Small Craft Advisory 902, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion...CORRECTED...
National Weather Service Anchorage AK
712 AM AKST Wed Nov 27 2019

.ANALYSIS AND UPPER LEVELS...

High pressure is located southwest of the far western Aleutians
and mostly benign conditions are currently seen generally west of
Unalaska. A broad upper trough encompassing much of the Bering is
bringing light westerly winds and scattered showers from the
Pribilofs westward to Saint Matthew Island. A relatively weak low
pressure system is approaching the eastern Aleutians and Alaska
Peninsula. The convergence of these two systems is leading to
southerly winds across the eastern half of the Bering/Aleutians, advecting
moisture northward. Thus, moderate rain is occurring this morning
over the Kuskokwim Delta. Cold air remains in place over
Southcentral and the Copper River Basin with a ridge centered over
the Yukon Territory. While skies are overcast closer to the
aforementioned trough, the air is too dry to currently support any
precipitation.

&&

.MODEL DISCUSSION...

Model agreement remains good over the Bering/Aleutians. The same
challenges remain with regards to the low approaching
Southcentral. The NAM still remains the warmest solution with
mostly rain for Anchorage and areas to the south. High resolution
models are beginning extend out to Wednesday evening and appear to
be on the warmer side as well. The GFS/ECMWF/Canadian models
remain colder. Confidence is above average for heavy snow in the
northern Susitna Valley as no matter which solution verifies,
temperatures will be cold enough for all snow and moisture will
be plentiful. Elsewhere, confidence is below average. A subtle
shift in the aforementioned low's position could greatly affect
precipitation type and amounts.

&&

.AVIATION...

PANC...Light winds and VFR conditions will persist through this
morning. Uncertainty remains with regards to the approaching low,
however precipitation is expected to begin this afternoon leading
to MVFR conditions as well as wind shear. Precipitation will
become heavier by evening with IFR conditions expected. This will
persist into Thursday morning along with the wind shear.

&&

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

This is a very dynamic and potentially changing weather situation
for Southcentral Alaska today through tomorrow. The key elements
are the winds, southwest flow aloft advecting in abundant
moisture, and the location of the arctic boundary over the western
Susitna Valley. The heavy snowfall in the Susitna Valley through
tomorrow is the part of the forecast with highest confidence.

The Kenai Peninsula Winter Weather Advisories both look likely to
occur, but with this system the timing and snow amounts may need
to be adjusted so be sure to keep apprised of the changing weather
situation if one is traveling on the Kenai Peninsula today through
tonight.

The winds in northern Cook Inlet, and especially around
Anchorage, are the trickiest part of the forecast. A large reason
for that is these winds will drive the temperature and precipitation
type. The biggest question with winds are whether they will remain
from the northeast or will the strong winds blowing through
Turnagain Arm be able to make it into the city? While some of the
highest resolution models are bringing in strong southeast winds to
the Anchorage Bowl this afternoon through Thursday, the synoptic
situation supports these winds turning left and heading down Cook
Inlet. Adding to the impact from this is that it looks like there is
a lot more moisture heading into Southcentral than it appeared even
yesterday. This moisture in southwest flow from 850 mb and higher is
being pumped over the colder air at the surface. Therefore, QPF
amounts were increased over the Cook Inlet region with the track
being just a little bit farther east. This brings in the potential
for some significant snowfall into Anchorage as long as it does not
turn to rain! Even if the southeast winds move into town, it looks
like they will not persist for a long period of time and then
temperatures will drop again as they move out over Cook Inlet. Rain
is more likely Wednesday evening and overnight with precipitation
type turning back to snow Thursday. All this is to say that this
could be a mainly rainy and windy event or it could turn into a
heavy snowfall in Anchorage, or periods of both, especially
depending on what part of Anchorage one is located.

&&

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

A stalled out front is acting as a railroad track for a series of
North Pacific lows that will be tracking north along it through
tonight. The stalled out front is currently over the Kuskokwim
Delta, where it has been for the past 24 hours. Cold air is inching
its way eastward towards the Kuskokwim Mountains. This has lead to
precipitation changing over to snow along the coast through Kipnuk,
with a mix of rain and snow now in Bethel. The cold air is expected
to temporarily end its advance at the Kuskokwim Mountains this
afternoon until the warm south to southeasterly winds east of the
mountains ease tonight. This will allow the cold air to continue
overspreading the area.

Meanwhile, a low currently south of Cold Bay is moving northward
along that front towards Bristol Bay this morning. Associated
rainfall has begun over much of the Bristol Bay area, and is
likely filling in across the Lower Kuskokwim Valley as well. The
rain may become heavy at times through the day for much of the
area as an unusually large amount of moisture makes its way
northward into Southwest Alaska. As mentioned above, continued
south to southeast winds over Bristol Bay and the Lower Kuskokwim
Valley are expected to help keep the precipitation as all rain
today. Thus, the Winter Weather Advisory has been cancelled. As
the full upper level trough moves into the Kuskokwim Delta
tonight, cold air will begin a full advance across the Kuskokwim
Mountains into the rest of Southwest Alaska. This cold air will be
much drier as well. As such, the precipitation is expected to end
from west to east rather quickly, with the back edge moving from
near Bethel around noon today to near Sparrevohn and Iliamna by
midnight tonight. A changeover to snow associated with the back
edge of the precipitation is possible, but accumulations will be
minor before ending. Additional lows tracking along the front will
mostly pass east of the area.

