553
FXUS62 KCAE 130809
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
409 AM EDT Mon May 13 2024

.SYNOPSIS...
High pressure moves offshore today as increasing moisture
supports an unsettled week with chances for showers and
thunderstorms through midweek. A bit drier air moves in for
Thursday before moisture returns for the weekend. Temperatures
near to slightly below average.

&&

.NEAR TERM /THROUGH TONIGHT/...
An upper trough currently over KS/OK will gradually shift
eastward through the day. As the trough approaches, deep
southerly to southwesterly flow will increase resulting in
moisture advection over the forecast area with PWATs rising to
around 1.5 inches by this afternoon. Current radar imagery
showing isolated showers across AL/GA with more widespread
showers and thunderstorms across MS associated with shortwave
energy moving along the Gulf Coast states around the base of the
upper trough.

Satellite imagery shows widespread high clouds and cloudy skies
are expected through the period with lowering cloud heights
through the day. Model guidance has trended to showing an
initial band of convection moving into the CSRA during the
15z-18z time frame although there will be significant dry air
in the lower atmosphere that likely results in virga until the
lower levels saturate. CAMs also trending toward an area of
stronger convection moving towards the CSRA and southward with
not much precipitation further north through the afternoon so
have pops increasing through the afternoon with highest pops in
the CSRA. HREF not showing much instability (CAPE less than 200
J/kg) so mainly expecting showers over the forecast area this
afternoon. Temperatures have trended slightly warmer, especially
over the central and eastern Midlands and Pee Dee region where
precipitation will arrive later, with highs ranging from the mid
70s upper CSRA to lower 80s Pee Dee region.

Tonight, as the upper trough continues its eastward movement,
isentropic lift will be maximized coincident with some upper
forcing with widespread light showers and isolated thunderstorms
developing after 03z and shifting northward through the night.
Overall rain amounts are not expected to be significant.
Temperatures overnight will be limited by developing lower
stratus clouds and some rainfall with lows expected in the lower
to mid 60s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Tuesday and Tuesday night: An upper trough is forecast to be
over the Mid-Mississippi Valley in the morning and propagate
east northeastward into the Ohio River Valley during the
overnight hours. An embedded shortwave within the larger scale
flow, is anticipated to move from along the Gulf Coast into the
Southeast. While there is some uncertainty amongst the model
guidance, latest trends tend to send this shortwave through on
the faster side, which could limit the amount of convection.
Ongoing convection over the Deep South could also limit
convection in our area. Model soundings show dry mid to upper
levels at the start of the period, gradually moistening as the
shortwave moves through the region. Despite the uncertainty in
the timing and the amount of convection with this round of
precipitation, still think most of the area will see some rain
as this wave moves through. With the drier air in the latest
guidance, forecast rainfall amounts have dropped as well.
However, ensembles show a wide range of precip amounts,
indicating plenty of uncertainty remains. For example, the Euro
ensemble members range from 0.1" to 2.0" for Tuesday and Tuesday
night. After this wave moves through, a dry slot is forecast to
move into the region, which should lead to clearing out this
round of precipitation. If the rain clears out early enough,
daytime heating should lead to additional destabilization in the
afternoon. HREF members show the potential for some refiring of
showers and thunderstorms late in the afternoon into the
nighttime hours. HREF mean CAPE in the afternoon and evening is
>1000 J/kg while the forecast bulk shear is in the 40-50 kt
range. These values are sufficient enough for a severe weather
potential. For what it`s worth, there is potential for severe
weather earlier in the day as well if the convection from the
Deep South can make it this far north. All of that said, there
is still uncertainty in both scenarios, thus SPC has kept the
Marginal Risk (1/5) for the forecast area on Tuesday, which
seems reasonable. Temperatures are forecast to be similar or
slightly cooler than Monday.


Wednesday and Wednesday night: The upper trough is forecast to
continue moving eastward through the Mid-Atlantic region through
the day. Lingering showers and thunderstorms remain possible as
it passes the region. There are differences within the model
guidance on how quickly the trough moves past the area, which
will affect how long the lingering activity sticks around. The
area begins to dry out Wednesday night as the showers exit the
area. Temperatures rebound some for Wednesday as highs are
forecast to be closer to average, or slightly above.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Brief upper ridging moves over the region for Thursday, which
keeps the area dry through the day. Then, moisture is
anticipated to increase again ahead of another trough that is
forecast to move across the region at the end of the week,
bringing another round of potential showers and storms. Guidance
begins to vary greatly with this system and beyond, so
confidence in the forecast for Friday and beyond is rather low.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
High confidence in VFR conditions through midday then increasing
chances of restrictions late afternoon into tonight.


Surface high pressure shifts offshore today allowing for winds
to shift to the southeast and eventually southerly by this
afternoon around 5 to 10 knots. Widespread high clouds will
continue to blanket the region with cig heights lowering through
the day as moisture advection increases ahead of an approaching
upper trough. Some light rain may move into the CSRA by 18z and
overspread the Midlands this afternoon but there is significant
dry air to overcome before restrictions are expected. Kept VCSH
this afternoon then bring in prevailing rain this evening with
some MVFR vsbys and cig restrictions. Cigs expected to
deteriorate further near the end of the forecast period. Winds
should stay up from the south to southeast tonight.

EXTENDED AVIATION OUTLOOK...Showers and thunderstorms and
associated restrictions are possible Monday night through
Wednesday and again on Friday.

&&

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

&&

$$