Severe Thunderstorm Warning 89, NWS Columbia, SC

Area Forecast Discussion
National Weather Service Columbia SC
154 PM EDT Sun Jul 7 2024

.SYNOPSIS...
Abundant moisture combined with an unstable air mass should
support scattered to numerous showers and thunderstorms
for each afternoon and evening through much of the next week.
Above normal temperatures are expected again, with Heat Index
values above 100 each day through next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key message(s) - Slow moving storms/potential for isolated flash
flooding.

The lowest clouds from earlier in the day have finally scattered
out, allowing for diurnal cumulus to begin building across the
forecast area as can be via satellite imagery. Most of the
cumulus clouds have been kept in check thus far, but a few have
been able build enough to produce a few showers in the low
country and far eastern Midlands. The most robust activity
remains in North Carolina. Latest hi-res guidance is hinting at
relatively low coverage this afternoon and early evening until
the activity from North Carolina slides through the area
overnight. However, PWATs remain well above average with values
above 2" and there is 1000-1500 J/kg of MLCAPE according to the
SPC mesoanalysis page. Therefore, shower and thunderstorm
activity is primed to develop quickly, so left PoPs relatively
high this afternoon into the evening. Upper level flow remains
light and the CAPE that's out there is of the long, skinny CAPE,
which will likely lead to slow-moving efficient rain makers. As
a result, the main threat today is the potential for isolated
urban to flash flooding across the area. Overnight lows will be
similar to the past couple of nights (mid 70s) as the
atmosphere hasn't really changed all that much.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Key Message(s):
- Anomalously high atmospheric moisture
- Scattered to numerous diurnal thunderstorms with isolated
  flash flood threat
- High heat index readings possible again by Tuesday.

Upper trough will continue over then central U.S., with western
Atlantic ridge influencing our region. Will mention that there
is a weak upper low on the western portions of the ridge, but it
will continue to weaken and move southward through the period as
the upper ridge begins to strengthen and push further west into
Tuesday. Plenty of moisture will be over the area, with southwesterly
winds aloft bringing Gulf moisture toward us, and low-level
moisture coming inland off the Atlantic. Afternoon and evening
convection appears likely as the sea-breeze moves inland each
day, with other mesoscale boundaries from prior convection all
being potential initialization points for convection too. High
pwat values will lend to potential for periods of heavy rainfall
in any slower storms. Severe threat is minimal, but can not rule
out some gusty winds in stronger storms through the period. Temperatures
should be a bit cooler Monday due to cloud cover with highs
expected in the lower 90s, then a return to the middle 90s and
higher heat index readings on Tuesday. Can not rule out the need
for another Heat Advisory on Tuesday as latest guidance is
showing some areas climbing above 108 degrees for periods
Tuesday afternoon.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Key message(s):

- Daily diurnal showers and thunderstorms
- Heat indices exceeding 100 degrees
- Isolated flash flooding threat

Models still showing upper trough across the middle of the
country, with our region under the influence of western Atlantic
ridge. The upper trough will begin lifting on Thursday, with
increasing upper ridging building back into our area by the
weekend. Weak surface troughs, along with sea-breeze
convection moving inland each afternoon, should aid in diurnal
development of scattered to numerous convection pretty much each
afternoon through the period. Heavy rainfall can be expected
with any storms, especially with pwat readings still forecast
above 2 inches each afternoon. High temperatures climb back into
the low to middle 90s by mid-week. Heat indices are expected to
exceed 100 degrees each day. Best chance to reach heat advisory
criteria appears to be Wednesday, especially with dewpoints
forecast in the upper 70s. Slightly lower dewpoints possible by
the end of the week will bring lower heat index readings, but
still expected at or above the century mark.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Generally VFR this afternoon and evening except in showers and
storms. Restrictions possible near daybreak tomorrow.

A cumulus field continues to develop as of 18z, with just a few
showers showing up on radar at this time. Expect the cumulus
field to continue developing along with shower and thunderstorm
activity. The greatest chance for storms to affect the
individual terminals is in the 19z to 00z timeframe, though
could extend beyond that as upstream activity moves closer to
the region. Winds outside of thunderstorms are expected to be
light, generally from the southeast less than 10 kts. After the
rain moves out tonight, restrictions become possible due to a
stratus deck moving in. There is uncertainty into how low the
ceilings get; however.

EXTENDED AVIATION OUTLOOK...Restrictions possible in diurnally
driven showers and thunderstorms each day. Early morning low
stratus possible.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...None.
GA...None.

&&