Gale Warning 364, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
416 PM AKDT Sun May 10 2020

.ANALYSIS AND UPPER LEVELS...

There is an upper level ridge over eastern Alaska and an upper
level trough over the Bering Sea and Aleutians. Southeast flow
aloft is over most of southern Alaska in between these two
features. This is bringing some clouds to the area, but very
little precipitation. Temperatures are well above normal at almost
all the southern mainland locations, and winds are fairly light.
A weak front is over the eastern Bering and western Alaska
Peninsula, producing some showers by not very much wind. A
slightly stronger front is over the central Bering and Central
Aleutians.

&&

.MODEL DISCUSSION...

The numerical models are in very good agreement through Tuesday
afternoon. There are some minor differences in the handling of
moisture and precipitation with an upper level short-wave trough
that slides through southern Alaska Monday and Monday night. In
spite of this, forecast confidence is above normal.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

Clouds will increase this evening as a front moves into the Gulf.
Light rain will move south to north over the Kenai Peninsula
early Monday through Tuesday morning under the front. This will
lead to high temperatures decreasing by approximately 10 degrees
from previous days. Convection remains possible along the Alaska
Range near the Copper River Basin, however any storms would be
very isolated. Partly to mostly sunny skies and warmer
temperatures will return Tuesday and Wednesday across the region.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

Cloud cover and shower activity will decrease this afternoon and
evening across the Kuskokwim Delta and Bristol Bay as upper level
high pressure noses in from the northeast. This upper level
ridging will be short lived as a second shortwave moves in from
the southeast late tonight into early tomorrow morning. The
showers from this shortwave will be primarily in the Kuskokwim
Valley as this shortwave is moving farther inland than the
previous shortwave. As a result, clouds will increase late this
evening across the Kuskokwim Valley with showers developing
tonight. The areas in the Kuskokwim Valley that will remain the
driest will be along the foot of the Alaska Range due to
downsloping. These showers will continue through Tuesday night
before tapering off from southeast to northwest. Conditions across
Southwest Alaska will then become warmer and drier as strong
upper level ridging advances southwestward behind the shortwave
with prevailing southeasterly flow aloft.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

A weakening occluded front (cold occlusion) has become nearly
stationary over the eastern Bering/Aleutians and continues to
bring cloud cover with showers throughout that area. Colder
temperatures are located over the western and central Bering west
of the frontal boundary. Large long period swell in the northwest
Bering will continue to abate this evening and tonight. A
negatively-tilted trough will continue to extend across the
central Bering from Siberia through Tuesday morning and continue
bringing cloud cover and showers across the central Bering and
Pribilof Islands. A low pressure system will approach the western
Bering/Aleutians late Monday morning, bringing Small Craft winds
to the area. Winds will increase Monday afternoon as the low moves
closer to the area. Gale force winds are likely Monday afternoon
as forecast soundings show Gale force winds between 1000-2000ft
AGL at PASY. Due to these strong winds in the lower levels, it is
likely the boundary layer will remain coupled and allow these Gale
force winds to mix down to the surface. A GFS/NAM blend is the
preferred solution as the ECMWF still shows the deepest low while
having the lowest wind speeds.

&&

.MARINE (Days 3-5 Wednesday through Friday)...
A low south of the Aleutians on Wednesday will move east into the
Gulf of Alaska by Saturday. Currently no gales are forecast with
this low, but they are possible over the Aleutians on Wednesday
and over the Gulf by late Friday.

&&

.LONG TERM FORECAST (Days 4-7 Thursday through Sunday)...
On Thursday there sill be an upper level low centered south of the
Alaska Peninsula and an upper high north of the Bering Strait.
Southern Alaska will be in a trough that is the westward extension
of a low over northern Canada. This trough will slowly slide
westward through Sunday. There are differences amongst the models
as to how strong this trough will be and where exactly it will set
up, so increasing amounts of ensemble means were used in the
forecast blend by next weekend. Even with the trough over southern
Alaska, temperatures are still expected to be above normal.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Warning: 155.
		 Flood Advisory: 155.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...AP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
MARINE/LONG TERM...LTD