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000
FXAK68 PAFC 310037
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
437 PM AKDT MON MAY 30 2016

.ANALYSIS AND UPPER LEVELS...
Near the southern mainland, two closed lows are visible in Water
Vapor satellite imagery. One is spinning along the southern gulf
and a second better organized system is over the Central Aleutians.
The Gulf low is moving an axis across the Western Alaska Range
with a line of rain stretched across eastern Bristol Bay to the
Kuskokwim Mountains. Both upper lows are nearly stationary and
pin-wheeling energy around their cores.

&&

.MODEL DISCUSSION...
Models are generally in good agreement with the transitioning pattern
into Wednesday. Not many changes were needed with the afternoon
package; the main adjustments were made for winds along the front
associated with the Aleutian storm system and to refine
precipitation and thunderstorm coverage.

&&

.FIRE WEATHER...
Diurnal convection will produce wet thunderstorms this evening as
low to mid level moisture increases along southeasterly flow. On
Tuesday, subsistence brings drier air down to the surface across
interior early in the day with the trend pushing south through
the afternoon. At the same time, an upper shortwave begins to lift
from the southern coastal areas. Thunderstorms are expected to be
wet, but if the air mass dries sooner than expected dry thunderstorms
could be possible across higher terrain surrounding the Kuskokwim
Valley.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Quieter weather is in store for the mainland with continued above
normal temperatures through midweek. Some lingering showers and
thunderstorms over the western Susitna Valley early this evening
should give way to clearing skies overnight. Tuesday will be
warmer and drier with Kodiak Island being the exception where a
front will bring steady wetting rain. Wednesday will continue the
warmer and drier trend with the chance for thunderstorm, mainly
along the Alaska Range, Talkeetna Mountains, and Copper River Basin.

The upper level disturbance that brought thunder to the area last
night is pushing into the southwest today. Lingering instability
and disturbances in the flow are helping showers early this
evening, however, the atmosphere is stabilizing quickly as upper
level heights build and subsidence increases. The next chance for
showers or thunderstorms comes on Wednesday as instability
increases and ridging aloft weakens.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The easterly wave moving over the area will bring showers and
thunderstorms through late this evening. The majority of the
thunderstorms should continue over the Kuskokwim Valley, Delta and
the higher elevations of northern Bristol Bay where the strongest
instability exists. On Tuesday, a frontal system currently moving
through the Aleutians will bring gusty winds to the Southwest
coast along with a chance of showers and thunderstorms primarily
for the Kuskokwim Delta and northern Bristol Bay, though a few
strikes over the Kuskokwim Valley can`t be ruled out. Showers and
Thunderstorms will then remain in the forecast into Wednesday as
a cold upper level trough dives southward from the interior,
especially for the Kuskokwim Valley and Alaska Range.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The low moving through the eastern Aleutians will spread Gale
force winds and rain into the eastern Bering and Pribilofs for
Tuesday before dissipating on Tuesday evening. This low will
however become nearly stationary as it dissipates near Dutch
Harbor, leaving widespread Small Craft winds and a chance of
rain for much of the area through mid-week.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Models are in agreement that Wed night into Thu a front will dive
south to the Alaska range where it slowly dissipates through Fri.
This front will be associated with showers and some thunderstorms
west and south of the Alaska Range Wed and Thu afternoons and
evenings. Otherwise showers can be expected over the rest of
mainland AK through this period. Persistent north flow across the
Bering will also bring some showers through Thu night. The day 3
forecast utilized the 12z NAM for continuity with the short term.

Beginning Thu evening the EC and Canadian hemispheric models dissipate
the front along the AK and Aleutian Ranges. A North Pacific low
begins to weaken as it approaches the Akpen. This feature
continues weakening into a separate low in the northern gulf,
which rapidly dissipates, and another near Cold Bay Sat morning.
The Cold Bay low weakens and is then reabsorbed by a third low
that remains south of the Eastern Aleutians beginning on Sunday.

