Heavy Rain Event for N. Texas this weekend (10/22 – 10/24)

 

 Latest Forecasts (Starting at Update #6 on Friday 10/23) Continued Here

Forecast Verification and Records Tied or Broken

◙  Record #1 [Broken] 2.58 inches of rain at DFW on Thursday 10/22 shattered the previous record for the date (2.19″) set in 1908.

◙  Record #2 [Broken] 3.55 inches of rain at DFW on Friday 10/23 shattered the previous record for the date (2.38″) set in 1920.

◙  Record #3 [Broken] the 2-day rainfall stands at 6.13 inches which is now the all-time greatest 2-day total ever recorded during the month of October.  It is the 11th greatest 2-day total ever recorded at anytime during the year (all months considered).  Records date back 117 years to 1898.

Final Rainfall Totals in North Texas

Final rainfall totals for DFW and North Texas from the heavy rain event of October 22, 23, and 24 (ending 5 am October 25) 2015. DFW Airport received 7.53"

Final rainfall totals for DFW and North Texas from the heavy rain event of October 22, 23, and 24 (ending 5 am October 25) 2015. DFW Airport received 7.57″

➡︎ Forecast Timeline: First Forecast (Sunday 10/18) | Update #2 | Update #3 | Update #4 | Results/Records Broken


Update #5 [Wednesday 10/21/15 at 3:40 pm]

***Flash Flood Watch***

A Flash Flood Watch is in effect from late Thursday night through Saturday Night [Issued at 3:38 pm on Wednesday 10/21/15]

Flash Flood Watch

Flash Flood Watch


Update #4 [Wednesday 10/21/15 at 3:30 pm]

No changes in overall thinking. However, I am increasing the rainfall amounts in my forecast.  I am now forecasting 4 to 7 inches of rain with isolated 10+ inches over a large part of North Texas, particularly the central and southeastern portions. To the northwest, I expect 3 to 5 inches of rain with isolated 7+ inches.

Forecast prepared Wednesday 10/21 at 3 pm

Forecast prepared Wednesday 10/21 at 3 pm

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Update #3 [Wednesday 10/21/15 at 12:30 am]

***Dangerous Heavy Rain Event Friday & Saturday***

◙ New data continue to support a significant rain event on Friday and Saturday. The ground is dry/hard from the drought, and that is conducive to flash flooding.

◙ Model-simulated atmospheric precipitable water content on Friday & Saturday continues to exceed the 99th percentile for this time of year and even falls among the top-5 highest amounts on record for the month of October based on a 65-year PWAT climatology. Granted, this is model-simulated, but the result is significant and meaningful nonetheless.

◙ Given the strength of the system, rainfall rates could easily approach 2 inches per hour within the heavier thunderstorms. The slow-moving nature of this storm system and the potential for quasi-stationary and/or training thunderstorms is what concerns me the most.

◙ I believe thunderstorms & heavy rain will tend to linger for long periods of time which could lead to flash flooding. I would be remiss if I didn’t up the ante and call this a potentially dangerous heavy rain event. I am now forecasting 3 to 5 inches of rain with isolated 7+ inches over a large part of North Texas.

◙ Flash Flood Watches are already being issued for much of West Texas. I truly believe that a watch will eventually be needed here in North Texas as the event nears.

Summary Thursday Night through Friday

  • Rainfall rates 1 to 2 inches per hour at times
  • Widespread 3 to 5 inches by Saturday morning
  • Isolated 7+ inches possible
  • Dangerous flash flooding possible Friday/Friday night
  • Rainfall amounts Thursday through Saturday may break the daily records and may also fall in the top 5 greatest rainfall events ever recorded on a single calendar day in the month of October

Records in Jeopardy:

  • Thursday (10/22): 2.19″ set in 1908
  • Friday (10/23): 2.38″ set in 1920
  • Saturday (10/24): 2.76″ set in 1949
  • Potential top-5 daily rainfall for any day in the month of October

I have updated the map to reflect the increase in rainfall amounts. Updates will be posted later today.

Forecast prepared Wednesday 10/21 at 3 pm


Update #2 [Tuesday 10/20/15 at 5:30 pm]

***Heavy Rain Event Late Week***

If you saw my forecast from Sunday, then you are pretty much caught up. However, I am upping the ante on rainfall amounts. This could be a significant rain event for North Texas.

◙ The chance of rain Thursday night through Saturday is near 100%.  Rainfall may be heavy at times.

◙ A slow-moving yet vigorous upper-level disturbance will approach the Southern Plains on Friday.

◙ In advance, deep moisture advection from the Gulf of Mexico will cause the atmospheric precipitable water content over North Texas to rise above the 99th percentile for this time of year (based on a 65-year PWAT climatology).

◙ This enormous amount of atmospheric moisture will be sufficient to produce rainfall rates greater than 1 inch per hour within the heavier thunderstorms.

◙ It appears that several shortwave disturbances will propagate around the larger upper low as it slowly moves across North Texas. I believe that this will cause multiple rounds of rain/thunderstorms beginning late Thursday and continuing through Friday. We may see a lull before additional rounds develop Friday night into Saturday.

◙ I expect 1 to 3 inches of rain by midnight Friday, followed by another 1 to 3 inches of rain on Saturday with the next shortwave.

◙ As always, some folks will see more than others; however, I am forecasting widespread 2 to 4 inches of rain across North Texas by Saturday evening (storm total). A few locations could easily receive more than 6 inches of rain from this system.

◙ This will be the most significant rain we have seen since the May floods. Also, the rainfall from this system has the potential to break daily rainfall records Thursday through Saturday.

◙ If trends continue, I would not be surprised to see a Flash Flood Watch issued by Thursday.

Records in Jeopardy:

  • Thursday (10/22): 2.19″ set in 1908
  • Friday (10/23): 2.38″ set in 1920
  • Saturday (10/24): 2.76″ set in 1949
  • Potential top-5 daily rainfall for any day in the month of October

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ONE model solution indicating excessive rainfall through Saturday.


First Forecast/Update #1 [Sunday 10/18 at 4 pm]

**Much-needed rain for North Texas this week**

◙ Unremarkable weather for the next couple of days, but clouds will increase Tuesday night. I expect Wednesday to be overcast for most of the day, which should help to keep temperatures in the 70s (although it will be humid). A disturbance may provide just enough forcing for some showers, mainly over the western 1/2 of North Texas prior to lunchtime. Rainfall amounts on Wednesday will be very light and the showers should be scattered.

◙ A stronger disturbance and a cold front will bring more significant rainfall into North Texas Thursday night through Saturday.

◙ The atmosphere becomes extremely moist on Friday, with atmospheric precipitable water content at or above the 99th percentile for this time of year (based on a 65-year PWAT climatology).

◙ Atmospheric forcing/lift should be more than sufficient to generate widespread rain and a few thunderstorms, and the atmospheric moisture content suggests to me that rainfall rates could be rapid (possibly greater than 1 inch per hour) within the heavier thunderstorms.

◙ If the atmosphere evolves in the way that I am forecasting, rainfall amounts may exceed two inches over parts of North Texas by Saturday evening (widespread 1 to 3 inches).

◙ A cooling trend will be underway during this period, with highs only in the 60s next weekend.

This is still 5 days away, but my confidence in this scenario is increasing. I will keep an eye on the data and will update throughout the week.

Forecast Summary [Posted Sunday 10/18 at 4 pm]:

  • Tonight: Low of 50º to 55º
  • Mon: Clear. High around 80º
  • Tues: Clear. Lower 80s
  • Wed: Overcast. Sct’d showers. Upper 70s.
  • Thurs: Mostly cloudy. High around 80º
  • Friday: Rain likely. Rain may be heavy. 70º to 75º
  • Sat: Rain likely. High of 63º to 68º

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