Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 191335

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
535 AM AKDT Mon Mar 19 2018


A cold front racing eastward across Southern Alaska right now is
the primary weather maker around the area. Ahead of the front,
conditions remain relatively mild, with areas such as Anchorage,
Palmer, and points south remaining all rain early this morning.
Further north in the Susitna Valley, light snow is being reported
in Talkeetna. Behind the front, much cooler mid-level air is
racing into Southwest Alaska, bringing with it some patchy fog.
Over the Bering, a much more unstable weather regime has set up
resulting in widespread cumulus across the region. The timing of
when the cold air gets to Anchorage will be critical in
determining if morning commuters are dealing with precipitation
that is wet or white.

In the upper levels, the aforementioned surface cold front is
accompanied by a strong jet, which is the reason it is moving so
quickly. The frontal passage will result in a pattern change over
all of Southern Alaska from the warm and wet pattern with upper
level ridging that we have been experiencing, to becoming a cold
and dry one with the dominant upper level feature influencing the
area becoming a trough.



The models remain in very good agreement through the next couple
days. Diminishing forecast uncertainty remains for the rest of
this morning as to whether or not the cold air reaches
Southcentral in time to change the areas seeing rain over to snow.
Behind the front, cold air draining through all of the gaps will
result in strong gap winds, and some uncertainty remains as to how
strong the winds and gusts will get. However, with a simpler
cold, dry pattern imminent across Southern Alaska this morning,
forecast confidence is above normal.



PANC... Steady rain this morning is causing MVFR conditions. Later
this morning, a possible changeover to snow may cause brief
periods of IFR conditions, along with gusty winds. By this
afternoon, the precipitation will clear, returning conditions back
to VFR, though gusty west to southwest winds will persist into the
evening. Several days of VFR conditions are expected through much
of the upcoming workweek as the pattern turns markedly drier.


An upper level trough moving over the South Mainland will bring
continued precipitation from the Kenai Peninsula northward before
all areas quickly clear out over the course of this afternoon. The
primary forecast challenge will however be determining
precipitation type, especially around Anchorage and the Matanuska
Valley this morning. Southeasterly winds along the Chugach Range
overnight have kept temperatures warm enough to bring just rain
to the area overnight, however as this wind diminishes and cooler
air moves back into the area, this is expected to transition to a
wet snow for a few hours this morning. This will mostly likely
occur during the morning commando, which may be heavy times,
however due to the warm temperatures and short duration of the
snow most areas should see less than inch of accumulation. Further
north over the Susitna Valley temperatures have remained cold
enough for just snow, but too warm from Talkeetna southward to
bring significant accumulations. As a result the snow advisory
remains until noon today, however just for areas north of
Talkeetna. This wave will quickly race over Southcentral today,
which should allow any snow that develops to end with clearing
skies in time for the afternoon commute.

The focus then shifts to the strong pressure gradient and cold air
advection that sets up behind the upper level low, which is still
expected to bring gale force winds to most of the Gulf with strong
outflow winds along the North Gulf Coast through Tuesday. The
strongest winds are still expected to occur in the Valdez/Thompson
Pass area where gusts up to 60 mph are possible as the strongest
core of winds push through on Tuesday. Without a strong cold dome
to pull from in the Copper River Basin, there is good confidence
that these winds should remain below warning level through



There are a few lingering showers on the King Salmon radar (PAKC)
and none on the Bethel radar (PABC). The latest metars at Iliamna
and Sparrevohn have been detecting snow this morning. With an
abundance of low level moisture, patchy fog will be possible this
morning for portions of Southwest. The GFS and the NAM both ping
into another shot of moisture today for the Kuskokwim Delta but
the southern half of Southwest looks a tad drier. A dome of high
pressure will build in from the Eastern Aleutians. With widespread
subsidence in place expecting dry conditions on Tuesday and into



At the surface, the remnants of a low near St. Matthew Island will
continue to decay and drift eastward.  A dome of high pressure
will build over the North Pacific and the Aleutians resulting in a
gradual warming trend with locations along the chain getting
above 40F. A new low is developing near Kamchatka and it is
projected to hug the peninsula bringing another round of gales to
Attu Island and Shemya as well as the Western Bering. The jet core
steering this low is projected to have the strength of 130+
knots. Anticipating gusty winds and rough seas beginning Tuesday.


.LONG TERM FORECAST (Days 3 through 7)...
The long term begins with ridging dominating the southern mainland
with the axis along the west coast. This setup leads to outflow
winds along the north Gulf coast which is supported by a shortwave
moving through the area. Behind the ridging is a front over the
western Bering. Both features will track east through Saturday
when the front finally makes it over Southcentral Alaska. The
pattern will become more active following the departure of the
ridging with a new system moving into the Bering Saturday. The
models are in decent agreement through early portions of the long
term but struggle further out in time leading to ensembles being
preferred later on in the forecast period over the deterministic


PUBLIC...Winter Weather Advisory 145.
MARINE...Gales 178 185 119 120 121 127 128 130 131 132 351
352 411 412.



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