This pattern will keep showers over mainland AK through the
weekend, with fairly dry conditions across the Aleutians and
Bering. When the low redevelops south of the chain on Sun, the
chance of precipitation will increase across the islands. The
forecast utilized the ensemble approach of WPC guidance which
also included the EC and Canadian models.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale Warning 138 150 155 165 170 172 179 180.
FIRE WEATHER...None.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...MTL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...DS





000
FXAK68 PAFC 301246
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
446 AM AKDT MON MAY 30 2016

.ANALYSIS AND UPPER LEVELS...

The mid-level high pressure system that has been entrenched over
the mainland for the past few days is beginning to retrograde to
the west, allowing a shift in the pattern for mainland Alaska.
Broad northerly flow on the eastern side of this high has brought
dry air and warm temperatures to the mainland over the past
several days. This is being enhanced by an upper level jet streak
that will move southward over the Southwest region. The beginning
of a series of stout easterly waves initiated showers and
thunderstorms yesterday afternoon and evening across nearly all of
Southcentral and parts of Bristol Bay in Southwest Alaska. Radar
shows that some of this shower activity has held together or
even increased through the night, given good dynamics aloft.

Further west, the pattern continues to be dominated by the upper
level high centered just north of the Bering Strait. A
strengthening low with widespread rain and gale- force winds is
approaching the Central Aleutians, but most of the Bering and Gulf
coast regions are being affected by marine stratus, as is evident
on visible satellite this morning.

&&

.MODEL DISCUSSION...
Model agreement was fairly high this morning and so confidence in
the short term forecast is high.

The stout upper disturbance over the Interior of the state will
push across Southwest Alaska today and then west across the
central Bering tonight on the south side of the upper high and
north side of the low over the Central Aleutians. This disturbance
will also leave a mid-level boundary extending back to the east
into the northern Gulf of Alaska, which will be the next wave to
impact Southcentral Tuesday. Easterly waves will continue to push
across Southcentral through mid-week, but may begin to encounter
resistance over Southwest by ridging moving in from the north.

The low reaching near the Central Aleutians later tonight will
remain nearly stationary through Tuesday night while weakening
before dropping south into the North Pacific Wednesday.

&&

.FIRE WEATHER...

Thunderstorm coverage will be the big question today as easterly
waves move across Southwest Alaska. The most likely areas to see
at least a storm or two are from the Copper River Basin west to
the Kuskokwim Delta, including the Susitna Valley, western Kenai
Peninsula, Alaska Range, and Middle Kuskokwim Valley. For now have
opted to go no higher than an LAL of 2 but there is potential for
some areas to see a little more organized coverage. Temperatures
and humidity values will moderate a bit from over the weekend with
the lack of strong northerly flow over the state.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

Unstable air will remain over most of south central Alaska today
as the upper level low and associated strong short-wave slowly
slide west. It will be a little more stable today than it was on
Sunday, but some thunderstorms are still possible...mainly over
the Copper River and Susitna valleys. Conditions will stabilize
tonight as the upper low moves into southwest Alaska and the ridge
to the north nudges into the area. The area will then settle into
a pattern with a ridge to the north and a trough to the south for
Tuesday and Tuesday night. This will keep things mainly dry,
except for some diurnal convection over the mountains and some
showers along the eastern Kenai peninsula.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...

A set of easterly waves pushing through today will bring showers
and a few thunderstorms to areas from the Alaska Range west
through the Kuskokwim Delta this afternoon and evening.
Afterwards, broad cyclonic flow aloft on Tuesday will keep a
chance of showers to the Kuskokwim Delta and Bristol Bay, while
sunny and warm weather begins to return to the Kuskokwim Valley.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

The gale-force low moving through the Aleutians will bring gusty
winds and rain to the region through Monday when it will begin to
dissipate over the Southern Bering through mid-week. To the west
of this low, northerly flow and cold air advection will allow for
persistent fog/stratus that has developed over the western
Bering/Aleutians to begin to diminish.

&&

.LONG TERM FORECAST (Tuesday through Saturday)...

