Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/03/21
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
802 PM PST Thu Dec 2 2021
Temperatures will vary from below normal near the coast, near
normal for the valleys, and above normal for the interior. Then
warming most areas Sunday into Monday to above normal as high
pressure develops along with locally gusty northerly winds. Then
cooler Tuesday through the rest of the week with a deepening
.SHORT TERM (THU-SUN)...02/759 PM.
Latest satellite and surface observations indicate widespread
stratus/fog across the coastal plain with clear skies elsewhere.
Current AMDAR soundings indicates marine inversion around 1400
feet deep. No significant winds are currently observed.
For the immediate short term, main focus will continue to be on
the marine layer stratus/fog. With weak onshore gradients (and
moderate 24 hour onshore trends), the inversion has deepened. So,
currently no dense fog is observed across the area. Later tonight,
as the stratus/fog pushes into the lower coastal valleys, there
could be some dense fog, but not likely widespread enough to
warrant any advisories. However, the situation will need to be
monitored closely overnight. Otherwise, the weather situation
should remain very benign with light winds and mostly clear skies
away from the marine layer.
Overall, current forecast has good handle on the immediate short
term. So, no significant updates are expected at this time.
***From Previous Discussion***
Solid marine layer stratus covers the central and southern
California coastline with many beaches staying overcast all day.
This combined with 3-4mb onshore trends has brought significant
cooling to the coastal valleys and Central Coast as most areas
are 15-20 degrees cooler than yesterday. However, above about
1500` elevation there has been little change in temperatures so
places like the Santa Clarita Valley, the higher portions of the
Santa Monicas, and the rest of the mountains and Antelope Valley
are very similar to yesterday.
AMDAR soundings indicate some deepening of the marine layer today
which should help mitigate dense fog near the coast but this means
likely dense fog issues farther inland into the coastal valleys.
So dense fog advisories may again be needed tonight into Friday
morning. Temperatures have likely bottomed out today for most
coastal valley and Central Coast locations but expect at least
some cooling to push into the interior sections Friday.
Not much change overall on Saturday as a weak upper low passes to
the south. Following that northerly gradients are expected to
increase as ridging nudges in from the north. Light north to
northeast winds could develop as early as Saturday afternoon
across the interior then increase Saturday night into Sunday
morning. ECMWF ensembles have really scaled back on the wind
strength and the gradient forecast has dropped to only -2mb. The
NAM is a little stronger and high res models still are showing
some gusts as high as 40 mph. Those would likely be very isolated
and at this point expecting most areas to be under wind advisory
thresholds. One possible exception could be southern Santa Barbara
County Saturday evening as the SBA-BFL gradient increases to
Most areas should warm up at least a few degrees Sunday as the
ridge axis is overhead and heights rise to around 584 dam. A
somewhat tricky temperature forecast though as there is potential
for more warming if the northeast gradient increases and we get
.LONG TERM (MON-THU)...02/210 PM.
A complicated weather pattern follows for the rest of next week
leading to a few possible scenarios. Models seems to agree on some
form of an inside slider coming through early Tuesday, though big
differences in strength. The vast majority of the ensembles favor
a mostly routine north to northeast wind event, maybe low end
advisory strength at best, though a handful are quite a bit
stronger and similar to the GFS deterministic. This particular
solution also spins up a strong eddy early Tuesday with the
possibility of some drizzle or light rain in LA County before the
northerly winds kick in. Wed/Thu weather mostly benign with
lighter winds and near to slightly above normal temperatures.
Beyond that there continues to be indications in the models for
increasing chances of rain later next week into the weekend.
However, it`s certainly not a slam dunk. The GEFS and Canadian
ensembles are more in favor than the ECMWF ensembles where not
even half of the solutions show any rain for southern California.
The 12z deterministic GFS is interesting showing a 528mb low right
over LAX next Friday afternoon. However, looking at the individual
GFS ensemble members this is by far an outlier with most of the
solutions in the 550-560mb range. Still quite a bit lower than
the EC ensemble mean which is near 568mb.
At 2320Z at KLAX, the marine layer depth was 1300 feet. The top
of the inversion was around 2600 feet at a temperature of 19 C.
High confidence in desert 00Z TAFs. Low to moderate confidence in
the remainder of TAFs. Timing of cat changes could be off by +/-2
hours. There is a 20 percent chance of marine clouds reaching
KPRB. There is a 20% chance of KSBA, KOXR, and KCMA only going as
low as IFR conditions. There is a 20% chance of KSMO, KLAX, and
KLGB developing LIFR conditions.
KLAX...Low to moderate confidence in the 00Z TAF. There is a 20%
chance in bkn002-004 with 1/2-1 SM from 04-16Z. High confidence
in no significant east wind component.
KBUR...Low to moderate confidence in the 18Z TAF. There is a 30
percent chance of marine clouds reaching the airfield as early as
High confidence that winds and seas will remain below SCA level
through Friday. High confidence in widespread SCA level NW winds
from the Central Coast to San Nicolas Island Saturday afternoon
through at least Monday. There is a 10% chance of Gale Force gusts
Sunday afternoon into Sunday night for the outer waters Southwest
of Point Conception to Northwest of San Nicolas Island.
