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Alaska Drought Monitor


000
FXAK68 PAFC 271400
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
500 AM AKST Mon Jan 27 2020

.ANALYSIS AND UPPER LEVELS...

On satellite imagery there is a low spinning southwest of Shemya
with an occluded front wrapped into it. There is a 180+ knot jet
core south of the western Aleutians. Northerly flow continues over
southwest Alaska which is the result of low pressure in the Gulf
Of Alaska and high pressure over the Bering Sea. This pattern has
been persistent and has been ushering arctic air into the region
resulting in dangerously low wind chills over southwest Alaska.
The radar at Middleton Island has detected an uptick in shower
activity compared to 24 hrs ago associated with a low south of
Chenega.

&&

.MODEL DISCUSSION...

For initialization purposes compared the returns at 6z on
Middleton island radar to the projected precipitation with the
GFS/NAM/ECMWF and Canadian. The NAM did well pinging into the
precipitation near Kayak Island while the GFS had the correct
orientation of the precipitation band associated with a weak
inverted trough south of Chenega and Seward. Even the high
resolution of the ECMWF was simply too broad brushed with the
precipitation over the Gulf Of Alaska. At 6z using the cyclonic
curvature as a proxy for the location of the low, the NAM and GFS
did fairly similar with the placement of the surface low south of
Montague Island. This was seconded by the 6z ASCAT (advanced
scatterometer) pass.

Models are in decent agreement with the longwave pattern keeping
the high amplitude trough over most of the mainland/Gulf and
placing the block over the Central Bering. However, they struggle
with the placement of the surface lows even in the near term and
the the divergence amplifies handedly Tuesday as a low moves from
the north Pacific and into the Gulf Of Alaska.

&&

.AVIATION...
PANC...VFR conditions are expected at the onset of this TAF
package. There is a low south of Seward and moisture is getting
wrapped around this feature. The expectations is that cigs will
develop over the aerodrome later today but at this point the cigs
should remain above 5,000 feet until 6z on the 28th. The winds
are expected to remain relatively light.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2; Sunday
night and Tuesday)...

An upper level trough situated across mainland Alaska will keep a
strong north to south pressure gradient and gusty outflow winds
across the region. Coastal locations, including Seward, Whittier,
and Valdez will continue to see these strong winds with the
continuation of polar lows developing over the Gulf of Alaska
today. The Middleton Island radar this morning has already
indicated snow showers moving into the north Gulf coast associated
with the the first polar low, which will move inland and lead to
blizzard conditions throughout the day for Thompson Pass. Areas
near Seward and Whittier will also see blowing snow and reduced
visibilities are expected through this evening with a winter
weather advisory in effect.

Winds begin to diminish across Southcentral late Monday as the
upper level trough begins to shift westward as a North Pacific low
begins to lift northward. By Tuesday morning, this strong storm-
force low will make its way into the southern Gulf. Expect a
strong pressure gradient to redevelop over Southcentral Alaska,
which will lead to another round of gusty outflow winds through
Wednesday. Kodiak City and areas along the north Gulf coast will
be areas to keep an eye on with this next system as it could lead
to advisory level snowfall amounts.

&&

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

The primary weather story continues to be the cold temperatures
and gusty winds causing very low wind chills across Southwest
Alaska. Nearly the entire area is under mainly clear skies, but
some ocean-effect snow is impacting the Kuskokwim Delta coast and
Nunivak Island near Hooper Bay and Mekoryuk. Low stratus clouds
are moving over the area east of King Salmon as well. The mainly
clear skies and gusty north winds continue most everywhere else.
The Wind Chill Advisories remain in effect through noon on
Wednesday. The coldest wind chills will be late tonight into
Tuesday morning. A strong low moving into the Gulf late Tuesday
night into Wednesday will increase the winds, but will also bring
some cloud cover which will modestly increase temperatures. Any
precipitation will be limited to areas right along the Aleutian
and Alaska Ranges.

&&

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

A very stagnant weather pattern will persist through Wednesday
night across the Bering. Strong cold air advection on northeast
winds will keep ocean-effect snow bands continuing across the
eastern half of the Bering, and along the Alaska Peninsula and
eastern Aleutians. High pressure over the central Bering this
morning will shift westward by Tuesday morning into the western
Bering. This will allow the cold air to move further west across
the basin. Otherwise, the coldest air will continue to stream
across the eastern Bering through Wednesday night, keeping the
temperatures well below average, with ocean-effect snow causing
briefly reduced visibilities, and large areas of heavy freezing
spray across the eastern Bering.

&&

.MARINE (Days 3 through 5)...
Gulf of Alaska: The leading edge of a storm force low enters the
southern Gulf Tuesday morning, bringing ample precipitation and
easterly winds across the Gulf Tuesday evening. While there is
high confidence in the strength of the low, there is lower
confidence on exactly where the low center tracks. We are
currently expecting the low center to track east of Kodiak Island
Wednesday morning, bringing a swath of easterly storm force winds
to the waters along the northern Gulf coast Wednesday. Westerly
gales will fill in across the Gulf on the backside of the low as
it lifts northward. It is possible that these westerly gales could
reach storm force levels Wednesday night. There is high
confidence that this low pressure remains nearly stationary,
becoming reinforced with additional energy in the upper levels for
the end of the week. Waves in excess of 20 feet are expected with
this low.

Bering Sea and Aleutians: Gusty northerly flow will persist over
the eastern Bering waters midweek. Gales will become more
widespread across the Bering as a low in the Gulf strengthens and
lifts northward. Enhanced winds through the usual gaps and passes
along the Alaska Peninsula will last through Thursday. Heavy
freezing spray is expected across much of the eastern Bering
waters, and the Pacific side of the eastern Aleutians.

&&

.LONG TERM FORECAST (Days 4 through 7)...
A storm force low in the Gulf of Alaska will slowly lift
northward and inland over Southcentral Wednesday night. The
northern Gulf coast will likely see ample precipitation through
Thursday. Model solutions continue to key in on reinforcing
features in the upper levels, leading to the possibility of
prolonged precipitation over the northern Gulf coast through the
end of the week as this system is revived by an upper level wave
Thursday into Friday. The remnants of this low look to finally
exit the Gulf to the east by the weekend, as an upper level ridge
approaches from the west. Meanwhile over the Bering, cold
northerly flow is expected to continue through the end of the
week. By the weekend another low approaches the western
Aleutians, bringing unsettled conditions for the beginning of
February.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Wind Chill Advisory 155 161. Blizzard Warning 131
(T-Pass). Blowing Snow Advisory 125. MARINE...Gale 411 413 414
150 155 165 170 172 173 174 175 176 177 178 179 119 120 121 127
128 130 132 131 138 139. Heavy Freezing Spray 121 127 129 130 138
139 141 414 150 155 165 171 179 185.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...PJS
SOUTHCENTRAL ALASKA...MO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JW
MARINE/LONG TERM...KO


000
FXAK69 PAFG 271532
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
632 AM AKST Mon Jan 27 2020

.SYNOPSIS...
Highlights are:
A very cold airmass will remain over Northern Alaska for the
coming week. Very cold wind chills occuring over the Eastern North
Slope, through Brooks Range and Alaska Range passes, and along the
much of the West Coast, and over the Steese and Elliott Highway
Summits will persist through mid-week and possibly through late in
the week. Temperatures will range from 30s and 40s below over the
Western Interior and North Slope, to the teens and 20s below in
cloudy or windy areas and along the West Coast and in cloudy or
windy areas of the Eastern Interior and Eastern North Slope.
There will be pockets of 50s below in the Koyukuk Valley and the
inland North Slope where conditions are clear and not windy.

Areas of snow will move north over the Eastern Interior and
Eastern North Slope through Wed, with temps in the teens and and
20s below when it is cloudy, then dropping into the 30s and 40s
below during the brief clearing periods between clouds and snow.


Aloft...
A very deep long wave trough stretching from the North Pole south
over Alaska into the Gulf of Alaska will persist through Fri then
become progressive over the weekend as a ridge builds over the
Gulf of Alaska and Mainland Alaska. This trough has h500 heights
of less than 5000 meters of most of Northern Alaska and has
brought a very cold airmass to to most of Northern Alaska that
will persist through the end of the week, then begin to moderate
over the weekend.

A series of weak short wave troughs are making their way north
over the Eastern Interior and Eastern North Slope in the southerly
flow on the east side of the long wave trough. These short waves
will bring periods of clouds and flurries to the Eastern Interior
and Eastern North Slope through Tue, with clearing south of each
short wave.

A weak short wave that lies from Denali to Old Crow will move to
Denali to Arctic Village by 3pm mon, to McGrath to Barter Island
by 3am Tue, to Anvik to Barter Island by 3pm Tue, and then weaken
slowly. There are mid to low level clouds and light snow or
flurries along this trough that will spread slowly north and west
with the trough. Clouds will scatter south of the trough.

