National Weather Service United States Department of Commerce


000
FXAK68 PAFC 120107
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
507 PM AKDT Sat Jul 11 2020

.ANALYSIS AND UPPER LEVELS...

A 500 mb low east of the Yukon Delta has been producing some
thunderstorms throughout the day in the Kuskokwim valley. This
upper level low will move southward through the next few days and
be the focus for thunderstorm activity this afternoon and evening,
and again Sunday. While Southcentral Alaska remains unstable and
conducive for thunderstorms today, they should be more widespread
in Southwest Alaska because of this upper level low.

The Bering Sea remains under high pressure causing low stratus
over the majority of it. A front along the Central Aleutians is
shearing apart as it runs into the ridge.

&&

.MODEL DISCUSSION...
Models are in good synoptic agreement through the early part of
next week with some more noise creeping into the pattern for the
second half of the week. This is most evident in the Bering Sea
where the GFS has a high in the central Bering and the ECMWF and
Canadian show a closed low in the southern Bering Sea. However,
this will mainly impact the Aleutian chain and the practical
difference may just be wind direction and whether there is
predominately fog or rain.

&&

.AVIATION...
PANC...
Winds have turned to the southeast this evening and could be gusty
at times off the Turnagain Arm. Showers will persist around the
airport into tomorrow, with some isolated thunderstorms around the
terminal this evening. Ceilings will drop under 5000 ft at times,
but should remain above MVFR conditions.

&&

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

The upper level low continues to drop south over western Alaska,
pushing ample moisture into the Southcentral region. This,
coupled with the unstable airmass, will produce isolated to
scattered thunderstorm activity across the Kenai Peninsula north
into the Susitna Valley and western Copper River Basin this
evening. The steering flow is out of the west, thus expect the
storms that do form to move to the east and mainly be along the
Talkeetna and Chugach Mountains. Some storms will form off the
Alaska Range as well and move across the Susitna Valley. Following
the convective activity tonight, west to southwest flow will
usher in more stable air along with more moisture, thus increasing
the chances of rain across much of south central Alaska Sunday,
particularly the Susitna Valley.

A surface low will be under the low over Southwest Alaska and a
surface low will form along a front south of the Alaska Peninsula
tonight. This low intensifies as it moves into the western Gulf of
Alaska Sunday night and Monday. In advance of this low a ridge
builds in the eastern Gulf of Alaska and intensifies Monday. The
interior thermal trough, while not strong, will be in place as
well. The combination of the intensifying ridge and interior
trough will be the driver behind the gap winds through the Chugach
Mountains as well as along the Copper River the next few days.

&&

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

An active pattern is set up across Southwest Alaska today as an
upper level trough digs into the region. Instability and
convection accompany this feature as it moves southward through
the end of the weekend. Thunderstorms have already developed over
the Kuskokwim Valley and interior Bristol Bay. Widely scattered
thunderstorms are expected to continue for interior locations,
with areas just north of New Stuyahok looking like a hot spot for
storms late this afternoon into the evening hours.

This pattern will continue into Sunday, though a bit weaker with
less thunderstorm activity expected as there is slightly less
instability in place. However, isolated thunderstorms remain in
the forecast, once again staying farther inland away from the
coasts. Quieter weather moves in to start the week on Monday with
showers tapering off across the Southwest.

&&

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

With high pressure across the Bering, fog and low stratus will
remain in the forecast over the next few days, with conditions
improving for the daytime hours. Low pressure continues to slide
eastward south of the Aleutian Chain, keeping relatively weak
winds with a chance of precipitation. However, there is some model
uncertainty start Sunday afternoon whether this area of low
pressure will develop into a closed low south of Kodiak Island,
which would bring more precipitation and stronger winds to areas
south of the Alaska Peninsula.

&&

.MARINE (Days 3 through 5: Tuesday through Thursday)...

