May 2021:

General Weather Discussions and Analysis
MH5
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Appears like I'm finally getting a moment of relief. Gauge reads 1.71" so far, all of that coming in about 45 minutes. Looks like the stuff NW up near Waller might continue to bow in this direction for round two.
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don
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WPC mentions that a High risk may be needed.

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
427 PM EDT Mon May 17 2021

Day 3
Valid 12Z Wed May 19 2021 - 12Z Thu May 20 2021

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM SOUTHERN
AND EASTERN TEXAS INTO FAR SOUTHWESTERN LOUISIANA...

The upper/mid-level trough forecast to be centered over the High
Plains into Mexico should transition from a neutral to slightly
negatively-tilted orientation during the period while the
deep-layer ridge over the eastern U.S. builds. This evolution
should slow the movement/progression of the convection and in fact
may promote back-building across eastern and southern Texas.
Models suggest very strong vertical motion will set up over much
of coastal Texas and areas inland. In addition low-level southeast
winds of 25 to 35 kts will continuously direct Gulf moisture
onshore (keeping precipitable water values anomalously high) which
will further fuel and maintain convective development. Most of the
guidance depicts another 2 to 6 inches and possibly isolated
higher totals falling over saturated areas, many of which will
have received several inches during the prior two days. The
72-hour footprint across this region has areal averages of 3 to 9
inches with isolated higher amounts certainly possible. A Moderate
Risk was issued for much of eastern/coastal Texas and far
southwest Louisiana. Several urban areas fall within this risk
area and will likely experience numerous areas of impactful
flooding. A Slight Risk covers most of the remaining eastern half
of Texas, southeast Oklahoma, western Arkansas and western
Louisiana. The Marginal Risk extends into west-central Texas, most
of Oklahoma, southeast Kansas, western Missouri, east-central
Arkansas and central Louisiana.

The afternoon update maintained continuity from previous issuance,
as the overall centroid of expected heaviest rainfall fits the
outlook reasonably well. Considerations that temper confidence in
specifics include a general model evolution toward less pronounced
instability with time over the course of the period and
uncertainty over the exact details of flow aloft by early
Thursday. Depending on how model consensus and confidence evolve
over coming cycles, potential may exist for an embedded narrow
High Risk area given that some locations may see 72-hour amounts
approaching 8-9+ inches.
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Cromagnum
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Meanwhile. Our west Texas pals have mesocyclones all over the place.

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djmike
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Crazy totals today. Growing concerns over the release of water at Dam B Rayburn and all of us downstream. They began lifting the flood gates today...The border usually goes under water at IH-10 then gets shutdown. Thats after all homes are flooded along the way. Plus the possibility of 15-20” more by this weekend. Gonna be a long nerve racking week. Stay safe everyone. Someone is gonna see Harvey/Imelda type floods unfortunately.
2C90874F-4B80-44EF-B5AE-7D31ADBAFB2C.jpeg
Mike
Beaumont, TX
(IH-10 & College Street)
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jasons2k
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1.66" here today. Some incredible footage on the news tonight.
Cpv17
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Picked up another inch here today bringing my 2 day total to 2.50”. Not much to talk about tonight. Models aren’t really showing too much for tomorrow at the present time. The only model that looks really interesting for tomorrow is the FV3.
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djmike
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Day 2. Hoping its a much better day. Unfortunately radar is already starting to pop along the coast and should move inland.
Mike
Beaumont, TX
(IH-10 & College Street)
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srainhoutx
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Mesoscale Precipitation Discussion 0199
NWS Weather Prediction Center College Park MD
801 AM EDT Tue May 18 2021

Areas affected...Southeast TX...Southern LA

Concerning...Heavy rainfall...Flash flooding likely

Valid 181200Z - 181800Z

Summary...Flash flooding will be likely this morning across
portions of southeastern Texas and south-central Louisiana with
efficient rainfall rates of 2 to 3 inches per hour being realized.
An additional 3-6 inches of localized rainfall is possible
through 1 pm, which will likely exceed very low flash flood
guidance in some cases.

Discussion...Regional Doppler radars and GOES-16 infrared
satellite imagery is indicating a rapid increase of intense
convection near and just inland from the Gulf Coast. This is
expected to persist going through the morning hours with a
corridor of enhanced moisture convergence in the surface to 850 mb
layer, combined with an incoming vortmax/MCV from the southwest.
Outflow boundaries between residual MCS's over southern Texas and
southeast Louisiana will likely merge and further aid in
convective development. There will be a sufficient supply of
instability with ML CAPE of 1500-2500 J/kg advecting northward.

