DFW: Heavy rain, thunderstorms, & flash flooding Memorial Weekend

Read Initial Forecast #1 | Use Radar/Advisory Tools on the DFW Page

Final Update [Rainfall Record Broken – Sunday 5/24]

DFW Airport received 3.31 inches of rain today (Sunday, May 24, 2015), which breaks the record for the greatest amount ever recorded on this date. The previous record was 3.28″ set in 1908. Records date back 117 years to 1898.

Here are some other statistics:
1) 13th-largest 1-day total ever in the month of May
2) 1.49″ fell in one hour this morn (2-3 am)
3) 2-day total (Sat+Sun) = 4.05″


Second Update [Posted Saturday 5/23 at 7 am]

No changes to the previous forecasts. The atmosphere is evolving as expected and atmospheric moisture is already increasing. One thing that concerns me as much as atmospheric forcing/precipitable water content is the tendency today/tonight for convection/showers/thunderstorms to “train” from south to north.

I have a strong feeling that we will see this training pattern develop as soon as showers begin to form this morning. Most likely, we will observe them “streaming” from south to north on radar, with a tendency to move repeatedly over the same areas. We call that “training”. This morning’s showers will be light to moderate; but intensity will increase this afternoon as upper-level forcing approaches. *If* we see convective elements train from south to north over repeatedly combined with rapid precipitation rates, we could easily see 2 to 4 inches of rain over many parts of North Texas by midnight. For now, we await the first showers to develop on radar, and the completion of the next full model suite. I will update later this morning, or as conditions warrant. Remember, a Flash Flood Watch is in effect.

This is my partial analysis using 6:30 am data. The warm front moved north of the metroplex overnight. Showers will develop this morning, and then thunderstorms will develop later today as the θe ridge to the south advects northward. Atmospheric precipitable water content will increase back above the 99th percentile for this time of year, and thunderstorms will be capable of rainfall rates of 1 to 2 inches per hour later today

Partial analysis as of 6:30 am Saturday 5/23. Colors and isolines represent θe (equivalent potential temperature)

Partial analysis as of 6:30 am Saturday 5/23. Colors and isolines represent θe (equivalent potential temperature)


Initial Forecast #1 [Posted Friday 5/22]

***Thunderstorms with Heavy Rain & Flash Flooding Sat PM – Sun***
If you have outdoor plans in North Texas/Oklahoma this weekend, you will definitely want to stay aware of weather conditions. I expect thunderstorms to develop west of D/FW Saturday, and overspread North Texas late in the day. Atmospheric precipitable water content will exceed the 99th percentile for this time of year, and thunderstorms will have the potential to produce rainfall rates up to 2 inches per hour. I believe thunderstorms will have the potential to train from north to south over the same areas through Sunday. Rainfall amounts appear to be excessive, and flash flooding will be likely (especially in the gray-shaded area from near DFW northward through Oklahoma).

Do not focus on the exact placement of my accumulation lines. They are drawn within an acceptable margin of error and I could have easily drawn them east/west of their current placement on this map. The idea is to illustrate where the heaviest rain will likely occur, with lesser amounts further away from the center of those areas. In D/FW, I expect 2 to 4 inches of rain, with locally higher amounts. These numbers are subject to change with future data. Also, these are only the totals through 10 pm Sunday. It appears that thunderstorms will taper off Sunday night (at least over North Texas/Oklahoma), but additional thunderstorms may develop Monday (especially over Central and North Texas) and those thunderstorms are not accounted for in the data shown on this map.

Although the severe parameters are not particularly impressive, the low-level shear and hodographs are somewhat disconcerting. The shear/helicity suggest the potential for some rotation with a few of the thunderstorms. I will keep a close eye on that. As always, I will update with future data, and you can use the free data tools on my website at any time.

My rainfall forecast through Sunday evening (most of the rain will fall before noon Sunday)

My rainfall forecast through Sunday evening (most of the rain will fall before noon Sunday)

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