Brisk Wind Advisory 14, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
447 PM AKST Sun Jan 26 2020

.ANALYSIS AND UPPER LEVELS...
A strong meridional pattern continues across the region as a deep
upper-level low over the western Gulf of Alaska and Kenai
Peninsula brings cold air to mainland Alaska. A strong upper-level
ridge continues to extend northwestward from the central
Aleutians to Russia. The upper-level flow is strongest over the
western mainland where the polar jet-stream is located. The
subtropical jet-stream remains south of 50N over the north Pacific
at this time. A second upper-level low remains southwest of the
Aleutians. An occluded front associated with this low currently
extends across the western Aleutians and is slowly inching
northward. This occluded front continues to bring gale force winds
to the western Bering.

Both GOES-17 visible satellite and Middleton Island radar imagery
show a surface low over the northern Gulf to the northeast of
Middleton Island. Shower activity associated with this surface low
is currently moving northwestward into the Cordova area and
eastern Prince William Sound.

Surface observations show a large temperature variation across
Southcentral ranging from about -15F to around 10F above, except
near 20 in Cordova. The strongest cold air advection is occurring
over the southwestern mainland as strong northerly winds continue
to advect arctic air into the area. Due to the cold temperatures
and strong winds, Wind Chill Advisories remain in effect through
Monday afternoon across southwestern Alaska including the villages
of Bethel and Dillingham for wind chills lower than -40F.

&&

.MODEL DISCUSSION...
Models remain in good agreement across the Bering/Aleutians and
have a good handle on the overall synoptic pattern at both the
surface and in the upper-levels. Due to this, the forecast
confidence remains high for this region.

Across the Gulf of Alaska and Southcentral, models have a good
handle and are in good agreement on the upper-level features but
have significant differences in their solutions of surface
features. Due to the strong disagreement at the surface, forecast
confidence remains low for this region.

&&

.AVIATION...
PANC...VFR conditions are expected with this TAF package. Light
snow may develop across the area late on Monday which could bring
ceilings down to below 5000ft AGL. Pressure gradients are
expected to increase which will cause an increase in the
northerly winds later this evening through tonight.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The tight north-south pressure gradients continue to funnel gusty
outflow winds across coastal Southcentral, with the strongest
winds occurring over Thompson Pass, the Valdez waterways,
Whittier, and Seward this evening. These winds will continue as a
system of complex polar lows spin up in the Gulf, keeping the
presure gradient tight.

The first of these lows is moving toward Cordova this evening and
is producing a heavy snow at times. This will move inland tonight,
with snow overspreading Thompson Pass, leading to blizzard
conditions. The second of these lows is currently in the southern
Gulf and will strengthen as it lifts northwest toward the eastern
Kenai Peninsula tomorrow. Its associated front will lift toward
Prince William Sound, helping to reinforce snow along the coast.
Snow will also spread west toward Seward and Whittier by Monday
morning, and, combined with the gusty outflow winds, will result
in reduced visibilities for these locations as well as Turnagain
Pass. The low and the front will be slow to lift inland, allowing
the strongest winds and snow to continue through late Monday.

The winds then wane Monday evening as the system lifts north and
a more southerly flow develops with lingering snow showers. This
will only be a brief respite, however, as a potent, storm-force
low then heads into the Gulf late Tuesday. The deep low pressure
system will reestablish the tight pressure gradient and ramp up
the gusty outflow winds through Wednesday. Snow and gusty winds
are also possible for Kodiak Island, as well as the immediate
Southcentral coast, by late Tuesday evening as the low and its
associated front track closer.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
The weather story remains persistent cold air for southwest
Alaska. The strong northerly to northeasterly flow keeping it cold
will persist at least through midweek. Therefore, wind chill
advisories were extended until Noon on Wednesday. These advisories
continue to be wind driven advisories. Minimum temperatures
aren't impressively cold, but gusty winds are driving apparent
temperature below -40F. The persistent nature of this pattern has
given us high forecast confidence, which is why we extended this
advisory until Wednesday. It should also be noted that areas of
gusty winds will have blowing snow. Otherwise, weather is quiet
for southwest AK.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
Cold air advection continues for the Eastern and Central Bering
Sea. Offshore flow from southwest Alaska is creating cold air
stratocumulus over water shortly after it leaves the edge of the
ice pack. Enough instability exists along the eastern Aleutians
that these clouds are producing snow showers. Blowing snow is also
expected in the Eastern Aleutians with windy conditions there.

The Western Bering continues to see strong easterly flow. Winds
will diminish in the Western Bering over the next few days, but
strong northerly flow in the Eastern Bering will persist. The
general steady-state of this pattern makes for a high confidence
level in the forecast through Wednesday.

&&

.MARINE (Days 3 through 5)...
Gulf of Alaska: The leading edge of a storm force low enters the
southern Gulf Tuesday morning, bringing ample precipitation and
easterly winds across the Gulf Tuesday evening. While there is
high confidence in the strength of the low, there is lower
confidence on exactly where the low center tracks. We are
currently expecting the low center to track east of Kodiak Island
Wednesday morning, bringing a swath of easterly storm force winds
to the waters along the northern Gulf coast Wednesday. Westerly
gales will fill in across the Gulf on the backside of the low as
it lifts northward. It is possible that these westerly gales could
reach storm force levels Wednesday night. There is high
confidence that this low pressure remains nearly stationary,
becoming reinforced with additional energy in the upper levels for
the end of the week. Waves in excess of 20 feet are expected with
this low.

Bering Sea and Aleutians: Gusty northerly flow will persist over
the eastern Bering waters midweek. Gales will become more
widespread across the Bering as a low in the Gulf strengthens and
lifts northward. Enhanced winds through the usual gaps and passes
along the Alaska Peninsula will last through Thursday. Heavy
freezing spray is expected across much of the eastern Bering
waters, and the Pacific side of the eastern Aleutians.

&&

.LONG TERM FORECAST (Days 4 through 7)...
A storm force low in the Gulf of Alaska will slowly lift
northward and inland over Southcentral Wednesday night. The
northern Gulf coast will likely see ample precipitation through
Thursday. Model solutions continue to key in on reinforcing
features in the upper levels, leading to the possibility of
prolonged precipitation over the northern Gulf coast through the
end of the week as this system is revived by an upper level wave
Thursday into Friday. The remnants of this low look to finally
exit the Gulf to the east by the weekend, as an upper level ridge
approaches from the west. Meanwhile over the Bering, cold
northerly flow is expected to continue through the end of the
week. By the weekend another low approaches the western
Aleutians, bringing unsettled conditions for the beginning of
February.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 131 (T-Pass).
 Winter Wx Advisory 125.
 Wind Chill Advisory 155 161.
MARINE...Gale Warning 127 128 130 131 139 150 155 165 170 172>178
                    180.
 Heavy Freezing Spray 121 127 129 130 138 139 141 150 155 165 170
                    171 179 185.
FIRE WEATHER...NONE.

&&

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