National Weather Service United States Department of Commerce


000
FXAK68 PAFC 161326
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
426 AM AKST Sat Nov 16 2019

.ANALYSIS AND UPPER LEVELS...

A mid-level shortwave lifting over coastal Southcentral this
morning is continuing to produce bands of showers from Prince
William Sound to Cook Inlet and north into the Mat-Su Valleys.
Temperatures across the aforementioned areas are sitting in the
lower 30s to lower 40s this morning. With temperatures at or above
freezing, the vast majority of the precipitation is falling as
rain, with a few pockets of mixed precipitation north of
Anchorage.

Over Southwest Alaska, a vertically stacked complex low over
Bristol Bay continues to produce bands of snow from King Salmon
and Iliamna west to Dillingham and Togiak. Temperatures across
the Bristol Bay region are in the mid to upper 20s. Farther north,
a northeast flow is pulling arctic air southward across the
Kuskokwim Delta and Valley where temperatures this morning range
from 0F to 10F.

The broad, cyclonic flow around the Bristol Bay low is also
continuing to drive colder air south across the Bering and the
eastern half of the Aleutian Chain. For the western half of the
chain, southeasterly winds along an occluded front is ushering in
some warmer air and rain.

&&

.MODEL DISCUSSION...

Models are in good agreement overall moving through the weekend
and into early next week. There is still some uncertainty with how
quickly the upper-level low currently over Bristol Bay tracks
east across Southcentral. The evolution of this will dictate how
much, if any, snow develops across the northern half of Cook
Inlet north to the Susitna Valley Saturday night into early
Sunday. The NAM was the outlier with regard to the 00z runs,
kicking the low east faster than other guidance, resulting less
precipitation as the bulk of the moisture exits toward the Copper
River Basin by the time the colder air moves in. The 06z run,
however, has a slower progression and is more in line with other
guidance (00z and 06z GFS). This slower trend would favor the
development of some snow with cold air advection and southwest
flow off Cook Inlet. Thus, although there is still some
uncertainty, the forecast package has trended to the slower
solutions with slightly higher PoPs and QPF, with a higher
likelihood for light snow accumulations for the Anchorage and
Mat-Su areas.

Further out in time, there is decent agreement in the long term
with two weather features bringing another surge of warmer air
back across the southern mainland by Tuesday and again Thursday.
With this influx of warmer air overriding the cold air in place
from the system this weekend, precipitation type will likely be
the biggest challenge again across a large portion of the forecast
area as we move through next week. This is highlighted more in
the long term discussion.

&&

.AVIATION...
PANC...Periodic light southerly winds early this morning will
again turn northerly around mid morning. VFR ceilings will
continue through noon, although lowering to around 4,000ft at
times as scattered showers move near the airport complex. Ceilings
and visibility will lower to MVFR through the afternoon as light
rain develops. Rain will mix with and change to snow mid to late
afternoon, continuing through the nighttime hours as winds turn
southerly again. There is the potential for IFR ceilings late
afternoon and evening during any snow fall. Conditions are
expected to improve early morning Sunday as precipitation exits
the area.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The upper low centered over southwest Alaska will move northeast
today into the area. This will bring in a colder air mass, with
850 mb temperatures over Anchorage dropping about 5 degrees C from
early this morning to late this afternoon. Dynamics near the core
of this low are pretty decent, and the flow aloft will become
southwesterly. This will bring precipitation to much of the area,
especially from Anchorage northward into the Matanuska and Susitna
valleys, as well as along the Gulf coast. Precipitation type
should switch over to snow at Anchorage by early evening, with
some accumulation expected. This system will then rapidly open up
and exit the area to the northeast by Sunday morning. The flow
aloft will remain southwesterly and thus there will still be
chances of snow through Sunday night, but chances of accumulating
snow will be low. The exception to this will over the Susitna
Valley, the Copper River basin and along the coast to the north
and east of Prince William Sound as an upper level trough crosses
Southcentral Sunday night.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Saturday
through Monday)...

A weak area of low pressure continues to spin near Bristol Bay,
with satellite and RADAR clearly depicting its center drifting
east as just comes ashore (as of 4AM AKST) near King Salmon. This
low is still producing some light snow showers for southwest
Alaska. Additionally, it did verify the winter weather advisory
for the Bristol Bay area yesterday when it caused bands of snow
to train over the area. Weather will quiet over the weekend after
the low exits to the east today. Cooling temperatures can be
expected as cold air is drawn south on the backside of the low.

