Gale Warning 654, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED
National Weather Service Anchorage AK
728 AM AKST Thu Nov 28 2019

.ANALYSIS AND UPPER LEVELS...

A broad upper trough dominates much of the Bering/Aleutians
leading to scattered showers across much of the Chain. Farther
east, strong southerly flow aloft downstream of the trough axis is
advecting copious amounts of moisture and gusty winds into
Southcentral. As a result, blizzard conditions are being
experienced at higher elevations across the Chugach Mountains with
heavy snow as well over portions of the Mat-Su. Lower elevations
including Anchorage and the western Kenai are currently seeing
rain. Highest winds are occurring over Turnagain Arm and the
Anchorage Hillside.

&&

.MODEL DISCUSSION...

The NAM is verifying the best thus far for the current system
with regards to the placement of the warm nose as well as the
gusty winds in the Anchorage area. Other models including the
ECMWF and RGEM are somewhat catching up with GFS again too cold.
As such, the NAM remains the preferred solution in the near-term.

&&

.AVIATION...

PANC...Wind shear will gradually diminish through the morning,
likely becoming non-significant by afternoon. VFR conditions will
generally persist, however periods of MVFR are possible as rain
continues.

&&

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

Fairly broad southwesterly flow aloft combined with an extensive
baroclinic zone, a deep southerly moisture fetch extends across
Southcentral Alaska. Snowfall should remain heavy today over much of
the Susitna Valley north of Willow, but will diminish late tonight
as the mid-level southerly flow weakens and becomes more
southeasterly. Likewise, higher elevations of the Glenn Highway east
of Palmer and over Hatcher Pass should see fairly steady snow
through this afternoon, but should see values diminishing tonight as
upslope enhancement diminishes with the mid-level wind shift. Warm
temperatures south of the Susitna Valley will generally keep most of
the precipitation at lower elevations as rain today, with some snow
at higher elevations. Downslope drying will become more of a factor
west of the Chugach later today/tonight. However, coastal areas of
North Gulf/Eastern Kenai Peninsula will see fairly steady
precipitation (mainly rain at lower elevations). Visibilities should
improve across Turnagain Pass later this morning with warming
temperatures.

Winds across Turnagain Arm and Higher elevations peaked overnight.
Warning level winds should end this morning, but winds are
expected to remain fairly gusty through Friday morning.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

A large upper trough is moving east this morning, with the low
level cold front quickly racing toward the Alaska Range. Deep
later southerly flow is being tapped ahead of this trough, and
this will create a situation favorable for heavy snow as
deformation banding sets up this afternoon and persists through
Friday night. Winter weather advisories remain in effect for the
Lower Kuskokwim Valley from Sleetmute east and areas northeast of
King Salmon. 8-16" of snow are expected across these locations
(lesser amounts for Sleetmute and locations along the westward end
of this snow band). Northerly winds will increase tonight and
will also support blowing and drifting snow. Elsewhere, northerly
cold air advection will keep the remainder of southwest Alaska dry
until Friday night as a very fast moving front moves into the
coast and quickly tracks east on Saturday. This will bring light
snow accumulations mainly to the Kusko Delta before the front
rapidly weakens.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

Broad northerly flow and cold air advection will support snow
showers (mixed rain near the Aleutians) through today. The
strongest flow will be just south of the Eastern Aleutians where
off coast northerly winds will increase to storm force (50 knots)
this afternoon. Attention quickly turns to a fast moving storm
force front which is already moving into the western Bering
Sea/Aleutians as Shemya is already gusting to near 50 knots from
the southwest. This front will bring a quick shot of rain along
the front as it quickly moves east and reaches the coast by Friday
evening. It will weaken as it shifts east and will only be low
end gale force by the time it reaches the coast. Behind this front
will be widespread southwest winds with rather strong cold air
advection and snow showers impacting most of the Bering Sea Fri
night and Sat.

Uncertainty increases on Sat through Sat night as a North Pacific
low forms along the jet stream and tracks somewhere along the
Aleutians. This will likely bring rain (possibly mixed with snow
depending on track) to most of the Aleutian Chain.

&&

.MARINE (Days 3 through 5)...
On Saturday afternoon, a fast paced low is expected to develop
along the eastern Aleutians and Alaska Peninsula with small craft
to gale strength winds around the core of the system. There is
high uncertainty on the track an strength of this system as it
races northeast toward the Gulf into Sunday. This storm should
definitely be monitored as it has the potential to rapidly
develop into a storm force system which could impact the eastern
Bering to the Gulf on Monday.

&&

.LONG TERM FORECAST (Days 4 through 7)...

The active weather pattern continues over southwestern Alaska
Saturday night into Sunday morning. A warm front associated with a
low in the Gulf will maintain warmer temperatures with the
possibility for liquid precipitation in the lower elevations and a
wintry mix of precipitation at higher elevations.

A continuously amplifying upper level jet continues to steer warm
and moist air from the subtropics into the region, with small
breaks in between, accounting for the continued stormy pattern
we've seen the past few weeks. An area of low pressure in the
North Pacific Saturday night looks to moves across the Aleutians
and somewhere into the northwestern Gulf Sunday morning into
Sunday night. While forecast uncertainty about the track is
evident, this looks to bring precipitation across the Aleutians
Saturday night and into southern Alaska and then Southcentral
Sunday into Monday with a wintry mix of precipitation. Sunday
afternoon another low situated in the northwestern Bering seems as
if it will track to the southeast towards the Alaska Peninsula
with uncertainty as to landfall Monday night into Tuesday morning.
Cold air looks to fully encompass the mainland around Monday
night as we sit under an area of high pressure with temperatures
dropping and a drying trend taking over. In summary, the next
several lows continue to bring impactful weather associated with
differing precipitation types through early next week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC... High Wind Warning: 101.
	Winter Storm Warning: 145.
 Winter Weather Advisory: 111 125 152 161
MARINE...Storm Warning: 150 178.
Gale Warning: 119 120 125 131 132 138 155 172-177 181 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AP
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
MARINE/LONG TERM...KH/CK

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