651
FXUS62 KCAE 181024
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
624 AM EDT Thu Jul 18 2024

.SYNOPSIS...
A stalled frontal boundary will lead to increased shower and
thunderstorm chances over the next few days, resulting in a wetter
than normal 7-day period. After today, temperatures are expected to
drop to near or slightly below normal levels through early next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Message(s):

- Scattered to numerous showers and thunderstorms this afternoon
  and evening, with the potential for strong winds and locally
  heavy rain.

An upper tough over the Great Lakes to Tennessee Valley region
continues to slowly sag southward as it drifts eastward. As a
result, a surface frontal boundary inches closer to the forecast
area through the day and becomes quasi stationary overnight.
This feature is expected to act as a trigger for more widespread
shower and thunderstorm activity then we`ve seen the past few
days. Like the past few days, there is potential from some
strong to severe thunderstorms again today, with damaging winds
being the primary threat with the activity. This is due to
enough instability (1500-200 J/kg), high PWAT values (~2"), a
bit of bulk shear (~20 kts), and inverted V forecast soundings.
These factors have prompted the Storm Prediction Center to put
the northern half of the forecast area in a Marginal Risk
(category 1/5) for severe weather. Although the bulk shear
values are on the lower side for a severe threat, it is slightly
higher than the past few days. Due to the high PWAT values,
locally heavy rains are possible today, which could lead to
isolated instances of urban or flash flooding. The HREF
ensemble guidance, along with other hi-res models, indicate that
the convection should start later in the afternoon, partially
due to a higher convective temperature. The models also indicate
that the activity will linger into the overnight hours before
moving out of the area.

With the later start to convection expected, afternoon highs are
expected to be above average again, generally in the mid to
upper 90s. Heat index values are likely to be around 105 this
afternoon, which is a few degrees below heat advisory criteria.
Overnight lows are expected to be a bit cooler tonight, dipping
down to the lower 70s for most.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
- Scattered to numerous afternoon and evening showers and
  thunderstorms with the potential for gusty winds and flash
  flooding
- Daytime temperatures expected to be near normal behind the passage
  of a cold front

Northern stream upper trough will push off the New England coastline
and leave a general troughiness in place over the eastern CONUS
as the ridge builds in the west. A weakening frontal boundary
will serve as a convective initiation point on Friday, enhanced
by a series of passing shortwaves through the first half of the
weekend. The supportive dynamics will increase the threat for
strong to severe thunderstorms, with CSU severe probabilities
highlighting the potential for mainly gusty winds as the most
likely hazard. Model SBCAPE values are generally between
750-1500 J/kg For now, SPC keeps us in general thunder, but if
the past several days have foreshadowed anything, it is possible
that the threat will be a bit more elevated. In addition, PWATS
in excess of 2" will continue to provide a threat for heavy
rainfall, with WPC ERO in the Slight category for the eastern
CWA on Friday.

Mid and upper level dynamics are a bit more sporadic and untimely on
Saturday, so do believe the severe threat will be slightly lower.
Nevertheless, PWATs remain above 2" and SBCAPE values should still
push at least 1000 J/kg.

Temperatures are expected to be near to slightly below normal on due
to the increased cloudiness and expected afternoon convection.

&&

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

-The pattern remains favorable for daily chances of afternoon
 and evening showers and thunderstorms

Ample moisture remains over the area under deep southwest flow with
a system moving through the middle of the country. While the stalled
frontal boundary will eventually wash out, the upper level pattern
will continue to look quite similar to previous days, with passing
shortwaves from time. As such, expect scattered to numerous showers
and thunderstorms to develop each afternoon and evening with
gradually decreasing convective chances early next week. It should
be noted that the NBM continues to depict near categorical PoPs
toward the middle of next week, but these values were decreased due
to some forecast uncertainty that inherently exists from days 5-7.

This pattern will also continue to support the continued risk for
localized heavy rainfall and flash flooding in addition to gusty
winds from any stronger thunderstorms. WPC carries at least a
Marginal Risk ERO into early next week. Daytime temperatures through
the period will be near to below normal, with mild overnight lows.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
Generally VFR conditions expected through the TAF period with
restrictions possible in convection.

Some scattered to broken mid-level cloud cover is moving
through the area this morning. Expect skies to become generally
clear before scattered cumulus develop ahead of shower and
thunderstorm activity this afternoon. This activity will likely
be near all terminals, with fairly good potential for the
activity to pass over the terminals. Will likely need to
introduce a tempo group in the next TAF update, but left it out
for now because the highest chances still appear to be 12+ hours
out. After the showers and thunderstorms subside, stratus and/or
fog is anticipated to develop very late in the TAF period. Winds
increase from the southwest today, gusting to around 20 kts
after 15z before subsiding some before the main rainfall
arrives.

EXTENDED AVIATION OUTLOOK...Periods of showers and
thunderstorms may cause restrictions each day. In addition,
brief early morning restrictions may become more likely around
sunrise. into the weekend.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...