MAY 2019: Wednesday Storm Complex/Scattered Showers To End May

[unome]

oops, put this on the wrong post earlier

https://mesonet.agron.iastate.edu/wx/af ... 1905032345


Area Forecast Discussion
National Weather Service Houston/Galveston TX
645 PM CDT Fri May 3 2019

.AVIATION...
VFR conditions this evening will deteriorate once again overnight.
Per hires guidance, ongoing shra tstms in the Hill Country should
evolve into a se/ese moving squall line across the region
overnight. There are various timing differences and details
between models so, in general, went with a compromise between the
HRRR and Texas Tech WRF in regards to timing advertised in the
00Z set of TAFS. Expect amendments thru the night as trends are
established. Most of the activity should be well east of the terminals
before sunrise followed by a break in the action. Will probably
need to throw mention of precip back into the TAFs at some point
during the day Sat as the atmos recovers and daytime heating
performs its magic. 47

[unome]

Mesoscale Precipitation Discussion 0189
NWS Weather Prediction Center College Park MD
641 PM EDT Fri May 03 2019

Areas affected...central to south-central TX

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

Valid 032240Z - 040405Z

Summary...Scattered areas of flash flooding are expected across
portions of central to south-central TX through 04Z. The
congealing of multiple cells into the evening should allow for a
few locations of very heavy rain with rainfall rates of 2-3 in/hr
and storm total as high as 4-6 inches.

Discussion...The combination of forcing ahead of a mid-upper level
shortwave approaching from west-central TX (seen on water vapor
imagery), diffluent flow aloft and plentiful instability has
allowed for the development of scattered to numerous thunderstorms
across central TX. The latest GPS derived precipitable water
values ranged from 1.4 to 1.7 inches across the region at 22Z and
MLCAPE was 1500-3000 J/kg per the latest SPC mesoanalysis.

As the shortwave over west-central TX continues toward the east
early tonight, convective coverage will continue to expand but as
the number of cells increases, the eventual congealing into an MCS
appears likely. Southerly 850 mb flow from the RAP is currently
forecast to range between 10-20 kt over southern/south-central TX,
but these values may be too weak if MCS development becomes robust
inducing stronger inflow, certainly in a storm-relative sense into
the complex. As a sufficient cold pool develops, movement of the
forecast MCS should be off toward the ESE and perhaps become less
of a flash flood threat as forward speed increases.

There has been decent support for this idea from recent runs of
the HRRR, the Texas Tech WRF and experimental NSSL WoF System.
Much of TX from the middle Rio Grande to locations near I-45 have
been rather wet over the past 24 hours and over the previous
couple of weeks. This has lowered Flash Flood Guidance and
increased susceptibility to runoff. The forecast models apparently
handling tonight's event well show support for maximum totals of
4-6+ inches of rain by roughly 04Z, which would lead to flash
flooding.

Otto

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

ATTN...RFC...WGRFC...

LAT...LON 31499658 30979555 30149522 29399597 28669762
27910015 28810087 29490153 30170113 31319830

[unome]

Mesoscale Discussion 0521
NWS Storm Prediction Center Norman OK
0648 PM CDT Fri May 03 2019

Areas affected...south central Texas

Concerning...Severe Thunderstorm Watch 127...

Valid 032348Z - 040045Z

The severe weather threat for Severe Thunderstorm Watch 127
continues.

SUMMARY...Storms will remain capable of producing damaging wind and
large hail over south central Texas through the evening.

DISCUSSION...Early this evening numerous storms persist over south
central Texas from Austin to near Del Rio. Storms remain within an
environment characterized by moderate instability and effective bulk
shear from 35-45 kt, but low-level hodographs are small. This
environment will continue to support some supercell structures, but
numerous storm mergers are occurring and an upscale linear growth
appears to be in progress. The cap is relatively weak in the
downstream warm sector, and storms will continue to forward
propagate as the cold pools consolidate. Both damaging wind and
large hail remain likely, but damaging wind may become the dominant
threat as storms evolve into a linear mode.

..Dial.. 05/03/2019

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

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

[unome]

Texas Storm Chasers has some great posts in their Twitter feed

https://twitter.com/TxStormChasers

staying on top of the weather in TX, as always

[unome]

Lower Colorado River Authority & NWS EWX have a tense night ahead, as do many other agencies that keep us safe across TX

https://twitter.com/LCRA
https://twitter.com/NWSSanAntonio
https://twitter.com/iembot_ewx

[srainhoutx]

8:00 PM Update from Jeff:

Complex of intense thunderstorms has developed from Del Rio to Austin.

Rainfall rates of 5.75 inches in 3 hours and 5.29 inches in 3 hrs have been recorded by the LCRA hydromet network around Austin leading to rapid onset flash flooding.

High resolution models bring this line of storms ESE/SE this evening into SE TX and then turn the line E across the remainder of SE TX later tonight while weakening some. Overall storms should be moving at a fairly fast forward motion which may help to cut back some on the rainfall totals tonight, but still will keep 1-2 inches widespread with isolated amounts up to 3-4 inches. Higher totals will be realized in any areas where cells develop and train ahead of the main line and recent model trends are wanting to favor areas NW of Harris County.

Think the main threat remains street flooding with high hourly rainfall rates and a potential damaging wind threat with any bow segments of the line. Trees will knock over easier in areas that have seen rainfall in the last 36 hours.