The latest CAM guidance suite, including the most recent HRRR, is
struggling to capture this new convection near the coast, and is
likely underdone with QPF output. One of the main aggravating
factors is the excessive rainfall over the past 24 hours across
much of this region, with some 5 to 10 inch totals observed across
portions of extreme southeast Texas, and along the Interstate 10
corridor in Louisiana. This has resulted in severely reduced
flash flood guidance for much of the outlook area, and it will not
take much additional rainfall to cause more flooding. Therefore,
episodes of flash flooding are considered likely through 1 pm
local time.

Hamrick

ATTN...WFO...HGX...LCH...LIX...
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Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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don
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PREV DISCUSSION... /ISSUED 435 AM CDT Tue May 18 2021/

SHORT TERM [Through Wednesday]...

..FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH THURSDAY MORNING...

Today marks the third consecutive day of unsettled weather for
most of TX. Another upper level shortwave rounding the base of a
trough associated with the slow moving cut-off upper low now
located over New Mexico, will pass over Central TX this morning
and then over Southeast TX later today with the split jet
strengthening over North and Central Texas. Several clusters of
storms are progged to develop over this region (east of a
dryline) and propagate east into Eastern TX today. Another pulse
of storms develops over that region this afternoon and could make
it through into Eastern TX sometime early tonight. Now...locally,
we could very well have our own set of showers and thunderstorms
developing today, mainly driven by the unrelenting unstable
airmass and the passing of the upper shortwave. 06Z NAM forecast
soundings once again contains MUCAPE values between the 3000-4500
J/kg around 18-00Z and 0 CIN along with 700-500MB lapse rates in
the 7 to 8 C/km range. Strong gusty winds and hail will be
possible with the stronger storms. An exact location and time for
storms is still hard to tell given that we may end up having a
combination of both locally developed storms, storms rolling in
from the W/NW, and possible interactions with several/lingering
outflow boundaries today and tonight. In other words, plenty of
opportunities for several bouts of rainfall. For the Day 1 ERO,
northern and eastern counties lie under a Moderate Risk for
excessive Rainfall, with the western central/central/south
central counties under a Slight Risk, and the southwestern
counties under a Marginal Risk. SPC Severe Thunderstorm Outlook
has a Slight Risk for severe thunderstorms along a line extending
from Colorado County northeastward into Trinity county. Elsewhere,
there is a Marginal Risk.

To continue the weather madness...tonight through Wednesday, the
trough will deepen southward and the low will move northeastward
into the southern High Plains in response to an upper low over
British Columbia propagating south southeastward into NW Conus.
The southward extension of the trough will allow for winds aloft
to turn almost entirely from south to north, and the split jet
edges closer to Southeast TX. Low level jet of 30-40 kts will
likely aid in storm development to our west again with several
clusters developing there, along with other storms evolving over
lingering boundaries in other sectors of TX. Expect activity to be
a bit more extensive Wednesday. The day/night is shaping up to be
our most problematic period with respect to heavy/torrential
rainfall causing multiple flooding concerns. In collaboration with
WPC, ALL of Southeast TX was kept under a Moderate Risk for
Excessive Rainfall for Wednesday (Day 2 ERO). The Flash Flood
Watch will extend through at least Thursday morning but has a
chance to be extended further through the end of the day Thursday.
Below is a quick reference of the Flash Flood Watch currently in
effect for all of Southeast TX.

----------------------------------------------------------------
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 [Wednesday Night through Tuesday]...

