National Weather Service United States Department of Commerce


367
FXAK68 PAFC 221246
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
446 AM AKDT Fri Mar 22 2019

.ANALYSIS AND UPPER LEVELS...

The longwave pattern features a high amplitude ridge that spans
from the Central Plains of the lower 48 and into the Canadian
Prairie, the Yukon Territory and the Alaskan Interior. Yesterday
the high temperature at Fairbanks was 53F. Meanwhile, the longwave
trough spans from the coast of Oregon across the Central/Eastern
Aleutians and into the northern Bering. At the surface, there is
a mature low southwest of Kodiak but the occluded front has moved
over the AKPEN and into the Gulf Of Alaska. The latest
ASCAT/advanced scatterometer data has detected gale force winds
south of the AKPEN and in portions of the northern Bering. The
radars at Middleton Island (PAIH) and Kenai (PAHG) have been very
active overnight and early this morning.

&&

.MODEL DISCUSSION...
The global models are in good agreement with the synoptic scale
features through 12z Sunday. Additionally, the GFS ensemble
members are tightly clustered with the high over Chukchi Sea, the
low south of the AKPEN and the low near Kamchatka. There are some
minor differences with the areal coverage of the precipitation
shield over Southwest AK and over portions of Cook Inlet. The
model of choice for the short term package again was the GFS. The
NAM finally came in line with the GFS so there are no major
discrepancies in the short term.

&&

.AVIATION...
PANC...The Kenai radar (PAHG) has been in precipitation mode all
night and has detected precipitation near Hope and near Susitna.
During this time, light rain has been falling at PANC and at the
WFO in Anchorage. There is precipitation falling that is below the
radar beam. Any additional rain that does fall this morning is not
expected to reduce visibilities and the ceilings will vary from
7,000 to 5,000 feet. VFR conditions and light winds at the surface will
persist. However, wind shear is possible from 12z-19z today.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Temperatures over the area will continue to be well above normal
over the next couple of days with southerly flow aloft and rather
high 500 mb heights. A vertically stacked low centered south of
Kodiak Island will slowly move towards the northwest today,
crossing the upper Alaska Peninsula this afternoon. A front
associated with this low that stretches from the Alaska Range near
Skwentna southeast across the northern Gulf will remain nearly
stationary through tonight. Winds with this front are fairly
strong, but will weaken as the parent low moves into Bristol Bay.
On Saturday afternoon the front will begin to move northward into
the Southcentral mainland as an upper level short-wave trough
slides northward. This trough and remnants of the front will then
push through Southcentral Saturday night. Snow levels will drop a
bit as the air mass behind this trough is a little colder. Surface
temperatures in the valleys, however, will remain well above
normal.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2...Fri and Sat)...
Breezy and very warm conditions will persist to end the week. This
is all courtesy of a sprawling area of low pressure that is
crawling slowly towards the south side of the Alaska Peninsula. It
should cross over somewhere near Chignik later this afternoon. It
is pushing gusty southeast winds (especially through the terrain
passes) across the entire area. It is also ushering an
unseasonably warm air mass for mid-March. High temperatures will
peak 10 to 15 degrees above normal once again today. Some showers
will be possible as this system pushes through, but nothing looks
overly heavy or organized. Just about all locations will continue
to rain (versus snow) expect for the higher mountains and the
northern tier of the YK-Delta early today.

Saturday will see the low lift north along the coast and out of
the area. The net effect will actually be to allow temperatures
(at least daytime highs) to cool a few degrees and winds to relax
a bit. Some lingering showers of rain and snow could hang on
around the coast, but most inland areas will remain dry. The
exception would be the far eastern portion of the Lower Kuskokwim
Valley where some moisture could sneak over the AK Range and
create some light snow near the Lime Village area.

Towards the end of the weekend and into early next week, attention
will shift back towards the Bering and the west coast as a few
strong fronts track towards SW AK.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2...Fri and
Sat)...
Two systems continue to be the major players for today. The first
is a bent back occlusion stretching from north to south from the
Pribilof Islands down to Dutch Harbor. The occlusion represents a
dividing line between warm air and southeast winds to the east,
and then cold and north winds to its west. Right along the
boundary, snow and blowing snow will continue this morning for the
Pribilofs down through Dutch Harbor. A Winter Weather Advisory
remains in effect for the Pribilofs. Along this boundary, gale-
force northerly winds will also persist.

