Wed May 15 2024

Valid 12Z Sun May 19 2024 - 12Z Thu May 23 2024

...Heavy rainfall/runoff threat for Kodiak Island and SouthCentral
Alaska Saturday...


...Guidance Evaluation and Preferences...

12 UTC GFS/ECMWF/UKMET/Canadian model pattern solutions still
offer less than stellar run to run continuity through medium range
time scales. A composite seems reasonable for this weekend, but
forecast spread increases thereafter. Opted to switch preference
to still compatible 12 UTC GEFS/ECMWF/Canadian ensemble means for
next week amid growing uncertainty. Of the models, the 12 UTC
GFS/ECMWF are in better larger scale pattern evolution agreement
with the GEFS/ECMWF/Canadian ensemble means next week to venture
for details.

...Overview and Weather/Hazards Highlights...

The southeastward digging of an amplified Arctic stream upper
trough and surface low/frontal system through the Bering Sea and
Southwest Alaska/southern Interior to the northern Gulf of Alaska
remains highlighted for this weekend. This should spread a swath
of enhanced winds and moderate rains across the broad region and
into Southeast Alaska before exiting Monday. The greatest risk of
heavier rainfall and associated runoff issues may be
Saturday/Saturday night for Kodiak Island and SouthCentral, so a
collaborated threat area is depicted on the WPC Hazards Outlook
chart linked below along with additional supporting WPC products.
The weather pattern remains unsettled into Monday over the
Mainland as upper ridging is temporarily eroded before rebounding
for through next midweek to renew warmth. However, it is a system
to monitor as an outlier 12 UTC Canadian model does not support
the rebounding of this ridge in a more progressive flow regime.
Meanwhile in most guidance, amplified upper trough and associated
and organized surface lows/frontal systems with some enhanced
winds/waves/rains remain slated to work across the northern
Pacific, Aleutians, the Bering Sea and toward Southwest Alaska
early next week. There is some opportunity for the subsequent
transfering of ample energy downstream into the Gulf of Alaska
into/through next midweek to monitor for growing predictability
and hazardous focus for the Alaskan southern tier.

Schichtel


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