Very unsettled weather looks to continue in the Wednesday night
through Friday time period. There will be a risk for locally heavy
rainfall that could lead to flooding, especially for locations that
have already received significant rains over the past several days.
Very high precipitable water values (>2 inches) being supported by a
strengthening and persistent low level jet in combination with an
increasingly divergent flow aloft as the upper low takes on a
slightly negative tilt could lead to backbuilding and training
showers and thunderstorms that will be capable of producing very
heavy rains in a short period of time for parts of our area. Our
entire forecast area has been placed in a Moderate Risk of excessive
rainfall in WPC`s Day 2 Excessive Rainfall Outlook and a Marginal to
Slight Risk on their Day 3 Outlook, and depending on how everything
unfolds, it is quite possible that parts of our area might need to
be upgraded on future updates. Would also not be surprised if we end
up needing to extend our Flash Flood Watch beyond Thursday morning.
Decent rain chances remain in the forecast into Saturday followed by
decreasing and much lower rain chances (mainly only across our far
western counties) Saturday night and Sunday as high pressure builds
in from the east and sends the deepest moisture axis westward. This
much more quiet and needed dry period will extend into the start of
next week.
Cpv17
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I’m beginning to think the Golden Triangle area and southern LA are going to be the winners from this event. Looks like it could be another rough day for them.
Last edited by Cpv17 on Tue May 18, 2021 8:23 am, edited 1 time in total.
Texashawk
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Is it my imagination, or has Louisiana gotten all the rain this year?
Cpv17
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Texashawk wrote: Tue May 18, 2021 8:16 am Is it my imagination, or has Louisiana gotten all the rain this year?
They usually do get more rain than us.
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don
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Yep they do on average ,due to their geographic orientation to the gulf.I'm getting really concerned about tomorrow into Thursday.As pretty much all mesoscale models are showing a large MCS slowing down over the area and back building as impulses collide with the system reinvigorating convection along a stalled boundary.
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jasons2k
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Once what's left of this MCV passes by, the sun should break-out and recharge things for this afternoon.
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tireman4
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859
FXUS64 KHGX 181206
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
706 AM CDT Tue May 18 2021

.AVIATION [12Z TAF ISSUANCE]...

Another rather difficult stormy TAF period expected again today
with SH/TS developing this morning and afternoon along boundaries
lingering from yesterday`s storms as well as those moving in from
Central and Northern TX. VCTS has been included for all TAF sites,
with TEMPOs likely to be issued as storms evolve. There will be a
mix of VFR to MVFR cigs throughout the TAF period with IFR
cigs/vis possible in and around TS. Heavy rain and strong gusty
winds will also accompany these storms and may be capable of
producing hail, particularly for storms over the northern half of
the CWA (CLL/UTS/CXO/IAH/SGR). S-SE winds at 10-15 KT will prevail
today but will become VRB at times due to storms and outflow
boundaries. Given the amount of instability as well as the
proximity of storms/boundaries, some turbulence can be expected.

&&

.PREV DISCUSSION... /ISSUED 435 AM CDT Tue May 18 2021/

SHORT TERM [Through Wednesday]...

..FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH THURSDAY MORNING...

Today marks the third consecutive day of unsettled weather for
most of TX. Another upper level shortwave rounding the base of a
trough associated with the slow moving cut-off upper low now
located over New Mexico, will pass over Central TX this morning
and then over Southeast TX later today with the split jet
strengthening over North and Central Texas. Several clusters of
storms are progged to develop over this region (east of a
dryline) and propagate east into Eastern TX today. Another pulse
of storms develops over that region this afternoon and could make
it through into Eastern TX sometime early tonight. Now...locally,
we could very well have our own set of showers and thunderstorms
developing today, mainly driven by the unrelenting unstable
airmass and the passing of the upper shortwave. 06Z NAM forecast
soundings once again contains MUCAPE values between the 3000-4500
J/kg around 18-00Z and 0 CIN along with 700-500MB lapse rates in
the 7 to 8 C/km range. Strong gusty winds and hail will be
possible with the stronger storms. An exact location and time for
storms is still hard to tell given that we may end up having a
combination of both locally developed storms, storms rolling in
from the W/NW, and possible interactions with several/lingering
outflow boundaries today and tonight. In other words, plenty of
opportunities for several bouts of rainfall. For the Day 1 ERO,
northern and eastern counties lie under a Moderate Risk for
excessive Rainfall, with the western central/central/south
central counties under a Slight Risk, and the southwestern
counties under a Marginal Risk. SPC Severe Thunderstorm Outlook
has a Slight Risk for severe thunderstorms along a line extending
from Colorado County northeastward into Trinity county. Elsewhere,
there is a Marginal Risk.

To continue the weather madness...tonight through Wednesday, the
trough will deepen southward and the low will move northeastward
into the southern High Plains in response to an upper low over
British Columbia propagating south southeastward into NW Conus.
The southward extension of the trough will allow for winds aloft
to turn almost entirely from south to north, and the split jet
edges closer to Southeast TX. Low level jet of 30-40 kts will
likely aid in storm development to our west again with several
clusters developing there, along with other storms evolving over
lingering boundaries in other sectors of TX. Expect activity to be
a bit more extensive Wednesday. The day/night is shaping up to be
our most problematic period with respect to heavy/torrential
rainfall causing multiple flooding concerns. In collaboration with
WPC, ALL of Southeast TX was kept under a Moderate Risk for
Excessive Rainfall for Wednesday (Day 2 ERO). The Flash Flood
Watch will extend through at least Thursday morning but has a
chance to be extended further through the end of the day Thursday.
Below is a quick reference of the Flash Flood Watch currently in
effect for all of Southeast TX.