Further west, another area of gales are moving towards the Western
Bering. These are associated with an occluded warm front that
should make it to Shemya this afternoon. As the precipitation
shield moves in, it should start as snow (with some limited
blowing snow possible as well) quickly transitioning to rain.
Sunday, this system will continue to trek east and take over the
Bering. The leading front will sling gale force winds across the
domain, with the possibility of some stronger west to southwest
winds following the front.

&&

.MARINE (Days 3 through 5)...

Gulf of Alaska... Expect generally benign conditions, with winds
diminishing and seas subsiding as a low in the Gulf of Alaska
fills.

Bering Sea... Confidence is high that a gale force low, with
potential will approach the western Aleutians Sunday, bringing
heavy seas and widespread gales to the central Bering and
Aleutians Monday. Some model solutions depict a swath of storm
force winds in the central Aleutians/eastern Bering Monday...while
we didn`t have the confidence to go that high with this forecast
package, the potential for storms will need to be monitored. The
low will weaken and shift northward towards eastern Siberia by
Tuesday and winds will diminish.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Wet weather will continue over Southcentral as several waves
associated with a North Pacific low rotate into the area. However,
confidence is building that dry weather is in sight for
Southcentral. Models continue to develop a longwave ridge over
Southcentral early next week. Daytime conditions will trend even
warmer than observed this week, though valley locations will
likely see cold nights driven by clear skies. The main question is
when the ridge will degrade, and model agreement is poor on that
decision. Some solutions show the ridge breaking down as early as
midweek, with a return to wetter weather following.

Looking farther west, a series of lows will move through the western
and central Bering throughout the long term, starting with a
potent low expected to approach the western Aleutians late Sunday.
With a moisture fetch almost to the tropics, expect heavy
precipitation ahead of the low. This low will be replaced by
another, much stronger (~950 mb) low moving quickly into the
Bering Mon. We will need to watch both of these systems closely
for potential coastal surf/erosion impacts as sea ice continues to
diminish along the west coast. A ridge in place over Southcentral
will likely diminish precipitation potential over the Southwest
mainland. Showers in cold air advection will persist behind the
second low in the Bering. A series of smaller lows will bring
periods of unsettled weather to the Bering and Aleutians through
next week, while conditions over the mainland will depend on the
progression of the upper ridge.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 195.
MARINE... Heavy Freezing Spray 185. Gale 351 352 119 125 130 131
132 136 137 138 150 414 413 411 170 171 172 173 174 176 177 178
179 185.

&&

$$

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



867
FXAK69 PAFG 221119
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
319 AM AKDT Fri Mar 22 2019

.DISCUSSION...
Near record warm conditions will continue over most of the
interior while ground blizzards develop this afternoon along the
North Slope Coast.

Aloft at 500 hpa, a strong ridge aloft extending from northwestern
Alaska to near Great Slave Lake will continue to hold in place
while a series of weak troughs move north and northwest through
the Bering Sea today and Saturday. A stronger shortwave will move
northeast into the central Bering Sea on Sunday and through the
Bering Strait Sunday night and Monday. The strong upper level
ridge builds back over Alaska early next week and will continue
through mid week.

On the surface a 1030 mb high pressure system north of Point
Barrow combined with a 970 mb low near Dutch Harbor will produce a
very strong pressure gradient along the coastal areas of the
North Slope this afternoon and will continue into Saturday
morning. Winds will increase rapidly this afternoon along the
coastal areas of the North Slope as high pressure builds to the
north of Point Barrow. Strong and gusty winds combined with recent
snowfall are expected to produce ground blizzard conditions
beginning this afternoon and will continue through through early
Saturday along the coastal areas of the North Slope. Blizzard
Warnings and and Winter Weather Advisories have been issued for
these areas.

In the Interior, high pressure aloft will keep conditions at or
near record warmth across the Interior through the weekend with
temperatures expected to reach into the upper 40s and lower 50s.
Some locations will nudge into the middle 50s this afternoon. The
snowpack continues to ripen nicely across the interior with no
significant hydrological issues noted at this time.

A weather front along along the Bering Strait will weaken today
as it moves north into the Chukchi Sea this evening. Expect
scattered snow showers along the West Coast today and tonight as
the front dissipates and moves to the north. A second front moves
northeast out of the Central Bering Sea into the Bering Strait,
Seward Peninsula, and lower YK Delta Sunday and will bring another
round of snow to the area. The front continues to move north with
a low that tracks just east of Wrangel Island Sunday evening.
Deep southwest flow develops along the southwest Brooks Range
Sunday afternoon and will likely produce a round of heavy snow
Sunday night and Monday morning the Western Brooks Range.

