Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/01/19
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
941 PM CDT Tue Apr 30 2019
.UPDATE...
The main update to the forecast is to trim back PoPs during the
overnight hours. Other than a very low chance across the Edwards
Plateau and Hill Country have removed all rain chances through about
1 am across the area. The storm near Ozona from earlier in the
evening has died out after producing 3 inch hail there. The only
thing on radar tonight are the bats north of Uvalde and near Bracken.
A few runs of the HRRR this evening did show a rogue supercell
forming across the Mexican mountains before dying as it approached
the border. There is no signal of any significant development per
the GOES-16 IR channels so these runs were disregarded.
For the second half of the night high resolution models do still show
some streamer showers across the area towards morning so have
blanketed the area with 20 PoPs for the light rain chances.
Looking ahead towards tomorrow the 00z runs of the NMM and ARW high
resolution models are in through tomorrow evening and they, along
with the 18z Texas Tech WRF, show the majority of the strong
thunderstorm activity staying to the north of South Central Texas
with outflows and some isolated showers and storms moving through
mid-afternoon into the early overnight hours tomorrow. These are
just the early model trends, and no adjustments to the ongoing
forecast were made at this time. A full forecast package with a look
at all the High Resolution and Synoptic Models will be issued during
the early morning hours Wednesday, with the next SPC Day One Outlook
expected around 1 AM local time.
&&
.PREV DISCUSSION... /ISSUED 639 PM CDT Tue Apr 30 2019/
AVIATION...
SHRA along and just west of I-35 and have kept VCSH at those sites
going through early evening with VFR skies. MVFR CIGs return later
this evening into overnight. There is a possibility of IFR CIGs early
in the morning, however, it will be brief as lower level flow keeps
the airmass mixed somewhat and have kept mention out. CIGs lift to
low end VFR around midday on Wednesday. Still expect SHRA/TSRA to
develop over West to North Central Texas and drift southeast into
Central Texas and the Hill Country during the afternoon into evening.
Have maintained VCTS at KAUS and VCSH at KSAT/KSSF. Southeasterly
winds of 10 to 20 KTs prevail with occasional gusts to 25 KTs.
Downdraft wind gusts up to 50 KTs are possible in and near TSRA.
PREV DISCUSSION... /ISSUED 244 PM CDT Tue Apr 30 2019/
SHORT TERM (Tonight through Wednesday Night)...
Isolated streamer showers continue beneath the cap this afternoon.
Aircraft sounding out of AUS do indicate some slight weakening of the
inversion around 750-700mb, but not completely eroded. Thus, for the
most part this evening we expect the deeper and more organized
convection to remain north of the CWA, where cap is eroded and in
closer proximity to better forcing. Although, we can`t rule out
isolated thunderstorms across the far northern CWA.
The next shortwave embedded in the southwest flow aloft will move
across portions of the southern Edwards Plateau and into West Central
Texas overnight and Wednesday morning. Most of the hi resolution
model guidance agrees the bulk of the convection will develop through
the morning and into early afternoon just to the north of the CWA.
Convective outflow boundaries may then move south into portions of
the northern CWA late afternoon. We do think the cap will be eroded
or weak enough to sustain convective development during peak heating
into portions of the northern CWA late Wednesday afternoon and early
evening, including most of the eastern Hill Country and Austin metro,
and this is where the higher PoPs are favored. Model forecast
soundings disagree with strength of cap across the southern half of
the CWA. The ARW indicates a complex of storms moving southeast to
the I-10 corridor while the NAM Nest, NMM, and Texas Tech WRF
weakening and dissipating the convection Wednesday evening just south
of Austin as the cap holds.
Where the cap does erode, there will be the potential for severe
storms given MLCAPE values near 3000 J/kg and deep layer shear values
around 40 kts. Can`t rule out some very large hail across the
northwest Hill Country and southern Edwards Plateau, where mid level
lapse rate are forecast to be an impressive 8-9 degC/km. In
addition, some pockets of 1-2" of rainfall are possible across the
far northern CWA.
LONG TERM (Thursday through Tuesday)...
There are still model differences for the forecast on Thursday, with
the ECMWF and Canadian developing convection in the afternoon across
the Hill Country, closer to a weak frontal boundary, while the GFS
and NAM12 maintain the convection and weak boundary north of the
area. PoPs are trending higher for Thursday night through Friday
night with the next mid level shortwave. It`s too early to pinpoint
timing and favored locations this far out, and there are some
indication in the models of convective feedback. Nevertheless,
showers and storms are likely at some point during this time frame.
A few stronger storms will be possible in addition to some pockets
of heavy rainfall, given anomalously high precipitable water values
pooled around 1.5-1.8" over potions of the region. The forecast
trends drier Saturday into Sunday.
The next shortwave, ahead of a deeper closed low digging through
southern California, is forecast to impact South Central Texas Monday
with another chance of showers and storms.
7 day rainfall totals over portions of the region could end up being
2-4" with some isolated pockets in excess of 6".
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 71 81 70 84 69 / 20 70 60 40 40
Austin Bergstrom Intl Airport 72 81 69 84 68 / 20 60 60 40 40
New Braunfels Muni Airport 72 81 69 84 68 / 20 50 50 20 40
Burnet Muni Airport 70 77 67 81 66 / 20 80 60 40 40
Del Rio Intl Airport 73 88 69 87 69 / 20 30 20 20 40
Georgetown Muni Airport 71 79 69 83 67 / 20 80 60 40 40
Hondo Muni Airport 72 87 69 88 69 / 20 40 30 20 40
San Marcos Muni Airport 71 81 69 85 67 / 20 60 60 20 40
La Grange - Fayette Regional 73 86 72 86 70 / 20 50 40 20 40
San Antonio Intl Airport 73 83 70 86 69 / 20 50 50 20 40
Stinson Muni Airport 73 84 71 86 70 / 20 40 50 20 40
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Aviation...04
Short-Term/Long-Term...Treadway
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
807 PM PDT Tue Apr 30 2019
.SYNOPSIS...30/742 PM.
Low clouds will cover much of the coast and valleys tonight through
Wednesday morning. Onshore flow will weaken on Wednesday to allow
for better clearing and slight warming. A weak ridge of high
pressure will build on Thursday and will lead to warming
temperatures through Friday. A low pressure system may arrive
over the weekend with increasing clouds and cooler temperatures.
&&
.SHORT TERM (TUE-FRI)...30/806 PM.
Deep marine layer and strong onshore flow pattern resulting in a
reverse clearing pattern this afternoon. LAX ACARS data showing
marine layer depth around 4600 feet across the LA basin this
evening, with satellite imagery showing low clouds well entrenched
across the coastal mountain slopes. Tonight should be a repeat
of last night in terms of marine layer coverage. Probably not
quite as damp as it was this morning as we`ll have some ridging
developing aloft and a lowering inversion but some isolated
drizzle is still possible near the foothills.
Low level winds turns weakly offshore on Wednesday morning across
interior sections which should allow for better clearing
Wednesday afternoon for those areas, however some low clouds
could still linger across coastal areas. As a result of the weak
offshore low level winds and better clearing expecting a
noticeable warm-up across interior sections.
*** From previous discussion ***
Warming trend to continue Thu/Fri as weak ridging aloft continues.
Daytime highs will be near normal. Marine layer will still have a
solid presence for coast and coastal valleys overnight but should
clear most areas by late morning.
.LONG TERM (SAT-TUE)...30/147 PM.
The ridge will start to shift east Saturday as another slow moving
cutoff upper low approaches from the west. A stronger onshore push
will lead to a cooler day in most areas and slower beach clearing.
Models continue to struggle with the path of the low. The GFS has
been a little more consistent while the ECMWF now halts the
eastward progression of the low about 500 miles west of the Bay
Area before shooting it due south off the northern Baja coast the
middle of next week. No way to really favor one or the other but
the operational GFS is pretty close to the GEFS mean forecast
which provides a little more confidence in that solution. This
would definitely be a cooler pattern with a better chance of at
least some drizzle if not light showers Sunday and Monday. Then
followed by weak northerly flow Tuesday and likely more sunshine
but still cooler than normal temps.
&&
.AVIATION...30/2352Z.
At 2300Z, there was a 2000 foot deep moist layer across the area,
with a top near 6300 feet and a temperature of 16 deg C. There
was no marine inversion at KLAX.
Moderate to high confidence overall in 00Z Tafs. MVFR cigs
expected for all coast and valley sites overnight, with cigs
lifting to VFR Wed afternoon. Timing is lower certainty with onset
of MVFR conds likely to differ by +/- 2 hrs from taf times.
KLAX...Moderate confidence in the 00Z TAF. There is a 20-30%
chance that cigs tonight will not drop into MVFR category but
remain VFR through the night. Otherwise, onset of MVFR cigs may
differ by up to 2 hrs from taf times.
KBUR...Moderate confidence in the 00Z TAF. There is a 20% chance
that cigs tonight will remain in the VFR category through the
night. Otherwise, onset of MVFR cigs may differ by up to 2 hrs
from taf times. Cigs should rise above MVFR between 15z-18Z Wed.
&&
.MARINE...30/739 PM.
Unseasonably light winds and small seas will persist through at
least Thu, with NW winds expected to increase some across the
outer waters Friday and Saturday. There is a 30% chance of Small
Craft Advisory level winds across the outer waters by Sat, and
across the nearshore waters south of Point Conception.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
.HAZARD POTENTIAL OUTLOOK (FRI-TUE).
No significant hazards expected.
&&
$$
PUBLIC...Gomberg/MW
AVIATION...Smith
MARINE...Smith
SYNOPSIS...Stewart
weather.gov/losangeles