Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 08/30/22
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
751 PM PDT Mon Aug 29 2022
.SYNOPSIS...29/144 PM.
High pressure will produce a prolonged warming trend with only a
minimal marine layer. By mid week very hot conditions will develop
with triple digit heat for many valley and mountain locations.
Even hotter conditions are expected over the Labor Day weekend
into early next week. This heat may be record breaking and will
produce a very high risk of heat illness.
&&
.SHORT TERM (MON-THU)...29/750 PM.
***UPDATE***
Latest satellite and surface observations indicate clear skies
across the district, except for a patch of stratus/fog between
Long Beach and Catalina Island. Current AMDAR soundings indicate
marine inversion near 800 feet deep. Typical onshore winds,
gusting to around 20 MPH, are observed across interior sections.
For the immediate short term, no significant issues in the
forecast. Based on current satellite trends, stratus coverage
overnight will be limited. Current forecast indicates stratus
developing overnight across the Central Coast as well as the
immediate coast of Ventura county. For now, see no reason to
deviate from this forecast, but would not be surprised to see the
stratus coverage be even more limited than current forecast. Given
the depth of the inversion, any fog that forms will likely be
dense. Other than the marine layer stratus, the weather is
expected to be very uneventful overnight.
Overall, current forecast has great handle on the immediate short
term. So, no significant updates are anticipated.
***From Previous Discussion***
Temperatures have started their climb today as onshore flow
weakens and high pressure builds in from the southeast. These
trends will continue through Thursday with temperatures reaching
the lower 90s across the inland coastal plain and 100-110 inland.
We may be approaching records in the valleys on Thursday but there
likely won`t be enough offshore flow to get records closer to the
coast where records in the high 90s. It won`t be quite as hot
along the Central Coast with this event but still 5-10 degrees
above normal. Overnight lows will be warming up as well,
especially in the foothills and lower mountains with lows in the
70s and lower 80s. This is just part one of the heat wave as
models continue to show an even hotter heat wave over the holiday
weekend and into early next week.
Models have also been consistent showing a moderate northerly
flow developing across the Santa Ynez Range this week. Gradients
peak Wednesday night at -4.5mb, suggesting a moderate Sundowner
event with peak winds up to 45 mph. These will mostly be focused
in the western foothills but some winds to the coast are likely as
well. With models showing 850 mb temps just under 40c that
evening we could see temperatures in the foothills around 100 and
upper 80s and 90s at the coast with the help of downslope warming.
The Excessive Heat Watch that was issued Sunday will be converted
to a Warning this afternoon for all the same areas, essentially
all areas except most beaches and the Central Coast. While not all
areas will technically be reaching warning criteria during this
first heat wave, given the duration extending into next week with
even hotter temps expected it was felt that going with just one
headline was best.
Marine layer coverage will be tricky this week as the upper high
expands and gradients weaken. It`s likely to become much shallower
and with the northerly flow increasing aloft expect the coverage
south of Pt Conception to decrease quite a bit.
.LONG TERM (FRI-MON)...29/219 PM.
On Friday the northerly flow weakens and an eddy circulation will
develop that will cause rapid cooling of the lower layers south
of Pt Conception as well as an increase in onshore flow. However,
in hot patterns like this this doesn`t always translate to
significant cooling at the surface. We`ll have more detailed model
info on this tomorrow as we move into the window of our higher
res models. For now have followed the slightly cooler blended
model trends for Friday, though it will still be 5-10 degrees
above normal and it likely won`t be enough to drop any of the heat
warnings.