The cold air moving in will drop low temperatures to around zero
for interior areas Sunday. This brief break in the weather will
give way to another low pressure system on Monday. We are taking
a look at possible blizzard conditions close to the coast late
Monday into Monday night with this system. Right now its looking
like warm, moist air will override cold air still in place at the
surface, creating snow. A stiff northeast wind will also develop
coming down the Y-K Delta, which could produce blowing snow,
depending on how strong the wind gets. If the setup is just right,
this could produce the first blizzard of the year. It should be
emphasized that we are in the beginning stages of analyzing this
scenario and right now its just a possibility. More to follow as
we take a closer look in the next day, so stay tuned and we`ll
issue advance notification if it does look like a blizzard will
occur. So for now, just something to pay attention to.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Saturday through Monday)...

Weather remains quiet in the Bering Sea. Northerly flow continues,
however snow showers associated with have tapered off. This flow
will slacken today and a pattern shift will take place tomorrow
with a low approaching the western Aleutians out of the north
Pacific. This will quickly be followed by another low taking about
the same track on Monday. Expected gale force winds, rain and
warming temperatures with these low pressure systems.


&&

.MARINE (Days 3 through 5)...

Beginning the extended period marine forecast on Monday, there
is high confidence that the Bering Sea will be in an active storm
pattern, with a 950-960 hpa storm centered over the central
Aleutians/Bering Sea with widespread gale force winds. This low
may eventually deepen to near storm force by Tuesday, but
certainty is lower as some of the energy may remain over the North
Pacific. The low will eventually weaken and exit the Bering on
Wednesday with another potential storm force low moving across the
Aleutian Chain on Thursday/Friday. Low track is uncertain, but
there is good confidence that this stormy pattern will unfold with
a strong low sometime Thu/Fri over the Aleutians, so mariners
should stay tuned for this in later forecasts.

Over the Gulf waters, Monday will begin rather quiet with sub-gale
force winds, but a series of strong gale force or possibly
stronger fronts and lows will barrage the Gulf from Monday night
through the remainder of the week as the aforementioned storm
track shifts from the Bering Sea to the Gulf.

&&

.LONG TERM FORECAST (Days 4 through 7)...

Beginning the extended period forecast on Monday evening, a new
storm cycle will be unfolding as another powerful near storm
force low moves east across the Bering Sea/Aleutians. With cold
air in place over Southcentral, and another strong warm front
moving into the Gulf of Alaska, this will set the stage for
another round of very unsettled wintery weather across the
Southern Mainland.

The first warm front plows into Southern Alaska Monday night,
driven by a powerful subtropical/polar jet stream moving into
Alaska in southwesterly flow. This will likely bring snow,
eventually turning to rain and/or freezing rain Tuesday and
Tuesday night, along with heavy snow for higher elevation passes.
The low track will be key for some inland areas on how quick they
turn to rain, but eventually, regardless of which global model you
look at, the low will eventually track far enough north by
Wednesday to erode most of the low level cold air, changing a lot
of low elevation locations to all rain (some exceptions include
the northern Susitna, Copper Basin, and Lower Kusko Valley). Right
on the heels of this first storm will be another on Thursday and
Friday, also plowing inland, although this one may not move as far
north, allowing for possible snow mixing in late week into the
weekend. Takeaway? It is going to be an active weather pattern
Monday night onwards and interested parties should be prepared for
a myriad of impacts, from heavy snow to heavy rain to possible
inland freezing rain.


&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 173-176.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...TM
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...BB
MARINE/LONG TERM...JA


000
FXAK69 PAFG 161327
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
427 AM AKST Sat Nov 16 2019

.SYNOPSIS...Gusty easterly winds will continue into Saturday
across the western Interior and west coast into Saturday. Some
light snow is expected across the southeastern Interior through
the weekend. Another round of strong winds and precipitation is
expected for the west coast by Tuesday.

.DISCUSSION... Aloft...Models in good agreement through 72 hrs.
We did a model blend for POPS and QPF over the Interior this
weekend. A closed 511 dam upper low is currently over Bristol Bay
this morning and will then track northeast across the Southern
Interior and become an open wave by Sunday morning over the
Interior. A 537 Dam high will move over eastern Russia on
Saturday. Upper level troughing will persist over the state Sunday
into Monday. Southerly flow will set up over the state on Tuesday
and an upper level low will move into the Bering Sea. Models still
differ on the placement of the low pressure system at this point.


Surface...A 1023 mb high pressure center located east of Wrangel Island
will weaken and drift westward toward Russia on Saturday. A 986
mb low pressure center over Bristol Bay will drift eastward toward
southwest Alaska Saturday then move inland Saturday evening. A 960
mb low will move into the Western Bering Sea by Tuesday morning.

Interior: A tight pressure gradient is still set up over the
Western Interior today. A wind advisory is still in effect for
zone 219 for Northeast winds 20 to 30 mph with gusts to 45 mph
over the hills and summits of the Upper Koyukuk Valley. Winds
expected to diminish this evening.

Some light snow will continue over the Central Interior today,
along a stalled frontal boundary. Up to an inch of snow is
expected for Fairbanks on Saturday. A shortwave will move from
west to east across the Interior on Sunday bringing the potential
for an additional inch of snow. On Tuesday, Chinook flow will
develop over the Southern Interior. Strong southerly gap winds
expected to develop in the Alaska Range. A front will push north
over the Interior Tuesday night into Wednesday. For areas from
Fairbanks south, the Chinook winds will limit the potential for
precipitation, although we will have to continue to monitor this
area for a wintery mix of precipitation as the front moves
through. Snow expected over the Northern Interior late Tuesday
night.

West Coast and Western Interior: Strong East to northeast
winds will continue through Saturday afternoon. Wind gusts up to
45 mph expected. Strong wind headlines are still out for much of
the coastline as well as wind advisories for zones 215 and 216.
These have been extended into Saturday afternoon. Winds will
diminish some by Sunday. Another round of strong winds and
precipitation is expected for the west coast by Tuesday.


Coastal Hazard Potential Days 3 and 4...Elevated surf is possible
for St.Lawrence Island and Diomede by mid week.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Advisory for AKZ215-AKZ216-AKZ219.

Heavy Freezing Spray Warning for PKZ200-PKZ210-PKZ220-PKZ225.

Gale Warning for PKZ200-PKZ210.

Small Craft Advisory for PKZ220.
&&

$$

JK NOV 19


000
FXAK67 PAJK 161421 CCA
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
515 AM AKST Sat Nov 16 2019

.SHORT TERM...A 980 mb low will track northeast into the
northeast gulf, just south of Yakutat, by Saturday evening. The
associated occluded front will sweep through the panhandle
Saturday, with the triple point feature south of Dixon Entrance.
Locally heavy rains this morning associated with the front, and
then diminishing some during the evening. Rainfall totals through
Saturday night are roughly 1 to 2.5 inches. A secondary wave over
the southwestern gulf Saturday morning will move east weakening
into a trough and across the southern panhandle early Sunday.
This feature will bring another minor burst of heavier rains to
the that region.

Associated with the first front is a period of Gales and Small Craft
Advisories spreading through the coastal waters of the panhandle and
southeast Gulf of Alaska. Some of the coastal areas are also
expected to gust to 40 mph for a couple of hours Saturday morning.

Southeast Alaska temperature profiles have most of the forecast area
expecting rain, although the White pass area, may see a mix of rain
and snow or a wet snow with minor accumulations near the passes
level.

Water levels around the Ketchikan area lakes and streams remain a
concern so a special Weather statement is presently in effect
regarding the near potential of flooding. We will continue to
monitor the situation in case it worsens and a product in regards
becomes necessary. Forecast confidence is average to above
average.


.LONG TERM.../Monday through Friday as of 10 PM Friday/...Little
changes were made to the longterm. Nudged winds up a little
during the Wednesday time frame with frontal passage. A wet
weather pattern is still expected through the forecast period. By
early Sunday a broad trough will be moving eastward over the gulf
and across the panhandle while a surface wave pushes across the
southern panhandle. Expect rain to transition to showers later
Sunday as cooler air aloft moves in behind the front and low
pressure lifts northeast into NW Canada. Early Monday an upper
shortwave will swing across the gulf towards the panhandle. This
will likely sustain showers continuing through Monday.

A brief break from the rain is possible Tuesday, especially across
the southern half of Southeast AK, before the next impactful
system is expected. An upper ridge will likely build across the
gulf late Monday into early Tuesday, but with a rather progressive
pattern in place, the ridge will make a quick exit into western
Canada by late Tuesday. A strong front is anticipated to develop
behind the ridge with gale force winds through the central gulf
and along the northern gulf coast Tuesday, slowly progressing
eastward through Wednesday. Ensembles and operational models show
increasing confidence of an atmospheric river event along the
northern gulf coast with a deep moisture plume lifting northward.
Much of the uncertainty will be in the timing of the event and
amounts, but good upper level dynamic supports a 24-hour period of
heavy rain along the NE gulf coast. GFS and ECMWF QPF values are
both suggesting upwards of 4 inches possible. Rain will then
slide south across the panhandle Wednesday into Thursday.
Southerly stream energy will continue to move through the gulf
through late week. More rain is anticipated Friday with strong
upper jet support and southwesterly flow. Overall forecast
confidence is above average with fairly decent clustered model
guidance.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until 3 PM AKST this afternoon for AKZ026-028.
Strong Wind until noon AKST today for AKZ023-027.
MARINE...Gale Warning for PKZ036-041-042.
Small Craft Advisory for PKZ022-031>035-043-051>053.

&&

$$

Bezenek/CC

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