Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
244 PM EST Fri Nov 22 2019
 
Day 2
Valid 12Z Sat Nov 23 2019 - 12Z Sun Nov 24 2019 

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE 
SOUTHERN APPALACHIANS...

...Southern Appalachians...
A shortwave in the southern stream will be crossing the lower MS 
Valley by early Saturday and will lift northeast across the TN 
Valley, central Appalachians and the Mid-Atlantic region through 
early Sunday. This will drive surface low pressure northeast up 
the west side of the Appalachians through Saturday evening, with 
secondary triple-point cyclogenesis then taking place over the 
upstate of the Carolinas and lifting quickly toward the Delmarva 
by early Sunday. Strong warm-air advection and moisture transport 
associated a 40 to 45 kt low-level jet will be the driver of an 
axis of moderate to heavy rainfall, with an emphasis on the 
southern Appalachians and adjacent foothills/Piedmont region of 
the western Carolinas. Large scale isentropic ascent will be 
complemented by right-entrance region upper-jet dynamics for 
robust forcing, which in conjunction with orographic/upslope flow 
will favor locally enhanced rainfall rates. The one mitigating 
factor will be a lack of instability, with the best instability 
remaining confined to the Gulf Coast states ahead of the 
approaching upstream cold front. However, some pockets of elevated 
instability (250 to 500 j/kg of MUCAPE), may result in some 
locally heavier convective elements, especially across areas of 
the southern Appalachians where the nose of the low-level jet will 
be aimed. 
 
The model consensus favors generally as much as 1 to 2 inches of 
rain, with some locally heavier amounts over the favored upslope 
areas of northeast GA and southwest NC. Overall, the lack of 
instability should temper the rainfall rates enough to limit the 
threat of flash flooding, but some localized runoff problems will 
be possible. Will maintain a Marginal Risk for excessive rainfall 
at this time for the southern Appalachians and western portions of 
the Carolinas.

Orrison

 
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt