May 2021:

[don]

The HRRR has trended substantially south with the mesoscale complex this evening, and is now showing very concerning totals this evening/night...

[sau27]

Well the 16z HRRR sure takes an interesting turn for tonight

[Stratton20]

Yeah this mode shows nearly 12-13 inches for my areadefinitely something to watch and concerning as well

[Texashawk]

The HRRR has trended substantially south with the mesoscale complex this evening, and is now showing very concerning totals this evening/night...

Gotta be some kind of feedback error. Nothing out there and it’s almost mid afternoon. Hope I’m right!

-Steve

[mcheer23]

The HRRR has trended substantially south with the mesoscale complex this evening, and is now showing very concerning totals this evening/night...

Gotta be some kind of feedback error. Nothing out there and it’s almost mid afternoon. Hope I’m right!

-Steve

Radar will become fairly active in the early evening hours. Storms will move in from the west.

[Iceresistance]

I'm glad to not be under a flood watch anymore, but Southern Texas is going to be HAMMERED! I know someone that lives down there . . .

[Stratton20]

Texashawk no its not a feedback error, this complex of atorms is expected later on this afternoon and evening, dont let the sunny skies fool you, the atmosphere is just getting recharged at the moment.

[srainhoutx]

Mesoscale Discussion 0671
NWS Storm Prediction Center Norman OK
0118 PM CDT Tue May 18 2021

Areas affected...Portions of south-central into east-central/coastal
TX

Concerning...Severe potential...Watch possible

Valid 181818Z - 182015Z

Probability of Watch Issuance...60 percent

SUMMARY...A threat for large hail, damaging wind gusts, and perhaps
a couple of tornadoes should increase this afternoon. Watch issuance
will probably be needed.

DISCUSSION...As of 1815Z an outflow boundary from earlier convection
extends from parts of south-central into east-central TX. Recent
visible satellite imagery shows this boundary has slowed, and it may
not make much more southeastward progress this afternoon. Mostly
clear skies ahead of the outflow boundary have allowed robust
diurnal heating to occur, with surface temperatures generally
warming into the low to mid 80s. A rather moist low-level airmass
characterized by surface dewpoints in the mid to upper 60s also
exists across this region. Continued heating of this moist airmass
coupled with somewhat steepened mid-level lapse rates will likely
support MLCAPE of 1500-2500 J/kg by late afternoon. Around 25-35 kt
of southwesterly mid-level flow associated with an upper low over
the southern/central High Plains should foster similar values of
deep-layer shear. Current expectations are for storms to gradually
increase in both coverage and intensity along/near the outflow
boundary this afternoon as convective inhibition continues to erode.
A mixed mode of supercell and multicell structures appears likely,
with both large hail and damaging wind gusts possible. Storms may
have a tendency to congeal into a bowing cluster with time, and
severe/damaging winds may eventually become the main threat. Some
risk for a couple of tornadoes could also exist with storms near the
outflow boundary where low-level flow and shear may be modestly
enhanced. A watch will probably be needed in the next couple of
hours, dependent on convective trends.

..Gleason/Guyer.. 05/18/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...HGX...FWD...CRP...EWX...

[Cpv17]

Texashawk no its not a feedback error, this complex of atorms is expected later on this afternoon and evening, dont let the sunny skies fool you, the atmosphere is just getting recharged at the moment.

Good to see you on here. You should post more often!

[Stratton20]

CpV17 I definitely will be posting more often haha

[txbear]

Likely to get a bit noisy here in the early evening. WRF wanting to go with a squall line this evening and HRRR (17z) is similar albeit later in the early morning hours. I think the solution is somewhere in between, perhaps a bit towards the WRF in timing, based on the slow advancement of that outflow boundary. That should line up well with the MD that srain posted on a watch (Severe T-storm I would suspect) probably being issued.

[don]

Decent shift south with the heaviest concentration of qpf on the latest WPC update.