Saturday any cooling that happened Friday will be going away as
onshore flow weakens again and the high over the west becomes even
stronger, as much as 600dam according to the ECMWF. Between that
and gradients actually turning lightly offshore Sunday and Monday
temperatures will likely be even warmer than the first wave this
week with valleys highs possibly up to 115 and inland coastal
areas close to 100. Chances for Downtown LA reaching at least 100
Sunday have gone up to 43% and chances for Woodland Hills
reaching at least 115 are 33%. It would likely require a stronger
offshore gradient to get temps that hot and the latest EC does
show a LAX-DAG gradient of -3.8 Monday, but it often is biased
too low. Since many of the current temperature records are from
the extremely hot 2020 Labor Day heat wave when temps in the
valleys reached 120 and 100-110 near the coast, it`s going to be
tough to break records in a lot of places. However, this will
still be a very dangerous and long lasting heat event for many
areas. The current heat warnings go through the last day of our
forecast period which is Labor Day, however it`s very likely they
will be extended into next Tuesday tomorrow as models show only
minimal cooling.
&&
.AVIATION...29/2319Z.
At 2215Z, the marine inversion at KLAX was based at 900 feet.
The top of the inversion was 3600 feet with a temperature
of 25 degrees Celsius.
Overall, moderate confidence in 00Z coastal TAFs and high
confidence in valley/desert TAFs. For coastal sites, lower
confidence due to vagaries of the marine layer stratus. Most
likely CIG/VSBY restriction will be confined to the Central Coast
(KSMX/KSBP) with 50% chance of CIG/VSBY restrictions at
KOXR/KCMA.
KLAX...Moderate confidence in 00Z TAF. There is a 20-30% chance of
IFR/LIFR conditions developing 08Z-16Z. No significant easterly
wind component is expected.
KBUR...High confidence in 00Z TAF with CAVU conditions anticipated
through the period.
&&
.MARINE...29/750 PM.
For the Outer Waters, moderate confidence in current forecast. For
tonight through Tuesday night, there is a 60-70% chance of Small
Craft Advisory (SCA) level winds across PZZ673/676. For Wednesday
through Saturday, there is a 60-70% chance of SCA level winds
across the entire Outer Waters.
For the Inner Waters north of Point Sal, moderate to high
confidence in current forecast. Tonight through Tuesday night,
high confidence in winds and seas remaining below SCA levels. For
Wednesday through Saturday, there is a 40-50% chance of SCA level
winds in the afternoon and evening hours.
For the Inner Waters south of Point Conception, moderate to high
confidence in current forecast. Across the western half of the
Santa Barbara Channel, there is a 30% chance of SCA level winds
during the late afternoon and overnight hours Tuesday night
through Wednesday. Otherwise, winds and seas are expected to
remain below SCA levels through Saturday across the rest of the
southern Inner Waters.
A building ridge overhead will squash the marine layer through the
week. So, if any fog develops over the coastal waters, the fog
will be dense.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning in effect from 11 AM Wednesday to 8 PM
PDT Monday for zones
53-54-59-88-342>345-348>353-355>359-363-365-547-548. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Wednesday for
zones 673-676. (See LAXMWWLOX).
&&
$$
PUBLIC...MW/Thompson
AVIATION...RAT
MARINE...RAT
SYNOPSIS...MW
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox
Area Forecast Discussion
National Weather Service Reno NV
218 PM PDT Mon Aug 29 2022
.SYNOPSIS...
A weak low pressure system may trigger isolated showers and
thunderstorms late today and tonight, with a few dry lightning
strikes and possible gusty outflow winds. Otherwise, expect hot
and dry conditions to prevail the rest of the week with highs
approaching record values by mid-week. These hot above average
temperature will likely extend through the Labor Day weekend.
&&
.SHORT TERM...Through Tuesday Night...
A weak negatively tilted trough will be passing by today, providing
enough forcing to generate showers and thunderstorms this afternoon.
After the trough passes, a ridge building in will bring well above
average temperatures and dry conditions.
The thunderstorms today will be on the drier side, even with PWAT
values between 0.60-0.70". Fast storm motions, high cloud bases,
and a shallow moisture layer will yield low precipitation with
these storms. The latest model guidance has been very consistent
in showing storms forming around US-95, moving northward from
southern Lyon county up to northern Washoe through the evening.
Main impacts with these storms will be gusty outflow winds up to
45 mph, blowing dust downstream from sinks/dry lake beds, and dry
lightning. For those at Burning Man, there is a 15-20% chance that
Black Rock City will see a rain shower tonight. After 8pm
tonight, a few very light showers may develop in Lassen county and
last until midnight.