The pattern heading into the middle of the week shifts toward
low pressure across the Gulf and ridging to the west. The Bering
will trend toward a drier and more stable environment from mid-week
into next weekend. Meanwhile, low pressure across the gulf advects
moisture across the southern mainland through the end of the week
bringing increased cloud cover and rain chances. After a
relatively dry Wednesday, a deformation zone sets up near the
Alaska range as another low pressure system digs toward the
eastern Beaufort sea coast on Thursday. This combined with several
upper level shortwaves moving around systems will initiate
convective diurnal showers through the weekend. Models are in good
agreement on this synoptic change, however, there are differences
in handling multiple upper level disturbances from the two
dominant lows. The NAM was used to handle the transition into
Wednesday and then switched to the ECMWF along with some of the
06Z GEFS MEAN in the extended range, which provided the best
consistency.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gales...165 170 172-175.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CC
LONG TERM...KH/CC





000
FXAK68 PAFC 300051
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
451 PM AKDT SUN MAY 29 2016

.ANALYSIS AND UPPER LEVELS...
The high pressure system that has been entrenched over the
mainland for the past few days is beginning to retrograde to the
west, allowing a shift in the pattern for mainland Alaska. Broad
northerly flow on the eastern side of this high has brought dry
air and warm temperatures to the mainland over the past several
days. Today, this is being enhanced by an upper level jet streak
that will move southward over the southcentral region. As the day
continues, winds have already started mixing down with gusty
winds ramping up in the Susitna Valley. This should bring down
dry air from aloft as well. Although the RH values are already low
at the surface there is a significant dry layer just above 700 mb,
as seen on this morning`s sounding from Anchorage. Mixing this dry
air down should continue dry conditions around the region.

A second feature of interest this morning is a trough moving in
from the east behind the high as it continues to retrograde. This
trough is expected to pick up what little mid level moisture is
available, and combined with the upper level instability generated
by the jet streak, lead to development of thunderstorms as the
trough moves westward. Satellite shows convective activity
already this morning and a few early lightning strikes near the
Al-Can border indicate that the instability is definitely there.

Further west the pattern continues to be dominated by the upper
level high. An upper level low just south of the Aleutians will
bring precipitation to the central Aleutians today, but most of
the Bering and the west coast is currently being affected by
marine stratus, as is evident on visible satellite this morning.
As the high shifts westward, flow should be transitioning to
offshore, pushing the remaining fog in the Kuskokwim Delta out
to the Bering Sea. Once this happens, conditions will dry out
significantly.

&&

.MODEL DISCUSSION...
Model agreement was fairly high this morning and so confidence
in the short term forecast is high, except for the lingering fog
along the Kuskokwim coast, which was not handled well by any
model. The NAM was chosen for detail resolution in the short term.
By the Tuesday time frame, models begin to diverge on the
solution of the Aleutian low and confidence in the forecast
decreases.

&&

.FIRE WEATHER...
Winds and dry air mixing down from aloft and thunderstorms are the
two main fire weather concerns for today. As mentioned, winds are
already kicking up in the Susitna Valley, and the Kuskokwim Valley
is also seeing near Red Flag conditions this morning. The struggle
will be along the Kuskokwim coast where fog has taken more of a
stronghold than expected this morning. Winds are expected to
become more offshore with the upper level support in the
afternoon, but the question still remains as to whether that will
happen in time to reach Red Flag criteria this afternoon and
evening. Best chances for that occurring are in the eastern side
of the zone, where skies remained clear this morning.