----------------------------------------------------------------
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 [Wednesday Night through Tuesday]...

Very unsettled weather looks to continue in the Wednesday night
through Friday time period. There will be a risk for locally heavy
rainfall that could lead to flooding, especially for locations that
have already received significant rains over the past several days.
Very high precipitable water values (>2 inches) being supported by a
strengthening and persistent low level jet in combination with an
increasingly divergent flow aloft as the upper low takes on a
slightly negative tilt could lead to backbuilding and training
showers and thunderstorms that will be capable of producing very
heavy rains in a short period of time for parts of our area. Our
entire forecast area has been placed in a Moderate Risk of excessive
rainfall in WPC`s Day 2 Excessive Rainfall Outlook and a Marginal to
Slight Risk on their Day 3 Outlook, and depending on how everything
unfolds, it is quite possible that parts of our area might need to
be upgraded on future updates. Would also not be surprised if we end
up needing to extend our Flash Flood Watch beyond Thursday morning.
Decent rain chances remain in the forecast into Saturday followed by
decreasing and much lower rain chances (mainly only across our far
western counties) Saturday night and Sunday as high pressure builds
in from the east and sends the deepest moisture axis westward. This
much more quiet and needed dry period will extend into the start of
next week.

MARINE...

SCA in effect for the Gulf waters. SCEC in effect for the bays.

Lower pressures over New Mexico and high pressure over the
eastern Gulf will maintain a moderate to strong onshore flow over
SE Texas through the next few days. Seas are expected to build to
around 5 and 7 feet across the Gulf waters today and are expected
to remain elevated through the end of the work week. A moderate
to strong onshore flow will persist into next weekend.

Strong Rip Currents will persist as well so use extreme care if
heading to any of the Gulf facing beaches. The strong and
persistent onshore flow will also drive water levels up and there
could be come coastal flood issues by early Wednesday into
Thursday. Water levels could reach 3.6 feet and a Coastal Flood
Advisory or Warning may be needed by Wednesday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 85 70 79 67 79 / 80 70 90 90 90
Houston (IAH) 85 73 82 70 80 / 60 60 90 90 90
Galveston (GLS) 84 75 83 73 81 / 50 50 80 90 90

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flash Flood Watch through Thursday morning for the following
zones: Austin...Bolivar Peninsula...Brazoria Islands...
Brazos...Burleson...Chambers...Coastal Brazoria...Coastal
Galveston...Coastal Harris...Coastal Jackson...Coastal
Matagorda...Colorado...Fort Bend...Galveston Island...
Grimes...Houston...Inland Brazoria...Inland Galveston...
Inland Harris...Inland Jackson...Inland Matagorda...
Madison...Matagorda Islands...Montgomery...Northern
Liberty...Polk...San Jacinto...Southern Liberty...Trinity...
Walker...Waller...Washington...Wharton.

High Rip Current Risk through late Thursday night for the
following zones: Bolivar Peninsula...Brazoria Islands...
Galveston Island...Matagorda Islands.

GM...Small Craft Advisory until 7 AM CDT Thursday for the following
zones: 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.

&&

$$

Short Term...24
Long Term...42
Aviation...24
Marine...24
Climate...42
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CRASHWX
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Looking at model runs come Thursday and Friday the fire house looks to be focused on the Triangle and SW Louisiana. Gonna be problematic at best. One of the local station Mets have said some areas will measure this weeks rain by feet...”some areas receiving 2-3 feet of rain” nevertheless Thursday and Friday look to be a problem...ANY IDEAS?
:ugeek: CRASHWX :ugeek:
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tireman4
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The sun is out. The convective temperature is low (80-81 degrees). Abundant tropical moisture feeding into the disturbance. Light to variable steering currents in the atmosphere. This afternoon will be interesting.
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jasons2k
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Yep the sun is doing its thing...
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Stratton20
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CrashWx at this point the heaviest rain could fall anywhere, I take the where the models place the biggest bullseyes with a hufe grain of salt
txbear
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Cromagnum wrote: Mon May 17, 2021 6:55 pm Meanwhile. Our west Texas pals have mesocyclones all over the place.
I was watching that as well. With the wonders of the internet, I checked one of the news stations out there and plain as day, classic mothership wall cloud. Probably gave the Lubbock folks quite the scare since it was sitting over a prime populated area there. Was able to find a screeshot from the news tower cam. Wow.
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