Extreme warmth over southern AK yesterday. Many locations set all time record highs. Anchorage hit 90. They only hit 80 once every 4 years on average...but by the end of next week, they may have 7-10 80+ days this season already.
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
526 AM AKDT Fri Jul 5 2019
.ANALYSIS AND UPPER LEVELS...
It has become a bit of a broken record to talk about the
stationary upper-level ridge over the southern mainland and the
upper-level trough upstream over the far western Bering; however,
this continues to be the synoptic pattern over the forecast area
as the upper-level rex block (high pressure north of low pressure)
remains firmly in place across the north Pacific. Speaking of
broken records, a plethora of daily and all-time records were set
across southcentral and southwestern Alaska yesterday as both the
ridge and the amount of subsidence (sinking air) reaches peak
intensity. More on this in the Climate portion of the discussion.
It was not hot and dry everywhere, though, as cooler temperatures
prevailed for some coastal locations (e.g. Seward, Whittier,
Kodiak), aided by either sea breezes or low stratus and patchy
Across the interior, scattered mid- and high-level clouds
continue to rotate around the northern periphery of the high,
extending from Bristol Bay east across the Alaska Range to the
Copper River Basin. Along the coast, the low stratus and fog
continue to spread out, with satellite imagery showing extensive
low cloud cover moving west over the Barren Islands and along the
eastern coastlines of Kodiak Island and the Kenai Peninsula.
Farther west, low stratus and fog is also building across the
eastern and central Bering and Aleutians in the wake of the slow-
moving trough over the western Bering. For places such as Cold Bay
and Saint Paul, visibility is reduced due to fog and mist with
ceiling of only a couple hundred feet.
Models are in fairly good agreement on the synoptic features and
overall pattern. One forecast challenge to note is that some of
the hi-res models, with the HRRR the most bullish, are suggesting
the expansion of a band of low stratus over the Barren Islands
rounding the southern coast of the Kenai Peninsula and moving
north along Cook Inlet in response to an increasing up-inlet
flow. Obviously, this scenario would throw a wrench in the cloud
cover and temperature forecasts for locations along the inlet,
Anchorage included. Confidence in this is rather low, however, as
the stratus currently sitting west of Augustine Island overnight
as yet to make any northward movement.
PANC...VFR conditions and light winds will persist. Visibility may
be slightly reduced at times through mid-morning as a light
southerly wind advects smoke over Anchorage from the Swan Lake
fire. The southerly wind is then expected to become westerly
around mid-morning, pushing the smoke away from the airport
Near-record breaking temperatures will remain a possibility
through the weekend as hot and dry conditions persist across
southcentral and southwest Alaska. Generally, winds will continue
to remain light and variable across interior locations, keeping
dense smoke from the Swan Lake fire trapped within the valleys of
the Kenai mountains. A southerly flow along the eastern coast of
the Kenai Peninsula should help provide some relief, keeping the
thickest of smoke north of coastal locations such as Seward
through the evening hours. The dense smoke, however, looks to
settle back in from Moose Pass south to Seward tonight as a light
northerly flow develops. A developing sea breeze and up inlet flow
will likewise help to scour out any lingering smoke around Homer
this afternoon. Areas of smoke will also continue for locations
south and east of the Montana Creek fire with a continued light
northerly transport wind. As stated in previous discussions, the
smoke may lift a bit during the afternoon and evening hours due to
daytime heating and increasing mixing heights. However, continued
subsidence and nighttime temperature inversions will also allow
the smoke to settle back down and fan out over the Western Kenai
and eastern Susitna Valley during the overnight hours.
The 4th of July 2019 was a day truly for the record books in the
climate department. Numerous high temperature records were set,
along with several ALL-TIME temperature records. Here is the list:
Site.............Type.......New Record...Old Record (Date/Years)
Anchorage Intl...ALL-TIME...90 degrees...85 degrees (Jun 14, 1969)
Merrill Field....ALL-TIME...90 degrees...87 degrees (Jun 27, 1953)
Palmer...........ALL-TIME...88 degrees...88 degrees (May 27, 2011)
Kenai............ALL-TIME...89 degrees...87 degrees (Jun 26, 1953 &
116 year old record!---> Jun 18, 1903)
King Salmon......ALL-TIME...89 degrees...88 degrees (Jun 27, 1953)
Anchorage Intl...Daily......90 degrees...77 degrees (1999)
Merrill Field....Daily......90 degrees...77 degrees (1999)
Palmer...........Daily......88 degrees...81 degrees (1979)
Kenai............Daily......89 degrees...75 degrees (2003)
King Salmon......Daily......89 degrees...84 degrees (1997)
Homer............Daily......78 degrees...71 degrees (2018)
Gulkana..........Daily......88 degrees...86 degrees (1958)
Iliamna..........Daily......86 degrees...79 degrees (1949)
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Overall hot and dry conditions will continue the next few days.
The center of the upper level ridge which brought all-time record
highs to a number of locations over southern Alaska yesterday will
remain directly overhead today and then begin to edge westward on
Saturday. This will produce daily record high temperatures again
today and many locations in southern Alaska. Areas inland will
likely see temperatures close to what they were yesterday, but
areas along Cook Inlet will see increased southwesterly winds
which are expected to edge temperatures down slightly from
yesterday`s levels, but remain hot.
