00z NAM Thoughts

Well, this latest run of the NAM is showing a potential tornado outbreak on Wednesday for areas south of D/FW and a flooding potential for basically the entire area especially for areas down by San Angelo and Abilene where current models are advertising a 4+ inch event for them. For Decatur, the NAM is advertising a 2 to 3 inch event with isolated 4 inch amounts. The NAM is showing a very large hole up and down the I-35 corridor where DFW may only see 1 to 2 inches with a light 1 inch amount down by Hillsboro/Meridian area. Here's the 84 hour accumulated rainfall map from the 00z NAM.

Now, the tornado threat is also there due to the upper low's proximity and how the atmosphere will be basically lifting and producing thunderstorms. The low will provide ample shear over Central Texas that could give thunderstorms the proper ingredients to produce a tornado or two. Up here in North Texas, we may be too cold to have tornadic or severe thunderstorms here as temperatures will be in the 40's and 50's. But if we can get the warm front, another ingredient needed in the making of severe thunderstorms, to move north enough, we may have to readjust our forecast. With an 80 to 90 knot jet streak over Central and East Texas, that along with modest moisture, warmer than usual temperatures, and shear from the cutoff low, all that combined with just enough instability could provide a tornado event for areas south of D/FW.

Now, to the potential start and ending to all of this mess on Tuesday, Wednesday and even into Thursday. The 00z NAM begins the light shower activity around 9am Tuesday and a lull begins Tuesday Night as we look off to the Big Bend for the heavy activity to fire. Here are the images for 9am and 9pm Tuesday.

So, as you can see around 9pm Tuesday, the full extent of the difluence in the atmosphere is beginning to become realized as the air splits between the jet stream and the low pressure across Midland/Odessa and San Angelo. Our showers from 9am have become thunderstorms from I-35 and points east towards the Arklatex region. 

Three hours later around midnight, that small mass of heavy rain becomes an extensive rain shield for Abilene and San Angelo. Rain intensity should begin to pick up at this point with more and more heavy scattered showers becoming the norm around midnight.

By 6am Wednesday, that is when we could see things pick up for an hour or two with still the main convective band still out west near Abilene and San Angelo. Vernon and Quanah could see some very heavy rainfall if this verifies. 

Then, the band of heavy showers and thunderstorms begins to move east, but somewhat weaker than previous runs and hours of the 00z, but nonetheless, heavy rain will still be the case even at 6pm Wednesday.  Some snow will be possible for sections of the Davis Mountains and New Mexico as there will be a cold pocket or two with this system.

Once the dry slot moves in around midnight Thursday, the rain ends for areas west of I-35 but, the event is still ongoing for DFW and east and southward with the NAM forming a squall line too. This squall line is racing northeastward on the next hour of the 00z with very heavy rain and potentially damaging winds with it. 

The current 00z only goes out to Thursday Morning, but we may have to watch areas near Wichita Falls and Vernon for another area of potential precip that could skirt them from the north in Oklahoma about 84 hours out.