As for the thunderstorms, conditions look good for the approaching
shortwave to kick off storms in the Talkeetnas and possibly down
along the Kenai as well. This wave will move westward into the
Kuskokwim Valley tomorrow, bringing widely scattered thunderstorms
to that region. For today, the layer of dry air close to the
surface brings a risk that a few thunderstorms in the Southcentral
region may be dry, although they will be isolated. As this trough
pushes westward, the upper level flow will change to be more
southerly, bringing more moisture in and lowering the risk for dry
thunderstorms in any location tomorrow.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Thunderstorms are popping up around the area this evening, while
slightly cooler conditions are expected through midweek. Scattered
to numerous showers are blossoming mainly along the Chugach and
Copper River Basin this evening while isolated lightning strikes
are showing up as well. These conditions will hold through the
evening before tapering off overnight. On Monday most of the
shower activity will be confined to the Kenai Peninsula in the
morning. As the system that produced these showers exits, a
slightly cooler air mass will come in behind it and will bring
cooler but still above normal temperatures to the mainland with
no precipitation forecast.

A weakening jet aloft combined with a shortwave trough and modest
instability is forcing showers and thunderstorms across the area.
Most of this activity is scattered in nature except for the
leading edge of the wave, over the Kenai Mountains, which is
producing quite a few lighting strikes. This trough will sit over
the southern Kenai Monday before exiting. The air mass behind the
exiting disturbance is much more stable though small pockets of
instability will exist over the terrain.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Ridging will continue to bring sunny and warm conditions to the
southwest mainland this evening, while a developing surface trough
will bring increasing offshore flow to the Kuskokwim River and
Delta. Over Bristol Bay, this trough will bring onshore flow to
most of the area, while weak instability will produce showers or
even a few cracks of thunder along the Alaska Range this evening.
As this onshore flow diminishes with clearing skies tonight,
patchy fog may develop for a few hours overnight for the low
lying areas of Bristol Bay.

An easterly wave will then push overhead on Monday, bringing
showers and a chance of thunderstorms to the Alaska Range for the
afternoon, which will then move westward into the Kuskokwim Valley
and Delta for the late afternoon and evening hours. Afterwards,
broad cyclonic flow aloft on Tuesday will maintain a chance of
showers for the Kuskokwim Delta and Bristol Bay, while sunny and
warm weather begins to return to the Kuskokwim Valley.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The gale force low moving through the Aleutians will bring gusty
winds and rain to the region through Monday when it will begin to
dissipate over the Southern Bering. To the west of this low,
northerly flow and cold air advection will allow for persistent
fog/stratus that has developed over the western Bering/Aleutians
to begin to diminish.

&&

.LONG TERM FORECAST (Tuesday through Saturday)...
The pattern heading into the middle of the week shifts toward
dominating low pressure across the gulf and ridging to the west.
The Bering will trend toward a drier and more stable environment
from mid week into next weekend. Meanwhile, low pressure across
the gulf advects moisture across the southern mainland through the
end of the week bringing increased cloud cover and rain chances.
After a relatively dry Wednesday, a deformation zone sets up near
the Alaska range as another low pressure system digs toward the
eastern Beaufort sea coast on Thursday. This combined with several
upper level shortwaves moving around systems will initiate convective
diurnal showers through the weekend. Models are in good agreement
on this synoptic change, however, there are differences in handling
multiple upper level disturbances from the two dominant lows. The
NAM was used to handle the transition into Wednesday and then
switched influence in the extended forecast to ECMWF along with
some of the 06Z GEFS MEAN which provided the best consistency.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 155 165 170 172 173 174 175 176 177.
FIRE WEATHER...Red Flag Warning 145 153 155.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...LF
FIRE WEATHER...LF
SOUTHCENTRAL ALASKA...MTL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...KH





000
FXAK68 PAFC 290033
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
433 PM AKDT SAT MAY 28 2016

.ANALYSIS AND UPPER LEVELS...
Dry conditions prevail across the southern mainland this
afternoon as high pressure remains the dominant weather pattern
with an upper ridge centered along the Seward Peninsula. Several
low pressure systems surround the ridge. To it`s southeast, low
pressure over British Columbia is moving a shortwave across the
eastern Gulf and Panhandle. To the west...a low centered south of
Dutch Harbor is stationary with a second low over Kamchatka moving
a strong shortwave across the Western Aleutians. At the surface,
the pattern over the southern Mainland is a weak trough between
ridging to the north and south. The Bering pattern is slightly
more active; however, the two surface features are filling with
one over the eastern Aleutians and the other just north of Shemya.
The next storm system to watch across the Bering is currently
organizing south of the Western Aleutians.

&&

.MODEL DISCUSSION...
Models are generally in good agreement with the synoptic pattern
through Monday night. The main challenge across the southern
mainland into Monday is the timing of an easterly wave which
brings thunderstorm potential for the Copper River Basin on
Sunday. For the Bering and Aleutians, the main focus shifts to the
developing storm system in the North Pacific which quickly moves
to the Western Aleutians Chain early Sunday. The NAM was favored
for Southcentral and the Gulf with the use of the GFS and ECMWF
for the Southwest and Bering.

&&

.FIRE WEATHER...
Elevated fire weather conditions are expected during peak heating
of the afternoons and evenings across the southern Mainland. The
greatest concern today is across the Susitna Valley where
temperatures are expected to climb into the mid 70s. A Red Flag
Warning was issued for warm and dry conditions combined with
stronger northerly flow which develops this afternoon as the
ridge to the north squeezes the pressure gradient as it shifts
southeast. Conditions will improve briefly overnight and then
return for much of Sunday. A warning is also being issued for the
Middle Kuskokwim Valley and inland areas of the Kuskokwim Delta,
as warmer and drier conditions spread westward on Sunday along
with stronger northerly flow.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The main story in today`s forecast will be the well above average
temperatures and dry conditions for parts of the Mainland. More
summer-type clouds will show up for most areas, especially over
the mountains. rain showers will begin to work into the eastern
Copper River Basin this evening and overnight spreading westward
through Sunday afternoon. Most of this activity will be concentrated
along the mountains but isolated showers can not be ruled out in
most areas. The only chance for thunderstorms will be in the
Copper River Basin tomorrow. Temperatures will remain above normal
with light winds through Monday.

As ridging aloft begins to slide off to the northwest tonight,
cooler air aloft filters into the area from the east. That cold
air will bring instability, especially over higher terrain, and
bring diurnal showers or even thunderstorms to the area.

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The southwest Mainland will continue to warm under sunny skies
and lighter winds this evening as ridging persists overhead. Sunny
and warm weather will continue over Kuskokwim Valley/Delta on
Sunday as well, along with increasing northeasterly flow in
advance of a developing surface trough. To the east over the
Alaska Range, weak instability will bring showers and possibly
even a strike or two through Sunday evening. These showers will
then spread throughout the southwest Mainland on Monday as a
shortwave moves overhead. There remains some uncertainty with how
strong this feature will be, but there in reasonable confidence
that this wave will spread showers throughout the area on Monday,
possibly with a few thunderstorms. If the shortwave becomes as
strong as the NAM is indicating, this would increase the confidence
in thunderstorm development, especially over Bristol Bay and the
Kuskokwim Valley.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The focus is beginning to shift to a Northwest Pacific low that
will increase to gale force as it moves into the western/central
Aleutians on Sunday. Model agreement is improving on the track of
this low...allowing gale force winds to be added to the forecast
for most of the central and eastern Aleutians into Monday.

&&

.LONG TERM FORECAST (Tuesday through Saturday)...
The dominant high pressure center creating warm and dry conditions
across the Mainland will slowly retreat to the west through early
next week. This will allow increasingly cyclonic flow to enter the
Gulf of Alaska and southern Mainland during the week. At this
point it looks likely that the most active weather will stay far
enough out to sea in the Gulf that most of the area will continue
to see a fairly good amount of sunshine, though diurnal shower
(and maybe thunderstorm) activity will slowly increase throughout
the week. Meanwhile, the Bering Sea and Aleutian region will
remain generally under the influence of high pressure and strong
low-level inversions that keep fog and stratus a persistent problem.
This large-scale weather pattern is very typical for this time of
year, and as such temperatures and sensible weather should follow
suit and be fairly close to climatology for temperatures and
precipitation across the forecast area next week.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...Red Flag Warning 145 153 155.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...MTL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...AMD





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