May 2021:

General Weather Discussions and Analysis
Iceresistance
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Cpv17 wrote: Sat May 15, 2021 3:25 pm Looks like the WPC has finally bought in, sorta:

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Well, I'm expecting more than Y'all down there & have a higher risk of Flooding, but the good news is that I live on top of a hill . . .
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tireman4
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This will be an interesting set of days coming up. We need the rain, but it always feast or famine ( to quote Jason) around these parts. Stay weather aware.
Kingwood36
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When is the rain going to start?
Cpv17
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Kingwood36 wrote: Sat May 15, 2021 7:26 pm When is the rain going to start?
If I had to guess I’d say around lunchtime or slightly before it.
Texashawk
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Surprising there’s not more chatter around here what with potential flooding rains and a possible tropical system later next week...
Iceresistance
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Texashawk wrote: Sat May 15, 2021 9:54 pm Surprising there’s not more chatter around here what with potential flooding rains and a possible tropical system later next week...
Model consistency issues with the potential Tropical System & I'm thinking that everyone is getting Flood-Ready . . .
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DoctorMu
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Out of town. TG we left the sprinklers off.

XUS64 KHGX 160226
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
926 PM CDT Sat May 15 2021

.SHORT TERM [Tonight through Sunday]...

Lead shortwave has pushed into the Coastal Bend this evening and
rains over the far west and southwestern areas have tapered off.
Have lowered rain chances across the area through 5 am then as the
next wave approaches have focused shower/thunderstorm chances
with the arrival of the wave. Models have broadly different
solutions on the timing and location of storms. So based on where
the greater lift with the upper speed max should begin over the
areas to the west/southwest and so have come to the conclusion
that the storms should focus over the southern areas. If they
initiate later then they would probably track into the northern
areas. Cloud cover should be extensive and temperatures only
rising into the upper 70s to around 80.

45

&&

.AVIATION [00Z TAF Issuance]...

Moisture axis feeding through the area should keep MVFR ceilings
over the southwestern areas this evening eventually expanding up
into the CLL and eventually LBX/SGR area between 12-15z. Then
after 15z expecting showers to be common and transitioning into
TSRA after 17z especially for areas CXO-IAH southward through the
afternoon. VCTS persisting in the afternoon with PROB30 TSRA.
After the round of storms in the afternoon will have lighter more
variable winds in the wake then CIGS will likely collapse into IFR
after 00z...especially over the northern half of the area.
45

&&

.PREV DISCUSSION /Issued 328 PM CDT Sat May 15 2021/...





.LONG TERM [Monday Through Saturday]...

As we head into next week, our concerns remain focused around the
possibility of multiple periods of showers and storms that may
produce locally heavy rain. The synoptic pattern will indeed be
favorable for such an outcome. Persistent southerly flow at the
surface will provide a steady stream of low-level moisture to the
region, with global models remaining in fairly good agreement in
their indication of PW values remaining in the 1.75-2.0 inch range
by Monday. Aloft, the continued but slow eastward propagation of
a closed low will place its center of circulation over the Four
Corners region by Monday afternoon. While Monday`s rainfall
chances are lower behind the departure of the upper shortwave on
Sunday, we continue to anticipate scattered precipitation coverage
throughout the day as the aforementioned upper low approaches.

Rainfall chances begin to increase on Tuesday as the development
of a split jet pattern at 300mb will place SE TX in a highly
favorable region for upper-level divergence. As a series of
disturbances embedded within the now negatively tilted upper
trough/low traverse the area, rounds of widespread showers and
storms will begin to develop by late Tuesday with some rainfall
potentially becoming heavy at times. Of greater concern is
Wednesday, by which the advance of the upper low and increasing
strength/more favorable positioning of the upper jet streaks will
enhance upper divergence even more. With abundant moisture in
place throughout the full column and model soundings indicating a
clear "skinny CAPE" profile typically seen during heavy rain
events, we are becoming more confident in the potential for
locally heavy rainfall and the potential for flash flooding on
Wednesday and into Thursday. While it`s still too late to
determine exact rainfall amounts given the ever-changing "bulls-
eyes" in each global deterministic solution, it`s increasingly
likely that most of SE TX will receive several inches of rain
during this time. As a result I have increased PoPs for most
locations to around 80%.

As upper-level support weakens by the end of the week with the
departure of the aforementioned upper low, the possibility of
heavy rainfall will consequently diminish as well. That being
said, the approach of a second upper trough to our west and a
persistent onshore flow pattern at the surface will continue to
favor active weather as we approach next weekend.

