Heavy Snow in Alaska, December 8, 2021

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
628 AM AKST Wed Dec 8 2021

.SHORT TERM...Satellite imagery this morning showing gale force
low in the NE Gulf coast continuing to rotate shower bands over
the AK Panhandle. This low is now expected to track over the
central panhandle and into British Columbia while weakening.
Precipitation has been a mix of snow and rain for many locations
due to warmer airmass in place overnight from southerly flow.
Temps should drop this morning as winds shift north, mainly for
the northern areas, before rising again. Breaks between showers
will keep uncertainty in precip timing and totals. Highest QPF
over the southern panhandle as the low moves inland, thus have
accumulations to a few inches possible but the continued mix of
rain should keep totals below advisory levels.

.LONG TERM.../Thursday morning through Sunday as of 6am
Wednesday/...A second impactful system is moving a bit faster
than forecasted towards the Gulf of Alaska for Thursday evening,
bringing widespread precipitation and wind gusts. As the main
front from this system passes, expect outflow winds to begin and a
large dip in the temperatures across the panhandle.

The mid-range begins with a lull between the two systems and a
quick break in the precipitation late Thursday morning.
Widespread precipitation starts late Thursday with those areas
starting as snow and then changing to a mix of precipitation
early Friday morning. Areas to watch for over 4 inches of snowfall
from this system include Yakutat, Haines, Juneau, and Petersburg.
In fact, given greater confidence in colder air and lower
thicknesses, we went ahead and posted a watch for Upper Lynn Canal
Thursday night into Friday morning. There are outside
possibilities for greater amounts in Yakutat and Juneau, but
warmer air and a changeover to rain are more likely in these
locations, and therefore would better limit accumulations to
something more manageable. NBM ensembles also depict some meatier
totals of at least advisory levels with 4 to 8 inches possible.
Hence, we issued special weather statements to explain ranges and
scenarios. Heavy rainfall at times expected in Sitka and
Ketchikan. Winds are expected increase in the Northern Lynn,
resulting in a warm- up and a possible changeover to rain Friday.
All locations across the panhandle should change back to snow late
Friday. Eyes will then shift to Sitka, Klawock, and Ketchikan
where snowfall may start to accumulate Saturday. This is highly
dependent on the track of the low, which is of low confidence.

Winds will pick up as the front moves in and gale-force barrier
jet forms off of Yakutat Thursday. The backside of the surface
low in the Gulf will have the strongest winds with storm-force
expected, but those winds should not encroach into our forecast
domain. As this surface low moves along SE along the coast, a
strong pressure gradients will result in outflow winds, with the
strongest gusts expected in the Northern Lynn region late
Saturday.

Temperatures will influence the outcome of the week and more
details are discussed below. The forecast anticipates the highest
temperature during the mid-term to occur Friday morning. Once
areas reach the high for that day, expect a consistent decrease
in temperatures through the weekend. For example, maximum
temperatures on Sunday will barely reach freezing in the southern
half of the panhandle and the northern portion is expected to
remain in the teens.

Anchorage has noted that the GFS is depicting the low well, so
decided to lean towards that model as well. This resulted in a
change to our probability in precipitation, and thus the snow
total forecast. The forecast was also shifted about 3 hours to
accommodate the front moving in quicker. Possibilities of strong
winds on land from this system have decreased, but with lower
forecast confidence.

/ Monday to Tuesday / Very cold outflow continues into Monday.
Ensemble means are still indicating standard anomalies of around -4
for the temperatures. The coldest will be near the northern portion
of the panhandle along the border area of Klondike and Haines Highways.
Model 850 Mb temperatures for Monday are in the -20 to -24 C range.
In addition to the cold temperatures, strong outflow winds are
looking to continue into Monday morning with northerly gales
forecast for Lynn Canal as well as some of the other gap areas.
For Tuesday, the pressure gradient becomes more east-west oriented
relaxing the outflow ahead of the next system moving into the
gulf.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale Warning for PKZ041>043-051-310.
     Small Craft Advisory for PKZ012-013-022-033-035-052-053.

