Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/18/19

Area Forecast Discussion

National Weather Service Denver/Boulder CO

 811 PM MDT Mon Jun 17 2019

.UPDATE...
Issued at 800 PM MDT Mon Jun 17 2019

Areas of rain and a few storms continue over the plains early this
evening. Meanwhile a weak upper level trough will move across the
area overnight. Thus expect scattered showers and and a few tstms
to continue past midnight over much of the area, however,
intensity will be lighter as compared to what occurred this aftn.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 230 PM MDT Mon Jun 17 2019

Afternoon convection is underway across the mountains
and foothills with heavy rain and small hail the main threats. So
far, storms have been producing about a half inch per hour or less
rainfall rates. PW values ranging from 3/4 to an inch over the
plains. Initially the Front Range urban corridor and adjacent areas
are a bit more stable with ACARS soundings over Denver still showing
weak stable layer near 700mb due to more cloud cover from this
morning. With time, storms expected to push east over the plains
and still looking at strong to severe storms further east of the
urban corridor with better surface heating. CAPE values still
expected to push 2000 J/kg but mid level flow only 15-25kt. With
several weak impulses aloft expect another round of storms through
the evening so will carry chance pops through at least midnight.

For Tuesday, expect another cool and showery day with another round
of showers and thunderstorms in the afternoon. Precipitable water
values will remain high on Tuesday, generally around one inch so
main threat will be heavy rain. Instability is a bit weaker on
Tuesday, generally under 1000 J/kg along with weak shear profile,
so severe weather threat will be lower. Temperatures will remain
in the upper 60s and lower 70s across lower elevations. Will keep
the likely PoPs going through Tuesday given the high moisture
levels.

.LONG TERM...(Tuesday night through Monday)
Issued at 230 PM MDT Mon Jun 17 2019

A shortwave trough axis will push across the area Tuesday night to
usher in drier air in northwesterly flow aloft. This will bring
gusty downslope winds to the foothills and nearby urban corridor,
keeping temperatures moderated.

A shortwave upper ridge will bring warmer and drier weather to
the area ahead of the next system dropping into the Pacific
Northwest. PWATs will be about one to two tenths drier compared to
the last two days, with values in the 0.5 inch range over the
mountains, 0.75 inch over the urban corridor and up around an inch
over the far northeastern corner of the state. Showers and weak
storms will be isolated to scattered in coverage, with gusty winds
and small hail the main impacts. Minimum temperatures will be
relatively warm overnight with a continued surface trough to the
lee of the mountains.

An upper low will travel east along the US/Canadian border
extending a trough into the Great Basin Thursday and Friday. Flow
aloft will turn flow more westerly Thursday before more
southwesterly Thursday night into Friday as a jet pushes down
across the northern Rockies. After the warm night, Thursdays
temperatures will likely be the warmest, with readings in the low
80s over the plains, and in the upper 50s to lower 70s over the
high country. Lift from the jet and low level moisture moving
north from the southern Great Plains into the surface lee low will
bring a higher chance for thunderstorms, especially near the
northern border. High values of shear will allow some of these
storms to have the chance to become severe each afternoon and
evening. Friday night, a cold front will drop south across the
area.

The upper trough will slowly transition across the forecast area
this weekend with cooler temperatures and daily showers and
thunderstorms, keeping our area green well into the month of June.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 800 PM MDT Mon Jun 17 2019

Showers and a few weak tstms have redeveloped over western
portions of Weld county and are slowing moving southeast. For now
will just mention vcsh in the taf as this activity should stay
northeast of DIA. Otherwise will see stratus develop overnight
around 09z. Winds have gone to a light northerly northeast and
should become southerly by 06z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...RPK
SHORT TERM...Entrekin
LONG TERM...Kriederman
AVIATION...RPK




Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 841 PM PDT Mon Jun 17 2019

.SYNOPSIS...17/809 PM.

Onshore winds will bring low clouds and fog across the coast and
valleys throughout the week, mainly for the morning and overnight
hours. Maximum temperatures will be slightly below normal across
the coasts and valleys and slightly above normal across the
interior.