Cady
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don
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0Z GFS qpf amounts....
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Cpv17
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don wrote: Sat May 15, 2021 11:34 pm 0Z GFS qpf amounts....
That’s nuts.
Texashawk
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Cpv17 wrote: Sat May 15, 2021 11:55 pm
don wrote: Sat May 15, 2021 11:34 pm 0Z GFS qpf amounts....
That’s nuts.
Quite a few people said it was nuts around September of 2017, too... 😬 I’d keep my antenna up on this one, folks.
unome
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area weather peeps will be busy this week

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Iceresistance
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I've never seen the WPC have a Moderate Risk of Flooding 3 days out that does not include a Tropical Cyclone!

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Look at the WPC QPF! :shock:
Image

The situation is looking very dire!
Cpv17
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Looks like on average most of us in southeast TX will pick up 7-10” with some areas approaching 20”.
Iceresistance
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Flash Flood Watch for ALL of DFW
...FLASH FLOOD WATCH IN EFFECT FROM 7 AM CDT THIS MORNING THROUGH
WEDNESDAY MORNING...

The National Weather Service in Fort Worth has issued a

* Flash Flood Watch for portions of north central Texas...northeast
Texas and south central Texas, including the following areas, in
north central Texas, Bell, Bosque, Collin, Comanche, Cooke,
Coryell, Dallas, Denton, Eastland, Ellis, Erath, Falls, Fannin,
Freestone, Grayson, Hamilton, Hill, Hood, Hunt, Jack, Johnson,
Kaufman, Lampasas, Limestone, McLennan, Mills, Montague, Navarro,
Palo Pinto, Parker, Rockwall, Somervell, Stephens, Tarrant, Wise
and Young. In northeast Texas, Anderson, Delta, Henderson,
Hopkins, Lamar, Leon, Rains and Van Zandt. In south central Texas,
Milam and Robertson.

* From 7 AM CDT this morning through Wednesday morning

* Rainfall totals of 3 to 6 inches, with isolated amounts near 8
inches possible through early Wednesday.

* Flooding may occur in urban and poor drainage areas. Heavy
rainfall may also cause flooding of creeks, streams, and rivers.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Watch means that conditions may develop that lead to
Flash Flooding. Flash Flooding is a very dangerous situation. You
should monitor later forecasts and be prepared to take action should
Flash Flood Warnings be issued.
And a Flood Watch from NWS-Norman for Central & Southern Oklahoma, & into Northern Texas . . .
...FLOOD WATCH IN EFFECT THROUGH WEDNESDAY MORNING...

The National Weather Service in Norman has issued a

* Flood Watch for portions of Oklahoma and northern Texas, including
the following areas, in Oklahoma, Atoka, Bryan, Caddo, Canadian,
Carter, Cleveland, Coal, Comanche, Cotton, Garvin, Grady, Greer,
Hughes, Jackson, Jefferson, Johnston, Kiowa, Lincoln, Logan, Love,
Marshall, McClain, Murray, Oklahoma, Payne, Pontotoc,
Pottawatomie, Seminole, Stephens, Tillman and Washita. In northern
Texas, Archer, Baylor, Clay, Wichita and Wilbarger.

* Through Wednesday morning

* Several rounds of heavy rainfall are expected today thru Wednesday
morning across portions of central, southern, and southwestern
Oklahoma, and north Texas. Many locations will receive 2 to 4
inches of total rainfall during this time, and some locations near
the Red River may receive over 6 inches.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flood Watch means there is a potential for flooding based on
current forecasts. You should monitor later forecasts and be alert
for possible flood warnings. Those living in areas prone to flooding
should be prepared to take action should flooding develop.
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don
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Looks like models are in a pretty good agreement with the formation of a large MCS in central Texas. That moves in and stalls over the area, due to the southeast ridge to our east.The Gulf inflow is strong enough that the MCS continues to back build,with small impulses coming in from the gulf from the strong inflow helping to refire convection once it starts to wain.
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Screenshot_2021-05-16 Models GFS — Pivotal Weather.png
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Katdaddy
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Flood Watch
National Weather Service Houston/Galveston TX
903 AM CDT Sun May 16 2021

