Area Forecast Discussion
Issued by NWS Anchorage, AK

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
508
FXAK68 PAFC 182335
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
335 PM AKDT Sun Aug 18 2019

.ANALYSIS AND UPPER LEVELS...
An Omega blocking pattern aloft continues with a amplified upper
ridge over the east-central Bering Sea with a trough either side.
A fairly pronounced short wave is dropping south across
Southcentral and is helping enhance brisk to strong dry northerly
surface winds, especially near channeled terrain and north/south
valleys. Some gusts in the 40 to 50 mph range were reported
across the Matanuska Valley, Anchorage Bowl, Valdez, and Copper
River Basin. Cooling in the low to mid levels today should keep
afternoon high temperatures a little lower than yesterday.
Although not as strong, dry northerly flow with generally fair
skies (except for cirrus) continues across Southwest Alaska.
Further west, a frontal band was evident south of the western
Aleutians. The pressure pinch between the frontal trough and ridge
to the east produced strong southeasterly winds across the
central and western Aleutians.

&&

.MODEL DISCUSSION...
Models through the short term are in fairly good agreement and
confidence is moderate to high. One area where models do differ
some is on the handling of the position of a frontal wave as the
front heads toward the eastern Aleutians Wednesday. The NAM is the
furtherest north and has the strongest winds. For now will lean
toward a further south low position and weaker wind solution.

&&

.AVIATION...
PANC...VFR conditions will prevail. Gusty northerly winds will
diminish across the airport complex overnight.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
The overall pattern has high pressure over the Bering with low
pressure to the east of mainland Alaska resulting in northerly
winds for Southcentral Alaska. A shortwave that moved through the
pattern this morning into early afternoon ramped winds back up
all around Southcentral Alaska, especially through gaps. However,
as the shortwave pushes farther to the south and the high tracks
farther west, winds will diminish through the night. This will
leave light winds for Southcentral Alaska from Monday into
Wednesday. The pattern shift will also result in temperatures
returning back to near normal. With the departure of the ridge,
the new unstable pattern will allow for afternoon showers in the
mountains Tuesday and Wednesday.

&&

.FIRE WEATHER...
Winds will begin to die down tonight, especially for the lower
elevations. This should allow temperatures to cool as a colder
air mass settles in. RH recoveries will be good in the valleys,
but could still be relatively poor over the ridge-tops above the
inversion. Monday and Tuesday will see temperatures return to near
normal as well as light winds. Tuesday will also see the return
of afternoon showers over the mountains.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
Strong upper level ridging over the eastern Gulf will shift to
the west and further offshore tonight through Monday as an upper
trough tracks south. The upper trough will cross the Bering Strait
early Monday morning to reach the Kuskokwim Delta Monday
afternoon and evening and the Bristol Bay area Monday night and
Tuesday. The trough will bring both a cooler air mass into the
area as well as a chance of precipitation. The best chances for
rain will be along the coast with scattered to isolated mountain
showers possible further inland. On Tuesday night and Wednesday
the upper level trough will sweep eastward with upper level
ridging to the west bringing drier conditions back in.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
The strong upper level ridge centered over the Bering will shift
to the northwest Monday and Monday night. A deep vertically
stacked North Pacific low will track slowly to the north with its
front reaching the west and central Aleutians Monday night and
Tuesday. A triple point low will form further south along the
frontal boundary and track to the east south of the eastern
Aleutians and Alaska Peninsula Tuesday night and Wednesday.

&&

.MARINE (Days 3 through 5: Wednesday through Friday)...
On Wednesday a surface low with a front across the western Bering
weakens into Thursday as a new low center develops south of the
Alaska Peninsula. This low will then be the focus Thursday and
Friday. There is high uncertainty in the track, strength and
timing of this system and should be monitored as it will likely
deepen quickly into a gale force system.

&&

.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...
The extended forecast beginning next Thursday continues with a
mostly dry pattern across the southern mainland...however, low
pressure will be active over the mainland and Gulf. Chances for
rain are broad brushed across the forecast area as an upper level
low near the northern Alcan border interacts with with a better
organizing system over the Gulf. To the west...a ridge slowly
builds across the western Bering Thursday through Sunday bringing
a stable air mass and low level clouds and fog with it. The
southwest mainland and eastern Bering will be under a gustier
northerly flow pattern as the pressure gradient between low
pressure to the east and ridging to the west vie for dominance.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 177 178.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...DK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
MARINE/LONG TERM...KH



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.