[Cromagnum]

Up in College Station tonight. Impressive lightning show to the west

[Cpv17]

Going to be a beautiful lightning show tonight. Hoping I can capture some pics!!

[unome]

Mesoscale Discussion 0523
NWS Storm Prediction Center Norman OK
0832 PM CDT Fri May 03 2019

Areas affected...south central through south Texas

Concerning...Severe Thunderstorm Watch 127...

Valid 040132Z - 040230Z

The severe weather threat for Severe Thunderstorm Watch 127
continues.

SUMMARY...Storms are expected to continue to pose a risk for
isolated hail and damaging wind across the remainder of south
central Texas within WW 127. Trends are being monitored for a
possible downstream WW.

DISCUSSION...A line of strong to severe storms continues southeast
at 30-35 kt through south central TX. Some bowing segments and an
occasional embedded supercell structure or two continue to be
observed. The downstream atmosphere is moderately unstable with
1500-2500 J/kg MLCAPE, but the 00Z CRP RAOB suggests convective
inhibition will undergo some increase this evening as the surface
layer cools. Despite this, sufficient organization within the line
and an organized cold pool would indicate that convergence along the
leading gust fronts might be sufficient to maintain the storms into
portions of south through southeast Texas next few hours.

..Dial.. 05/04/2019

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

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

LAT...LON 28229896 28869703 30199648 30049581 29409562 28719606
27779757 27609871 27869925 28229896

[srainhoutx]

NWS San Antonio/Austin pleads with San Antonio and Austin Media to tell people to stay home! Nighttime and Flash Flooding do not mix. Same can be said for our Metro Houston and surrounding areas.

[unome]

tornado warnings keep popping up as well

https://twitter.com/nwstornado
https://twitter.com/NWSSevereTstorm
https://twitter.com/NWSFlashFlood
https://alerts.weather.gov/cap/tx.php?x=1

[srainhoutx]

Monitoring for an New Weather Watch coming shortly. Looks like part of Metro Houston will be included. Watch could extend until 3:00 AM

[srainhoutx]

Rotation being noticed in Washington/Burleson Counties

[srainhoutx]

Severe Thunderstorm Watch issued. Detailed graphic and text coming momentarily

[srainhoutx]

WATCH COUNTY NOTIFICATION FOR WATCH 128
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
859 PM CDT FRI MAY 3 2019


THE NATIONAL WEATHER SERVICE HAS ISSUED SEVERE THUNDERSTORM WATCH
128 IN EFFECT UNTIL 3 AM CDT SATURDAY FOR THE FOLLOWING AREAS

IN SOUTH CENTRAL TEXAS THIS WATCH INCLUDES 1 COUNTY

JACKSON

IN SOUTHEAST TEXAS THIS WATCH INCLUDES 14 COUNTIES

AUSTIN BRAZORIA BRAZOS
BURLESON COLORADO FORT BEND
GALVESTON GRIMES HARRIS
MATAGORDA MONTGOMERY WALLER
WASHINGTON WHARTON

THIS INCLUDES THE CITIES OF ALVIN, ANGLETON, BAY CITY, BELLVILLE,
BRENHAM, BROOKSHIRE, BRYAN, CALDWELL, CLUTE, COLLEGE STATION,
COLUMBUS, CONROE, DICKINSON, EAGLE LAKE, EDNA, EL CAMPO,
FIRST COLONY, FREEPORT, FRIENDSWOOD, GALVESTON, GANADO,
HEMPSTEAD, HOUSTON, LAKE JACKSON, LEAGUE CITY, MISSION BEND,
MISSOURI CITY, NAVASOTA, PALACIOS, PEARLAND, PECAN GROVE,
PRAIRIE VIEW, ROSENBERG, SEALY, SOMERVILLE, SUGAR LAND,
TEXAS CITY, THE WOODLANDS, WALLER, WEIMAR, AND WHARTON.

$$


THE NATIONAL WEATHER SERVICE HAS ISSUED SEVERE THUNDERSTORM WATCH
128 IN EFFECT UNTIL 3 AM CDT SATURDAY FOR THE FOLLOWING AREAS

THIS WATCH INCLUDES THE FOLLOWING ADJACENT COASTAL WATERS

MATAGORDA BAY GALVESTON BAY
COASTAL WATERS FROM FREEPORT TO MATAGORDA SHIP CHANNEL TX OUT
20 NM
COASTAL WATERS FROM HIGH ISLAND TO FREEPORT TX OUT 20 NM
WATERS FROM FREEPORT TO MATAGORDA SHIP CHANNEL TX FROM 20 TO
60 NM
WATERS FROM HIGH ISLAND TO FREEPORT TX FROM 20 TO 60 NM

[txbear]

Thoughts on whether this will hold into the metro area, or hit the wall of capped atmosphere and dissipate? It’s been pretty stout except for those locales north.

[Cpv17]

Giddings is about to get quite a storm. Purple cell on radar headed their way.

[srainhoutx]

Thoughts on whether this will hold into the metro area, or hit the wall of capped atmosphere and dissipate? It’s been pretty stout except for those locales north.

Good chance this squall line pushes all the way to the Coast and offshore. I've seen not chatter or data suggesting any capping issues.

[CAK]

Kingwood got wrecked pretty bad. I measured over 5" of rain in 30 minutes. Streets flooded that didn't even come close to flooding in Harvey. Tree's down everywhere. Wow.

[Katdaddy]

Looks impressive on satellite this evening.