Flood in Alaska, July 1 to 3, 2019

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
501 PM AKDT Sun Jun 30 2019

.ANALYSIS AND UPPER LEVELS...
The strong upper level ridge that has been over the region the
past few days is being flattened over Southcentral Alaska by an
upper level trough over Southwest Mainland Alaska which is
associated with an upper level low near Wrangell Island.
This is providing southwest flow over the Bering sea and
Southwest mainland Alaska which is bringing moist marine air into
that region. The atmosphere over the Susitna Valley and Copper
River Basin is more unstable today due to the flattened ridge
evidenced by a strong thunderstorm early this afternoon over the
Talkeetna Mountains in the western Copper River Basin. This ridge
has flattened but will reassert itself over the entire region
again by Tuesday.

&&

.MODEL DISCUSSION...
Models are in very good agreement over the region through most of
the week. The main question is just how strong the re-developing
ridge gets later in the week. The ECMWF model shows stronger
ridging and warmer temperatures than the GFS. High resolution
models are being used for the lower- atmosphere winds.

&&

.AVIATION...
PANC...Smoke remains the main issue around the PANC area. While
smoke and resultant haze will persist in the area it is expected
that the winds near the fire will shift enough to allow some of
the heavier smoke to move out of the area by this evening.
Otherwise VFR conditions will continue.

&&

.FIRE WEATHER...Swan Lake Fire...Western Kenai Peninsula:
Hot conditions continue over the fire with the 80 degree mark
being eclipsed by noon today. Hot and dry conditions are expected
to continue through the week over the fire site.

Winds have shifted to the West-Southwest and that will keep the
smoke going into the Anchorage and Mat-Su areas this afternoon
through early evening. Transport winds are expected to shift by
this evening to bring more of the smoke toward the Seward area
instead of as much going into Anchorage and the Mat-SU valleys
tomorrow and Tuesday. Conditions will remain hazy with the smoke
in Anchorage and Mat-SU, but conditions should be improved.
Seward and Moose Pass will be a different story with increased
smoke Monday into Tuesday.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
(Sunday through Tuesday)

Today featured a nice reprieve from the warmer afternoon
temperatures for locations along the Kenai Peninsula and Anchorage
Bowl and near the Knik Arm. This was courtesy of increased smoke
density and/or (depending on location) a southwest onshore flow.
Monday will feature cooler conditions for the remainder of the
area, as 850 mb temperatures cool 3 or 4 degrees Centigrade,
behind a passing mid-level disturbance to our north that is just
giving us a glancing blow.

However, all numerical guidance continues to show the ridge of
high pressure rebuilding for the middle to end of the week, with
similar afternoon high temperatures to what we just experienced,
and a good chance of it being even warmer due to increased mid-
level heights and resultant warmer 850 mb temperatures. Adding to
this mix will be a potentially stronger offshore flow, which
would only help to warm temperatures more through frictional
heating due to the downslope effects.

&&

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

Clouds and any lingering isolated showers in association with a
surface trough and trailing upper-level shortwave traversing east
across the southwest mainland will diminish overnight as a ridge
begins to build back into the region from the west. Over Bristol
Bay, a persistent light onshore flow will help keep some low
stratus and patchy fog over coastal areas through tomorrow
morning. A second system will then lift toward the coast from the
eastern Bering, bringing another round of clouds and rain late
Monday into Tuesday. Interior Southwest Alaska should remain dry
with this system, with the best chance for wetting rain confined
to the Y-K Delta. Conditions remain unsettled along the coast
Wednesday as yet another weakening front approaches from the
Bering.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

Widespread low stratus remains from the Pribilofs south and east
across the eastern Aleutians and AKPEN underneath a ridge of high
pressure building back in in the wake of the trough now over
Southwest Alaska. Farther west, a surface low south of Shemya is
lifting a front over the western and central Aleutians with
widespread rain overrunning this feature. As this system lifts
north over the western Bering overnight, rain and gale-force
winds will spread over the central Bering and Pribilofs. This
system then stalls and weakens as it enters the eastern Bering
Tuesday into Wednesday

&&

.MARINE (Days 3 through 5)...
Wednesday through Friday will be characterized by high pressure
rebuilding over southern Alaska. There is high confidence in this
setup that will result in winds below gale force throughout the
marine areas.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Models are in good agreement that a strong ridge will rebuild over
southern Alaska mid this week and remain into the weekend. Hot
and dry conditions will persist across the southern mainland with
above average temperatures and light winds expected.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood warning 145.
MARINE...Gale 173-177, 412 413.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...PD
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TM
MARINE/LONG TERM...DK

SPECIAL WEATHER STATEMENT...CORRECTED
National Weather Service ANCHORAGE AK
849 PM AKDT Sun Jun 30 2019

AKZ101-111-121-125-141-145-012000-
Anchorage-Matanuska Valley-Western Kenai Peninsula-
Western Prince William Sound-Copper River Basin-Susitna Valley-
Including the cities of Anchorage, Eagle River, Indian, Eklutna,
Palmer, Wasilla, Sutton, Chickaloon, Kenai, Soldotna, Homer,
Cooper Landing, Whittier, Seward, Girdwood, Moose Pass,
Glennallen, Eureka, McCarthy, Paxson, Slana, Talkeetna, Willow,
and Cantwell
849 PM AKDT Sun Jun 30 2019

High river conditions are expected along the Matanuska, Skwentna,
Klutina, Eagle River, Sixmile, Talkeetna, Kenai at Cooper
Landing, Kenai Keys, and Kenai below Skilak Lake. Water levels are
expected to continue and/or rise into Action Stage and Bankfull
conditions until Friday Jul 5. No significant impacts are
expected along these rivers.

A Flood Warning has been issued for the Yentna River at Fish
Creek.