Winter Storm Watch 16, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
341 PM AKST Tue Dec 7 2021

.SHORT TERM...A front passing over the panhandle has caused snow
for much of the region followed by a wind shift to the SW and a
slight warm up. Winds continue to be gusty in many places and that
will keep temperatures just on the warm side of freezing this
evening, limiting accumulations somewhat. Hyder remains under an
advisory until midnight when the warm up is expected to reach
them around the same time the bulk of the precip is past.

Despite the fropa, the parent low remains over the northern gulf
west of Yakutat. This low will be the main cause of showers
continuing through Wednesday. CAA behind the front also means that
the showers will trend back to primarily snow showers.
Accumulations will be highly variable with "nice" breaks in
between. A quick couple inches is likely with some of the showers,
particularly along west facing slopes, such as the Juneau area,
both Tuesday night and Wednesday.

The northern gulf low looks to slowly weaken to a trough then
settles over the Icy Strait region on Wednesday. Location of the
trough will cause some direction adjustments for the inside
waters, ie. S-SW winds on the south side of the trough and N-NE
winds on the north side.

.LONG TERM.../Thursday morning through Sunday as of 3pm
Tuesday/...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 snowfall 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. 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.

/ Sunday to Monday / Some minor timing differences between them,
however, most model solutions are indicating that a high amplitude
long wave trough moves into the eastern gulf and SE AK. This will
allow the colder air to spill southeast to the Yukon Territory
and Northwestern British Columbia. Very cold outflow looking to
start Sunday and continue into Monday. Ensemble means are looking
at standard deviations 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. 850 Mb
temperatures look to be near -20 to -24 C.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind until 6 PM AKST this evening for AKZ018.
     Winter Weather Advisory until midnight AKST tonight for AKZ029.
MARINE...Gale Warning for PKZ041>043-052-310.
     Small Craft Advisory for PKZ012-013-021-022-033>035-051-053.

&&

Ferrin/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.

&&