Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/12/22
Area Forecast Discussion
National Weather Service Indianapolis IN
1021 PM EDT Tue Oct 11 2022
.Forecast Update...
Issued at 1020 PM EDT Tue Oct 11 2022
Forecast remains on track so far this evening; no major changes were
made. A plume of mid-level moisture continues to advect in from the
southwest. A residual elevated mixed layer resides just above the
surface, as noted on recent ACARS soundings out of IND. Combined
with another substantial dry layer around 500mb, rain showers
streaming in from the west have had a difficult time making it
beyond a Terra Haute to Lafayette line. Continued moisture advection
should allow some rain to eventually overcome these dry layers, but
amounts will generally remain under 0.10". In addition to the rain
chances, the surface pressure gradient is expected to tighten
overnight allowing winds to become gusty tomorrow. The
aforementioned sounding out of IND has a decent inversion at the
surface and that may prevent winds from reaching their full
potential until after sunrise. Once enough mixing occurs wind may
gust upwards of 30kts at times.
&&
.Short Term...(This evening through Wednesday)
Issued at 300 PM EDT Tue Oct 11 2022
Highlights...
* Increasing showers tonight
* Line of showers/thunderstorms tomorrow with high wind gusts
possible
* Non-thunderstorm wind gusts up to 30 MPH
Rest of Today and Tonight...
A deep trough and associated surface low will provide unsettled
weather across the Midwest over the next few days. SW return flow
upstream of the trough will increase mid level moisture. This will
take some time to reach the surface, but will provide wide spread
cloud cover over most of the region. Isentropic lift through this
saturated layer will lead to some precipitation. However, a
significant near surface dry layer will inhibit much of the rain
from reaching the surface. Sprinkles will be possible along the I-74
corridor, with <0.05" of rain possible over NW central Indiana
through this evening.
QPF chances increase for NW central Indiana overnight as diurnal
cooling aids in decreasing the surface dew point depression,
allowing some of the rain within SW return flow to reach the
surface. This will slowly progress eastward as a low level cold
front develops over the Plains/Northern Great Lakes. By tomorrow
morning portions of the Indy Metro and westward will have scattered
to isolated rain showers. Temperatures will have a difficult time
decreasing with extended cloud cover and SW flow keeping the PBL
from decoupling. The only locations that could see noteworthy
cooling will be SE central Indiana where cloud cover will be more
scattered. Expect lows in the low 60s with mid to upper 50s possible
for SE central Indiana.
Tomorrow...
Scattered showers will continue for western portions of central
Indiana, slowly eroding a near surface dry layer pushing into the
region. A narrow stream of low level moisture will be advected ahead
of the low level boundary increasing shower coverage by the early
afternoon for western central Indiana.
As the front pushes through tomorrow afternoon, showers and even
some low topped thunderstorms will be possible. The increased
surface moisture within the periphery of the front should allow for
a narrow zone of instability, enough for some convection to occur.
These showers will likely be capped at around 500-400mb, limiting
updraft growth and therefor lightning. However, any
shower/thunderstorm that does develop could provide high wind gusts
given a 40-50kt LLJ. Winds outside of showers will still be breezy
within a well mixed environment. Expect sustain winds around 15MPH
with gusts up to 30 most of the afternoon.
Temperatures will vary throughout central Indiana as well mixed
areas should get into the low to mid 70s. To the NW, with high
moisture and cloud cover, temperatures will be in the upper 60s.
&&
.Long Term...(Wednesday night through Tuesday)
Issued at 300 PM EDT Tue Oct 11 2022
Wednesday Night Through Sunday.
The system that will bring showers and a few storms to central
Indiana will exit the area Wednesday night with a few lingering
showers expected through midnight. A weaker secondary front will
then pass through later into the overnight hours with a few light
showers being the only impact. Cooler than normal temperatures will
then arrive for Thursday into the weekend as a seasonably strong
upper level closed low pivots around the Great Lakes. The mixing
layer on Thursday afternoon will deepen to around 750mb which will
allow for occasional wind gusts to 35 mph. Temperatures will be
favorable for patchy fog across the northern counties Thursday
night, but think winds will remain elevated enough to limit the
coverage to more sheltered areas.
Another weak cold front will pass through central Indiana around
Saturday but with the cold dry air in place that will be advecting
into the area during the late week, confidence in precipitation
chances is low. Do think there could be a few light
showers/sprinkles, but with both the uncertainty as to whether it
will rain or not and the timing of the front, will keep POPs minimal.