CA...Beach Hazards Statement in effect from 4 AM PST Friday
through Sunday morning for zones 34-35-40-41. (See LAXCFWLOX).
.HAZARD POTENTIAL OUTLOOK (SUN-THU).
Large high tides may result in minor coastal flooding each morning
through Monday. Gusty north to northeast winds will result in
elevated fire weather conditions Sunday and Monday.
Area Forecast Discussion
National Weather Service Phoenix AZ
502 PM MST Thu Dec 2 2021
.UPDATE...Updated Aviation Discussion.
Unseasonably warm temperatures and dry conditions with light winds
will be common across the region through at least the weekend.
Afternoon temperatures are likely to be within a few degrees of
daily records through the period. A more active weather pattern
will take hold by early next week, with a series of weather
systems affecting the Southwest Tuesday and Wednesday, and again
during next weekend. Rainfall amounts are expected to be limited,
but temperatures will trend downward closer to seasonal normals
by late next week.
Satellite imagery this afternoon shows scattered clouds near 10
thousand feet across south-central Arizona, especially anchored
near and downwind from mountain peaks. ACARS soundings reflect a
modest moist layer at this level transported generally
northwestward amidst a broader cyclonic circulation surrounding a
series of weak upper lows extending from northern Mexico into the
eastern Pacific. Broader scale ridging is more dominant across the
west, and is shunting a belt of strong westerlies into the Pacific
Northwest and Northern Rockies. The warm temperatures across the
region reflect the anomalous heights in place, with daytime
readings continuing to remain around 10 degrees above normal for
Into this weekend, temperatures will trend downward slightly as
one of the aforementioned weak upper lows moves into Arizona and
the upper ridge begins to lose its stranglehold over the western
US. Other than occasional cloudiness, moisture will continue to
remain meager and not bring any precipitation chances to the
region through at least Monday. Another slightly stronger closed
low will advance eastward early next week as the northern stream
becomes more amplified and the primary jet dives southward across
the Great Basin and southern Rockies. Individual model members are
becoming more consistent showing a pronounced shortwave trough
moving through Tuesday, with an increasing number breaking out
some precipitation across south-central Arizona. NBM QPF guidance
remains fairly lackluster on Tuesday with the 50th percentile
values at 0.00" for nearly the entire CWA, but the 90th
percentile depicts close to 0.25" of rain possible. The
orientation and antecedent atmospheric conditions will not favor a
widespread soaking rain regardless, but if trends continue to
support a strong and dynamic trough moving through, rain potential
will likely increase for southwest and south- central Arizona.
Later in the week, uncertainty increases considerably due to the
large pattern shift underway with potential solutions ranging from
a strong bowling ball type low moving through the Southwest, to a
pattern featuring a series of open shortwave troughs. WPC cluster
analysis highlights strong negative mid-level height anomalies
over the northern Rockies for nearly every solution, but the
details of where and how the northern stream jet and associated
amplification magnitude evolve vary considerably. NBM guidance is
slightly more bullish than earlier in the week for precipitation
in the Friday through Saturday period, so a somewhat pronounced
signal is already evident in ensemble guidance. Temperatures may
also finally return closer to seasonal normals during this period,
with highs in the 60s possible.
.AVIATION...Updated at 0000Z
South-Central Arizona including KPHX, KIWA, KSDL, KDVT:
Winds will continue to be light, mainly favoring normal diurnal
trends through the period. Speeds are also favored AOB 6 kt.
Skies remain clear to mostly clear with the occasional FEW mid-
high clouds near 11 and 25 kft.
Southwest Arizona and Southeast California including KIPL and KBLH:
No aviation impacts are expected through the TAF period. Winds
will remain light and variable AOB 6 kts although with some NW
winds at KBLH tonight. Skies to remain clear to mostly clear with
FEW high clouds. There is a small (10%) chance of some fog developing
in the Imperial Valley Friday morning though the chances were too
low to include in the TAFs.
Saturday through Wednesday:
Dry conditions and occasional high clouds will be common through
the period. Temperatures will remain well above normal through at
least Monday before a mostly dry weather system moving through on
Tuesday brings temperatures closer to normal. Winds through the
period are expected to remain light with only occasional daytime
breezes. Min RH values are likely to fall between 15-25% for most
locations each day. Max RH values will be 35-55% each day.
Moisture levels rise slightly by the middle of next week.
Record high temperatures:
Date Phoenix Yuma El Centro
---- ------- ---- ---------
Dec 2 84 in 2017 85 in 1959 85 in 1949
Dec 3 81 in 1940 86 in 1958 90 in 1958
Dec 4 83 in 1979 83 in 1958 84 in 1940
Dec 5 82 in 2012 84 in 1958 85 in 1938
Dec 6 83 in 1939 83 in 1966 87 in 1938