May 2023

General Weather Discussions and Analysis
Texashawk
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Almost looks like a tropical storm coming in off the Gulf right now. Crazy. We’re also now in a moderate risk of flooding… that escalated quickly
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482
FXUS64 KHGX 140922
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
422 AM CDT Sun May 14 2023

...New SHORT TERM, LONG TERM, MARINE, HYDROLOGY...

.SHORT TERM...
(Today through Monday Night)
Issued at 415 AM CDT Sun May 14 2023

The Flood Watch has been expanded northeastward based on the latest
radar trends and high-resolution model guidance, more on that in the
Hydrology section towards the bottom of the AFD. A corridor of 1.8"-
2.0" PW values (90th percentile: ~1.74") will remain steady over
Southeast TX throughout the day. Offshore this morning, an embedded
shortwave trough will continue to drift northward throughout the day
and act as the lifting mechanism for the sufficient moisture in
place. This is already evident with the widespread rainfall going on
near Matagorda Bay early this morning. Some models indicate that
this may evolve into a mid level low with a subsequent surface low
developing as it pushes inland late this morning. As of ~330am CDT,
radar reflectivity reflects some slight spin to it offshore, so it
definitely appears that it'll make a run at a surface low
developing.

A 25-30 kt LLJ looks to develop west of I-45 this morning as well
and in combination with sufficient instability (1000-1500 J/kg
CAPE), there will be favorable support for the development of
showers/thunderstorms. Long story short, widespread rainfall is
expected to continue into the afternoon hours across Southeast TX,
but especially for areas along and west of I-45. The trends from the
HRRR have been fairly consistent showing a swath of 3-6" of
additional rainfall today across portions of Southeast TX where
training occurs. Isolated higher totals will be possible. We'll have
to monitor rainfall rates as well, we've already seen rates of 2-
3+"/hr yesterday and will likely see this today as well. As a result
of all of that, WPC has increased the excessive rainfall outlook to
a moderate (level 3 out of 4) for most of Southeast TX.

Rainfall begins to taper off going into the late afternoon/evening
hours as we lose the favorable dynamic forcing. As far as
temperatures go, with widespread rainfall and overcast cloud cover
prevailing today we won't get too warm. Expect high temperatures to
top out in the upper 70s to low 80s. Going into Monday, a 588-590
dam mid level high slides in overhead from the east, so cloud cover
will break up enough to raise temperatures into the mid to upper
80s. Some locations further east could even reach the 90°F mark. A
weak cold front still looks to approach us late Monday night, but
will be washing out as it does so. The main impacts we'll get from
this front is persistent chances of showers/storms going into the
overnight hours and at least a brief break from the onshore flow. As
a result, most locations may see temperatures in the upper 60s on
Monday night.

Happy Mother's Day to all of the moms out there! We really wish we
could have better weather for y'all today, but it's going to be a
wet one with localized flooding possible. Please be sure to have
multiple ways of receiving any potential flood warnings today, check
roadway conditions before you venture out, and if you see any water
on roadways...turn around, don't drown.

Batiste

&&

.LONG TERM...
(Tuesday through Saturday)
Issued at 415 AM CDT Sun May 14 2023

The pattern changes to a more seasonal during the long term period.
Upper ridging weakens and shifts eastward on Tuesday as a weak
cool front attempts to cross the region during the day. Latest
trends continue to bring a weaker front, so it might washes out
before reaching the coast. Given some PV anomalies aloft and high
low level moisture, showers and thunderstorms will be possible as
the "front" approaches the area. Depending on the location of the
"front" and any other boundary (-ies), rain/storm chances will
continue on Wednesday. The best chances will fall in the aftn with
peak heating. Upper ridge builds in to our west by mid-week,
increasing NW flow aloft and subsidence to our area. Therefore,
lower precipitation chances are possible through Friday. A
deepening upper low will develop over the Great Lakes later this
week, dragging a cold front southward into the Southern Plains and
Southeastern CONUS this weekend. This FROPA is progged tt bring
rain and storms chances by Saturday. Behind the front, a strong
ridge of high pressure builds in over the Plains, bringing drier
conditions into the upcoming week.