&&

PRB/JWA/KRT

Visit us at http://www.weather.gov/Juneau

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE JUNEAU AK
114 AM AKST WED DEC 8 2021

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

1045 AM     SNOW             6 SSE HAINES            59.15N 135.38W
12/07/2021  M7.0 INCH        PKZ012             AK   TRAINED SPOTTER

            7 INCHES OF WET SNOW AT MUD BAY, 32 DEGREES
            WITH 42 INCHES ON THE GROUND.

1000 AM     SNOW             2 W MENDENHALL VALLEY   58.37N 134.65W
12/07/2021  M3.3 INCH        PKZ031             AK   CO-OP OBSERVER

            3.3 INCHES OF NEW SNOW AT AUKE BAY OVER THE
            LAST 24 HOURS.

0800 AM     SNOW             YAKUTAT                 59.55N 139.73W
12/07/2021  M10.0 INCH       YAKUTAT            AK   TRAINED SPOTTER

            5 ADDITIONAL INCHES ON TOP OF THE 5 ALREADY
            REPORTED FOR A TOTAL OF 10 INCHES. CURRENTLY
            RAINING.

1210 PM     SNOW             PETERSBURG              56.81N 132.95W
12/07/2021  M5.0 INCH        PETERSBURG CENSUS AAK   TRAINED SPOTTER

            5 INCHES AT PETERSBURG. 31 DEGREES AND STILL
            SNOWING.

0600 AM     SNOW             1 S MENDENHALL VALLEY   58.36N 134.59W
12/07/2021  M4.5 INCH        JUNEAU             AK   PUBLIC

            REPORT OF 4 TO 5 INCHES ESTIMATED NEAR THE
            JUNEAU AIRPORT. SOCIAL MEDIA REPORT.

0630 AM     SNOW             JUNEAU                  58.31N 134.42W
12/07/2021  M3.8 INCH        JUNEAU             AK   PUBLIC

            3.8 INCHES SINCE 830 PM LAST EVENING.
            LIGHTLY SNOWING. THE PERIOD OF THE SNOW
            EVENT WAS 24 HOURS.

0700 AM     SNOW             MENDENHALL VALLEY       58.37N 134.59W
12/07/2021  M3.0 INCH        JUNEAU             AK   NWS EMPLOYEE

            3 INCHES OF NEW SNOW AT GLACIER VALLEY
            ELEMENTARY.

0755 AM     SNOW             1 SSW JUNEAU            58.29N 134.43W
12/07/2021  M5.9 INCH        JUNEAU             AK   NWS EMPLOYEE

            5.9 INCHES BETWEEN 9 PM MON AND 8 AM TUESDAY
            AT WEST JUNEAU. THE PERIOD OF THE SNOW EVENT
            WAS 24 HOURS.

0800 AM     SNOW             DOUGLAS                 58.28N 134.39W
12/07/2021  M7.0 INCH        JUNEAU             AK   NWS EMPLOYEE

            ESTIMATED 6 TO 8 INCHES OF SNOW IN DOUGLAS
            OVERNIGHT.

0800 AM     SNOW             1 S MENDENHALL VALLEY   58.36N 134.59W
12/07/2021  M3.7 INCH        JUNEAU             AK   TRAINED SPOTTER

            TOTAL SNOW NEAR VALLEY RESTAURANT.

0800 AM     SNOW             MENDENHALL VALLEY       58.37N 134.59W
12/07/2021  M4.0 INCH        JUNEAU             AK   TRAINED SPOTTER

            4 INCHES IN THE MENDENHALL VALLEY. SNOW AND
            RAIN NEAR NUGGET MALL.

0800 AM     SNOW             JUNEAU                  58.30N 134.42W
12/07/2021  M5.4 INCH        JUNEAU             AK   CO-OP OBSERVER

            5.4 INCHES 24 HOUR TOTAL AT JD WASTE WATER
            TREATMENT PLANT.

0900 AM     SNOW             3 NW JUNEAU             58.33N 134.48W
12/07/2021  M4.0 INCH        JUNEAU             AK   NWS EMPLOYEE

            ESTIMATED 3 TO 5 INCHES ON NORTH DOUGLAS.

