Plaincast

Messages

Low potential for rain and thunder early tomorrow morning, mainly north of Interstate 40. Then, isolated to scattered thunderstorms in the afternoon, with most likely time for a severe storm with damaging winds between 2 pm and 6 pm EDT in northeastern TN and southwestern VA.

Hot and humid tomorrow with heat indices reaching into the low 100sF, as high as 105F in the lower elevations of the southern Valley.

Cold front yields a drier air mass Wednesday through Friday, with regular summer temperatures and humidity. Rain chances return this weekend.

Discussion

Humid but otherwise pleasant weather this afternoon. Humidity will increase slightly tomorrow, while we wait for an incoming cold front to provide some marginal relief and knock us back down to regular summer conditions. Heat indices in the southern valley tomorrow afternoon should once again climb into the low 100sF. We will likely be near heat advisory criteria for portions of the valley south of Interstate 40, at or around 105F feels like.

Not feeling very confident about the degree to which we see severe thunderstorms tomorrow. Certainly from a parameter space, the overall numbers are favorable between supportive overall shear, a couple thousand MLCAPE, and enough time between morning cloud cover and destabilization in the afternoon hours. On the other hand, overall upper dynamics arent too favorable for severe weather, the morning remnants of the storms upstream of us may induce a backside sinking motion in the atmosphere, which could then inhibit updraft strength later in the day. The HREF only has very low probabilities for strong updraft speeds and experimental AI guidance along with traditional CAMs are also struggling to depict widespread convective coverage. Theres a few model s that are active, namely the Euro, RRFS, MPAS. The main threat with this will be damaging wind gusts with discrete thunderstorms. I think a tornado threat is very low, between probably too high LCLs and trending weaker low level helicity, thats not as b ig on my radar as yesterday. More objective HREF and experimental guidance also keep probabilities really low but the ML nadocast is still carrying a 2% tornado risk, so again wouldnt rule it out outright. Otherwise, if storms are able to fire and reach their full potential, the environment is prone for damaging winds 60 to 70 mph, fueled by midlevel dry air and plenty of storm energy to power strong downdrafts. Small to maybe 1 hail as well, though the high freezing heights of July will be melting any hail falling.

Theres potential for morning showers and maybe a thunderstorm early tomorrow morning, but guidance has been consistent in weakening these storms or outright dissipation. Then theres a nonzero risk we see scattered convection in a northwest to southeast direction through the day over southwest Virginia, but again, low confidence. The upper jet looking its best at 06z in the morning is not the greatest sign for significant severe. Overall the risk for severe weather is low, and in the narrow timeframe of say 2 pm to 6 pm EDT, mainly focused in northeastern Tennessee and southwestern Virginia.

Beyond Tuesday well have rain chances diminishing in the mountains overnight with the passage of the cold front, and then a drier air mass leads to regular summer vibes through the back half of the week with likely dry weather. A new upper trough arrives in the Eastern US by this Saturday, and its this trough that will also bring about the next bout of rain chances in time for the weekend.