Heavy rain and strong thunderstorms are LIKELY on Sunday! - UPDATED SATURDAY 9 AM
Over the last couple of days, confidence has slowly increased regarding potential for widespread heavy rain and strong to possibly severe storms. Right now, we are most concerned with heavy (perhaps flooding) rains being the most impactful threat, but a severe threat also exists.
Starting Sunday, lots of clouds and spotty rain are expected as the most widespread showers and storms remain to the WEST. By late morning, that axis of rain and storms will be spreading into the area.
From 11 AM through about 4 PM, we’ll have to be on guard for strong to severe storms. While we aren’t expected to see a lot of sun, dew point temperatures exceeding 65 F in spots with air temperatures around 70 F will be considered enough energy for which developing storms to utilize.
The wild card will be how far that energy extends UP into the atmosphere – for now, the environmental lapse rate (how fast the air temperature decreases) through the atmosphere remains relatively tame, e.g. 5.5 – 6.0 C/km. However, the lapse rate from the surface up to about 10,000 ft is more impressive (closer to 7 C/km), and this parameter has been shown to be favorable for severe storms.
Despite the questionable energy available for storms, wind energy will MORE than sufficient for organized storms. In fact, it might be a little “too” much wind energy given meager available instability. Lift will be maximized as the area remains favorably positioned in the right-rear quadrant of an upper-level jet streak as well as toward the left-exit region of a 50kt+ low-level jet.
Regarding storm mode, the aforementioned veer-back-veer (VBV) look to the wind profile looks to be more veered with height now, suggesting a mixed mode of line segments and/or cellular activity embedded within a large shield of rain. The take away message here - the "look" to the radar Sunday will be quite messy with lots of rain and storms, so the "textbook" signatures you might be use to seeing may not occur.
Lastly, and of perhaps most concern, is the very heavy rains expected with this system. There will be a plethora of moisture and deep southerly flow throughout the column, creating anomalously high precipitable water levels and deep warm cloud depths. All signs point to at least inch of rain falling for most areas, with localized areas of 2”+ falling…creating a localized flash flooding risk.
BOTTOM LINE – widespread rain and storms are likely on Sunday with some severe weather threat expected. If more energy builds than currently expected, there will be a higher threat. For now, the highest potential for severe weather appears to be over the eastern Upstate (outlined in orange) into parts of the NC Piedmont/Foothills. Here, a heightened tornado threat could develop. Have a way to get watch and warning information, and have your severe weather action plan ready to go.
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