JM

&&

.AVIATION...
(06Z TAF Issuance)
Issued at 1138 PM CDT Sat May 13 2023

Mostly VFR across the area, though MVFR ceilings will be mixed in,
especially near convection. Periods of shra/tstms anticipated
into around 10-12z along the I-45 terminals, possibly followed by
a brief lull, then additional precip development after 16z with
heating and additional surges of moisture rolling in from the
Gulf. Visibility restrictions and wind variability will be common
in/near the heavier rain. Otherwise, a mix of MVFR/VFR in the
morning gradually lifting in the mid-late morning hours. Though
there is some uncertainty, expect precip to wind down near the
coast ~20z and well inland 0-2z. 47

&&

.MARINE...
Issued at 415 AM CDT Sun May 14 2023

Scattered to numerous showers and thunderstorms will continue to
increase in coverage today as different disturbances move through
the region. Light to moderate southeast winds will persist today
with seas around 5 to 6 ft. Strong gusty winds, heavy rain and
frequent lightning can be expected with the strongest storms. In
general, caution flag continues through early this evening, with
winds approaching advisory levels at times. Daily chances for
isolated showers and thunderstorms will continue this week. Light
and variable winds are possible on Tuesday as a weak front attempts
to make its way offshore. However, onshore winds will prevail
through most of the week.

JM

&&

.HYDROLOGY...
Issued at 415 AM CDT Sun May 14 2023

The Flood Watch (goes through 7pm CDT Sunday) has been expanded
further northeastward and now includes Harris, Montgomery, Grimes,
Waller, Austin, Fort Bend, Galveston, and Brazoria Counties in
addition to those that were in the initial watch. This is based on
both radar trends along with the persistent QPF trends in high-
resolution model guidance. Over the past several hourly runs, the
HRRR has depicted a swath of 3-6" of additional rainfall over
portions of Southeast TX along the I-45 corridor. Excessive rainfall
has already occurred on Saturday with western Montgomery County
receiving an estimated 4-6" of rain. Montgomery County OEM reported
that multiple roadways are not passable in the western portion of
the county as a result. Soils are fairly saturated, so the
additional rainfall that is expected today will quickly runoff and
could lead to additional localized street flooding and flooding in
low-lying/vulnerable areas.

There are multiple river flood warnings out mainly in Jackson and
Lavaca Counties along the Lavaca/Navidad rivers as some sites have
crested into minor and even moderate flood stage. Rainfall continues
to fall in this area this morning, so we will have to monitor QPF
trends causing additional rises along area rivers, creeks, and
bayous. This includes monitoring bayous and creeks in and around
Harris County as well as there are indications that some may reach
top of bank if the HRRR QPF forecast verifies.

Batiste


&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 79 68 84 67 / 70 30 30 20
Houston (IAH) 81 70 88 69 / 70 20 20 20
Galveston (GLS) 80 74 83 73 / 40 20 20 10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch through this evening for TXZ198-199-210>213-226-227-
235>238-313-335>338-436>438.

High Rip Current Risk through this evening for TXZ436>439.

GM...Small Craft Should Exercise Caution through this evening for
GMZ330-335-350-355-370-375.

&&

$$

SHORT TERM...Batiste
LONG TERM....JM
AVIATION...Cady
MARINE...JM

IMG_1803.png


Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
436 AM EDT Sun May 14 2023

Day 1
Valid 12Z Sun May 14 2023 - 12Z Mon May 15 2023

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS...

...Texas...
The Slight risk was trimmed back even more across TX with this
issuance, however a relatively narrow Slight risk remains across
portions of southeast TX. Observational trends at 08z show a well
defined vort max offshore the TX coast, with this feature expected
to move inland today and likely help focus a flash flood risk.
There remains some question as to the strength of this feature as
it moves northward across east TX, and thus also the degree of
convective organization. Recent observational trends seem to
suggest this feature is pretty well defined, and recent HRRR runs
have generally been trending upwards with QPF. The environment is
supportive of efficient rainfall, with high PWS, sufficient
instability and wind profiles supportive of some backbuilding of
cells on their southern flank. So these observational and HRRR
trends are a bit concerning, and after discussion internally and
with HGX, we made a late call to upgrade a portion of this area to
a Moderate risk. Overall there is pretty good agreement on the
axis amongst HREF members, recent HRRR runs and the Gem Reg, so
not much uncertainty there. The uncertainly deals more with the
magnitude of the event. Whether cells stay disorganized and
generally transient in nature, or if they grow deeper, become more
organized and then show some backbuilding characteristics. We are
leaning towards the latter scenario, hence the MDT risk upgrade,
and some locally significant flash flooding could evolve from a
setup like this.