The Jekyll and Hyde nature of Alaska weather can be seen with the
way this same high pressure is also causing widespread fog and
stratus over the entire Gulf of Alaska. This has caused locations
right along the coast to get fog and much cooler temperatures
along the north Gulf Coast and eastern Kodiak Island. This fog and
stratus will be quite persistent and is not expected to dissipate
or move out of the area any time soon.
This brings the forecast challenge the next few days for the Cook
Inlet region up to and including Anchorage. With this pattern,
the stratus usually pushes up Cook Inlet from the Southwest. The
uncertainty with this is whether it will be able to do this due to
the unusually hot temperatures. Will the temperatures cause
enough vertical mixing to keep the inversions from developing
strong enough to advect the stratus up the Inlet? Or will the
stratus be able to ride the southwest flow up the Inlet (or at
least part of it) and drastically drop temperatures in the marine
airmass? I am going with the first option as it seems like the
most likely situation in light of the past few days. The second
scenario is worth watching.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Sunday Night)...
Record heat in King Salmon and Iliamna yesterday was caused by an
incredibly strong upper level high that is parked over
Southcentral. This dome of hot air extends westward across much of
Southwest Alaska. With surface high pressure building off the
Bering coast, breezy northeast winds are expected to persist
across the Kuskokwim Delta today. The hot, offshore winds will
allow temperatures across the Kuskokwim Delta to warm into the
lower 80s today. Meanwhile further east, winds have diminished a
bit across the Lower Kuskokwim Valley and Bristol Bay areas,
though temperatures are expected to once again top into the upper
80s to near 90 across the Lower Kuskokwim Valley, with mid to
upper 80s expected across Bristol Bay.
The upper level high will begin to slowly shift westward this
weekend, moving over Southwest Alaska by Sunday afternoon.
Fortunately it will also be slowly weakening by this point. The
weakening is not expected to do much for high temperatures, which
will remain roughly the same across most interior areas through
the weekend. Offshore northeasterly winds will continue drying the
area out as relative humidity values drop below 30 percent over
the Lower Kuskokwim Valley by Sunday.
One area that will be bucking the hot temperatures trend will be
along the coast. Winds are expected to switch to out of the
southwest along Bristol Bay by Saturday afternoon, persisting into
Sunday. It will take until late Sunday night for the same to
happen over the Kuskokwim Delta. The onshore winds in these areas
will be like turning on the air conditioner, keeping high
temperatures much more comfortably cool in the 70s by Sunday.
The next few afternoons, it will be possible for showers to
develop along the area mountains. Any showers may drift off the
mountains into the nearby foothills, which will help quite a bit
with locally cooling down the temperatures.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3: Today
through Sunday Night)...
There will be a few weak systems impacting portions of the area.
The primary one will be the edge of the upper level high which,
while producing offshore winds, will continue pushing most of the
marine stratus and fog out away from the coast. The front over the
western Bering will continue drifting westward and dissipate
later today. A North Pacific low will track well south of the
central and eastern Aleutians Saturday and Saturday night. Its
northern periphery will skim through the islands, which may
locally produce some light rain along with breezy easterly winds.
A stronger North Pacific low will approach the western and central
Aleutians Sunday afternoon into the overnight, before stalling
just south of the islands late Sunday night into Monday morning.
.MARINE (Days 3 through 5)...
(Sunday through Tuesday)
...Bering Sea and Aleutian Coastal Waters...
High pressure will build westward from southcentral Alaska and
influence the northeastern half of the region, with dry
conditions expected. Further southwest, an area of low pressure
passing along or south of the chain will spread some showers into
the region. Otherwise, look for seas less than 10 feet and
sustained winds to remain below gales (and possibly small craft as
...Gulf of Alaska...
High pressure will continue to dominate the weather through the
period, with winds and waves remaining below small craft
.LONG TERM FORECAST (Days 3 through 7)...
(Sunday through next Thursday evening)
The numerical guidance remains in good agreement for Sunday,
before quickly diverging in model continuity for Monday and
beyond. The main issue seems to be the temporal displacement of
the ridge center, with the GFS model being the fastest and
furthest northwest, as it has the low over the Seward Peninsula by
Monday afternoon. The Canadian model, however, repositions the
high pressure center to north of Fairbanks, while the ECMWF
takes a middle ground approach and has it centered between Bethel
and McGrath. A similar scenario across the southwestern Bering
exists, with the GFS the quickest to undercut the ridge, and the
other two models slower. The model spread only increases each day
In general, we prefer the Canadian solution for the ridge to break
down slower, given the lack of any strong mid or upper level
disturbances to break down the ridge or displace it as fast as
some models suggest. Typically, when one of these weather
patterns gets "locked in place" the models struggle with pattern
change and are all too often too quick to make said change. This in
turn keeps temperatures warmer for a longer period of time.
Perhaps the bigger issue is they all agree on several disturbances
rounding the top of the ridge, dropping south across Southcentral
and into portions of southwest Alaska. Long range instability
projections show more than enough instability for at least some
thunderstorms to develop, with boosts of ascent accompanying each
vort max, in a favored north to northeasterly wind flow,
potentially raising wildfire concerns even more.
PUBLIC...Dense Smoke Advisory: 121.
SYNOPSIS AND MODEL DISCUSSION...TM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JPW