Small Craft Advisory 725, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
437 AM AKDT MON SEP 12 2016

.ANALYSIS AND UPPER LEVELS...
The low that has been bringing rain to much of the southern
mainland now sits over the west coast of Alaska. The gradient
between this low and ridging that extends across the eastern Gulf
through the Panhandle has brought strong winds to Southcentral
Alaska. Additionally, the shallow layer of strong southeasterly
winds moving over the Chugach Mountains in between Whittier and
Anchorage has created mountain waves over the area. Out west
another system is approaching the Western Aleutians with its front
already pushing in over the Western Aleutians.

&&

.MODEL DISCUSSION...
The models are in good agreement with the movement of the synoptic
features through the mid term. The 00Z NAM was slower than the
others with the system moving through the southern Bering in the
mid term, but the 06Z run has caught up with the pack. This good
agreement has resulted in high confidence and the use of the
higher resolution models. However, even with high confidence,
challenges remain with localized rainfall amounts and channeled
winds.

&&

.AVIATION...
PANC...Wind shear improves this morning as the flow tapers down
behind the front with gusty conditions through Tuesday morning as
the pressure gradient remains tight. The storm system to the west
will initiate showers as it moves shortwaves across the region into
Tuesday morning. A significant shortwave expected to move across
this evening is being monitored as it may produce a few
thunderstorms...however, confidence is low for this development
over the terminal and was not included with the 12Z TAF package.

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

Heavy rain continues along the North Gulf Coast and Prince William
Sound this morning in association with a strong warm front pushing
inland. Nearly five inches of rain fell near the Seward Airport in
the last 12 hours resulting in rapid rises along the Resurrection
River and Salmon Creek. For this reason, a Flood Advisory is in
effect for this area. The concern extends east to Eastern Prince
William Sound for the remainder of today as well as forecast
precipitation amounts have been trended upward with the morning's
forecast package, with 3 to 6 inches likely through today. This
will likely result in rapid rises on streams in these areas as
well. We have opted to cover this with a Special Weather Statement
this morning, and this area may require a Flood Advisory later
today.

Meanwhile, as low pressure tracks northeast across the northern
half of Alaska, the favorable south-north pressure gradient will
allow for gusty winds to continue across Southcentral Alaska
through much of today and tonight in the warm sector behind the
warm front which continues to barrel inland over Southcentral this
morning, though high winds will no longer be a concern. A
secondary trough approaches the area later today and tonight and
will bring drier and cooler air to the region by Tuesday from
west to east. This cooler and drier regime will be short- lived
before the return flow begins to weakly re-establish itself by
late Tuesday night.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The upper level trough connecting the tail of the bent back
occlusion with the remnants of the original parent low currently
stretches along the west coast of Alaska running from Saint
Lawrence to Nunivak Island and south across the Alaska Peninsula.
As this trough shifts onshore this morning, showers will increase
in coverage and intensity with the potential for isolated
thunderstorms shifting from Bristol Bay and the Alaska Peninsula
inland and into Southwest Alaska across the greater Bristol Bay
area and Kuskokwim Valley through this afternoon. Additionally, as
the trough swings inland, west to northwest winds will pick up
rather substantially over the Kuskokwim Delta this morning
through afternoon.

Ridging will build in along the coast tonight, acting to
stabilize the atmosphere from west to east and shift the winds
aloft to a somewhat drier northwesterly flow. Showers will taper
off following the same pattern from west to east overnight. Fog
will become a concern along the coast and further inland in the
recently dampened valleys as skies clear through Tuesday morning.
Generally dry weather will continue through Tuesday with clouds
from the next incoming frontal system reaching Southwest Alaska
coast late Tuesday night.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The frontal system bringing Gales and pushing into the western
Aleutians this morning will continue east...reaching the central
Aleutians and Bering tonight and the eastern Aleutians Tuesday.
The associated parent low will follow along and track to the east
just south of the western Aleutians tonight and Tuesday and then
move into the central Aleutians and southern Gulf Tuesday night.
A developing triple point/frontal wave will swing into the Alaska
Peninsula Tuesday night.

&&

.LONG TERM FORECAST (Days 3 through 7)...

The fall-like pattern looks to continue through next weekend with
a high amplitude longwave trough encompassing the Bering Sea. The
amplification of the trough will create some downstream ridging
over the Alaska mainland which should allow for a brief period of
drier, sunnier and warmer weather over parts of Southcentral and
Southwest Alaska Tuesday afternoon. However, this will be short
lived as the trough encompassing the Bering Sea will become
anchored near Adak and Atka and quickly erode the ridging
downstream. Numerous shortwaves will be forced across Alaska
through the second half of the upcoming week with abundant cloud
cover and scattered to numerous rain showers. Models hint at this
trough gradually shifting eastward over time but diverge in
deciding how quickly it does so and the orientation of the trough.
However, with pretty good certainty, it looks like there is no
clear cut end to this upcoming showery pattern and looks like fall
is here to stay.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gales 119 125 128 170 172-178 181.

&&

SYNOPSIS AND MODEL DISCUSSION...DK
AVIATION...KH
SOUTHCENTRAL ALASKA...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...MC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1229 PM AKDT MON SEP 12 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1222 PM     NON-TSTM WND DMG PALMER                  61.60N 149.11W
09/12/2016                                      AK   PUBLIC

            PUBLIC REPORTED VIA SOCIAL MEDIA IMAGES OF ROOF DAMAGE TO
            THE OLD SENIOR CENTER IN PALMER

1222 PM     NON-TSTM WND DMG EAGLE RIVER             61.32N 149.57W
09/12/2016                                      AK   PUBLIC

            PUBLIC REPORTED VIA SOCIAL MEDIA OF TREES DOWN IN THE
            EAGLEWOOD SUBDIVISION IN EAGLE RIVER

1222 PM     NON-TSTM WND DMG 2 WNW GLEN ALPS         61.11N 149.75W
09/12/2016                                      AK   NWS EMPLOYEE

            NWS EMPLOYED RELAYED PICTURES OF WIND DAMAGE INCLUDING A
            DOWNED TREE AND DAMAGED FENCING

0955 PM     NON-TSTM WND GST 1 W GLEN ALPS           61.10N 149.71W
09/11/2016  M81 MPH                             AK   MESONET

            MESONET SITE EW0989 REPORTED A GUST OF 81 MPH AT 955 PM

&&

LINGRAM