Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/02/23
Area Forecast Discussion
National Weather Service Indianapolis IN
932 PM EDT Thu Jun 1 2023
.Forecast Update...
Issued at 932 PM EDT Thu Jun 1 2023
The light east and northeast winds have advected in dew points in
the upper 40s to lower 50s over areas near and east of Interstate
65. Meanwhile, dew points will also gradually fall into the 50s over
areas to the west. Kept scattered cloud cover over the Wabash Valley
the next few hours, otherwise good radiational cooling setup and
with the drier near surface and boundary layer, not expecting fog to
be an issue except at perhaps briefly over sheltered areas west of I-
65 toward daybreak. Overnight lows in the upper 50s east to middle
60s southwest continue to look good, although there may be localized
sheltered cooler spots as is often the case with radiational
cooling.
&&
.Short Term...(This evening through Friday)
Issued at 243 PM EDT Thu Jun 1 2023
Generally quiet conditions persist across the region as of this
writing. With the exception of a very isolated shower or
thunderstorm across our west, this should continue through the short
term period.
Cumulus has been building slowly through the afternoon so far, with
the biggest buildups occurring west into Illinois. In terms of
appearance, the overall evolution of the cu field appears very
similar to yesterday. However, one minor difference exists that is
not apparent to the eye. It can be seen in recent ACARS soundings
out of Indianapolis...which shows a slightly drier column especially
in the mid to lower levels. This added dryness has largely prevented
shower and storm development across Indiana, while Illinois remains
within a deeper moisture profile. Nevertheless, some showers or even
a thunderstorm remains possible across our west which is of course
closer to the better moisture.
No convective hazards are expected today. Bulk shear is low, roughly
10kts. Around 1500 J/kg CAPE exists which is not low, but with a
modestly dry column, meager mid-level lapse rates, and little to no
surface forcing...convective potential will be very limited.
All showers, thunderstorms, and associated cumulus will diminish
after sunset. Winds out of the east should gradually become
northeasterly with time, and dry air wrapping around the ridge to
our north with filter in to the region. This dry air advection
should limit ground fog compared to last night. Expect similar low
temperatures compared to the previous couple of nights, generally in
the mid to lower 60s.
As dry air continues to flow in from the northeast, the lower
humidity will allow Friday to feel a bit better despite slightly
higher temperatures. Deeper mixing depths and broad large-scale
subsidence should allow for temperatures in the lower 90s for most
locations. Relative humidity could dip to as low as 20 to 25
percent, which may pose a slightly elevated fire risk given how dry
much of the area has been. Winds should be light, thankfully, with a
few gusts to as high as 15kts during the afternoon hours.
&&
.Long Term...(Friday night through Thursday)
Issued at 243 PM EDT Thu Jun 1 2023
Friday Night Through Sunday.
Generally dry and quiet conditions are expected for the weekend with
only small chances for pulse thunderstorms during peak heating. A
broad and weak ridge of high pressure will be in place by through
the early weekend as a low pressure system slowly sinks in from the
northeast. The center of the ridge will gradually be moving to the
west early weekend as a response to the approaching low which will
allow for a return to the northeasterly surface winds and a gradual
drop in afternoon dewpoints.
This will create slightly elevated fire weather conditions with
afternoon minRH around 20-25 percent although the winds will be
light enough to limit the overall threat. With the arrival of drier
air, coverage of afternoon showers and storms will also gradually
lessen into the weekend with PWATs near the 25th percentile and a
PBL of almost 10kft on Saturday. This dry airmass and plenty of
sunshine will also allow for a continuation of 90 degree days
through Saturday.
Monday Through Thursday.
The pattern tries to change early next week but with little changes
in the overall weather pattern as the upper level flow becomes more
northerly as the aforementioned low pressure system begins to move
back to the east. Gulf moisture remains locked to the far southern
states with dry air and little to no precipitation chances. A
reprieve from the heat looks likely though with the more northerly
surface flow advecting cooler air into the area which should keep
temperatures limited to the low 80s by Wednesday. Warmer air then
begins to work back in for Thursday as the ridge begins to gradually
strengthen again.
&&
.Aviation...(00Z TAF Issuance)
Issued at 646 PM EDT Thu Jun 1 2023
Impacts:
- Can not completely rule out a shower or thunderstorm at KLAF
and KHUF through 01z
Discussion:
There is a very low chance for a brief shower or thunderstorm at
KLAF and KHUF per radar trends and with a weak boundary nearby.
Otherwise, high confidence in VFR flying conditions as the light
east winds will keep the boundary layer dry for this time of year
and should prevent fog from forming overnight. The dry low levels
will likely also keep even diurnal cu from forming Friday afternoon
per local cu development progs.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...MK
Short Term...Eckhoff
Long Term...White
Aviation...MK
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
838 PM PDT Thu Jun 1 2023
.SYNOPSIS...01/540 PM.
Strong onshore flow will linger across the region through Friday.
There will be plenty of low clouds west of the mountains through
Friday morning, with some clearing likely Friday afternoon.
Slightly warmer temperatures are expected Friday with additional
warming Saturday, then a weak upper low will bring slight cooling
on Sunday. A stronger upper low will bring cooler weather Monday
through Wednesday, with a slight chance of showers late Monday
through Tuesday afternoon.
&&
.SHORT TERM (THU-SUN)...01/810 PM.
***UPDATE***
Forecast concerns for the overnight period include the extensive
low cloud cover over Ventura and Los Angeles Counties, thanks to a
very deep marine layer around 5000 feet deep and strong onshore
flow. Stratus clouds are now extending over portions of the
coastal slopes, as far inland as the western Antelope Valley
Foothills, up to Tejon Pass, and the lower portion of the Ventura
Mountains. The strong onshore flow (LAX to Daggett gradient of 9.8
mb at 600 pm is producing gusty southwest winds through Soledad
Canyon into the Antelope Valley foothills. Lake Palmdale has been
experiencing wind gusts of 52 to 58 mph for several hours, with
gusts to 45 mph further to the northwest in the hills. A Wind
Advisory was issued for these locally damaging gusts, this evening
through 300 am Friday.
An upper ridge will begin to build over the region on Friday, and
with the combination of rising heights aloft and decreasing
onshore gradients, believe that better clearing is likely than
what has been seen the past few days. However, while gradients are
weakening, they will still be somewhat strong, enough so that the
coastal areas and some coastal valleys could see only partial
clearing in the afternoon. Less complete clearing would lead to
slightly cooler temperatures in these areas Friday afternoon.
***From Previous Discussion***
Overall, 12Z models in good synoptic agreement through the short
term period. At upper levels, ridge will build over the area
through Saturday then will start to weaken on Sunday (as upper low
develops to the west). Near the surface, moderate to strong
onshore gradients will persist.
For the short term, the main issue will be the marine layer
stratus and its impact upon temperatures. Current AMDAR soundings
indicates marine inversion around 5000 feet deep and subsequent
clearing of stratus is rather minimal this afternoon. With the
rising H5 heights through Saturday, the marine inversion should
become a bit more shallow each day with slightly less inland
penetration each night (although there still will be plenty of
stratus across the coastal valleys). Hopefully with the more
shallow inversion and slight weaken of the onshore gradients, the
stratus will clear more significantly Friday and Saturday. For
Saturday night and Sunday, will expect relatively persistent
stratus behavior with good clearing Sunday afternoon.
With the building upper ridge and lessening marine influence, most
areas should see a warming trend through Saturday with little
change on Sunday. So, by Saturday and Sunday, most areas should
have high temperatures near or slightly above seasonal normals.
.LONG TERM (MON-THU)...01/201 PM.
Overall, 12Z models continue to exhibit decent synoptic agreement
through the extended period. Main feature of note will be weak
upper low that moves over Southern California Monday/Tuesday then
wobbles northward Wednesday/Thursday. Deterministic and ensembles
differ in the details, but indicate the same general idea.
With the upper low overhead Monday/Tuesday, cool and unsettled
weather is expected. Cyclonic flow will help to dramatically
increase the depth of the marine inversion, bringing an return of
a June-Gloom pattern. Also, there will likely be some light rain
or drizzle from the deep inversion at least Monday morning, if not
also Tuesday morning. Additionally, there may be enough moisture
to generate some scattered showers across the area Monday and
Tuesday (with the best chances of convective activity over the
mountains). Looking at ensembles, there are definitely more
members indicating some light precipitation across the area. So,
current POPs look good. Still too early to include any mention of
thunderstorms, but there definitely is at least a non-zero chance
of some mountain thunderstorms with the low overhead.
For Wednesday and Thursday, the upper low moves northward. So, any
threat of precipitation should be very limited. However, cyclonic
flow will persist. So, there will likely be the continuation of
June-Gloom conditions.
&&
.AVIATION...02/0037Z.
At 0015Z at KLAX, the marine layer was 3400 feet deep. The top of
the inversion was around 5000 feet at a temperature of 13 C.
High confidence in KWJF and KPMD.
Low to moderate confidence in remaining TAFs. A deep marine layer
remains in place, but a weak inversion continues to lead to more
disorganized low cloud cover. Cigs may vary between VFR to MVFR,
with some brief clearing possible at some coastal sites during the
early evening hours, 00Z-04Z. There is a 30 percent chance of
better clearing Fri afternoon.
KLAX...Low to moderate confidence in the 00Z TAF. CIGs are likely
to vary between MVFR to VFR, but category changes between VFR to
MVFR could be off by +/- 3 hours. No significant easterly wind
component is expected.
KBUR...Low to moderate confidence in the 00Z TAF. CIGs are likely
to vary between MVFR to VFR, but category changes between VFR to
MVFR could be off by +/- 3 hours.
&&
.MARINE...01/828 PM.
For the outer waters, moderate to high confidence in Small Craft
Advisory (SCA) level winds into Saturday night, with a 40% chance
of continuing through Saturday night. Winds may drop off each
night from the waters south of Point Sal to San Nicolas Island,
but good confidence they will restrengthen to advisory levels by
the afternoon hours. Steep, choppy seas affecting the northern
outer waters will likely drop off by Friday evening and remain
below advisory levels through Wednesday. Then, good confidence in
conditions remaining below SCA levels Sunday through Wednesday.
For the inner waters, there is a 30-40% chance of SCA level winds
expanding into the western portion of the Santa Barbara Channel
Friday afternoon through evening. Steep, choppy seas may affect
the western portion of the Santa Barbara Channel through late
tonight. Otherwise, good confidence in conditions remaining below
advisory levels.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory in effect until 3 AM PDT Friday for zone 381. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for zone
670. (See LAXMWWLOX).
Small Craft Advisory in effect until 9 PM PDT Saturday for
zones 673-676. (See LAXMWWLOX).
&&
$$
PUBLIC...Thompson/Smith
AVIATION...Smith
MARINE...Lund
SYNOPSIS...DB/Smith
weather.gov/losangeles
Experimental Graphical Hazardous Weather Outlook at:
https://www.weather.gov/erh/ghwo?wfo=lox