High pressure lingers across the Bering with easterly winds and
waves across the southern half and southerly winds and waves over
the northern half through Thu. High uncertainty comes with the
initial position and track of a North Pacific low, bringing
problems its movement and wind directions with said low through
Thu. Confidence is good for less than small craft winds and waves
south of the Aleutians through Thu.

Over the Gulf, a low center will track across the Gulf, however
certainty is low for frontal positions through Thu. East to
southeast winds and waves are expected across the Northern Gulf
with less than small craft speeds. We expect a shift to northerly
winds and waves around Kodiak Island and the western Gulf by Thu.

&&

.LONG TERM FORECAST (Days 3 through 7)...
By Tuesday, the upper level low that is near Southwest Alaska
today will have moved over Kodiak Island and be in the central
Gulf of Alaska. This will start the period with high pressure over
Southwest Alaska and a front along the north Gulf coast. The high
pressure is not terribly strong but should spread over
Southcentral Alaska for the middle of next week. Southwest Alaska
will be susceptible for low stratus to advect into the region off
the Bering Sea, though rainfall should mainly be afternoon and evening
showers over higher terrain.

Afternoon and evening showers are also likely over interior parts
of Southcentral Alaska throughout the period.

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...SA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AH
MARINE/LONG TERM...MK/EZ


000
FXAK69 PAFG 112020
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
1220 PM AKDT Sat Jul 11 2020

.SYNOPSIS...
Very pleasant mid summer weather continues over northern Alaska
with seasonal temperatures in the upper 60s and lower 70s, mostly
clear skies, and just enough breeze to help keep the mosquitoes
at bay over the Central and Eastern Interior. A weak front
currently over the Alaska Range will be the focus for scattered
showers this evening and tonight. The front will push north into
the Southern Interior tomorrow and will again be the focus for
scattered showers and isolated thunderstorms. Scattered rain
showers and isolated thunderstorms are expected this afternoon and
evening over the Western Interior and over much of the Southern
Interior and the Eastern Brooks Range on Sunday. in the Alaska
Range will push north on Sunday.

&&

.DISCUSSION...
Models...
The 12z model suite initialized well against the 12z surface
analysis and verified well against the 18z surface analysis. Model
spread is minimal from model run to model run as well as across
model families.

North Slope and Brooks Range...
High pressure northwest of Utqiagvik and low pressure near Banks
Island continue o produce onshore winds resulting in low ceilings
and areas of dense fog that pushes in over the coastal areas
after midnight and then eventually burns off by late morning.
Expect similar conditions tonight before a strong cold front
pushes south out of the Arctic Ocean on Sunday afternoon. Expect
gusty northerly winds along with sprinkles or flurries Sunday
night and Monday and minor snow accumulations above two thousand
feet in the Western Brooks Range Sunday night into Monday.

West Coast and Western Interior...
A weak low pressure over the Central Interior combined with a
thermal trough extending southwest into the the lower YK Delta and
northwest to near Ambler will be the focus for scattered rain
showers and isolated thunderstorms this evening. Scattered rain
showers and isolated thunderstorms are expected near the Alaska
Range as well as in the foothills of the Brooks Range on Sunday
afternoon and evening. Expect seasonal temperatures in the 50s and
60s along the coast and in the upper 60s to lower 70s in the
Western Interior. Winds are expected to remain light.

Central and Eastern Interior...
Very pleasant mid summer weather this afternoon and evening over
the Central and Eastern Interior with no thunderstorms expected
and only very isolated rain showers possible. A weak frontal
system currently stalled over the Alaska Range will push north
into the Southern Interior on Sunday and merge with a thermal
trough that will produce scattered showers and isolated
thunderstorms. The showers and thunderstorms will drift north with
the front and thermal trough through Monday into the Central
Interior. This afternoon and evening will be warm and dry over NE
Interior with highs in the 70s and RH in the 25-35% range.
Temperatures will be near normal Sunday and Monday.

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

&&

.FIRE WEATHER...
A weak low pressure trough that lies over the south slopes of
the Brooks Range will persist into Sunday. This trough will
produce isolated PM showers today, and isolated PM thunderstorms
on Sunday.

A weak frontal system currently stalled over the Alaska Range will
push north into the Southern Interior on Sunday and merge with a
thermal trough and will produce scattered showers and isolated
thunderstorms. The showers and thunderstorms will drift north
with the front and thermal trough through Monday into the Central
Interior. Today will be warm and dry over NE and NW Interior with
highs in the 70s and RH in the 25-35% range, while the remainder
will be near normal. Temperatures will be at or below normal
Sunday and Monday with slowly rising relative humidity values over
the Interior.

&&

.HYDROLOGY...
Water is rising on rivers draining into the Tanana River and over
the Tanana River, but no flooding is expected.

Scattered to widespread rain showers in the Alaska Range through
Sunday could drop another quarter to one half inch of rain and
cause rapid rises on small streams along with possible rock and
mud slides in the steep terrain of the Alaska Range through Sunday
night.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory for PKZ210.
&&

$$

CCC JUL 20


980
FXAK67 PAJK 112256
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
256 PM AKDT Sat Jul 11 2020

.SHORT TERM...The system that has been driving the weather in SE
Alaska over the past few days has begun winding down. Aloft, a
trough is steadily pushing eastward across the Gulf, with a
weakening low associated with it at the surface reflecting this
movement. While rain showers remain, especially throughout the
southern panhandle, it is expected that these will diminish in
coverage overnight on Saturday, and as the low departs, will
become more scattered across the panhandle on Sunday. On Sunday,
as ridging briefly builds in to replace the departing system, it
does look like some areas, particularly the southern panhandle,
could see some breaks in the clouds, though much of the area will
continue to experience abundant cloud cover.

The reprieve will not last long however, as the next system takes
aim at the panhandle. A low pushing into the Gulf from the Pacific
will bring with it a frontal band primed to hit SE Alaska. Model
guidance is currently split on exactly when this band will
actually arrive in the panhandle, but the consensus currently
falls between Monday afternoon and Tuesday morning, with the NAM
bringing the front in sooner while the GFS maintains a slower
approach. When the front does arrive, it currently looks like it
will bring a healthy amount of moisture support, setting the
stage for more abundant rain across the area, as well as stronger
winds in the outer coastal waters.

Fire weather danger is expected to remain minimal, as high
temperatures will continue to be limited to the upper 50s or 60s,
and lingering rain showers will help mitigate the chance of parts
of the area substantially drying out. Forecaster confidence is
average.

.LONG TERM.../Monday through next Friday/ As of 10pm Friday.
Monday starts off with a chance of showers in the forecast, but
overall the first part of the day looks decent. Then a new system
moving across the gulf from the west will cause increasing
clouds and POP, but models differ quite a bit on timing and
position of that. The 11/00z model runs show the ECMWF is the
fastest and the GFS is the still slowest keeping the low over the
western gulf much longer while the Canadian is in between.
Generally the consensus is still for rain to move in Monday night
and for Tuesday to be the most likely wet day of the week. In
previous runs the most models were taking a slightly further south
track than today, but have kept the focus of highest POP over the
south since they will get it with either track. Due to the expected
cloudy/rainy weather on Tues, went below NBM/WPC guidance for
high temperatures and closer to MOS, but may need to lower them
more into the mid 50s.

Once the low weakens and moves through on Wednesday, there are
signs of more ridging for the end of the week that could give us
some breaks. But there is a lot of uncertainty in this forecast.
The GFS brings another low to quickly replace the first and keep
showers going and the Canadian generates a low to the south.
Model snow levels and temperatures still show a slight increasing
trend however, so any sunny breaks should be in the 60s.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...None.

&&

$$

GFS/Ferrin

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