Freezing Rain Advisory 1, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
434 PM AKST Mon Feb 13 2017

.ANALYSIS AND UPPER LEVELS...
There is an upper level low over the eastern Bering Sea as well as
the eastern Aleutians and western Alaska peninsula. Strong
southerly flow over the Gulf of Alaska is pushing warm and moist
air into southern Alaska. An upper level impulse is currently over
Southcentral Alaska with another over the Gulf heading rapidly
northward. On the back (west) side of the low, cold air is pouring
southward across the central Bering Sea.

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.MODEL DISCUSSION...
The numerical models are generally in good agreement for the short
term portion of the forecast (through Wednesday afternoon). The
Nam is the preferred model, which is a little slower and less
aggressive with the individual impulses moving north into
southern Alaska.

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.AVIATION...
PANC...Generally VFR conditions are expected. Some snow and rain
showers could bring conditions briefly down to MVFR through
Tuesday morning. Southerly winds should increase late Tuesday
morning.

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.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Deep southerly flow ahead of a broad trough over the Bering will
keep conditions generally wet and warm into Tuesday. As of early
this evening, downsloping from the Chugach Mountains has brought
partial clearing to much of Southcentral, however this is
expected to quickly fill in by late this evening as another
developing waves moves into the Western Gulf. Temperatures aloft
from the Anchorage sounding have warmed enough since this morning
to melt any precipitation that does fall from this next system to
liquid. Temperatures remain just below freezing around much of
Southcentral, so any there is a risk of areas of freezing rain
early this evening as temperatures slowly rise above freezing.
However, even as this occurs, slippery road surfaces may still
develop as the ground remains very cold soaked.

Further to the east, the developing wave will bring another round
of snow throughout the Gulf Coast into Tuesday morning.
Temperatures however have warmed enough, especially near the
coast, for any precipitation to fall as rain or a wet snow,
limiting any significant accumulations from falling. Along
higher elevations, especially through Turnagain Pass and Thompson
Pass, temperatures remain cold enough to support up to an
additional foot of snow into Tuesday morning.

Starting Tuesday, conditions will begin to improve from south to
north as the wave makes landfall and dissipates. This will be the
beginning of the end of the short lived warm/wet pattern change as
temperatures will begin to cool enough throughout the Gulf Coast
and Southcentral to support accumulating snow. Right now the best
chance of snow appears to be on Wednesday as yet another wave
develops in the Gulf.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The front has brought snow and strong winds to areas around the
Kuskokwim Delta and Bristol Bay. This has resulted in blizzard
conditions for the Kuskokwim Delta and snow and blowing snow for
Bristol Bay that will last until around midnight tonight when
the heavier snow will start to diminish. However, lighter snow
will persist around southwest Alaska as the main low stays near
the Alaska Peninsula into Wednesday, but there does not look to be
the combination of heavy snow and strong winds for more blowing
snow or blizzard conditions that would reduce visibility to one
half mile or less. Uncertainty remains for snowfall over southwest
Alaska, especially Tuesday, as the models differ with both timing
and intensity.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The low over the eastern Bering is bringing strong winds and snow
to the Pribilof Islands which is bringing blizzard conditions to
the islands that will last into Tuesday evening. The Eastern
Aleutians will also seeing blowing snow conditions due to the
continued strong northerly winds and snow showers, but there does
not look to be enough snow for visibilities to drop below one half
mile for any extended period of time.

Moving into Wednesday, the northerly winds and snow showers will
continue but will be diminished and should not result in
significant blowing snow. There is still some uncertainty with how
much snow will fall for the Eastern Aleutians through Tuesday as
the models are struggling with the placement of the snow bands.
This will play an important role for where the worst blowing snow
conditions will setup.

&&

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

Beginning the long term forecast Wednesday evening a closed arctic
low will be dominating the regional weather pattern. Continued
cold northerly flow will be over the Bering Sea with that cold air
wrapping all the way around the cyclone into Southcentral.
Shortwave disturbances wrapping around the low will keep snow
threats across all Southern Alaska locations including the coast.
However, the noise in the pattern is high enough where there is
low confidence on the placement of the stationary front or weak
troughs rotating toward the coast. This pattern will persist
through Monday before the trough finally weakens and moves
eastward.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 155 195.
		 Winter Weather Advisory 131 141 145 161.

MARINE...Gale 125 130 139 173 174 179 181 185.
		 Storm 119.
 		 Heavy Freezing Spray 165 179 185.

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SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...JA