...OK/KS into the Mid MS Valley...
A Slight risk was introduced across portions of northeast KS into
central/northern MO and southwest IL. An interesting setup here,
with what is pretty much a backdoor cold front dropping south
southwest into the region through the day. Meanwhile weak vort
centers lifting northward in the deep layer southerly flow should
interact with this front and help organize convective development.
One piece of energy is the remnant MCV currently over the TX
Panhandle (as of 08z) and the other is the strung out pieces of
vorticity streaming north out of TX and OK. Convection should
break out this afternoon within the Slight risk area, with some
merging of cells possible as south to north moving cells move into
the frontal axis. Most of the KS and MO portion of the Slight risk
has below average soil saturation and streamflows, so FFG is high.
Thus flash flooding here may tend to be more isolated in nature
for the afternoon/evening hours. However there is a decent signal
for potential continued training convection overnight over
portions of northeast KS into adjacent areas of MO. In fact the
00z HREF shows 5"+ neighborhood probabilities of over 30%, and 3
hour FFG exceedance probabilities get over 30% as well. This type
of nocturnal convection that is being depicted by several of the
models tends to be very efficient warm rain driven. Confidence is
only average, but the ingredients do appear to be there for a more
focused flash flood threat by tonight. Over the eastern edge of
the Slight risk FFG is lower, and 3 hr FFG exceedance
probabilities in the HREF are actually over 50% from far eastern
MO into southern IL. So scattered FFG exceedance seems pretty
likely here, which should translate into at least some flood
impacts within any more susceptible basins/urban areas.

The Slight risk area aligned well with the overlap in convergence
and the highest PW anomalies (approaching mid May max values). It
is also aligned with the highest HREF probabilities and a Slight
risk area depicted by our GEFS based CSU machine learning ERO. So
all in all seems to be pretty good agreement on this area
experiencing some flash flood risk today/tonight.

This Slight risk is surrounded by a broader Marginal risk.
Ingredients do support a localized heavy rainfall threat across
much of OK/KS into portions of the MS valley not in the Slight
risk. The Slight risk was placed where the best organized threat
appears to be, but the risk of localized flash flooding exists
with the Marginal risk as well...just expected to be more isolated
in nature.

Chenard

Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
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don
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Here's the flood watch
image1 (2).png
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don
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Theirs a feeder band over the city right now the rain has been torrential.Looks like it should move out though.Another round looks to happen later this morning going into the afternoon...
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Rip76
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Getting hammered in the Woodlands.
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don
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Now that the meso low is inland new storms are already starting to form.As the low pulls moisture inland another feeder band may setup.The HRRR has the main corridor of training being along the I-45 corridor.Could be a busy day.(The system is basically a Tropical Disturbance)
Iceresistance
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The rainfall rates were likely insane
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don
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New band moving in, this rainfall is crazy heavy. I'm getting concerned there could be widespread street flooding in the urban areas today if these bands continue to train.
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don
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I think we can consider this the first tropical disturbance of the season for us.
mcd0294.gif
esoscale Precipitation Discussion 0294
NWS Weather Prediction Center College Park MD
1033 AM EDT Sun May 14 2023

Areas affected...southeastern TX

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

Valid 141432Z - 141915Z

SUMMARY...Flash flooding will be likely for portions of
southeastern TX through 19Z. Where training axes of rain set up,
potential for rainfall rates of 2 to 3+ in/hr can be expected.
Given wet antecedent conditions due to recent rainfall, the risk
for flash flooding is higher than average, at least locally.

DISCUSSION...A combination of radar and early morning visible
satellite imagery showed that the mesoscale circulation that came
ashore across Matagorda County was located in Wharton County at
14Z. The highest rain rates (1.0-1.5 in/hr) have been located east
of this circulation where a plume of 500-1000 J/kg MLCAPE was
located. The axis of thunderstorms that moved up along the I-45
corridor around 12Z have since weakened in intensity, likely due
to weak near surface based CIN but inhibition rapidly decreases
and instability rapidly increases with eastward extent into
southeastern TX. Low level confluence in the wake of the
circulation over Wharton County has been responsible for a recent
uptick in convection over Brazoria County, contained within a
plume of precipitable water that was between 1.7 and 2.0 inches.

Continued convective development is likely in the short term with
bands of heavy rain developing and training from south to north
where rainfall axes align with the mean steering flow oriented
from SSE to NNW. Given the environment in place, rainfall rates
should be able to reach 2-3 in/hr at times but the potential for
highly localized rates in excess of 3 in/hr cannot be completely
ruled out. portions of southeastern TX, especially near, west and
north of Houston have recorded 2 to 4+ inches of rain over the
past 24 hours, increasing the potential for runoff from heavy
rain. While coverage might be somewhat limited, the potential for
at least localized flash flooding is considered likely over the
next few hours.

Otto
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jasons2k
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Unfolding pretty much like I expected…
Cpv17
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Another 1.63” here this morning, bringing my total up to 6.11” since last Sunday.

Looks like the rain is done for me till tomorrow. Doesn’t appear to be much rain in the forecast once we get past the middle of this week.
Stratton20
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Yah today looks like the last widespread rain chances for a while, upper level ridging will dominate for the foreseeable future after this, besides a very weak front
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don
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I think the front will be able to produce widespread showers and storms also.Then after the front we may move into our normal diurnal driven summer time storm pattern.(20%-30% pops)
Last edited by don on Sun May 14, 2023 11:29 am, edited 2 times in total.
Cpv17
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Stratton20 wrote: Sun May 14, 2023 11:07 am Yah today looks like the last widespread rain chances for a while, upper level ridging will dominate for the foreseeable future after this, besides a very weak front
Yeah. I can see the CPC taking us outta the above normal precipitation forecast and replacing us in neutral or slightly below normal. That’s fine because we need some time to dry out. Hopefully the rain will return later in May.
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don
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More widespread rain may be back on the menu though sometime next week as several models are cutting off another Baja Low.Sending disturbances into the state with a northwest flow also in place.I wouldn't put too much stock in the models on anything beyond 5 days right now as the pattern is messy (with a noisy subtropical jet) and even with ridging the pattern could allow systems to "sneak" under the ridge.Just because the low resolution global models are not showing high qpf amounts in this range doesn't mean there isn't a potential for heavy rain.If you believed the models a couple of days ago today should not have been a washout,but here we are...😉
Last edited by don on Sun May 14, 2023 11:42 am, edited 1 time in total.
Cpv17
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don wrote: Sun May 14, 2023 11:36 am More widespread rain may be back on the menu though sometime next week as several models are cutting off another Baja Low.Sending disturbances into the state.I wouldn't put too much stock in the models on anything beyond 5 days right now as the pattern is messy (with a noisy subtropical jet) and even with ridging the pattern could allow systems to "sneak" under the ridge.If you believed the models a couple of days ago today should not have been a washout,but here we are...😉
This is true. You never really know what the hecks gonna happen regarding the weather. We ended up probably getting more rain than the San Antonio area and that wasn’t supposed to happen. Pretty big bust for that area.
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jasons2k
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Cpv17 wrote: Sun May 14, 2023 11:40 am
don wrote: Sun May 14, 2023 11:36 am More widespread rain may be back on the menu though sometime next week as several models are cutting off another Baja Low.Sending disturbances into the state.I wouldn't put too much stock in the models on anything beyond 5 days right now as the pattern is messy (with a noisy subtropical jet) and even with ridging the pattern could allow systems to "sneak" under the ridge.If you believed the models a couple of days ago today should not have been a washout,but here we are...😉
This is true. You never really know what the hecks gonna happen regarding the weather. We ended up probably getting more rain than the San Antonio area and that wasn’t supposed to happen. Pretty big bust for that area.
This did surprise me too.

Things can change quickly. Just yesterday we were saying this system was going to stick around through Thursday…
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don
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It looks like after this wave another band may form with some daytime heating sometime this afternoon/evening as the low lifts north of us.That band could be more organized than the bands this morning.We'll see...
Screenshot 2023-05-14 at 11-36-36 Models HRRR — Pivotal Weather.png
Screenshot 2023-05-14 at 11-41-10 Models HRRR — Pivotal Weather.png
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djmike
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What happened to the expected flooding in Central Southern Texas? Looks like Houston, who wasn’t expected to see much is getting the brunt. Funny how mother nature does what she wants.
Mike
Beaumont, TX
(IH-10 & College Street)
TexasBreeze
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I see signs of that new band already forming out into the gulf.
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