815
FXUS62 KCAE 211909
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
309 PM EDT Sat Sep 21 2024

.SYNOPSIS...
High pressure building over the region, resulting in generally
dry and warm conditions through Sunday. A return to more
seasonable conditions is expected early to mid week along with
daily slight chances for showers.

&&

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

- Above average temperatures this afternoon.


Very quiet weather is ongoing. Satellite imagery and SPC
mesoanalysis reveals strong ridging is impinging on the
Carolinas, keeping cumulus flat across the forecast area. Temps
are above normal today, with readings already in the upper 80s
early this afternoon for most areas. With 850 hPa temps 15-17C
per SPC Mesoanalysis, expect highs to generally sit near 90F for
most. Ridging and surface high pressure will continue to build
into the area tonight, with quiet weather likely continuing.
Shortwaves passing over the northeastern axis of the 500 hPa
ridge may force very isolated showers tonight but these really
aren`t expected to be much and PoPs were kept low. Lows tonight
should generally range from 65F to 70F as lower dewpoints push
southwestward out of NC and help keep the surface a bit cooler.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Key Message(s):

- Upper ridge dominates over the area with above temps

The upper ridge axis will build over the forecast area this
period while shortwave energy dives southeastward through the
Mid-Atlantic region on Sunday and shifts the upper trough off
the Mid-Atlantic coast. A series of shortwaves will continue to
spill over the ridge Sunday and Monday before the ridge axis
shifts off the southeast coast. Surface high pressure centered
over New England will extend southward and along the coast of
the Carolinas into early next week. Forecast soundings continue
to show a capping subsidence inversion and this should limit
convection on Sunday but this feature weakens Monday and
Tuesday. PW values remain around 1.5 inches on Sunday, but do
increase along the SC/NC border on Monday/Monday night to around
2.0 inches. The atmosphere appears to be too capped on Sunday,
but by late Monday afternoon/evening there could be a few
isolated showers/thunderstorms across the northern Midlands.
The rising 500mb heights should support continued above normal
temperatures with highs expected in the lower to possibly mid
90s on Sunday. Monday high temperatures may be a bit cooler
across the northern Midlands due to slightly cooler 850mb temps
but highs should range from the mid 80s north to lower 90s
south. Overnight lows will also continue above normal with
temperatures upper 60s to lower 70s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Key Message(s):

- Chances of rain increase by midweek with limited confidence
- Continued above normal temperatures

The extended forecast features a lot of uncertainty regarding
the evolution of the upper level pattern and possible tropical
development near the Yucatan Peninsula. Medium range ensembles
diverge on the 500mb pattern evolution beyond Thursday after
being in reasonable agreement earlier in the week. The upper
ridge axis shifts east of the forecast area Tuesday afternoon
allowing for increasing chances of rain with deeper
southwesterly flow and PWATs rising to around 130-150 percent of
normal. The GEFS/CMC/ECMWF all try to bring a trough into the
central portion of the country then cut the system off by
mid/late week. However, the depth and location of this
development differs from model to model and run to run.
Additionally, the high pressure ridge along the southeast coast
settles differently depending on the model.

This leads to lower confidence in the forecast, especially the
probability of precipition through the period. It does seem
reasonable that chances of rain will increase later in the week
given increased moisture and may be reasonable to expect
isolated diurnal convection late in the week. The other
uncertainty in the forecast revolves around a possible
development of low pressure near the Yucatan Peninsula moving
into the Gulf of Mexico by mid/late week. The deterministic and
ensemble forecasts indicate something over the eastern half of
the Gulf of Mexico during the period, but timing and location
still very uncertain. It will most likely take the system to
actually begin forming for the models to have a better handle on
timing and location along with the developing mid/upper level
pattern across the eastern portion of the country.

Temperatures are expected to remain above normal and warm with
NBM probabilities of max temperatures above 85 degrees at 80% or
higher across most of the area through Thursday. Slightly
cooler temperatures expected by Friday and Saturday with
increasing clouds and possible rain.

&&

.AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
Generally VFR conditions anticipated through the TAF period.

Flat, fair weather cumulus has developed underneath mid and
upper level ridging pushing into the southeastern CONUS. Surface
high pressure is gradually traversing the southeastern US. Winds
are light and variable for the most part at all TAF sites as we
sit under this surface high and they will likely remain light
through the period, maybe shifting to southwesterly as we get
into the day on Sunday. Otherwise, it looks very quiet. Clouds
should remain VFR and fog isn`t expected as a strong (15-20
knot) low-level jet develops tonight and keeps the surface just
mixed enough to prevent fog or stratus. Expect fair weather
cumulus to develop again tomorrow.

EXTENDED AVIATION OUTLOOK...No significant impacts to aviation
expected through Wednesday.

&&

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

&&

$$

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