0900 AM     SNOW             1 N MENDENHALL VALLEY   58.39N 134.59W
12/07/2021  U4.0 INCH        JUNEAU             AK   OFFICIAL NWS OBS

            4 INCHES TOTAL AS OF 9 AM AT THE JUNEAU
            FORECAST OFFICE. THE PERIOD OF THE SNOW
            EVENT WAS 24 HOURS.

0600 PM     SNOW             1 SSW JUNEAU            58.29N 134.43W
12/07/2021  M7.9 INCH        JUNEAU             AK   NWS EMPLOYEE

            EVENT TOTAL. THIS UPDATES THE PREVIOUS TOTAL
            OF 5.9 THROUGH TUE MORNING. MOST OF IT FELL
            MONDAY NIGHT INTO MID-DAY TUESDAY. A LITTLE
            RAIN MIXED IN TUESDAY AFTERNOON. THE PERIOD
            OF THE SNOW EVENT WAS 21 HOURS.

0800 AM     SNOW             PELICAN                 57.96N 136.23W
12/07/2021  M5.2 INCH        HOONAH-ANGOON      AK   CO-OP OBSERVER

            5.2 INCHES OF NEW SNOW IN THE LAST 24 HOURS
            AT PELICAN.

0900 AM     SNOW             GUSTAVUS                58.41N 135.74W
12/07/2021  M4.0 INCH        HOONAH-ANGOON      AK   TRAINED SPOTTER

            4 INCHES AT GUSTAVUS.

1000 AM     SNOW             HAINES                  59.23N 135.45W
12/07/2021  M7.1 INCH        HAINES             AK   TRAINED SPOTTER

            REPORT OF STORM TOTAL OF 7.1 INCHES SINCE
            YESTERDAY AFTERNOON AT HAINES.

1210 PM     SNOW             7 SSE HAINES            59.14N 135.37W
12/07/2021  M4.5 INCH        HAINES             AK   TRAINED SPOTTER

            STORM TOTAL AT MUD BAY. JUST STARTED RAINING
            AT 33 DEGREES AND S WIND.

&&

Special Weather Statement
National Weather Service Juneau AK
532 AM AKST Wed Dec 8 2021

AKZ017-090300-
Cape Fairweather to Cape Suckling Coastal Area-
Including the city of Yakutat
532 AM AKST Wed Dec 8 2021

...WINTER STORM POSSIBLE LATE THURSDAY AFTERNOON THROUGH EARLY
FRIDAY...

There is a possibility of significant snow developing in the
Yakutat Borough from late Thursday afternoon through early Friday
morning. Snowfall amounts could range from 3 to 7 inches depending
on how much warmer air slides into the region. The timing of
temperature rise is uncertain and therefore confidence in snowfall
accumulations is poor.

We are also studying the possibility of strong gusty winds
Thursday night. Gusts could rise to around 50 mph.

Should confidence rise in significant snowfall amounts, a winter
weather advisory or winter storm warning will be posted.

AKZ025-090300-
Juneau Borough and Northern Admiralty Island-
Including the city of Juneau
532 AM AKST Wed Dec 8 2021

...WINTER STORM POSSIBLE THURSDAY NIGHT THROUGH FRIDAY MORNING...

Another winter storm could threaten the capital city Thursday
night through Friday morning. Some scenarios present the
possibility of another 4 to 8 inches of snowfall accumulation
during this time. However, southerly winds could bring in warmer
air and a transition to rain, especially early Friday morning.
This would keep total snowfall accumulations to a more manageable
1 to 4 inches. Should confidence rise in the greater amounts and
a colder system, a winter weather advisory or a winter storm
warning will be posted. Please stay tuned to our website, NOAA
weather radio, or local media for changes to the forecast.