[srainhoutx]

Mesoscale Precipitation Discussion 0202
NWS Weather Prediction Center College Park MD
311 PM EDT Tue May 18 2021

Areas affected...Portions of South Texas and Central Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 181911Z - 190100Z

Summary...The threat of flash flooding will persist across
portions of South Texas and Central Texas during the afternoon and
early evening as cells build into a moist and unstable atmosphere
where flash flood guidance values have been lowered recently.

Discussion...Thunderstorms capable of producing downpours should
become more numerous this afternoon and evening as low level
outflow from this morning's MCS pushes southward into a region
where ML Cape values of 3500 to 5000 J per kg are expected by 21Z.
In addition, 1-hour and 3-hour flash flood guidance values have
lowered into the 1.5 to 2 inch range by recent rainfall. An
outflow boundary associated with the convective complex earlier
this morning will help focus a moisture flux convergence max which
gradually pushes south and east during the afternoon and early
evening.

Latest radar trends and hi-res CAM guidance has started to show
intensification of cells moving out of Kendall and Medina
counties. These cells will move into a region where precipitable
water values increase to around 1.5 inches and where the RAP runs
show MLCAPE building to more than 5000 J per kg. This suggests
that some 1.5 to 2.5 inch per hour rainfall rates could occur.
The lowered flash flood guidance, in part, reflects the recent
rainfall (also shown in the NASA SPoRT 0-40 cm soil moisture
percentile product) as well as the terrain of the Hill Country.

Given the antecedent conditions, instances of flash flooding are
possible.

Bann

ATTN...WFO...CRP...EWX...FWD...HGX...

[jasons2k]

Don’t have time to post details but the tornado watch just went up.

TORNADO WATCH OUTLINE UPDATE FOR WT 188
NWS STORM PREDICTION CENTER NORMAN OK
230 PM CDT TUE MAY 18 2021

TORNADO WATCH 188 IS IN EFFECT UNTIL 900 PM CDT FOR THE
FOLLOWING LOCATIONS

TXC001-013-015-021-029-031-041-051-055-089-091-123-149-161-177-
185-187-209-225-255-259-285-287-289-313-331-339-395-407-453-455-
471-473-477-491-493-190200-
/O.NEW.KWNS.TO.A.0188.210518T1930Z-210519T0200Z/

TX
. TEXAS COUNTIES INCLUDED ARE

ANDERSON ATASCOSA AUSTIN
BASTROP BEXAR BLANCO
BRAZOS BURLESON CALDWELL
COLORADO COMAL DEWITT
FAYETTE FREESTONE GONZALES
GRIMES GUADALUPE HAYS
HOUSTON KARNES KENDALL
LAVACA LEE LEON
MADISON MILAM MONTGOMERY
ROBERTSON SAN JACINTO TRAVIS
TRINITY WALKER WALLER
WASHINGTON WILLIAMSON WILSON
$$

[don]

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 188
NWS Storm Prediction Center Norman OK
230 PM CDT Tue May 18 2021

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of
South-central/East-Central Texas

* Effective this Tuesday afternoon and evening from 230 PM until
900 PM CDT.

* Primary threats include...
A couple tornadoes possible
Scattered damaging wind gusts to 70 mph likely
Scattered large hail and isolated very large hail events to 2
inches in diameter possible

SUMMARY...Increasing severe thunderstorm development is expected
initially across south-central/east-central Texas through mid/late
afternoon, particularly in vicinity of an outflow boundary that has
generally stalled in a southwest/northeast fashion across the
region. A moist environment, modest strength low-level winds in
conjunction with the influence of the outflow boundary could support
a tornado risk aside from more prevalent damaging winds and isolated
large hail.

The tornado watch area is approximately along and 80 statute miles
east and west of a line from 65 miles northwest of Lufkin TX to 55
miles south southeast of San Antonio TX. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU8).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.

[txbear]

Don’t have time to post details but the tornado watch just went up.

Here to eat my crow in anticipating the watch type haha.

They went with Tornado. 18z HRRR is running now, but Skew T looks a bit more favorable to back up SPC's decision to go tornado with a bit more in lower and mid-level shear. I would think that as the evening progresses, an additional watch of some sort will come down the pike as the storms progress eastward.

[don]

WPC has upgraded most of the area to a Moderate risk today.And they also have us in a Moderate risk for the next two days now.