Tomorrow will be the beginning of the "Heat Wave" as a southwesterly
flow sets up, drawing in warm, dry air. High temperatures across
western NV will be flirting with the 100 degree mark, while Sierra
communities will be in the mid to upper 80`s. Typical westerly
zephyr winds with gusts of 25 mph will set up today and tomorrow.
-Justin
.LONG TERM...(Wednesday onward)...
No major changes to the extended forecast as strong high pressure
builds over the western US and brings to bear an extended period of
well above average daytime temperatures to the region. Ensemble
cluster guidance projects further strengthening of the central area
of high pressure over the Great Basin, central Rockies, and Desert
Southwest through the remainder of this week through the Labor Day
weekend.
ECMWF Extreme Forecast Index only solidifies the notion that this
late summer “Heat Wave” over the region will continue into next week
with the largest variances still remaining west of the Sierra. But
blended guidance still consistently shows a 1-in-3 chance for lower
valley temperatures over western NV extending into the low triple-
digit range with the best chance for the highest temps occurring
during the upcoming holiday weekend. The date for the last 100F temp
recorded at the Reno-Tahoe International Airport for any September
may well move to the right beyond the current Sept 5 date reported
in 2020.
With high confidence it can be said, as in previous discussions,
that this upcoming prolonged range of above normal temperatures will
bring periods of moderate to high heat health risks or western
Nevada valleys that carryovers into the Labor Day weekend and may
well extend into early next week.
* Moderate Risk - those sensitive to heat, especially those who lack
effective cooling and/or adequate hydration (pets, elderly, kids
included).
* High Risk - covers much of the population, especially those in the
moderate risk category.
A couple of weak embedded upper short waves that passing Wednesday
and again Friday through the Pac NW look to brush farther south
over the northern areas of CA/NV, and bring some enhancement to
local winds for areas along and north of I-80. Burners at the
Black Rock City could experience increased periods of patchy
afternoon blowing dust over the playa during these trough
passages. But don’t expect the winds to bring any immediate relief
from the heat as high pressure maintains its steady grip over the
western US. The typical late afternoon-early evening zephyr wind
gusts around 20-25 mph may not be much help mitigating the ongoing
heat over the region as well.
Labor Day Adventurers - Be prepared for the heat! Pack extra
hydration/cooling, including but not limited to extra shade options
and other sun protection, lots of hydration via water or
electrolytes, and review the signs of heat illness to stave off a
visit to the emergency room. -Amanda/Edan
&&
.AVIATION...
* VFR conditions will prevail for the upcoming week with potential
for density altitude impacts from Wednesday onward for rotor and
fixed winged aircraft as temperatures rise well above average.
* Low chances (5-10%) for isolated thunderstorms directly impacting
main terminals later this evening. Occasionally lightning, along
with gusty- erratic outflow winds ranging 30-35kts could extend
outward enough to impact western NV terminals (RTS-RNO-NFL-LOL)
this evening and NE CA later tonight. -Amanda
.FIRE WEATHER...
Isolated dry thunderstorms remain possible late this afternoon
into the early evening hours. The best chances for a few storms
will be in west central Nevada late this afternoon as daytime
heating coincide with a weak upper level wave moving over the
region. There are signals for some convection in NE California
overnight, but with limited upper level instability and a very
dry airmass, lightning will be unlikely. Any storms that do form
will be high based and moving rapidly to the north around 20-30
mph this afternoon, limiting rainfall.
After today, a long period of hot and dry conditions with typical
afternoon breezes is expected as high pressure builds over the
west coast. A slightly stronger wind day is possible on Friday.
Hot and dry are a typical precursor to increased fire weather
conditions so we`ll be keeping an eye on the eventual break down
of the high pressure for the next period of potential fire
critical weather conditions. -Zach
&&
.REV WATCHES/WARNINGS/ADVISORIES...
NV...None.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno