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

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Katdaddy
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Cant believe May 2019 is around the corner and some wet weather on the way.
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srainhoutx
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Tricky forecast later this week as May begins. A weak frontal boundary as well as a Coastal trough could make for a messy Friday throughout the coming weekend for our Region. The main forecast challenges will be any cold pools and outflow boundaries left behind from thunderstorms to our N on Thursday. Also mesoscale features that we just cannot accurately predict beyond 6 to 12 hours will likely play a role in the sensible weather forecast for that time period.
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srainhoutx
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An extended rainy pattern looks to take hold as May begins...

NWSWGRFC‏Verified account @NWSWGRFC · 23m23 minutes ago
As we head into our next rain/flood event, your federal partners are working together to keep you informed. The @NWSWGRFC and @USGS_Texas have tons of valuable information, and now is the time to become familiar, before it rains! #txflood

04302019 WGRFC 7 Day D5ZmWFqWsAEfNfK.jpg
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Katdaddy
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Another active severe weather day will occur across the S Plains again this afternoon. The SPC has an Enhanced Risk area across NW TX and N Central TX which is surrounded by a Slight Risk area.

29 tornadoes reported to the SPC yesterday. Remain weather across this afternoon and evening across Central TX, N TX, E TX, SE OK, and SW AR.

Across SE TX there is a slight chance of thunderstorms this afternoon and Thursday and will continue to monitor outflow boundaries to the NW of SE TX. Friday and Saturday still look to bring SE TX a threat for strong to severe thunderstorms and locally heavy rain.
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srainhoutx
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Wednesday morning weather briefing from Jeff:

Active weather pattern has returned to TX and the southern plains with near daily rounds of severe weather expected through the end of the week.

Upper air blocking over the Pacific and the Atlantic has resulted in a slow moving upper air trough over the W US that is creeping into the plains. At the surface a strong onshore flow has brought a humid and unstable air mass into TX with surface dewpoints running in the low to mid 70’s over much of the region. Air mass has remained strongly capped over much of SE TX the last two days resulting in little to no shower or thunderstorm development. Cap remains in place this morning, but a stronger short wave trough will move closer to SE TX this afternoon and help to weaken the capping north of HWY 105. Showers and thunderstorms will be possible in this area this afternoon. This evening a cluster of strong to severe thunderstorms may approach areas around College Station from central TX, but how far south this activity makes it is questionable. Think the greatest risk for severe weather today will be across C and N TX.

Late tonight into early Thursday morning a few of the high resolution models are suggesting a weakening line of storms will move toward our central counties from the TX Hill Country. Again, capping looks to be an issue south of I-10, but areas north of I-10 could see a quick round of storms early Thursday morning. I am not overly confident in any scenario on how activity may play out this evening and overnuight.

Another round of storms is expected Thursday across TX and some of this activity could affect the area, especially north of I-10. Additionally, any sort of boundary left over from storms early Thursday could erupt with renewed development Thursday afternoon over the area.

Friday/Saturday:
Greatest threat period appears to be evolving Friday afternoon into Saturday as a weak NNE to SSW moving cool front moves into the area Friday afternoon during peak heating. Air mass will become very unstable on Friday afternoon with CAPE values over 2500 J/kg and steepening lapse rates with the approach of a well defined disturbance our of NE MX. Expected numerous thunderstorms to develop over the region Friday afternoon and evening…some may be severe. SSW moving boundary will be nearly perpendicular to the S low level inflow which will increase Friday evening helping to transport deep Gulf moisture into the region with PWS nearing 1.8 inches. Upper level winds will be out of the SW, which is likely across the boundary, but there is concern for cell training into Saturday morning. Still some details to work out with this period, but severe weather and heavy rainfall will be possible Friday evening into Saturday.

Looks to be a brief break in the weather Sunday, before another strong system arrive early next week. Once again severe weather and heavy rainfall will be possible next Monday and Tuesday as this active pattern continues.

Hydro:
Heavy rainfall over N/C TX the last few weeks has resulted in a significant rise on downstream area rivers. The Trinity is above flood stage at Riverside and then on the lower portion of the river at Liberty and Moss Bluff. The Brazos is elevated, but below flood stage from Hempstead to Rosharon. The Navasota has fallen below flood stage at Normangee.

Additional heavy rainfall today-Saturday over much of N/NC TX will likely generate new flood waves on the Brazos, Trinity, and Navasota basins into next week. With the wet pattern likely lasting into next week, potential flooding along these rivers will be increasing as rainfall totals pile up over time.
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The I-10 wall of cap remains...
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"In the Year of Cap."
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Every year is the "cap"...lol Welcome to life on the Gulf Coast... ;)
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srainhoutx wrote: Wed May 01, 2019 2:12 pm Every year is the "cap"...lol Welcome to life on the Gulf Coast... ;)
It has been for several years. I don't recall it always being this way though, spring after spring, year after year, however.
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"At the surface a strong onshore flow has brought a humid and unstable air mass into TX with surface dewpoints running in the low to mid 70’s"

Jeff wrote the above, this morning.

My humble question is: Is an onshore flow ever humid and stable?
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jasons wrote: Wed May 01, 2019 5:10 pm
srainhoutx wrote: Wed May 01, 2019 2:12 pm Every year is the "cap"...lol Welcome to life on the Gulf Coast... ;)
It has been for several years. I don't recall it always being this way though, spring after spring, year after year, however.

Not even close. Last Spring was a little on the dry side but the Spring of 2016 and 2017 were extremely wet around here with lots of flooding.
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I think a big reason why we haven’t seen much rain around here is because it’s been too cloudy and not allowing temps to heat up to really destabilize the atmosphere.
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A line of slow moving thunderstorms are moving SE across N portions of SE TX this morning. This line will likely make it to the I-10 corridor before falling apart. Friday afternoon through Saturday morning continue to look active for SE TX.
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Storms associated with the Mesoscale Convective System that impacted the Dallas/Fort Worth area last night look to be weakening as the outflow boundary nears the I-10 Corridor. South of I-10 looks fairly capped from data received from aircraft flying into and out of Hobby.

The left over boundary, daytime heating and a couple of disturbances rippling across Central and SE Texas this afternoon/evening may spark additional thunderstorm development. The 06Z GFS and a couple of the short fuse mesoscale models are pinpointing storm development near Austin and College Station late this afternoon. We will see how that plays out as the day progresses.
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I woke-up to a nice surprise. I got one of the cells that held together. Having a decent rain to start the day and the timing is perfect since the lawn was fertilized just yesterday.
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.8 inches in Magnolia. I’ll take it.
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srainhoutx
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Thursday morning weather briefing from Jeff:

The joys of forecasting on the meso scale….

Today:
Models have not preformed well at all with the current Mesoscale Convective System (MCS) moving across the region. Capping has held strong south of I-10, but has broken N of I-10 allowing the N TX complex to move into the northern half of the area this morning with heavy rainfall. Surface outflow boundary has progressed well south of the main line and currently extends from Sugar Land to Downtown Houston to Winnie and continues to move southward. Back edge of the complex is roughly along HWY 6 from College Station to Hempstead and clearing rapidly to the east.

Surface boundary has made much more southward progression than expected and will likely stall near the coast later this morning. Capping remains in place south of I-10, but another shortwave is approaching from the W and will help to erode the cap today over the region. Convection allowing models show storms re-developing this afternoon across our western counties and near the stalling outflow boundary as the lift from the shortwave arrives. Not sure any of these solutions will actually pan out and the air mass…especially north of I-10 will need some time to recover from the morning activity. A few strong storms and heavy rainfall will be the threat if storms develop this afternoon.

Friday:
Another complex of storms will develop over SW TX this evening and move toward our region tonight into Friday along with a weak cool front and another upper level shortwave trough. Friday looks active over the area with widespread showers and thunderstorms. Timing remains difficult as the SW TX complex could arrive by early morning, which would change the entire convective outlook for Friday, or the complex could weaken as it approaches (similar to today) and then the front and lift work on an unstable air mass to produce a much more significant round of weather Friday afternoon and evening. Cannot rule out severe storms with damaging winds and hail on Friday as well as additional heavy rainfall.

Hydro:
Overnight training rainfall N of Dallas resulted in 3-6 inches of rainfall on the upper Brazos and upper Trinity basins. Additional rainfall of 2-4 inches over much of the Trinity and Brazos basins is going to result in downstream rises…some to flood stage and potentially into moderate or major flooding on the Trinity.
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Nothing yet south of town, but that's fine with me as I have tilers grouting my patio today. It can do whatever it wants tomorrow.
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Ounce wrote: Wed May 01, 2019 5:15 pm "At the surface a strong onshore flow has brought a humid and unstable air mass into TX with surface dewpoints running in the low to mid 70’s"

Jeff wrote the above, this morning.

My humble question is: Is an onshore flow ever humid and stable?
Bump, por favor.
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Got 1.05” here.

As for the question, yes there is and it depends a lot on the season and other conditions. For example, a sea breeze can be more stable than hot air that’s inland. That’s why oftentimes in summer, you see the sea breeze clear out the cumulus field as it sweeps inland, because the air is cooler. It acts like a mini front.
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