This is a large shift in the models from just 24 hours ago, whereas
a westward trend in the precipitation had been noted yesterday
morning, now all are trending right back east again. Thus, the prior
forecast of cold, mostly cloudy, but mainly dry weather has also
returned for most of Southwest Alaska for Thanksgiving. The
exception to this will be along the Alaska and Aleutian Ranges,
where the models have come into much better agreement that this will
be where the railroad track of precipitation stalls out again on
Thanksgiving Day. Exactly where the western edge of precipitation
sets up is still in question, and communities such as Iliamna,
Igiugig, and Sparrevohn will likely see some snow. Since the cold
air will be well entrenched by then, there is no doubt that the
precipitation will be in the form of snow.

On Thursday night, the models continue to suggest that the
moisture will begin moving back to the west. This would result in an
accumulating snow everywhere east of the Sleetmute to King Salmon
line. Snowfall amounts are still in question at this point, but
amounts above 6 inches overnight are within the realm of
possibility. On Friday, the rapidly weakening upper level trough
will move through, but with a continuous supply of moisture, it may
not result in a full stoppage of the snow, but it should certainly
taper in intensity through the day. Another front will move into the
Kuskokwim Delta coast Friday night, and despite it being a warm
front, at the moment it appears it will remain cold enough for a
brief period of snow for the area.

&&

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

A stalled out front over the Eastern Bering will begin moving
eastward again today, exiting into mainland Alaska by tonight.
Behind the front, a cold, Siberian air mass is producing
widespread snow shower activity over all of the rest of the
Bering, though near the Aleutians, temperatures are just warm
enough that some of that shower activity may be in the form of
rain. The showers will continue through the eastern Bering
through Thanksgiving Day. For the western Bering, a strong front
will move in during the day Thursday, producing gale force winds
and steady rain as it moves through. The front will sweep eastward
across the Bering, reaching the Pribilofs during the day on
Friday, and approaching the Kuskokwim Delta coast Friday evening.
As the front tracks across the Bering, it will be steadily
weakening, such that by the time it reaches Southwest Alaska, it
will be down to showers as far as intensity goes and the winds
will be down to small craft advisory levels. Yet another cold,
Siberian air mass follows behind this front so the area will go
back to scattered snow showers with a mix of sun and clouds.

&&

.MARINE (Days 3 through 5)...

On Friday, a storm will bring gale to storm force winds to the
Eastern Aleutians, Alaska Peninsula and Western Gulf as one low
tracks just south of the Gulf and another low to the west drives
a strong front across the Bering. A brief break between storm
systems should occur on Saturday; however, there is a fast paced
low expected to develop along the eastern Aleutians Saturday
afternoon. There is high uncertainty on the track and strength of
this system as it races toward the Gulf into Sunday.

&&

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

An active weather pattern will remain over Southcentral Thursday
night into Friday morning. A warm front associated with a low in
the Gulf combined with cold air over the region will create the
conditions favorable for a wintry mix of precipitation throughout
southern Alaska.

A strong upper level jet looks to keep a warm front associated with
the low in the Gulf over Southcentral through the early to middle
part of the weekend. This warm front will take some time to displace
the cold air that will be over the region, leading to a wintry mix
of precipitation changing over to rain in some areas by Friday
evening. A low in the eastern Bering looks to move inland late
Friday night into Saturday morning which would bring warmer
temperatures and the possibility for a wintry mix of precipitation
to southwestern Alaska. A North Pacific low late Saturday night
seems as if it will move across the Aleutians, bringing with it
ample precipitation along with some uncertainty on its track. This
low may remain over the eastern Bering Sunday night or it could make
its way into the northern Gulf towards Prince William Sound. Cold
air could move as far south as the Alaska Range Sunday night,
dropping temperatures once again, while warmer air looks to remain
south of the Range to end the extended forecast period. All in all,
the unsettled weather continues with impacts relating to
precipitation types across the entirety of the region due to warm
and cold air masses alternating as they move across the region.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Storm Warning: 145.
 		 Winter Weather Advisory: 121 125.
MARINE...Storm Warning: 150.
Gale Warning: 119 120 125 130-139 141 155 160 172 177 178 185.

&&

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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
217 PM AKST WED NOV 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0140 PM     NON-TSTM WND GST 16 NNW HOPE             61.12N 149.81W
11/27/2019  E55 MPH          ANCHORAGE          AK   PUBLIC

            CHUGACH ELECTRIC REPORTED TREES ON POWER
            LINES AROUND HUFFMAN AND OCEANVIEW AT
            1:40PM. SAID ABOUT 1,490 PEOPLE ARE WITHOUT
            POWER. HIGHEST WIND OBSERVATIONS IN THE
            GENERAL VICINITY AROUND THE TIME OF THE
            REPORT SHOWED SUSTAINED 30 MPH GUSTING TO 55
            MPH.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
218 PM AKST WED NOV 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0140 PM     NON-TSTM WND GST 16 NNW HOPE             61.12N 149.81W
11/27/2019  E55 MPH          ANCHORAGE          AK   UTILITY COMPANY

            CORRECTS PREVIOUS NON-TSTM WND GST REPORT
            FROM 16 NNW HOPE. CHUGACH ELECTRIC REPORTED
            TREES ON POWER LINES AROUND HUFFMAN AND
            OCEANVIEW AT 1:40PM. SAID ABOUT 1,490 PEOPLE
            ARE WITHOUT POWER. HIGHEST WIND OBSERVATIONS
            IN THE GENERAL VICINITY AROUND THE TIME OF
            THE REPORT SHOWED SUSTAINED 30 MPH GUSTING
            TO 55 MPH.

&&

ED

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
247 PM AKST WED NOV 27 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0243 PM     SNOW             27 NNE CHASE            62.77N 149.64W
11/27/2019  E8.0 INCH        MATANUSKA-SUSITNA  AK   PUBLIC

            SPOTTER REPORTED 8 INCHES OF SNOW IN
            CHULITNA.

&&

ED