Red Flag Warning 7, NWS Anchorage, AK

194 
WWAK61 PAFC 041711
RFWAER

URGENT - FIRE WEATHER MESSAGE
National Weather Service Anchorage AK
911 AM AKDT Sat Jun 4 2022

AKZ145-050600-
/O.CON.PAFC.FW.W.0007.220604T2100Z-220605T0600Z/
911 AM AKDT Sat Jun 4 2022

...RED FLAG WARNING REMAINS IN EFFECT FROM 1 PM THIS AFTERNOON TO
10 PM AKDT THIS EVENING FOR LIGHTNING FOR THE SUSITNA VALLEY...

* Timing...1 PM to 10 PM AKDT Today.

* Location...Susitna Valley.

* Lightning Activity Level...6 (Dry lightning).

* Winds...Northeast 5 to 10 mph. Gusts to 25 mph near 
  thunderstorms.

* Relative Humidity...As low as 18 percent.

* Temperatures...In the mid 70s to near 80.

* Impacts...Dry lightning significantly increases the risk of 
  new fires developing across the area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A red flag warning means that critical fire weather conditions
are imminent or occurring now, or will shortly. It is directed
toward fire agencies, and through them to the public.

&&

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
520 AM AKDT Fri Jun 3 2022

.ANALYSIS AND UPPER LEVELS...

An east-west oriented upper level ridge still remains in place
across much of southern Alaska this morning. However, the ridge is
finally starting to break down some with heights lowering. Two
vertically stacked upper level lows (the same ones that we have
been talking about for days now) remain present this morning with
one to the south of the Western and Central Aleutians and the
other one moving eastward towards British Columbia. Underneath the
upper level ridge, much of Southcentral remains under mostly
clear skies with decent radiational cooling. Also, mid to high
level clouds can be seen on nighttime microphysics imagery over
the northeast Copper River Basin from remnant showers that
occurred yesterday evening. Same thing can be seen across
Southwest Alaska especially over the Kuskokwim and Kilbuck
Mountains. The low pressure system south of the Aleutians and
Bering continues to keep the area unsettled with occasional
showers from time to time and breezy conditions.

&&

.MODEL DISCUSSION...

Model guidance remains in decent agreement on the synoptic
features out through Day 2. The main forecast issue overnight
continues to be with the upper level shortwave that will be
meandering about the Alaska Range over the weekend and determining
if the thunderstorms that occur will be dry or wet. Most model
forecast soundings are showing a fairly dry lower atmosphere over
Southwest as well as Southcentral leading to high LCL (Lifting
Condensation Level) heights. See Southcentral and Southwest
section for more details on potential for dry lightning.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 2: Today
through Saturday night)...

Hot temperatures will continue through Saturday with temperatures
10 to 15 degrees above normal with some areas near or breaking
record high temperatures. The high pressure that has brought the
hot and dry air over the area is beginning to weaken with a weak
shortwave moving across the Copper River Basin today and westward
this evening. This wave combined with instability will be the
focus of showers and isolated thunderstorms. These storms will be
high based as the lower levels of the atmosphere are very dry with
only light amounts of precipitation expected in the valleys with
a bit more in the higher elevations. Additionally, gusty winds
will be possible with these storms due to evaporational cooling
allowing the air to accelerate downward. Saturday a weak area of
low pressure with vorticity, or spin in the atmosphere, will
combine with unstable air to spark another round of showers and
isolated thunderstorms. These storms will continue to be dry in
the low levels but may have a bit more moisture to work with as
storm coverage will increase, and the storms will be very slow
movers so this will give the air more time to add moisture.

&&

.FIRE WEATHER...