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
434 PM EDT Tue May 18 2021

Day 1
Valid 2005Z Tue May 18 2021 - 12Z Wed May 19 2021

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS AND CENTRAL GULF COAST...

20z Update: Main change was to expand the Moderate risk
southwestward across south TX. The last several runs of the HRRR
are focusing a training west/east oriented convective complex from
just east of San Antonio towards Houston. In fact the beginning of
this activity is developing as of 2030z. This should continue to
grow upscale and push eastward through the overnight hours, with a
swath of 4-7" of rain appearing likely...resulting in areas of
flash flooding, some of which could be significant in nature.

Chenard

[don]

Area Forecast Discussion
National Weather Service Houston/Galveston TX
318 PM CDT Tue May 18 2021

...Dangerous Flood Event Possible Through Wednesday Night...

.SHORT TERM [Through Wednesday Night]...

Some sunshine this afternoon has allowed for enough heating to
generate some showers and thunderstorms. An outflow boundary over
Central Texas will move toward SE TX toward evening and this feature
will likely produce scattered to numerous showers and storms this
evening especially over the western half of the CWA. Instability is
impressive and some of the storms could be strong to severe. SPC has
just placed the NW/W part of SE TX in a Tornado Watch through 02z.
In addition to the potential for strong winds and isolated
tornadoes, there will be a risk for more heavy rain tonight. The
16z, 17z and 18z HRRR are doing a great job and it looks similar to
the 12z WRF-NSSL. It looks like the line will move across the
western half of the CWA between 00-03z. Will continue to mention
locally heavy rain tonight and some possibly severe in the wx grids.
As for rainfall potential tonight, it looks like widespread rainfall
of 1 to 3 inches with isolated pockets exceeding 5 inches. Again,
can`t stress enough that flooding impacts will be tied to where the
rain falls and how quickly it falls.

On Wednesday, the broad upper trough shifts east and takes on a
slightly negative tilt. There are some significant height falls as
the system approaches. PW values are between 1.80 and 2.00 inches
and upper level divergence looks impressive with a spitting jet and
SE TX lying in a RRQ. Will continue to mention locally heavy rain
and maintain the Flash Flood Watch. Another 1 to 3 inches of rain
possible on Wednesday but the lift/jet dynamics are impressive and
would not be surprised to see some 3 to 6 inches totals in addition
to what falls tonight.

The moist axis is directed at SE TX Wednesday night into Thursday so
additional showers and thunderstorms look possible. The splitting
jet structure is less well defined but SE TX will still lie in a RRQ
through Thursday morning. WPC has SE TX in a Moderate Risk for
Excessive Rain on both Wednesday and Thursday and this is tied
closely to how much rain falls tonight and Wednesday. Will continue
to message 4 to 8 inches with isolated totals possibly exceeding 10
inches. Again, these numbers are in flux and dependent on whether
training develops and how intense rainfall rates will become. The
Flash Flood Watch remains in effect through 12z Thursday but it may
need to be extended. 43

&&

----------------------------------------------------------------
FLASH FLOOD WATCH IN EFFECT THROUGH THURSDAY MORNING

"An additional 1 to 3 inches of rain with locally higher totals will
be possible today. A stronger upper level disturbance will bring yet
another round of heavy rain Wednesday into Thursday with additional
rainfall totals of 2 to 4 inches of rain with again locally higher
totals possible. Storm total rainfall by Thursday morning will
average between 4 and 8 inches with isolated totals possibly
exceeding 10 inches. The flood threat will be strongly dependent on
where the rain falls and how quickly it falls."

.LONG TERM [Thursday Through Tuesday]...

Forecast models remain a bit inconsistent on when they expect
Thursday morning`s rain to taper off. Either way, rain showers will
linger throughout the day with greater than 2" PWATs persisting and
a passing shortwave. The WPC has placed our southeastern counties
(including Harris County) in a moderate risk for excessive
rainfall for Thursday and the rest of the CWA in a slight risk.
This is due to the rainfall received in these areas over the past
couple of days, so it will not take much to get flooding to occur
in these spots. If you`re looking forward to an extended break
from the rain, unfortunately you`ll have to wait until Saturday.
Surface high pressure moves in and ushers in drier air over the
region. PoPs linger for a little while longer over our western
counties through Saturday night as the dry air will flow in from
east to west.

[Cpv17]

image4d.pngArea Forecast Discussion
National Weather Service Houston/Galveston TX
318 PM CDT Tue May 18 2021

...Dangerous Flood Event Possible Through Wednesday Night...

.SHORT TERM [Through Wednesday Night]...

Some sunshine this afternoon has allowed for enough heating to
generate some showers and thunderstorms. An outflow boundary over
Central Texas will move toward SE TX toward evening and this feature
will likely produce scattered to numerous showers and storms this
evening especially over the western half of the CWA. Instability is
impressive and some of the storms could be strong to severe. SPC has
just placed the NW/W part of SE TX in a Tornado Watch through 02z.
In addition to the potential for strong winds and isolated
tornadoes, there will be a risk for more heavy rain tonight. The
16z, 17z and 18z HRRR are doing a great job and it looks similar to
the 12z WRF-NSSL. It looks like the line will move across the
western half of the CWA between 00-03z. Will continue to mention
locally heavy rain tonight and some possibly severe in the wx grids.
As for rainfall potential tonight, it looks like widespread rainfall
of 1 to 3 inches with isolated pockets exceeding 5 inches. Again,
can`t stress enough that flooding impacts will be tied to where the
rain falls and how quickly it falls.

On Wednesday, the broad upper trough shifts east and takes on a
slightly negative tilt. There are some significant height falls as
the system approaches. PW values are between 1.80 and 2.00 inches
and upper level divergence looks impressive with a spitting jet and
SE TX lying in a RRQ. Will continue to mention locally heavy rain
and maintain the Flash Flood Watch. Another 1 to 3 inches of rain
possible on Wednesday but the lift/jet dynamics are impressive and
would not be surprised to see some 3 to 6 inches totals in addition
to what falls tonight.

The moist axis is directed at SE TX Wednesday night into Thursday so
additional showers and thunderstorms look possible. The splitting
jet structure is less well defined but SE TX will still lie in a RRQ
through Thursday morning. WPC has SE TX in a Moderate Risk for
Excessive Rain on both Wednesday and Thursday and this is tied
closely to how much rain falls tonight and Wednesday. Will continue
to message 4 to 8 inches with isolated totals possibly exceeding 10
inches. Again, these numbers are in flux and dependent on whether
training develops and how intense rainfall rates will become. The
Flash Flood Watch remains in effect through 12z Thursday but it may
need to be extended. 43

&&

----------------------------------------------------------------
FLASH FLOOD WATCH IN EFFECT THROUGH THURSDAY MORNING

"An additional 1 to 3 inches of rain with locally higher totals will
be possible today. A stronger upper level disturbance will bring yet
another round of heavy rain Wednesday into Thursday with additional
rainfall totals of 2 to 4 inches of rain with again locally higher
totals possible. Storm total rainfall by Thursday morning will
average between 4 and 8 inches with isolated totals possibly
exceeding 10 inches. The flood threat will be strongly dependent on
where the rain falls and how quickly it falls."

.LONG TERM [Thursday Through Tuesday]...

Forecast models remain a bit inconsistent on when they expect
Thursday morning`s rain to taper off. Either way, rain showers will
linger throughout the day with greater than 2" PWATs persisting and
a passing shortwave. The WPC has placed our southeastern counties
(including Harris County) in a moderate risk for excessive
rainfall for Thursday and the rest of the CWA in a slight risk.
This is due to the rainfall received in these areas over the past
couple of days, so it will not take much to get flooding to occur
in these spots. If you`re looking forward to an extended break
from the rain, unfortunately you`ll have to wait until Saturday.
Surface high pressure moves in and ushers in drier air over the
region. PoPs linger for a little while longer over our western
counties through Saturday night as the dry air will flow in from
east to west.

Some areas could see double or triple those totals I bet.

[Cromagnum]

Radar lighting up like a Christmas tree out towards San Marcos.