A second weak short wave trough in the Gulf of Alaska will move to
along the Alaska range by 3am Tue, to Minchumina to Eagle by 3pm
Tue, then merge with the first short wave on Tue night. There will
be mid level clouds and flurries with this trough with clouds
becoming scattered south of it as well.

A strong short wave trough south of the Aleutians is stretching
east and will eject significant energy into the long wave trough
on Tue, which will move to the northern Gulf of Alaska Tue night,
and over the Eastern Interior Wed into Thu. This will bring snow
and slightly warmer air to the Interior Wed and Thu.

Surface...
A 1032 mb high over the Chukchi Sea will weaken slowly through
Wed. A ridge of high pressure stretching from this high
east over the North Slope of Alaska will persist through Tue then
move north of the Arctic Coast on Wed. A low pressure trough
stretching from north of Prudhoe Bay to Atqasuk will move to
Barter Island northeast by 3pm Tue, and then dissipate.

Stratus along with patchy fog and flurries accompany the trough.
West winds 15-20 kt along the Eastern Arctic Coast are occuring
east of this trough, with the winds decreasing west of the
trough. This is causing Wind chills to 50 to 70 below in zones 203
and 204. North winds 15-30 mph blowing out of this high through
Brooks Range Passes are causing very cold winds chills along the
south slopes of the Brooks Range. This is also causing blowing
snow through passes.

A ridge of high pressure stretching from the Chukchi Sea south
over the Bering Sea will persist through Wed. A low pressure
system in the northern Gulf of Alaska will weaken slowly through
Tue. The gradient between these systems is causing north winds of
10-25 kt along the West Coast, with Capes and Points of the West
Coast having the strongest winds and coldest wind chills. This is
also causing NE winds along with blowing snow and cold winds
chills over Summits of the Elliott, Steese and Dalton Highways
south of the Yukon River. This is also causing north winds gusting
to 30 mph and cold wind chills and blowing snow through Alaska
Range Passes.

A very strong low developing in the southern Gulf of Alaska on
Tue will move to the Northern Gulf of Alaska on Wed with an
occluded front moving to the Kenai Pen to Burwash Landing by 3pm
Wed. This will spread snow to the SE Interior Wed and Wed night
and over much of the Interior on Thu. This will also enhance north
winds between the Brooks Range and Alaska Range on Wed and keep
the cold wind chills going.

&&

.DISCUSSION...
Models initialize well aloft at 00Z. Models show similar
solutions through 3pm Tue, then start to see differences on
timing and strength of strong low moving north over the Gulf of
Alaska Tue night and Wed.

850 mb temperatures range from -22C along the West Coast to -35C
over the Eastern Interior and Eastern North Slope. 850 MB temps
will remain cold into Tue, then begin to slowly increase Tue night
and Wed, with a more sharp increase on Thu.

With precip, models are similar through Tue with bands of light
precip moving north over Eastern Interior/Eastern North Slope. On
Wed the NAM and ECMF bring precip into the Eastern Interior a bit
quicker than the GFS. Given the entrenched low low cold air
over the SE Interior which will act as cold air damming against
the Alaska Range and limit downslope flow there, expect the
precip to develop more quickly as shown the the NAM and ECMF.

At the surface, models verify well at 06Z, and models show
similar solutions through 3pm Tue. After that time, the GFS
consolidates several surface low centers in the Gulf of Alaska
into one very deep center, while the NAM and ECMF maintain 2
separate centers. Given the spacial separation of the 2 low
centers on Tue, expect them to maintain as 2 separate centers into
Wed.

Bottom line is we prefer a blend of the ECMF, GFS, NAM through 3pm
Tue for clouds, precip, winds, then use a blend of the NAM and
ECMF for winds, clouds, precipitation for Tue night and Wed.
Expect model surface temperatures to have fair amount of error in
this very cold airmass, but the North Slope and Western Interior
should remain in the 30s and 40s below through Tue night, with
slight moderation Wed, while the Eastern Interior and Eastern
North Slope range from the teens and 20s below when cloudy and
snowing, to 30s to 40s below during the brief clear periods
through Wed.


Coastal Hazard Potential Days 3 and 4...None.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory for AKZ203-AKZ207-AKZ208-AKZ209-AKZ210-
AKZ212-AKZ213-AKZ214-AKZ215-AKZ217-AKZ220-AKZ221-AKZ225-AKZ226.

