Small Craft Advisory 394, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
507 AM AKDT Sat May 9 2020

.ANALYSIS AND UPPER LEVELS...

The upper level weather pattern is a very complex over Alaska and
the Bering this morning, as the pattern buckles and eventually
reorients itself. A large vertically stacked low and associated
trough is over the far western Bering, northwest of Attu. A 135 kt
southerly jet streak represents the leading edge of this trough. A
skinny ridge is ahead of it over the Eastern Bering and Aleutians.
A second upper level low well south of Kodiak is drifting
southward away from Alaska. A larger ridge is over western North
America along the Alaska-Canada border. Broad southeasterly flow
is in place over much of mainland Alaska. Thus, Gulf moisture
continues to move into the coastal Chugach and Kenai mountains,
but any precipitation remains confined to the coast. Isolated
sprinkles and light rain are impacting a few areas of inland
Southcentral. Satellite shows widespread cloud cover overspreading
Southcentral, while the skies over nearly all of Southwest Alaska
are mostly clear. Temperatures area-wide are in the 30s and 40s,
with the largest temperature falls this morning where skies are
clear over Southwest Alaska. Cloud cover associated with the
strong jet over the central Bering is now moving into the
Kuskokwim Delta coast.

&&

.MODEL DISCUSSION...

The model agreement on the large-scale remains very good, which in
turn keeps forecast confidence high. Due to the aforementioned
complex upper level pattern, a series of shortwaves tracking
northwestward around the low and trough south of Kodiak are not
well-agreed upon in the models. The impact of that will be whether
rain impacts coastal Southwest Alaska Saturday night, and how much
rain is picked up. There is decent agreement on the track of the
shortwaves.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist. The winds will
turn out of the southeast due to the normal thermal trough
developing in the Susitna Valley this afternoon, but are not
expected to become gusty.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

A weakening occluded front over the northern Gulf drifts slowly
south today as higher pressure builds aloft over the mainland.
Clouds and rain(mainly Gulf/eastern Kenai Peninsula) will
dissipate allowing for some sunshine and warming temperatures.
Many areas inland today will see afternoon highs in the low to
mid 60s with lower 70s over the Copper River Basin and portions
of the Susitna Valley, cooler temperatures along the coast
afternoon sea breezes. As inland temperatures warm during the day
RH values will drop with some locations seeing values in the
lower 20s. Generally warm and dry conditions will continue inland
into Sunday. The Kenai Peninsula will be the exception as a weak
frontal zone, associated with broad southeasterly flow aloft,
moves north and brings clouds and increased changes of rain Sunday
through Sunday night. Winds overall will be on the light side
over the mainland through the weekend with sea breezes along the
coasts and local regimes inland. However, there will be brief
period of gusty southeast winds out of the Knik River Valley this
afternoon.

&&

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

For the most part, the weather pattern across southwest Alaska
will remain relatively quiet. An upper level shortwave associated
with a low in the Gulf moves over Southwest tonight, bringing
showers to the Bristol Bay coast. By Sunday morning, this
precipitation will spread northward, reaching the Kuskokwim Delta
coast before tapering off Sunday night. By the start of the next
workweek, a stronger upper level disturbance moves in from the
southeast, bringing increasing chances for rain across interior
locations.

&&

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

The big story out west is the large area of low pressure in place
across the western Bering. The associated front continues to move
eastward over the Pribilofs this morning bringing gusty southerly
winds before stalling over the eastern Bering this evening. On
the backside of this low, storm force winds are expected for the
western Aleutians today before they taper by the evening as the
low center lifts northward. A showery regime is expected across
the western Bering for Sunday as colder air fills in. By Monday
morning, another low approaches the western Aleutians bringing
another round of gusty southerly winds and rain to start the week.

&&

.MARINE (Days 3-5 Monday through Wednesday)...
The pattern for the first half of next week will consist of low
pressure over the Bering Sea and Aleutians, and high pressure over
mainland Alaska and the Gulf. Winds are expected to stay below
gale force, with small craft advisory winds limited to the
Aleutians and Bering.

&&

.LONG TERM FORECAST (Days 4-7 Tuesday through Friday)...
The pattern for next week will consist of a ridge over mainland
Alaska and a trough over the Bering Sea and Aleutians. The pattern
will have a negative tilt, with the interface between the ridge
and trough roughly over southwest Alaska. The main forecast
challenge is the degree to which clouds and precipitation will be
over southwest Alaska (and possibly Southcentral by Thursday
night) at that interface between the trough and ridge.
Temperatures will mostly be above normal.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Warning: 155.
		 Flood Advisory: 155.
MARINE...Storm Warning: 178.
		 Gale Warning: 131 175 177 179 185 411-414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JPW
SOUTHCENTRAL ALASKA...BC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...TM