Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Tue May 7 2024
Day 3
Valid 12Z Thu May 09 2024 - 12Z Fri May 10 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHEAST U.S....

...Southeast...
The strong spring system over the Central U.S. will begin to
elongate/stretch in a lengthy positive tilted shortwave trough by
the start of the forecast period and sink southward toward the
region. Earlier convection from the previous day is likely to push
outflow boundaries and a cold front through the region while
another embedded shortwave trough is expected to move through in
the southern stream. Altogether, this should put the region in a
favorable region of forcing for ascent. Deeper moisture is expected
to pool along/ahead of the surface boundaries and will be
characterized by PWs greater than 1.5", which is around 2 std above
the climatological normal for this time of year. With sufficient
instability developing that will overlap with the better forcing
and moisture, rounds of thunderstorms are expected to develop along
the boundary before slipping south/southeast toward the Gulf
Coast. By this point in the storm system evolution, the flow is
likely to be more parallel to the overall storm motions and this
could favor some repeating rounds or training convection
particularly over portions of MS/AL. The environmental ingredients
will support intense rain rates over 1-2"/hr at times and this
could bring scattered instances of flash flooding and for this
update, the Slight Risk inherited looks good was largely unchanged
from the previous forecast.


...Central Appalachians to the Northeast...
Low pressure is expected to track from the lower Ohio Valley to
the eastern Great Lakes over the forecast period as shortwave
trough energy aloft and height falls over the region. A strong
southwesterly flow in the low levels will bring higher moisture,
characterized by dewpoints in the upper 50s to lower 60s and PWs
above 1", especially from the Central Appalachians and southern
areas of the NOrtheast. With the uncapped and warm/moist
environment, there should be scattered to numerous showers and
thunderstorms that develop that will be capable of producing
isolated/localized rain rates in excess of 1-1.5"/hr at times. This
could cause isolated flash flooding, particularly for some of the
areas that have seen recent heavy rainfall and more saturated
ground conditions as well as urban locations.

Taylor