Small Craft Advisory 222, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
445 AM AKDT Tue Mar 14 2017

.ANALYSIS AND UPPER LEVELS...
The longwave trough is continuing to deepen over the mainland and
Gulf of Alaska this morning as it is reinforced by a trio of
shortwaves dropping southward from the arctic, the first of which
is now exiting the area south of Kodiak Island. In terms of
sensible weather the story remains very much the same as in
recent days with dry offshore flow promoting clear and cold
conditions across the bulk of the southern mainland. A tight
pressure gradient and cold air flowing out of the interior
continues to support gusty north winds across Southcentral AK,
especially through favored areas such as Valdez/Thompson Pass and
the Matanuska Valley. These winds are periodically being enhanced
by the numerous upper level waves transiting the region. A broad
surface low is spinning in place over the central gulf, bringing a
few showers to the coastal waters but keeping locations along the
north gulf coast limited to increasing mid level cloudiness as
the dry offshore flow has thus far prevented any precipitation
from reaching the ground. Out west, strong high pressure anchored
over the western Bering continues to yield benign conditions
across the region.

&&

.MODEL DISCUSSION...
Continued to utilize Hi-Res NAM guidance for the morning package
as outflow winds remain the primary short term forecast
challenge. Models remain in good synoptic agreement through the
latter half of the week as the mainland trough continues to deepen
and the Bering ridge weakens slightly but remains in control.

&&

.AVIATION...
PANC...VFR conditions and northerly winds will persist through
Wednesday morning. Increased gustiness is expected by early
afternoon as another disturbance drops southward across the Cook
Inlet region.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Colder air will continue to pour southward as a series of short-
waves drop south across the state through Wednesday. This will
lead to tightening pressure and thermal gradients which in turn
will lead to strengthening winds, especially through coastal gaps.
Expect widespread gusty winds, especially during the daytime
hours. Temperatures will show an overall downward trend, though
there will still be large swings between night-time and day-time
temperatures thanks to the long hours of sunshine.

A low complex will persist over the Gulf, with surface lows and
upper level short-waves rotating around a fairly stationary
center. Some waves will try to push onshore along the north Gulf
coast and Prince William Sound, though the strong offshore flow
and very dry low level air will limit precip chances. If any snow
does reach the ground it will be very light.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The forecast seems to be stuck on repeat. Stuck between a trough
in the Gulf and a ridge in the Bering, the mainland will continue
to see arctic air advected southward by these two systems. The
large scale pattern holds through for the next two days, producing
continued cold, clear, and windy conditions for most of the
mainland. The strongest winds will reside at higher elevations,
and around the Greater Bristol Bay region. Temperatures will
continue to creep lower, but March sun and strong northerly wind
will keep them elevated from what could be realized with current
850 mb temperatures.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
High pressure remains in control of the Bering Sea. A weak
boundary on the north/east side of the high will keep chances for
snow across the central Bering. Otherwise, the main story is gusty
winds through the Alaska Peninsula, where storm-force gusts
through bays and passes can be expected for the next couple days.

&&

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

High pressure will persist over the eastern Bering and mainland AK
on Thu. Cold air over the interior will intensify the pressure
gradient along the Gulf coast with occasional gusty outflow
conditions through channeled terrain. Impulses moving around the
Gulf low will provide coastal sections with a chance of light
snow. In the west, gusty channeled flow will persist through the
AKpen, while a small craft to gale force front with rain and snow
moves over the western and central Aleutians.

For days 4 through 7...High pressure will persist over the
northern Bering and mainland AK through the weekend. With
persistent cold air over the mainland and low pressure oscillating
around the Gulf, periods of gusty outflow winds can also be
expected. Some snow is also possible along the Gulf coast. In the
west, the front will stall over the western and central Aleutians
during the weekend, with rain and snow and some gale force winds.
The rest of the Aleutians as well as southwest AK will remain dry
through the weekend.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None
MARINE...Gale Warning 119 120 121 127 128 130 131 132 136 137 138
					  139 150
		 Heavy Freezing Spray Warning 121 127 138 139 141

&&

SYNOPSIS AND MODEL DISCUSSION...CB
AVIATION...CB
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MTL
LONG TERM...DS