May 2023

[tireman4]

00
FXUS64 KHGX 091133
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
633 AM CDT Tue May 9 2023

...New AVIATION...

.SHORT TERM...
(Today through Wednesday Night)
Issued at 401 AM CDT Tue May 9 2023

An active and wet pattern will be the theme today and tomorrow. WPC
has upgraded much of our region (including in the Houston Metro
area) to a Moderate Risk (level 3 of 4) for Excessive Rainfall
through Wednesday. A robust mid/upper trough/low is currently
situated over south-central Texas. The system is producing strong
mid/upper level vorticity. Lift will increase this morning and
afternoon as mid/upper vorticity is advected in our direction. Deep
onshore flow will tap into high instability and moisture levels over
the Gulf. RAP analysis show MUCAPE values over 3000 J/kg over the
Gulf while much of the southern and western half of the CWA are
experiencing MUCAPE values of at least 1500-2000 J/KG. PWs are
approaching 1.5 inches and will likely rise to near 2.0 inches
today. With little to no inhibition, convective development appears
likely. Given the instability parameters, we cannot rule out an
isolated strong to severe thunderstorm. That being said, the primary
concern by far will be locally heavy rainfall capable of producing
localized street flooding and rising creeks and bayous. This becomes
even more apparent when noting the relatively weak vertical shear as
well as the favorable corfidi upshear values, as per forecast
sounding analysis, suggesting the potential for backbuilding MCSs.


Though the CAMs guidance are in good agreement that there will be
areas of heavy showers and thunderstorms today, there is less
agreement regarding the exact location of heaviest rainfall. HREF
ensemble means indicate widespread rainfall totals of 1.0-2.0 inches
are likely through tonight. However, HREF ensemble QPF max show the
potential for locally much heavier totals. The ensembles are
particularly bullish regarding locally heavy rainfall totals late
tonight into Wednesday morning, particularly for the southern half
of our CWA. By Wednesday afternoon, the aforementioned mid/upper low
might drift far enough north to shift the bulk of the heavy rainfall
threat north of our CWA. Widespread rainfall totals of 1.0-3.0
inches are expected through Wednesday. Areas that experience locally
heavy and training showers/thunderstorms could have totals as high
as 5.0-7.0 inches. If HREF ensemble max QPF has anything to say
about it, rainfall totals could locally approach 10 inches.

Remember to have multiple ways of receiving weather warnings. Do not
drive across water covered roads.

Self

&&

.LONG TERM...
(Thursday through Monday)
Issued at 401 AM CDT Tue May 9 2023

Not significant changes were made to the long term period. Unsettled
weather is progged to continue through at least early next week with
periods of showers and thunderstorms.

A longwave trough deepens over the Rockies, while a well defined
sfc low and the associated frontal boundary extend over the Plains
by Thursday. This boundary will continue to be the main focus for
increasingly moisture advection (humid Gulf airmass) over TX,
leading to isolated to scattered rain and thunderstorms. With
saturated soils from previous rainfall and high precipitable
water, minor street flooding and/or river/creek rises can be
expected. This threat is outlined by WPC in their Day 3 Excessive
Rainfall Outlook with a marginal threat over SETX. Lower rain and
storm chances can be expected on Friday as as the main forcing
remains farther north of the area with the aforementioned upper
trough over the High Plains.

Attention then turns to south TX/northern Mexico as a sfc low and
a mid to upper level trough develop and move northward across
central TX late Friday into Saturday. As of now, the most active
axis of heavier precipitation looks to remain west of SETX.
However, forecast soundings keep suggesting a saturated BL with
PWs in the 1.7-2.0 inch range across parts of the region. Thus,
will continue with rain/storm chances, mainly west of I-45.
Unsettled weather continues early next week ahead and along of an
approaching cold front that is expected to enter the region on
Monday.

With mostly cloudy skies and precipitation chances, temperatures
will remain near to slightly below average for this time of year.

