A complex low pressure system over Bristol Bay brought a warm front through the Kenai Peninsula. Cold air was entrenched throughout Southcentral from a high pressure system in the Interior.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS AFC wrote it up.
A complex low pressure system over Bristol Bay brought a warm front through the Kenai Peninsula. Cold air was entrenched throughout Southcentral from a high pressure system in the Interior. This produced overrunning, which brought heavy snow and strong winds to the Kenai Peninsula.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Anchorage, AK wrote its last area forecast discussion before the first event at Dec 30, 5:23 PM AKST, 11 hours 32 minutes earlier.
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
523 PM AKST Sat Dec 30 2017
.ANALYSIS AND UPPER LEVELS...
A pattern change is beginning over southern Alaska, transitioning
from cold and dry to warmer and wetter. There is an upper level
low over the central and eastern Aleutians that stretches
northward through the central Bering Sea. An occluded front
extends from the Kuskokwim Delta through the Pribilofs. Warm moist
air is surging northward into the western Gulf and southwest
Alaska along a fairly strong front. A triple point low is
developing south of Kodiak Island and moving northward. High
pressure is along the Canadian border, slowly retreating to the
northeast. High pressure is over the western Bering and Northeast
Russia, with northerly flow at the surface over the Bering Sea
west of the Pribilofs.
&&
.MODEL DISCUSSION...
The numerical models are in fairly good agreement through Monday
afternoon. There are still some differences in the exact location
of the triple point low moving through/near Kodiak tonight, but
timing of the front is very close. The models now agree fairly
well on the strong low that will move towards the Alaska Peninsula
on Monday, and all are within about 5mb of each other. Due to the
difficulty in predicting the transitions of precipitation type
and temperatures with the pattern change, the forecast confidence
is near normal despite good model agreement.
&&
.AVIATION...
PANC...VFR conditions will persist. Northerly winds are expected
at the surface, with strong southeasterly wind aloft. This will
give wind shear through Sunday morning, which will abate in the
afternoon as the responsible weather system moves north.
&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A strong low moving north toward the Alaska Peninsula tonight,
combined with a strong leading weather front continuing it's
journey through the Gulf will begin the transition to a more
active weather pattern for the southcentral area. Gales to storm
force winds will spread north across the Gulf marine areas through
Sunday morning. Inland areas will see increasing gap flows this
evening through Sunday night in favored locals (Turnagain Arm,
Portage Valley, Mat Valley). Winds in these areas will continue to
strengthen tonight through early Sunday morning before peaking in
the afternoon, then briefly diminishing Sunday night. The
strongest of these gap winds will be along Turnagain Arm and
Portage Valley, where winds will exceed 60 mph tonight through
early Sunday afternoon. Snow will intensify across the eastern
Kenai Peninsula tonight into Sunday afternoon, combined with
strong winds to produce some blizzard conditions from Portage
Valley through Turnagain Pass. The challenge for this area on
Sunday is if the air warms enough for the snow to change over to
rain, or a mix in Portage Valley. Currently, confidence is
slightly higher in snow persisting through Sunday afternoon, when
some rain can start to mix in with the snow as temperatures rise
from the influx of warmer winds. Either way, higher elevations
of the Seward Highway should remain mostly snow through Sunday
night.
Elsewhere, snow will likely mix with rain along the Coast, with
downsloping limiting snow west of the Chugach Range. The exception
would be upslope enhanced snow along the Alaska/Aleutian Ranges
over western Cook Inlet/Susitna Valley. Kodiak will see moderate
rain at times today and tonight until the front passes to the
north Sunday. By Monday morning, another strong front will begin
to track through the Gulf and into the northern Gulf coast/Cook
Inlet region by Monday evening, bringing another round of wet and
gusty weather to the region.
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
An active weather pattern persists through Tuesday bringing a
challenging wind and precipitation forecast. A front along the
Southwest diminishes late tonight, however gusty winds and
precipitation continue through the weekend as another strong
disturbance develops along the base of the Bering trough. This
developing system moves another surface low north across the
region on Sunday. Strong easterly flow limits the amount of
precipitation with both systems as the low centers remain track
across the eastern Bering. The upper level waves will be strong
enough to support precipitation bands which overcomes downsloping
at times. The most challenging conditions are expected across the
Kuskokwim Delta where temperatures warm considerably just off the
surface. A shallow cold pool will not be scoured out by the
up gliding air mass moving from the North Pacific. Kept the
winter weather advisory for snow and blowing snow out through
midnight, however brief white out conditions may occur tonight and
blowing snow may redevelop on Sunday.
&&
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
A broad trough along the Bering keeps active weather through
Tuesday. Cold air advection keeps precipitation mainly snow along
the western waters with a mix of rain and snow along the eastern
Chain and Alaska Peninsula as temperatures moderate in the mid 30s
to low 40s. Gale force marine winds are expected along area waters
with the strongest system tracking across the Alaska Peninsula
Monday to the eastern Bering on Tuesday.
&&
.LONG TERM FORECAST (Days 3 through 7)...
The front associated with a 960 mb low crossing the Alaska
Peninsula and moving into Bristol Bay, will lift north from the
Gulf of Alaska over southcentral Alaska Monday evening. Strong
southeasterly flow will bring abundant precipitation to the Gulf
Coastal regions and adjacent mountains particularly along east to
southeast facing slopes with both heavy rain near sea level and
snow higher up and in colder sheltered valleys potential
concerns. Additionally, the tight pressure gradient will bring
strong east to southeast winds to the typical favorably oriented
gaps and valleys as well as into the Anchorage Bowl late Monday
night through Tuesday morning, while downslope warming increases
temperatures in these windy areas into the upper 30s to low 40s.
The strong southeasterly flow will diminish through the day on
Tuesday as the surface low fills and tracks north towards to the
Kuskokwim Delta coast. An upper level trough rotating around the
south side of this low will spread cold air aloft across the
Alaska Peninsula Tuesday and into Southwest and Southcentral
Alaska Tuesday night and Wednesday. Ridging will begin building
over mainland Alaska Thursday and Friday in response to a deep low
north Pacific low crossing the central Aleutians and tracking
into the Bering. Uncertainty remains high regarding this system
but current model runs are forecasting the minimum depth of the
surface low to be around 940 mb. The associated front will reach
Southwest Alaska Friday night or Saturday then stall as it hits
the large upper level ridge. Cold westerly flow and snow showers
will prevail over the Bering in the broad upper level trough that
forms once the low lifts north, while in southcentral Alaska under
the large ridge, fog and low stratus will be the main forecast
challenge for the end of the week.
&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 125. Winter Weather Advisory 155.
MARINE...Gale 119 125 132 136-139 141 150 155 160 179-181 185.
Storm 120 130 131.
Heavy Freezing Spray 181.
&&
SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...TP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...JR1 blizzard. Local standard time, as filed.
Portage ASOS reported 12 hours of blizzard conditions. Blizzard conditions were also reported in the east end of Kachemak Bay by a spotter.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Alaska in 2017Every state in 2017This day in weather historyWarnings in Alaska, December 2017
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 727017.