Gale Warning 22, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
513 AM AKST Sun Jan 20 2019

.SHORT TERM.../Through Monday/...Satellite imagery and surface
analysis Sunday morning show the remnants of a low pressure system
spread across the southern and central panhandle. Snow is
currently being reported from Wrangell to Juneau, with rain
continuing to the south. A weak area of surface low pressure
across the eastern gulf will remain Sunday along with mid-level
onshore flow. This should keep light precipitation ongoing
throughout the day. A weak shortwave over the northern gulf will
move east over the northern panhandle Sunday night, helping to
develop more precip across the northern areas through Monday.
Precip type is expected to stay as snow through Sunday night near
and north of the Icy Strait corridor, with snow totals ranging
from 1 to 3 inches. Temperatures will slowly be warming today
across the central panhandle as a southern push makes its way
further north. This will likely drive the freezing line north of
Icy Strait by Monday afternoon.

Upper ridge will build over southeast AK early Monday followed by
strong SW'rly jet. A developing strong low pressure system will
approach the southeastern gulf by Monday evening and move towards
the outer coast late Monday night. Model agreement has improved
with the location and strength of this low, but still uncertainty
remains whether it will move towards the central or southern
coast. Currently leaning towards the more middle ground approach
of the 00z GFS. Likely the southern panhandle will be impacted by
a gale force front and heavy rain Monday night. Winds over the
northern inner channels will likely flip back to the north late
Monday with an increasing northerly gradient. Forecast confidence
is average through the short term period.

.LONG TERM.../Tuesday through Sunday as of 10 pm Saturday/...One
word description of the long range forecast: uncertain.

A reason for the uncertainty is split flow at 250 mb jet level.
Have seen major shifts in each model run, including ensembles.
Latest GFS has been showing deepest lows moving into the gulf
(resulting in stronger winds) but also had more breaks in precip
through the week.

What consensus there is indicates above average predictably with
mid level ridging over the eastern AK gulf and panhandle with
troughing to the west over the tip of the Aleutians and N Bering
Sea. Low confidence in the embedded smaller scale waves. The
interaction of these waves moving eastward and riding over the
ridge will determine practical weather. Where these waves will
track, when will they move and and how strong they are depend on
which model and model run you look at. Do expect southerly flow
with very warm air moving into the region which will mix to the
surface (850 mb temps +1-2 standard deviation above normal
resulting in temps as high as 6c) and potential for significant
QPF (most likely in the form of heavy rain) mid week.

Decided to keep with the inherited forecast with some use of
WPC/NBM and stay away from deterministic models until a more
stable pattern becomes established or at least better indication
of superior model initialization. Expect the forecast to change
as we get a better handle on the advancing waves (timing and
strength of winds and precip). However, it is unlikely that any
changes will drop temps enough for a significant snow event.
Forecast confidence is very low.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ012-013.
     Small Craft Advisory due to Seas for PKZ041-042.

&&

DDH/PRB

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JUNEAU AK
1214 PM AKST SUN JAN 20 2019

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

0840 AM     HEAVY SNOW       WRANGELL                56.47N 132.40W
01/20/2019  M5.0 INCH                           AK   CO-OP OBSERVER

            NEW SNOW TOTAL 5.0 INCHES AT WRANGELL AIRPORT

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JUNEAU AK
1218 PM AKST SUN JAN 20 2019

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

0850 AM     HEAVY SNOW       PETERSBURG              56.81N 132.96W
01/20/2019  E0.0 INCH                           AK   CO-OP OBSERVER

            NEW SNOWFALL 6.0 INCHES OVERNIGHT AND STILL SNOWING.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JUNEAU AK
1223 PM AKST SUN JAN 20 2019

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

1215 PM     HEAVY SNOW       9 SE PETERSBURG         56.72N 132.79W
01/20/2019  M0.0 INCH                           AK   TRAINED SPOTTER

            NEW SNOWFALL 3.0 INCHES TODAY. HAS CHANGED TO RAIN.

&&