... A low pressure system developing near the central Gulf Coast will spread tropical moisture across the region through the first half of the work week. The low will exit off the Carolina Coast by early Wednesday, and a more typical summertime pattern will return for the latter half of the week, and into next weekend.
NEAR TERM /THROUGH TONIGHT/... As of 1100 am: Precipitation bands are beginning to fill in from the south late this morning as southeasterly flow forcing begins to interact with develop 1500+ sbCAPE. Will raise southern tier PoPs a touch and sharpen up the N to S gradient in this update.
Otherwise, the previous thinking continues with a weak/quasi- tropical disturbance centered across the lower Miss Valley beginning to wobble toward the area. Ahead of this feature, tropical moisture, characterized by precipitable water values of around 2 inches are starting to slowly overspread the area from the south. This along with weak height falls approaching the area from the Deep South is expected to result in development of numerous to widespread convetion over NE GA and and the Upstate of SC this afternoon. An arc of subsidence just ahead of the tropical moisture is expected to result in a wedge of lower theta-e air across much of the western NC today, and in fact, short term models depict little in the way of precipitation along the I-40 corridor this afternoon. Sufficient mid- level dry air may persist just ahead of the tropical moisture surge to allow for one or two storms to produce a microburst or two this afternoon, but the overall severe weather threat is expected to diminish as profiles take on more tropical characteristics. Max temps will range from about 5 degrees below normal across roughly the southern third of the area, to around climo across northern areas.
Going into tonight, as tropical moisture continues overspreading the area from the south, and weak ripples are forecast to lift NE around the southern/ eastern periphery of the upper low, at least one additional surge of scattered/numerous convective coverage appears likely, warranting continuation of high chance to likely pops across western areas through at least midnight. As time goes on, high PWATs, weak steering currents (mean cloud bearing winds of 5-10 kts from the SE) will result in a slow uptick in the risk for localized excessive rainfall. Said risk should eventually be of most concern across the southern mtns, where deep SE flow could promote cell anchoring and/or training.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 230 AM EDT Monday: A baggy upper trough will slowly track east across the Southeast Tuesday thru Wednesday. An associated weak sfc low will bring plenty of tropical moisture as its center tracks just south of the forecast area. The deep moisture and easterly 850 mb flow will provide widespread clouds and precip. Signals for excessive rainfall are still murky. The better instability and low- level convergence will be along a frontal zone from the I-20 corridor and south. But both the GFS and ECMWF do have a local maximum of QPF response over the I-85 corrdior. There is also a possibility that QPF could get focused along the eastern escarpment thanks to persistent upslope flow. Awaiting new Day 2 ERO from WPC, but expect at most a marginal risk. Nevertheless, expect likely to categorical PoPs and temps 6-10 deg below normal Tuesday. Moist easterly flow will continue thru Tuesday night, resulting in lingering chc PoPs. Lows will be slightly above normal.
As the trough and associated sfc wave shifts east, we will have a rebound in temps and more instability in the aftn. Despite less supportive upper levels for lift, expect above climo PoPs to continue. Temps still just a little below normal, but it will feel humid.
LONG TERM /THURSDAY THROUGH SUNDAY/... As of 245 AM EDT Monday: The upper level baggy trough never completely goes away in the wake of a quasi-tropical low that will track along the East Coast Thursday thru Friday. In fact, by Friday, another trough will dig across the Midwest and carve out a deeper longwave trough across the eastern CONUS for the weekend. Above climo PoPs look to continue possibly thru Saturday, then finally some drier air works in as the trough axis begins to shift east on Sunday. Convection will be mainly diurnally driven and more focused on the mountains. Temps will be at or slightly above normal thru the period.