Monday and Tuesday.
Another seasonably strong upper level closed low will push through
the broader area of troughing Sunday into Monday and will set the
table for the first potential widespread freeze across central
Indiana. The latest model trends have been to strengthen this low
pressure system and bring an influx of colder air into the area.
Current thoughts are that sub-freezing temperatures are likely
Monday night with the potential for a hard-freeze across much of the
area. There may be a few lake enhanced clouds/light showers across
the northeastern counties Tuesday, but confidence is low and will be
dependent on the axis of the low to mid level jet.
&&
.Aviation...(00Z TAF Issuance)
Issued at 831 PM EDT Tue Oct 11 2022
Impacts:
* Decreasing cloud ceilings through the period to
* Wind gusts up to 35 kts through the day Wednesday
* Southwesterly wind shear expected Wednesday morning for KLAF and
KHUF
* Showers and thunderstorms tomorrow could have high wind gusts.
Discussion:
Clouds will continue to increase in coverage through the period as
well as decease in height, dropping to 4,000 ft by the end of period
as showers move through the area. Through tonight, KLAF will see
VCSH but towards daybreak, the line of rain will push eastward with
chances for rain at all sites through the day. Isolated stronger
cells could have higher wind gusts, otherwise non-thunderstorm winds
will be sustained around 15 to 20 kts out of the southwest and gusts
could reach up to 35 kts tomorrow. There will also be a wind shear
threat from early morning to midday for KLAF and KHUF, but can`t
rule out the threat reaching other TAF sites during that timeframe.
The heaviest rain is expected in the afternoon. The lines of showers
could briefly lower visibilities and drop ceilings to high MVFR
as they move through.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Update...Eckhoff
Short Term...Updike
Long Term...White
Aviation...KH
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
812 PM PDT Tue Oct 11 2022
.SYNOPSIS...11/221 PM.
Atypical weather continues much of this week as an upper level low
supports widespread night to morning low clouds and cooler than
normal temperatures. Afternoon thunderstorms across the mountains
today and Wednesday may spread west into coastal areas for the
overnight hours. Unsettled weather may return for the weekend.
&&
.SHORT TERM (TUE-FRI)...11/811 PM.
***UPDATE***
Latest satellite/surface observations indicate partly to mostly
cloudy skies across the area. Doppler radar data indicates
scattered showers and isolated thunderstorms east to west across
Los Angeles county and the adjacent coastal waters.
For the immediate short term, main focus will continue to be on
the upper low, currently spinning 70-80 south-southwest of
Catalina Island, and moisture/instability rotating around the
low. Looking at the high resolution model data (HRRR, HREF, SREF,
etc.) there will continue to be a threat of showers and
thunderstorms overnight across the district, with only San Luis
Obispo county likely to avoid any showers/thunderstorms. At this
time, best chances look to be south of the Channel Islands
overnight. So, will keep POPs in the forecast for the evening and
overnight hours. Will likely let the FLOOD WATCH expire at 1000 PM
as intensities with overnight activity are not expected to be too
problematic.
Other than the continued shower/thunderstorm threat, only other
issue will be the marine layer stratus. Currently, AMDAR soundings
indicate marine inversion around 1500 feet deep. With continued
onshore gradients, stratus/fog should be able to reform and move
into the coastal valleys overnight (although debris clouds from
convective activity could make stratus development a bit more
haphazard).
Overall, current forecast has good handle on the immediate short
term. So, no significant updates are expected at this time.
***From Previous Discussion***
A Flood Watch continues for Los Angeles county mountains and
desert through this evening. See below and in the FFALOX for
details.
The upper low pressure system continues to wobble well offshore
this afternoon. Resulting weak east to southeast flow aloft
continues to pull in mid-level moisture atop a stubborn and
unseasonably deep marine layer. While the best upper forcing with
this system remains offshore, moderate instability of 500-1000
CAPE has supported isolated to scattered convection forming mainly
along the high terrain due to differential heating. As
anticipated, storms are slow moving with back building and
training of storms already apparent. The Flood Watch in effect for
interior Los Angeles county looks reasonable as we have already
seen rainfall rates approaching a half of an inch per hour with
0.31 inches recorded in just 15 minutes west of the Bobcat burn
scar. Rainfall rates of 0.5 to 1 inch per hour will be possible
within heavier cells through this evening. We will note the
greatest concern is for recent burn scars such as the Bobcat burn
scar. Although it is just outside of the current Watch, the Fish
burn scar also bears watching should convection drift south off of
the mountains.
