838
FXUS62 KCAE 041803
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
203 PM EDT Thu Jul 4 2024

.SYNOPSIS...
Atmospheric moisture increases into the weekend with isolated
to scattered showers and thunderstorms each day beginning
Friday. Above normal temperatures are expected Friday and
Saturday with Heat Index values up to 110 possible. Atmospheric
moisture remains high through the long term supporting a chance
of showers and thunderstorms each day.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Message(s):
- Hot with heat indices between 100-105 this afternoon.

Upper ridge over the Gulf coast region extending into the area.
At the surface, high pressure dominates over the southeastern
States. There is a weak trough over central NC extending south into
the central Midlands. Cumulus is increasing near the trough due to
some weak convergence and slightly higher low- level moisture than
other areas. The air mass appears a little drier in the southern
Midlands and CSRA where dew points are in the mid 60s. Temperatures
trends on track for highs in the upper 90s. The air mass appears
capped. The CAMS suggest some showers and thunderstorms will develop
in higher terrain in NC and move east this afternoon, but these
showers should stay north of the Midlands due to ridge aloft.
Surface ridge weakens a bit and moves off the coast tonight. The
models indicate low-level moisture will increase overnight with
overall precipitable water around 1.90 inches by morning. The
guidance low temps imply muggy conditions with lows only down to the
mid to upper 70s and some high thin clouds.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Key Message(s):
- A Heat Advisory is in effect from 11am to 8pm Friday
- Low threat of severe thunderstorms and flash flooding Saturday

Heat: Moisture increases on Friday pushing Heat Index values up
to 110. MOS dewpoints in the afternoon are in the low to mid
70s which are several degrees higher than the previous day. With
warming 850mb temps and only widely scattered convection
expected, we will likely see highs in the upper 90s to around
100 degrees. Despite PWAT values around 1.7 to 1.9 inches, upper
ridging over the FA should be sufficient to suppress widespread
convection. Dewpoints continue to increase on Saturday with
PWAT values over 2 inches. However increased convergence ahead
of a front and some shortwave energy moving into the region will
promote higher convective coverage than Friday. So confidence
in a Heat Advisory for Saturday is limited. Convection and cloud
cover should keep us cooler than Friday.

Thunderstorms: An upper level trough will move into the Great
Lakes region then into New England this weekend. The associated
front will remain west of the area however increased convergence
ahead of the front and rising atmospheric moisture will lead to
scattered or numerous showers and thunderstorms for Saturday
afternoon. Shortwave energy rounding the base of the trough may
also support convection in the afternoon and evening. PWAT
values as high as 2.5 inches indicates potential for flash
flooding however the threat will be hampered by 10 to 20 kt
cloud layer winds. The flash flooding potential may be limited
to training storms or urban areas. A tall, skinny CAPE profile
suggests limited updraft strength but precip loading may promote
isolated downbursts in some of the deeper storms.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Key Message(s):
- Daily afternoon thunderstorms expected for much of the period

A fairly persistent synoptic pattern dominates the long term
period. Global ensembles favor positive 500mb height anomalies
over the Southeast with mean PWAT values very steady around 2
inches through the end of the long term. With near or above
normal atmospheric moisture and weak ridging in place, we would
expect a common summertime pattern of diurnal showers and
thunderstorms with temperatures near or a little above normal.
As is typical for the season, there could be an isolated severe
threat each day.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR forecast.

Scattered cumulus this afternoon across central SC, fewer low clouds
near the AGS area where it is slightly drier. In general, high
pressure in place across the area. The ridge will move off the coast
tonight and southwest flow will increase. This will result in
increasing moisture into Friday. Overnight, expect cumulus to
dissipate after sunset with a few mid and high level clouds at
times. Guidance is not indicating any low clouds or fog overnight
and the boundary layer appears mixed so low risk of fog. Winds will
be southwest 5 to 10 knots this afternoon and become light after
00z. The air mass will become weakly to moderately unstable after
15z Friday. A few showers may be developing, especially in east-
central GA.

EXTENDED AVIATION OUTLOOK...Restrictions possible mainly associated
with diurnally driven convection each day. The greatest convective
coverage expected Sat/Sun afternoon.

&&

.FIRE WEATHER...
Key messages(s):
-Hot and dry conditions continue through Independence Day.
-Rainfall probabilities increasing Friday through early next week.

Hot and dry conditions will continue through Independence Day with
increasing moisture and chances of showers and thunderstorms Friday
into early next week. Although there was some rain late in the
weekend and into early this week the hot and dry conditions over the
past few days and through Thursday will generally minimize any
improvement from the rain. Moisture will begin increasing Thursday
but rain chances will hold off until Friday with scattered afternoon
and evening thunderstorms mainly along and north of I-20 then
spreading eastward Saturday into early next week. Temperatures will
also be a concern with afternoon highs in the upper 90s to around
100 which will push heat index values to 110 Friday and possibly 105-
110 Saturday.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...Heat Advisory from 11 AM to 8 PM EDT Friday for SCZ016-018-
     020>022-025>031-035-037-038-041-115-116-135>137.
GA...Heat Advisory from 11 AM to 8 PM EDT Friday for GAZ040-063>065-
     077.

&&

$$