An upper level ridge that has been so persistent across much of
Southern Alaska for the past week will continue to break down
further today. As a result, most of the subsidence that has been
occurring aloft will virtually be eroded today aiding in shower
and thunderstorm development. Any thunderstorms that do develop
will have high LCL (Lifting Condensation Level) heights of
approximately 8,000-10,000' with very dry air beneath this level.
Therefore, any storms that do develop are likely going to be dry
thunderstorms which will be capable of producing dry lightning
especially around the Alaska Range and the northeast Copper River
Basin. Also, due to the very dry low levels, any rain that does
fall is expected to virtually evaporate (virga) before reaching
the ground. When looking at the forecast atmospheric profile
(soundings), we do see an inverted V shape to it meaning that any
of these storms could produce gusty winds underneath them. Heading
into the weekend, there is still uncertainty as to if any storms
will be dry or wet but each day will basically set up the next. As
we continue to put a little more moisture into the air each day,
eventually, we should have wet thunderstorms.

&&

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

Fire weather, both convective and non-convective, remains a
concern for much of Southwest Alaska. Hot and dry conditions will
continue through Sunday as temperatures climb into the high 70s
and relative humidities dip as low as the teens and twenties.
Northerly winds pick up on Friday and Saturday as two weak
surface troughs push across Bristol Bay.

Convective activity will increase as the longwave ridge over the
Southern Mainland continues to break down. Weak instability will
lead to isolated rain showers across Southwest Alaska this
afternoon, with no lightning expected. Lightning becomes a
concern by Saturday afternoon, when a robust shortwave approaches
from the north. This shortwave will likely provide enough forcing
to produce thunderstorms on both Saturday and Sunday afternoons.
Saturday's thunderstorms will be isolated with little associated
rain. As such, lightning associated with these storms could
potentially start a fire. Fire danger lessens into Sunday
afternoon. Though the shortwave moving across Southwest on Sunday
will likely produce more thunderstorms, the influx of moisture
will also produce more rain.

&&

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

Little has changed with the vertically stacked low spinning near
the Western Aleutians. The low and its front will continue to
weaken before dipping south on Saturday. Winds will largely be
below 25 kt, except through gaps and passes north of the Eastern
Aleutians. Rain along the front in the Eastern Aleutians, and
rain showers around the low center in the Central Aleutians, will
slowly taper off into Saturday. With high pressure being
displaced towards the Bering Strait by the vertically stacked low,
the marine stratus will likely continue to lift and fog will be
less of a concern. However, as the low dips south Saturday and
high pressure slowly spreads across the Bering Sea, low stratus
and fog may return.

&&

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

Expect winds less than 35 kts and seas less than 20 ft for the
Saturday through Monday period.

&&

.LONG TERM FORECAST (Days 4 through 7: Monday through Thursday)...
A wetter pattern looks to develop over Southcentral early next
week and help to displace a persistent ridge of high pressure over
the region as of this moment. Models continue to depict a
longwave trough settling into the Gulf by Monday with a weak
surface trough over the eastern Bering and interior Southwest.
This pattern change will bring southeasterly flow from the Gulf
into Southcentral with increasing rain chances from Monday into
the latter half of the week. Mildly cooler temperatures and some
much needed drought relief are forecast. Precipitation chances are
also expected to spill over into Southwest as Monday’s wave of
low pressure departs Southcentral. Timing of increased
precipitation chances for Southwest will wait until Tuesday, but a
steady series of smaller disturbances, being brought in from the
longwave trough over the Gulf, will keep precipitation chances in
the forecast for mainland Alaska through Thursday. High pressure
over the western Bering looks to change little and will have
trouble gaining any additional footage as multiple smaller
disturbances traverse the region. This will likely lead to
continued marine stratus and areas of fog west of the Pribilofs
and over the Western/Central Aleutians, as well as milder winds in
the wake of a departing Aleutian front into the North Pacific on
Monday. Something to keep an eye on will be the potential arrival
of a new trough of low pressure digging southeastward from the
northern Bering and into the Kuskokwim Coast/Bristol Bay area
Wednesday into Thursday. This second source of convergence and
moisture would see increasing rain chances develop from Kuskokwim
Bay southward into the Alaska Peninsula toward the end of the
period.

&&

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

&&

SYNOPSIS AND MODEL DISCUSSION...MV
SOUTHCENTRAL ALASKA...RC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KC
MARINE/LONG TERM...DAN