Wind Chill Warning for AKZ204-AKZ206.

Winter Weather Advisory for AKZ218.

Brisk Wind Advisory for PKZ210-PKZ220.

&&

$$

JB JAN 20


145
FXAK67 PAJK 271415
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
515 AM AKST Mon Jan 27 2020

.SHORT TERM...Active winter weather pattern due to spit flow
pattern in place for the AK Gulf and Panhandle. Currently a
weakening front is over the AK Panhandle tracking eastward with
shortwave moving north along the front. Over the far NE Gulf a
series of surface low pressure systems continue to rotate around
each over with precip bands pushed to the panhandle coast. Winter
Weather Advisory for Yakutat remains in effect through 6 pm Monday
evening due to these fronts. Main issue is a very strong
low/front tracking into the SE Gulf tuesday evening into
Wednesday. Still uncertainty on exact timing/track of the low and
front however what is expected are strong winds (potential storm
force), high seas (30+ ft), and heavy precipitation (rain to the
south and snow to the far north.) With this said a Winter Storm Watch
has been issued for Haines and Skagway areas with snow totals of
12 to 24 inches possible from Tuesday evening into Wednesday
afternoon.

Temperatures definitely not following a diurnal trend. As winds
shifted to the south Sunday into Sunday night temperatures rose
into the low to mid 40s. However westerly flow moved in cold air
mass that had dropped down from the AK interior into the panhandle
coast. Early Monday morning Skagway and far northern locations
were around 40 F while Sitka Hoonah, Juneau and most of the
panhandle were in the low to mid 30s. Precip for this morning,
with the exception of Yakutat, was snow/rain mix with central and
northern locations switching to mostly snow. Due to convective
nature with colder air aloft moving and the mixed precip type in
snow totals for today and tonight will be highly variable but
mostly in the 1 to 4 inch range.

Models still not handling details that well due to the split flow
pattern. Overall limited changes but for the Tuesday evening
system with 700 mb jet upward of 100 kt and surface low pressure
possible dropping down to 942 mbs the likelihood of at least
storm force winds for the Gulf and Panhandle coastal area winds
gusts near 50 to possibly 60 mph is looked better. Forecast
confidence however is still below average due to model detail
differences, but higher for overall synoptic pattern.


.LONG TERM.../Wednesday through Sunday/...The active weather
pattern appears very likely to continue in the extended range
into the weekend. The split flow pattern that is in place is
challenging in the sense that Southeast AK could experience rain
or snow, but small details that are difficult to devine in the
long term forecast are not quite available. We do know that
precipitation will likely continue to fall each day through
Saturday, and if snow does fall, it could be impactful.

Ensemble agreement is good in the overall synoptic pattern over
the Gulf of Alaska. Large upper trof will remain in place across
the western parts of AK extending over the W gulf. Early Wednesday
an upper shortwave rotating around the trof will move N across
the eastern gulf and lift across the panhandle. At the surface the
low pressure system remains and issue with a complex of multiple
waves possible as the low moves northward into the N gulf through
Wednesday. Low level temperatures will briefly warm as the front
lifts north across the panhandle early Wednesday, but colder air
is expected to wrap in behind the low and across the E gulf and
panhandle later in the day. Currently expecting this system to
provide a rain/snow mix across the Icy Strait corridor, including
Juneau, while the more impactful snowfall is likely across the N
Lynn areas including Haines and Skagway where temperatures will
likely remain near or below freezing.

Another wave will move NE out of the NPAC into the SE gulf by
Thursday morning. This system has the potential to the be an
impactful wind event where and if it makes landfall across the
panhandle. Operational models all depict a rapidly developing low,
but handle the details very differently. The placement of the low
will also determine where impactful snow will be possible
Thursday. Did increase winds to gales in the E gulf but future
work will need to be done with better consensus. By Friday, there
is more disagreement between the models, but still expect a
surface low to be churning in the N gulf through Saturday. By
Sunday there is a chance for a brief break as a ridge moves east
across the gulf and panhandle. Overall forecast confidence is
average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Storm Watch from Tuesday evening through Wednesday
afternoon for AKZ018-019.
Winter Weather Advisory until 6 PM AKST this evening for AKZ017.
MARINE...Gale Warning for PKZ051-052.
Small Craft Advisory for PKZ022-041>043-053.

&&

$$

PRB/DDH

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