Stormy Halloween?

Forecast Discussion:

Good Monday evening everybody. The highly anticipated rainfall event this past weekend, for the most part, went relatively well across south central Texas, given the 4-10+ inches of rainfall that fell across the weekend. Since last Thursday, Camp Mabry has picked up 6.03 inches of rainfall, with the majority of that rainfall falling on Saturday as the remnant mid and high level moisture of Hurricane Patricia interacted with a strong upper level storm system, a surface cold front, and plentiful amounts of low-level Gulf of Mexico moisture. Saturday had the potential to be a lot worse across the area. Austin Bergstrom International Airport received 7.55 inches since Thursday, with the majority of that rainfall falling on Saturday. Thankfully we received more benefits from the rainfall than problems. The Hidden Pines Fire was effectively squashed out, area creeks, rivers, and lakes feeling nice rises, and a nice drop in temperature and humidity across the area. 

Below is a look at what Doppler radar imagery looked like at 5:30 a.m. Saturday morning, notice the very heavy tropical downpours extending from Kendall, Blanco, Travis, Williamson and Milam Counties...those heavy downpours exploded over a southward-moving cold front. Thankfully that line of heavy downpours moved through at a time when most people were safely at home and not out on area roadways.

Rainfall Totals across central Texas (past week) courtesy of the LCRA's Hydromet Network:

Generally speaking, 5-12 inches of rainfall fell across Travis County/Austin Metro area with 7-12 inches falling across fire-stricken Bastrop county. 

You can visit the website used to get the image above HERE.

The remnants of Hurricane Patricia, now known as the “ghost of Patricia,” combined with a dynamic upper level storm system allowed a strong area of surface low pressure to develop just off of the Texas coast during the day on Saturday…as that surface low moved off to the northeast along the Texas coast, the pressure gradient tightened across south central Texas around the low’s counter-clockwise rotation, hence the reason for the strong, gusty northerly winds across the area since Saturday and the nice influx of cool Canadian air behind the rains. That low is now moving into the southeastern United States and is creating very gusty winds and widespread precipitation across the central and eastern Gulf Coast.

With higher pressure building in from the west, expect a stretch of nice and dry weather Tuesday through the day on Thursday. Highs will manage to rebound into the 80s Tuesday and Wednesday with overnight lows generally in the 50s before another weak front is set to move through the area during the afternoon/evening hours on Wednesday. Highs drop slightly behind that front on Thursday into the upper 70s to near 80°F thanks to a brief northerly wind shift. Southerly winds look to return as soon as Thursday night to the area.  

Halloween Weekend Rain Maker (Some stronger storms may be possible):

Okay folks, this is where things look to get interesting. I’m currently tracking a strong low pressure system currently located south of Alaska…this system will be digging southwest toward the west coast of the United States over the coming days and will eventually approach central Texas as a potent upper level storm system Thursday afternoon and through the area over the upcoming Halloween weekend. Moisture will come surging back into the area late Thursday into Friday ahead of the approaching trough, or atmospheric valley, of low pressure as upper level divergence increases across Texas. This upper level divergence creates favorable conditions for showers and storms across our area as early as Thursday night through Halloween. As of now, we have the potential to see several rounds of showers and storms across the area. While moisture levels will not be nearly as high across the area as they were this past weekend, they will still be plenty high to create the potential for heavy rainfall. The forecast strength of this approaching storm system and the strong southwesterly wind flow, and upper air divergence out ahead of it will work together to give us a good chance for showers and storms. Given the potentially dynamic nature of this system, the threat for a few stronger/marginally severe storms may be possible with small to moderate hail, gusty winds, and deadly cloud to ground lightning being the main threats. Still quite a bit of uncertainty on this system, however, we will begin to have a better grip and understanding of what lies ahead for us in the coming days. Please stay tuned to the latest forecast and understand that this upcoming weekend has the potential to be quite wet/stormy across the area.

500mb Height Map showing upper level vorticity, or spin in the atmosphere...the red/yellow blob over Louisiana and Mississippi is this past weekend's storm system, the mess south of Alaska is our next storm system! Pretty cool, huh?

Very early rainfall accumulation forecasts are estimating an additional 1-3 inches of rainfall may be possible across the area.