Models continue to indicate a strong storm developing in the
Central Bering Sea Monday morning with heavy precipitation moving
into the lower YK Delta, Norton Sound and the Seward Peninsula
through the day Monday. The track of the storm to the west of St
Lawrence Island will take the strongest winds well west of the
West Coast and combined with a quickly moving storm should help
minimize coastal flood concerns however Surge models continue to
indicate a rise in sea levels beginning early Sunday, though
offshore winds prior to the event should mitigate any significant
rise. Strong southerly flow ahead of the storm may still cause
elevated surf, mainly along south-facing shores. We will continue
to monitor for additional developments.


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

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning for AKZ201-AKZ203-AKZ204.

Winter Weather Advisory for AKZ202-AKZ213.

Gale Warning for PKZ210-PKZ225-PKZ230-PKZ235-PKZ240-PKZ245.

Brisk Wind Advisory for PKZ220-PKZ235-PKZ240-PKZ245.
&&

$$

CCC MAR 19



382
FXAK67 PAJK 221422
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
622 AM AKDT Fri Mar 22 2019

.SHORT TERM.../Through Sat night/ Another relatively quiet morning
across the panhandle today with clouds being the main headache.
Cloud cover has been rather chaotic overnight with periods of
overcast skies giving way to large holes of clearer skies
every now and then. There are some scattered to isolated light rain
showers and patchy fog across the northern inner channels and
north gulf coast to contend with as well. Satellite imagery
continues to show that the front across the gulf is not making any
progress toward or away from the panhandle keeping all of its
rain and wind confined to areas well offshore.

Main focus of the short range is the short wave that will be
riding north along the front that will finally push it into the
panhandle late Fri night into Sat. Rain will sweep northwest late
Fri night into Sat as the wave moves rapidly NW along the outer
coast. This system is moving so rapidly that the rain will not add
up to much before it is over. Likely amounts will be around 0.25
inches or less total. Current guidance also paints this system as
a rather potent wind maker so winds have been increased for land
and marine areas as a result. The low level jet accompanying the
wave will be on the order of 50 to 55 kt at 850 mb more then
enough for gusts of 40 to 50 mph. The southern panhandle will be
under the gun first late Fri night with the rest of the outer
coast and central inner channels seeing it early Sat morning. The
highest wind are expected to be rather short lived (3 hours or
less) at any given location given how fast and how small the
feature that is producing them is. Exact timing is a little
uncertain as some of the guidance is suggesting that the feature
could move through faster then what was previously depicted so
stay tuned for possible updates on timing.

Behind this short wave is some noticeably cooler air. Guidance is
showing lowering thickness values and 850 mb temps dropping from
above 0C to below 0C across the panhandle by Sat afternoon. High
temps for Sat and low temps for Sat night will be noticeably
cooler, but still a good 5 degrees above normal for this time of
year.

Main changes were with the short wave coming through on Fri night
and Sat with winds and some timing changes with precip. Main
guidance used was the Gfs.

.LONG TERM.../Sunday through Friday as of 10 pm Thursday/
Yet another mid to upper tropospheric blocking pattern looks to
emerge over the next week. Both the US and European ensembles are
bullish in building heights over the Gulf and northward into the
central and eastern interior of Alaska Sunday and continuing
through the work week. This will effectively prevent significant
storm systems from approaching SE Alaska.

Higher heights to our north and west will promote generally north
to northeast low level flow through the week. During the winter
months, this is typically a colder and drier pattern for the
Panhandle. GEFS and European ensemble 850mb temperature anomalies
indicate very little cold air will be able to build over NW Canada
and thus warm, dry, and pleasant weather is likely to be the rule
next week with highs in the 50s and overnight lows dropping into
the 30s.

Winds over the inside waters will generally be northerly or
northeasterly. A few more aggressive model solutions indicate the
potential for a brief late season outflow event early next week
but the lack of a true arctic airmass to the north casts some
doubts on this prospect.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind late tonight for AKZ027-028.
MARINE...Gale Warning for PKZ036-052.
Small Craft Advisory for PKZ035-041>043-051.
Small Craft Advisory due to Seas for PKZ022-053.

&&

$$

EAL/DEL

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