With the upper low wobbling north and northwest tonight, it may
pull isolated shower and thunderstorm activity west of the
mountains once again, with short range ensembles particularly
excited about the Channel Islands and vicinity. As the night
progresses, lingering activity will likely become suppressed to
over the coastal waters.
Wednesday afternoon to night, a spoke of organized upper energy
(vort max) is expected to rotate north through the region. This
synoptic support and moderate to strong mid-level lapse rates
should support more widespread convection than today, especially
west of Los Angeles county, into Ventura and Santa Barbara
counties. Storms will be faster moving than today, possibly
limiting flash flood concerns, although greater storm coverage
could lead to more in the way of training (back to back) storms.
Also, the aforementioned dynamics could support isolated showers
and thunderstorms into coastal areas, especially from western Los
Angeles county north to Santa Barbara county. In fact, the Weather
Prediction Center has much of southwest California in a day 2
(Wednesday) marginal risk for excessive rainfall. So at least
isolated, advisory level flooding or debris flows are possible,
especially near recent burn scars.
In addition to flood concerns, moderate DCAPE values and short
term ensembles support an isolated damaging microburst wind
threat, especially for Wednesday.
Thursday into Friday the upper low will drift north near the
Central Coast and back southwest. It looks to lose its moisture
tap, so we may see at least a break in convective activity. Below
normal height and cyclonic flow aloft will probably retain ample
night to morning low cloud presence. Marine layer patchy drizzle
is possible each morning to the west of the mountains.
Temperatures throughout the period will be at or below normal with
no significant wind concerns.
.LONG TERM (SAT-TUE)...11/221 PM.
Above normal agreement in ensemble guidance (GEFS ECS GEPS)
increases confidence that the upper low will push into the Baja of
california this weekend. Should it make a relatively close pass,
wrap around shower and perhaps thunderstorm activity will be in
play, especially for eastern Los Angeles county. The proximity of
the low should keep a low cloud pattern in place, although
offshore trends will likely squash the marine layer into coastal
areas. Moderate northeast flow at low levels should greatly limit
any flood concerns, although should thunderstorms form, they could
quickly scoot into coastal areas.
Forecast confidence drops off early next week. It appears a pop up
ridge will bring at least brief warming and drying trends ahead of
a possible secondary trough dropping into the region from the
northwest.
&&
.AVIATION...12/0112Z.
At 2341Z at KLAX, the marine layer was 1300 feet deep. The top of
the inversion was near 3100 feet with a temperature of 21 C.
Low to moderate confidence in TAFs. Timing of flight cat changes
could be off by +/- 2 hours. Shower and isolated thunderstorms
have decreased across the area this evening, but chances remains
through Wednesday night for sites south of KSMX. Flight cats
may fluctuate between IFR and MVFR in and near convection. Lower
confidence in coastal TAFs due to overnight to morning marine
layer clouds.
KLAX...Moderate confidence in TAF. Timing of flight cat changes
may be off by +/- 2 hours. There is a 20% chance of no clearing
through the period. Slight chance of isolated showers and Tstorms
may cause bouncing of flight cats between IFR and MVFR tonight.
Any east wind component should be less than 6 kt.
KBUR...Moderate confidence in the TAF. Timing of flight cat
changes could be off by +/- 2 hours. Slight chance of isolated
showers and Tstorms may cause bouncing of flight cats between IFR
and MVFR.
&&
.MARINE...11/119 PM.
No changes to the marine forecast in the afternoon issuance.
Cutoff low pressure system approaching the coast will continue
to bring isolated showers and thunderstorms to much of the coastal
waters through the morning. Any thunderstorms that develop will
be capable of producing brief heavy downpours, gusty winds, and
dangerous cloud to ocean lightning.
For the Outer Waters, moderate confidence in the forecast.
Conditions should remain mostly below Small Craft Advisory (SCA)
levels through Friday. There is a 20 percent chance of SCA winds
Thursday and Friday across all of the outer waters.
For the Inner Waters, high confidence in winds and seas remaining
below SCA levels through Friday.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Flood Watch in effect until 10 PM PDT this evening for zones
54-59. (See LAXFFALOX).
Flash Flood Watch in effect until 10 PM PDT this evening for
zones 54-59. (See LAXFFALOX).
PZ...NONE.
&&
$$
PUBLIC...Munroe/Thompson
AVIATION...Phillips/Sweet
MARINE...Sweet/Lund
SYNOPSIS...Munroe
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox