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AFG Warnings  Issued: 06/27/2017 06:06:26 AM AST Click for text

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000
FXAK69 PAFG 282156
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
156 PM AKDT Wed Jun 28 2017

.DISCUSSION...
The 12z model suite initialized with few differences between model
families however the model suite continues to play catch up with
the observations. The 06z model suite initialized with a 2 to 4 mb
gradient deficit between the surface high pressure near Banks
Island and the thermal trough over the interior as well as the low
in the Gulf of Alaska. The 12z models suite also initialized with
few differences between model families however the 2 to 4 mb
gradient deficit has diminished to 1 to 2 mbs between modeled and
observed SLP`s. The expected and observed impacts of the models
initializing with weaker gradients will be that observed winds
will likely be slightly stronger than modeled winds. Model spread
remains minimal in the the short range but has increased spread in
the mid range as compared to yesterdays 12z model suite especially
past Saturday. Considerable spread has crept into the model suite
in the long range.

Aloft at 500 hpa, the longwave trough over the southern Chukchi
Sea extends south through the Bering Strait and through the
central Aleutians. An upper level ridge remains over northern
Alaska and extends southeast into the southern Yukon and will
slowly move east over the Yukon and Northwest Territories through
Friday. A series of shortwaves will rotate north along the west
coast around an upper level low over the central Bering Sea
through the weekend.

On the surface a 1018 mb high pressure system located 200 nm west
of Banks Island will drift to the east and be located over Banks
Island Friday. East winds will continue along the eastern north
slope and will bring periods of low clouds and fog especially
along the the coastal areas to the east of Barrow.

Over the central and eastern interior isolated thunderstorms are
expected along and to the north and east of the thermal trough
which currently extends along a Ambler to Bettles to Eagle line.
Weak downslope flow will limit thunderstorm activity south and
east of the trough over the central and eastern interior however
an isolated thunderstorm is possible this evening. Red Flag
temperature criteria will likely be met over much of the central
and eastern interior Thursday and Friday as temperatures reach
into the mid 70s. Red Flag minimum relative humidity criteria will
likely be met over much of the central and eastern interior as
relative humidities drop into the mid 20s in over the eastern
interior and into the 20s and 30s over the central interior. Red
Flag criteria for winds are not expected to be met over the
central and eastern interior however localized areas along and
near Alaska Range passes and foothills will approach criteria
this evening as well as Thursday and Friday.

Over the west coast and western interior a series of shortwaves
will move north through the area and will be the focus for periods
of rain and for scattered rain showers.

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

&&

.FIRE WEATHER...
Near Red Flag conditions are expected this evening and again
Thursday afternoon and evening over the Yukon Flats as temperature
and minimum relative humidity criteria will be met lacking only
wind criteria. Red Flag conditions for minimum relative humidity
will likely be met this evening and again on Thursday afternoon
and evening along and near the Alaska Range Passes. Winds will
come close to meeting Red Flag criteria in these areas this
evening and again on Thursday afternoon and evening.

&&

.HYDROLOGY...
Expect glacial rivers will be rising through the weekend as
temperatures and freezing levels remain above normal.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Brisk Wind Advisory for PKZ235-PKZ240-PKZ245.
&&

$$

CCC JUN 17


000
FXAK68 PAFC 290112
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
512 PM AKDT Wed Jun 28 2017

.ANALYSIS AND UPPER LEVELS...

Water vapor satellite imagery shows two closed low pressure
systems impacting southern Alaska and surrounding waters this
afternoon. The newest closed low formed quickly overnight as
shortwave energy rounded the base the broad trough that expands
across the Bering to the central Gulf of Alaska. This low center
was located approximately 200 miles south of Kodiak Island early
this afternoon and is advecting abundant subtropical moisture
over the gulf and across Bristol Bay. Rain developing along the
surface low associated with this system, is along a band stretching
across the central gulf to Kodiak Island to the Aleutian Range.
Gusty small craft winds have increased along the this boundary
from the south and east directions. Visibilities reductions along
the frontal band are less than one mile as indicated by automated
stations from Kodiak Island.

To the west, the second upper low is a mature system spinning 250
miles north of Saint Paul Island. This stacked system is losing
momentum on it northward track as it dissociates from the
subtropical jet which lies near 45N. Low clouds and patchy fog
encompass the Bering along with a few showers as weak shortwaves
circulate around the core.

&&

.MODEL DISCUSSION...
Models are in general agreement through Friday however they are
lacking in agreement between on refined details of precipitation
timing and coverage. The main edits for in the short term were
focused on rain chances during the next two days as this is the
main challenge for the end of the week.

&&

.AVIATION...

VFR conditions are expected to prevail through the next TAF
package. Gusty south flow tapers off late this evening, remaining
light through Thursday afternoon. Rain spreads into Anchorage from
the gulf later this evening and continues through Thursday as a
weak boundary stalls across the region.

&&

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

Satellite imagery this afternoon depicts another impressive surge
of Pacific moisture moving north toward the Gulf Coast in
association with a left-exit region of the subtropical jet
stream. Rain will work inland starting from the Kenai Peninsula
then into Anchorage and the Susitna Valley by tomorrow. The
Matanuska Valley may see a bit more downslope flow, so for now,
the best chances of rain will be from Anchorage South and then
northward toward the Alaska Range. Strong gap winds down Turnagain
Arm will weaken tonight as the pressure gradient bends the wind
down-inlet. The front will weaken along the coast Thursday night
and Friday with precipitation tending to favor the coast. Inland
drying will result in slightly warming temperatures Friday and
SAturday, and possibly some breaks of sun.

&&

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

We remain in this pattern of the upper low over the central Bering
Sea rotating pulses of energy around it along the Aleutians to the
Bering Sea coast. One such pulse is now pushing through the
Kuskokwim Delta today producing widespread rain. This trough moves
north out of the Kuskokwim Delta region by this evening. The
overall flow weakens this evening and we should see a break in the
rain. In Bristol Bay, moisture from a low moving north into the
western Gulf of Alaska will spread across the Aleutian Mountains
and Alaska Range tonight increasing the chance for rain. The cross
barrier flow is not very strong, but we will likely see less rain
on the lee side of the mountains while the Kilbuck and Ahklun
Mountains will see heavier rain Thursday. Thursday night and
Friday the Gulf low will weaken and move across the eastern Alaska
Peninsula into Bristol Bay. Therefore we expect a continuation of
the wet cool weather over the Bristol Bay zone Friday.

&&

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

The persistent Bering Sea low will remain the dominant feature for
the weather through Friday. It will move to the northwest as it
weakens, thus wind along the Aleutian Islands will diminish. A
low forming south of the western Aleutians becomes entrained in
the flow of the Bering Sea low and will rapidly move along the
Aleutians to the Alaska Peninsula as an open trough by Friday. The
main impact of this system will be increase rain potential.
Following this weak system we have yet another storm moving into
the western Bering Sea Friday. The front will move through the
western Aleutians Friday bringing minimum gale force wind as it
does.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Long term models have not come into any closer agreement than they
were yesterday on the timing or placement of low pressure systems
in the Bering Sea and Gulf of Alaska. The same general pattern
continues with a strong jet streak diving into the western Gulf of
Alaska Sunday night, however the models diverge greatly on surface low
development and movement. GFS favors a further north solution
while EC pushes the low further south along the Gulf of Alaska
border. Both models continue to favor a wet Sunday and Monday for
most of the mainland but GFS does harbor some hope that things
might dry out a little bit for the Tuesday holiday. Meanwhile in
the Aleutians, model variability is high, with EC indicating a
rainy low pressure system moving through, and GFS indicating broad
westerly flow with significantly less precip. By Tuesday
afternoon, both models move a ridge into the eastern Bering, which
would dry things out in Western Alaska for the evening of the 4th
of July. Current thinking is to not adjust the long term
forecast, which would continue to bring rain through the early
part of next week.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale 119 120 131.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...JA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...SA
LONG TERM...LF


876
FXAK67 PAJK 282230
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
230 PM AKDT Wed Jun 28 2017

.SHORT TERM...Wednesday night through Friday night...A high
pressure system over the eastern Gulf will move inland tonight
and exit the region. A low pressure system developing across the
Northeast Pacific will move north into the Southwest Gulf Thursday
night. A front associated with the low pressure system will move
into the eastern Gulf Thursday night. Showers are likely across
the northern portions of the panhandle tonight. Rain chances will
increase on Thursday across most of the panhandle as the low
pressure system advances northward and the frontal boundary moves
into the eastern Gulf. Temperature values Thursday will continue
similar to temperatures which occurred over the past few days
across southeast alaska. Cloudy to mostly cloudy skies will
prevail across the region with a few breaks occurring across the
southern areas of the panhandle tonight and Thursday.

Into Fri another short wave will be riding north along the front
bringing another round of rain to most of the panhandle. Timing has
most of the rain coming for Fri night. This feature is also bringing
some wind into the area but nothing more then 15 to 20 mph and
mostly for the southern panhandle and outer coast with 25 kt winds
for the near coastal waters of the gulf. Increased winds in these
areas as a result. GFS and Nam were main models of choice for the
short range period.

.LONG TERM...Saturday through Tuesday...As of 1030 PM Tues...We
continue to see an upper level ridge with an associated high
pressure at the surface progress east out of the area during the
early weekend timeframe. Precipitation chances will increase as
we move into the weekend, which is in line with the approach of a
surface front, the increasing onshore flow, and plentiful moisture
available. Winds were increased for the post-frontal time period
for northern Lynn Canal late Sunday. Additional shortwaves moving
out of the parent upper level low situated over the gulf will
impact the area Sunday through the rest of the time period of
interest and will continue the likely PoPs trend, with a possible
drier period beginning Tuesday. We`ll continue to monitor
developments for next week.

We strengthened Friday`s front by nudging to the NAM/GFS and made
minor adjustments to the period beyond with WPC guidance. But
overall, few changes were needed. Overall confidence is average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ042-043-051-052.
Small Craft Advisory due to Seas for PKZ041.

&&

$$

BM/EAL/Voveris

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