The transition between summer and fall this year has been a wet one for the southern half of the US. After persistent, heavy rainfall earlier this month, parts of TX and the Southeast are closing in on monthly records for this time of year. A brief respite this weekend will not last long as yet another system is expected to rain down on Halloween plans Wednesday night. This Sunday afternoon, model guidance is beginning to converge on a low pressure system that will make its way from TX up the Mississippi River and to the Northeast, bringing rain and possible flooding along with it.
This is your Sunday Storm.
We’ve seen it before; a shortwave trough, a surface low, and the associated cold front all working together to bring rain and storms to TX and the Mississippi River Valley. However, this month has been particularly wet already for many places in eastern and central TX, bringing more rain in one week than has been seen by some all year. From Michael to the undead Willa-turned-nor’easter, most of the Southeast has seen its fair share of excessive rain this month as well. Heavy precipitation from developing cells within this week’s system could push some cities over the record for October monthly rainfall.
By late Tuesday/early Wednesday, a low pressure center will have developed at the surface along with a budding cold front to go with it. As the cold front interacts with the warm, moist air ahead, sheared flow along the boundary will encourage clouds and precipitation mostly just along the front. Rain is expected to begin Wednesday morning in eastern TX, dropping up to 3 inches in some areas. 2 or even 3 inches is enough in some places to push monthly totals near or over record. Dallas has already accumulated 14.52 inches of rain this month, making it the wettest October for the city on record and one of the overall wettest months in history. Three more inches could put this total close to the April 1922 monthly record of 17.64 inches. Fortunately, it’s more likely that Dallas sees closer to 1-2 inches, but higher amounts are certainly still possible.
Just south of Dallas, Waco TX was on track to have the driest year yet from January to August. Now as of yesterday, Waco is experiencing close to its wettest Fall from September to October with 17.04 inches. A few more inches from this upcoming system will easily put 2018 in the number 1 spot. Corpus Christi, already about 8.5 inches over average for the year, can also expect an inch or two of rain Wednesday, quite literally raining on many Halloween plans.
Guidance remains inconsistent for more specific timing and strength of this developing surface low. However, there’s a strong overall signal for heaviest rainfall and strongest convection to stretch from the mid to lower Mississippi River Valley. Confidence increases as most models show the system move northeast, from eastern TX to the mid-Mississippi Valley to the Great Lakes region and Ohio Valley. Previously mentioned Gulf moisture that had been pushed into the lower Plains will now come into play to provide the moisture needed for this downpour. 1-2 inches from widespread showers can be expected Wednesday night and Thursday, with any developing storms increasing local totals to 4+ inches. Thunderstorms, some severe, are likely to break out along the cold front as it follows its low pressure center across the eastern half of the country. It is expected to track to the northeast, with both the GFS and ECMWF agreeing on its movement into the Ohio River Valley by late afternoon Thursday.
At the end of the week, the Northeast could see the tail-end of the system, with heavier rains expected to the south, and showers tapering off to the north. Convection in any developing cells is expected to mostly be limited due to deep layers of shear, keeping tornado possibilities low. However, as we move into the week, the pieces will finally begin to fully fit together.
Watch out for tomorrow morning’s 5 Things to Watch, where we’ll talk about all the weather-related news you need to know for your week.