&&

.SHORT TERM (MON-THU)...17/840 PM.

Weak upper level trough of low pressure combined with strong
onshore flow continued to bring a deep marine layer pattern
to Southwest California today, with low clouds lingering across
some immediate coastal areas through the afternoon hours. For
this evening, satellite imagery showing a chaotic low cloud
pattern, but expecting low clouds to fill in across most coastal
and valley areas overnight into Tuesday morning. Latest
ACARS data showing marine layer depth around 3000 feet across
the LA basin this evening. Over the next 24 hours, expecting
the marine layer depth to decrease a bit due to rising
heights and a slightly weaker onshore gradient. In fact,
latest 00Z NAM model showing a weak low level northeast
flow pattern across interior sections on Tuesday morning.
This should allow the low clouds to burn off better on
Tuesday.

There were some afternoon cloud build-ups over the the
mountains this afternoon. Latest 00Z NAM model showing
slightly better moisture/instability for Tuesday afternoon,
so will continue with slight chance of convective showers
for the Ventura county mountains. Cannot totally rule out
an isolated thunderstorm, but at this point would say
the probability is around 10 percent for the Ventura county
mountains. If any storms were to develop, model soundings
suggest they would be high-based, with gusty downdraft winds
being the biggest threat (due to inverted-v type sounding
structure).

*** From previous discussion ***

Heights increase on Wednesday as the trof axis moves further south
and the Pacific high nudges back in from the west. Subsequent warming
aloft will strengthen the capping inversion. Onshore flow will
increase back to Monday`s levels. Both of these things will slow
clearing in the valleys and allow only partial clearing across
the coastal areas.

Afternoon high temperatures will run about 5 degrees below normal
along the coasts and valleys due to the marine layer and strong
onshore flow but will rise to slightly above normal across in the
interior on Wednesday and Thursday due to the higher heights.

Gradients of over 10mb suggest the already strong onshore flow
will increase on Thursday. Expect slow marine layer clearing in
the valleys and very limited clearing along the coasts. It will be
windy across the Antelope Valley. Temperatures will cool a few
degrees.

.LONG TERM (FRI-MON)...17/205 PM.

The gradient remains exceptionally strong into Friday with
conditions similar to those on Thursday. Gradients relax
somewhat over the weekend as the upper-level low moves to the
northeast. The night through morning low cloud pattern will
persist but there will be somewhat better afternoon clearing
although beach clearing will be questionable.

The pattern looks very zonal for our area by Monday as a large
upper-level low centers itself about 250 miles west of Seattle,
and we are at the southern extend of the feature with westerly
flow aloft. Temperatures should warm a bit.

&&

.AVIATION...18/0028Z.

At 0015Z at KLAX...The marine layer was 3000 feet deep. The top
of the inversion was around 4500 feet with a temperature of 18 C.

High confidence in TAFs. Strong onshore flow pattern and deep
marine layer resulted in delayed burnoff of low clouds this
afternoon, with some coastal areas continuing to see cigs
as of 00z. Low clouds and fog expected to spread into most
coastal/valley areas overnight, however marine layer depth
not expected to be quite as deep as this morning. With weak
low level offshore wind influence across the interior, look
for better clearing on Tuesday afternoon, especially valleys.

KLAX...High confidence in TAF. MVFR cigs expected to prevail
across most of the forecast period. There is a 30 percent chance
of clouds burning off on Tuesday afternoon.

KBUR...High confidence in TAF. With deep marine layer pattern
in place, expecting low clouds to quickly redevelop later this
evening. Higher probability of clouds burning off by late morning
or early afternoon on Tuesday.

&&

.MARINE...17/821 PM.

Winds and seas will likely remain below Small Craft Advisory
(SCA) levels through at least Thursday. There is a 30% chance for
a low end (SCA) for Friday afternoon across the outer waters.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

.HAZARD POTENTIAL OUTLOOK (THU-MON).

No significant hazards expected.

&&

$$

PUBLIC...Gomberg/jld
AVIATION...Gomberg
MARINE...Sweet
SYNOPSIS...Phillips/B

weather.gov/losangeles