DFW: Thunderstorms with Locally Heavy Rain Today (11/22/14)

A vigorous upper-level disturbance is moving into West Texas this morning.  The trough axis (and associated forcing) will not move east of the area until tonight.  As the system approaches North Texas, a copious amount of Gulf moisture continues to advect into North Texas.  As of 11 am, much of the area has already seen some showers and a few thunderstorms throughout the morning.  However, as the stronger forcing moves into the area, I do expect more intense thunderstorms with the potential for heavy rain this afternoon and evening.

Valid 3 pm today: Upper level disturbance moving into Texas (500-mb vorticity and geopotential height).

Valid 3 pm today: Upper-level disturbance moving into Texas (500-mb vorticity and geopotential height).

Unseasonably Moist Atmosphere

One of my primary concerns today is the potential for rapid rainfall rates, particularly this afternoon and evening.   Atmospheric precipitable water content exceeds the 99th percentile for this time of year, based on a 64-year PWAT climatology.  The following map shows the anomalously high precipitable water content over the Southern Plains (based on the 12Z high-res GFS).

Atmospheric precipitable water content anomaly, valid this afternoon/evening (11/22/14). To determine the percent of normal, multiply the legend by 100.

Atmospheric precipitable water anomaly this afternoon/evening (11/22/14).  % of Normal = Legend x 100.

When the atmospheric precipitable water content is this high, thunderstorms can produce rapid rainfall rates in excess of 1 inch per hour.  It wouldn’t surprise me to see some thunderstorms later today producing rainfall rates greater than 2 inches per hour.  Compounding the heavy rain threat today is the potential for training thunderstorms, until the trough axis reaches North Texas.  The deep-layer wind profile to the east of the upper-level disturbance suggests that thunderstorms may align themselves in a south/southwest to north/northeast pattern, with individual cells moving toward the northeast within those quasi-linear segments.  When thunderstorms train (i.e., persist over the same areas through their alignment and reformation), the rapid rainfall rates discussed above can cause the total rainfall amounts to add up quickly.  While I am still forecasting 1 to 3 inches across the area, it would not surprise me to receive reports of locally higher amounts (greater than 3 inches in a few spots).  Some urban and small-stream flooding is possible later today, and I will certainly keep an eye on radar trends as the thunderstorms develop.   This is a rough estimate of rainfall amounts through midnight.

Forecast rainfall amounts through midnight.

Forecast rainfall amounts through midnight.

Other Hazards

Heavy rain is my primary concern today.  However, frequent lightning is also possible with the thunderstorms, particularly this evening.  Some of the stronger thunderstorms could produce gusty winds.  I do not expect widespread severe weather in North Texas, but I can’t rule out an isolated strong to marginally severe thunderstorm.

Forecast Summary

  • Atmospheric precipitable water content today exceeds the 99th percentile for November, based on a 64-year climatology.
  • When precipitable water content is that high, rainfall rates can exceed 1-inch per hour with the heavier thunderstorms.
  • Much of the area will receive 1 to 3 inches of rain.
  • The chance of rain today through this evening is 100%.
  • Frequent lightning and gusty winds possible with the thunderstorms.
  • Rain ending this evening.
  • Temperatures today in the lower 60s.

Special Update (Saturday 11/22 4:45 pm): This is the radar image at 4:45 pm.  Heavy rain is developing over the metroplex, with the heaviest rain approaching from the west.  Rainfall rates may exceed 1 inch per hour in the heaviest activity this evening.

Radar image at 4:45 pm CST (Saturday 11/22/14)

Radar image at 4:45 pm CST (Saturday 11/22/14)

Interactive Radar

Use our interactive radar to follow the thunderstorms as they develop.  If you want to view other data layers, just click the “layers” button in the lower right hand corner of the radar window.  To view the future radar (predictive radar for the next 24 hours), just click the “future” button, then animate using the arrow.