JM

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 626 AM CDT Tue May 9 2023

MVFR / IFR cigs are expected to gradually rise through the early
afternoon. Meanwhile, TSRA/SHRA activity approaching from the
west will move across the region later this morning and into the
afternoon hours. Though isolated stronger thunderstorms are
possible, the primary concern will be heavy rainfall and frequent
lightning. TSRA activity may taper later in the day. Cigs are
expected to drop once again tonight. There may be another round of
TSRA activity very late tonight or tomorrow morning. The presence
of the aforementioned TSRA greatly complicates the wind forecast
today. Though we are predicting a prevailing SE flow, winds in and
near any TS could become quite variable. Therefore, the wind
forecast is low confidence.

&&

.MARINE...
Issued at 401 AM CDT Tue May 9 2023

A few disturbances will be moving over the region in the next few
days, resulting in scattered to numerous showers and thunderstorms.
Therefore, increasing rain and storm chances from south to north can
be expected today. Erratic winds, heavy rain and frequent lightning
can be expected with the strongest storms. Moderate south to
southeast winds will persist through at least Sunday. Seas around 5
to 6 ft can be expected at times. Offshore flow will be possible by
early next week after the passage of a cold front.

JM

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 82 67 81 69 / 60 40 60 10
Houston (IAH) 81 69 81 72 / 80 40 60 20
Galveston (GLS) 80 73 81 75 / 70 40 50 20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch from 10 AM CDT this morning through Wednesday
evening for TXZ199-200-210>214-226-227-237-238-300-313-337-
338-437>439.

GM...Small Craft Should Exercise Caution until 10 AM CDT this morning
for GMZ335-350-355-370-375.

&&

$$

SHORT TERM...Self
LONG TERM....JM
AVIATION...Self
MARINE...JM

[MH5]

Mesoscale Precipitation Discussion 0244
NWS Weather Prediction Center College Park MD
905 AM EDT Tue May 09 2023

Areas affected...south-central to southeastern TX

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

Valid 091304Z - 091800Z

Summary...Localized flash flooding will be possible across
portions of south-central to southeastern TX through 18Z. Rainfall
rates of 1-2"/hr will be likely with 2+ in/hr possible at times.

Discussion...Infrared/radar imagery this morning showed an
interesting pattern across southern TX with an MCV/mid-level
closed low just south of San Antonio and another MCV roughly 100
miles east of Corpus Christi. MRMS derived rainfall rates have
shown 1 to 2+ in/hr along an eastward surging outflow boundary
that was over Matagorda Bay at 1245Z, tied to the circulation
closer to San Antonio. The environment depicted by the 12Z SPC
mesoanalysis indicated MLCAPE of 1000-2500 J/kg and PWATs of 1.5
to 1.9 inches along the middle TX coast, certainly supportive of
high rainfall rates.

850-300 mb flow was from the south at 10-20 kt between San Antonio
and Houston with low level (850 mb) winds of 20-25 kt, supporting
upwind Corfidi vectors from north to south. Areas of heavy rain
are likely along the middle to upper tX coast tied to the eastward
propagating cold pool over the next 1-2 hours along with
additional convective development out ahead within the unstable
airmass later on this morning. Increasing upper level diffluience
will occur as a negatively tilted upper tough axis along the Rio
Grande edges eastward, aiding with lift across the region. Some
backing of the deeper layer mean flow is expected late this
morning for the upper TX coast along with possible strengthening
of the 850-700 mb flow, ahead of the approaching MCV offshore as
it nears Galveston Bay. Rainfall rates of 1-3 in/hr are expected
with localized totals of 3-4 inches through 18Z which may result
in some areas of flash flooding.

Otto

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

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

LAT...LON 30539640 30529547 30509447 30139393 29839390
29469396 29239433 29079473 28439591 28059668
28329708 28869721 29179735 29619775 29959773
30469721

[tireman4]

A line that had been moving Northeastward from the south I was watching. About an hour later, another line forms right in front of it, moving in the same direction. This could be a long day.

[Cromagnum]

A line that had been moving Northeastward from the south I was watching. About an hour later, another line forms right in front of it, moving in the same direction. This could be a long day.

I just drove through that new line. Big old fat pounding rain.

[MH5]

Looks like everyone is in for a wet morning, but all the mesoscale models seem to propagate this initial band through at a decent clip. Think tomorrow appears to be the more concerning day for most as the low slowly pulls NE with what appears to be some healthy feeder bands. Depending on the position of the low and the axis of that band, could definitely lead to some trouble spots.

[don]

A Flash flood watch has been issued and a MODERATE Risk for flooding has been issued for today and tomorrow.

hgx (2).png (10.86 KiB) Viewed 989 times

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
316 AM EDT Tue May 09 2023

Day 1
Valid 01Z Tue May 09 2023 - 12Z Tue May 09 2023

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN SOUTHEAST
TEXAS...

...Texas/Louisiana...
A southerly low level flow, backing during the morning and early
afternoon hours, combined with an incoming upper level low should
lead to ample moisture, instability, and effective bulk shear to
support another day of organized convection capable of producing
heavy to potentially excessive rainfall though over a broader
area, with hourly rain totals expected to peak around 2.5". Model
indicate the potential for local amounts in the 3-7" range but
dispersion remains, with the best overlap existing across
southeast TX, especially within 00z HREF guidance. The highest
probabilities of 5"+ from the 00z HREF were squarely over Houston
TX, where two rounds of heavy rainfall are hinted at by the HREF
-- one from the morning into early afternoon and another late in
the period/early Wednesday morning as the low-level jet ramps up.
The MU CAPE gradient, currently edging back to the northwest after
Monday evening's activity, should recede back to the Gulf Coast
during/after periods of heavy rainfall as instability inland
exhausts. The best onshore flow appears targeted into portions of
the Middle and Upper TX coast, which fits the guidance overlap and
conceptual models. Some additional eastward shift was made to the
risk areas near the Gulf Coast for the Slight and Marginal Risks,
more into southwest LA, and was based on the 00z HREF output.
Because of the heavy rainfall on Monday along with the backing 850
hPa flow during the morning and early afternoon, upgraded places
in and near the heavy rain footprint in Southeast TX to a Moderate
Risk per coordination with the EWX/New Braunfels TX,
HGX/Houston-Galveston TX, and LCH/Lake Charles LA forecast offices.
/quote]

[don]

This rain means business, thank goodness the thunderstorm clusters are moving at a decent clip this morning.But it will saturate the grounds more.

[don]

[Stratton20]

Already a day 5 moderate risk of flash flooding for saturday has been issued for central and parts of western texas, you rarely see a moderate risk issued this far out so thats very concerning, the state is about to get slammed this week

[don]

Flash flood warning issued. 4 inches of rain has already fallen this morning on the northeast side of town!

Flash Flood Warning
TXC201-091745-
/O.NEW.KHGX.FF.W.0007.230509T1609Z-230509T1745Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Houston/Galveston TX
1109 AM CDT Tue May 9 2023

The National Weather Service in League City has issued a

* Flash Flood Warning for...
Central Harris County in southeastern Texas...

* Until 1245 PM CDT.

* At 1109 AM CDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Between 2 and 3 inches of rain
have fallen. Additional rainfall amounts of 1 to 3 inches are
possible in the warned area. Flash flooding is ongoing or expected
to begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar.

IMPACT...Flash flooding of small creeks and streams, urban
areas, highways, streets and underpasses as well as
other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
Northwestern Pasadena, Galena Park, Jacinto City, Greater Fifth
Ward, Near Northside Houston, Northside / Northline, Greater
Heights, Aldine, Cloverleaf, Greater Greenspoint, Channelview,
Houston Gardens, Settegast, East Houston, Kashmere Gardens, East
Little York / Homestead, Eastex / Jensen Area, El Dorado / Oates
Prairie, Pleasantville Area and Denver Harbor / Port Houston.

This includes the following Low Water Crossings...
Woodford Street at Carpenters Bayou, Tidwell Road at Greens Bayou,
Deer Trail Drive at Halls Bayou, Gulf Bank Road at tributary of
Halls Bayou, Lockwood Drive at Hunting Bayou, Granville Drive at
Little White Oak Bayou, White Oak Drive at Little White Oak Bayou,
Interstate 610 at the Wallisville Outfall, Market Street at
Tributary of Carpenters Bayou, Pardee Street at Schramm Gully,
Interstate 10 East of Wayside , Interstate 45 at Beltway 8 North,
Interstate 45 at Greens, Interstate 610 North at US 59, Railroad
underpass on N Shepherd Drive, US 59 at Kelly Street, Lone Oak Road
at tributary of Halls Bayou, Sunnywood Drive at Halls Bayou, Minden
Street at bridge, Caddo Rd at Greens Bayou, Dillard Street just west
of N Shepherd Dr, Wrightwood Street at Little White Oak Bayou and
Hickman Street by Hunting Bayou.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don`t drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Be aware of your surroundings and do not drive on flooded roads.

&&

[don]

On satellite the system looks like a depression or subtropical system.It also Looks like a weak feeder band is trying to form over the area.

https://weather.cod.edu/satrad/?parms=s ... =undefined

[don]

This system reminds me of the Louisiana inland Depression of August 2016.

[jasons2k]

On satellite the system looks like a depression or subtropical system.It also Looks like a weak feeder band is trying to form over the area.

https://weather.cod.edu/satrad/?parms=s ... =undefined

Been monitoring this. As the initial outflow pushes off to the northeast, we could see new inflow/convergent bands re-established across the Houston area. Gonna be an interesting few days coming up.

[Rip76]

On satellite the system looks like a depression or subtropical system.It also Looks like a weak feeder band is trying to form over the area.

https://weather.cod.edu/satrad/?parms=s ... =undefined

Been monitoring this. As the initial outflow pushes off to the northeast, we could see new inflow/convergent bands re-established across the Houston area. Gonna be an interesting few days coming up.

Watching this as well. Appears to be a bit ahead of schedule in moving out, no?

[tireman4]

On satellite the system looks like a depression or subtropical system.It also Looks like a weak feeder band is trying to form over the area.

https://weather.cod.edu/satrad/?parms=s ... =undefined

Been monitoring this. As the initial outflow pushes off to the northeast, we could see new inflow/convergent bands re-established across the Houston area. Gonna be an interesting few days coming up.

I have a bad feeling about this.......

[jasons2k]

Two areas are going to get slammed over the next few days.
1) area centered around a developing warm core over Central Tx, especially at night.
2) areas to the east and southeast with inflow off the Gulf.

I think there is a high probability of a Central Tx flooding event with an attendant flood threat along the coast, especially over urban areas and metro Houston.

[tireman4]

&&

.AVIATION...
(18Z TAF Issuance)
Issued at 1234 PM CDT Tue May 9 2023

Areas of SHRA/TSRA will continue across SE Texas this afternoon
and will result in mixed MVFR to VFR conditions along with VRB
winds that may gust up to 25 KTS at times. Chances of SH/TS are
expected ebb this evening into tonight, but another round of
SHRA/TSRA is expected overnight into early Wed morning. Hi-Res
models are still having a hard time with when/where the strongest
activity will occur; the general thinking is that the next defined
round of storms will develop sometime between 08-15Z, but this
timeframe can shift an hour or two ahead and/or behind. Thus,
went with the mention of VCSH/VCTS for this package and will
likely handle the next round of wx with TEMPOs. Apart from this,
cigs will be a little tricky...sites that have or had storms may
see some cigs scatter out for a few hours, but can build back to
MVFR overnight.

24

&&

[Stratton20]

Models are spitting out 15-20 inches for central texas, could be a nasty flood threat, im not that concerned about that event here locally as the warm core low should be far enough west that it will keep the heaviest rains away from our area, also upper level ridging will be nosing in from the east so thats another reason why the heavy rains will be confined to central and west texas, just got to get through tomorrow with little issues and it will be back to a more typical summer like pattern with daily storm chances

[tireman4]

Jason alluded to this and I agree...Jeff points this out...

[Cpv17]

Models are spitting out 15-20 inches for central texas, could be a nasty flood threat, im not concerned about it here locally as the warm core low should be far enough west that it will keep the heaviest rains away from our area, also upper level ridging will be nosing in from the east so thats another reason why the heavy rains will be confined to central and west texas, just got to get through tommorow and it will be back to a more typical summer like pattern with daily storm chances

Personally, I’m not really concerned about it either. That line this morning wasn’t much. Picked up .75”.