TXZ210>212-226-227-235>237-335>337-436-437-162100-
/O.NEW.KHGX.FF.A.0003.210516T1403Z-210516T2100Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Colorado-Austin-Waller-Wharton-Fort Bend-Inland Jackson-Inland
Matagorda-Inland Brazoria-Coastal Jackson-Coastal Matagorda-Coastal
Brazoria-Matagorda Islands-Brazoria Islands-
Including the cities of Brookshire, Pearland, Bellville, Bay City,
Columbus, Hempstead, Wharton, Missouri City, Pecan Grove, Palacios,
Lake Jackson, Surfside Beach, Freeport, First Colony, Clute, Eagle
Lake, Alvin, Waller, Sugar Land, Prairie View, Sealy, Rosenberg,
Edna, Ganado, El Campo, Mission Bend, Angleton, and Weimar
903 AM CDT Sun May 16 2021

...FLASH FLOOD WATCH IN EFFECT UNTIL 4 PM CDT THIS AFTERNOON...

The National Weather Service in League City has issued a

* Flash Flood Watch for portions of south central Texas and
southeast Texas, including the following areas, in south central
Texas, Coastal Jackson and Inland Jackson. In southeast Texas,
Austin, Brazoria Islands, Coastal Brazoria, Coastal Matagorda,
Colorado, Fort Bend, Inland Brazoria, Inland Matagorda, Matagorda
Islands, Waller and Wharton.

* Until 4 PM CDT this afternoon

* Slow-moving showers and thunderstorms that have developed this
morning have produced rainfall rates of 2-4 inches per hour across
portions of Jackson and Matagorda Counties. 6 inches of rain have
already fallen over portions of this area. Additional showers and
storms are expected to develop across the area today, which will
pose a threat of flash flooding. The Watch may need to be expanded
or extended across portions of SE Texas depending on how
conditions develop during the day.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Exercise caution if traveling today. If you encounter flooded roads,
do not attempt to drive through floodwaters. Turn Around, Don`t
Drown!
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Katdaddy
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Flash Flood Warning to SW Houston:

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Houston/Galveston TX
935 AM CDT Sun May 16 2021

The National Weather Service in League City has issued a

* Flash Flood Warning for...
Central Jackson County in south central Texas...
Southern Colorado County in southeastern Texas...
Southwestern Wharton County in southeastern Texas...

* Until 1130 AM CDT.

* At 935 AM CDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Between 1 and 3 inches of rain
have fallen across portions of the area. Flash flooding is ongoing
or expected to begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Doppler radar.

IMPACT...Flooding of small creeks and streams, urban areas,
highways, streets and underpasses as well as other
drainage and low lying areas.

* Some locations that will experience flash flooding include...
Edna, Ganado, Cordele, Morales, Louise and Lake Texana Dam.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don`t drown when encountering flooded roads. Most flood
deaths occur in vehicles.
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srainhoutx
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Sunday morning weather briefing from Jeff:

A wet week is in store for SE TX with frequent rounds of thunderstorms and heavy rainfall.

Flooding and flash flood threat will increase with time.

A short wave is approaching the area this morning with numerous showers and thunderstorms starting to develop over the area and this will continue through the day. Storms have anchored over portions of Matagorda into Jackson Counties this morning where flash flood warnings are currently in effect and this will be the story this week. Main upper level storm system over the SW US will eject several disturbances across TX and these disturbances will interact with a near constant flow of tropical moisture off the Gulf of Mexico to produce rounds of storms and heavy rainfall with each disturbance. Given the feed of moisture, the potential for slow moving and training storms, and high moisture levels, heavy to excessive rainfall will be possible.

Heavy rain is likely from today through the end of the week, and while it will not rain the entire time, there will be several rounds and grounds will saturate and run-off will increase with time. Concern for today is the slow storm motions currently being seen to the SW of the urban areas as such storm motions and rainfall rates over more urban areas would quickly lead to street flooding.

Main concern period may be in the Wed-Thurs time as the main upper level storm moves into TX and SE TX comes under very favorable rainfall production pattern with a steady stream of moisture and strongly divergent winds aloft that would tend to support training of lines and clusters of storms. However there could be flooding and heavy rainfall and nearly any time from today-Friday.

Rainfall Amounts:

Rainfall totals over the next 5 days will likely average 4-6 inches over the region with isolated amounts of 8-10 inches. Hourly rainfall rates of 1-3 inches will be possible with the stronger storms. Rises on area rivers will certainly be possible given the widespread nature of this event along with the multiple rounds of heavy rainfall. While totals will be spread out some over time, the concern of short term excessive rainfall rates resulting in flash flooding is possible in this pattern.

5-Day Forecasted Rainfall Amounts:
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tireman4
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Please stay weather aware today until the end of the week.
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