River Flood Advisory 8, NWS Columbia, SC

Area Forecast Discussion
National Weather Service Columbia SC
315 PM EDT Tue Jun 20 2023

.SYNOPSIS...
A moist pattern, with above normal rainfall chances and below normal
high temperatures, will continue for several more days with an upper
level low nearly stationary just to our west. Some slightly drier
air may work into the region by the weekend and provide a return to
more typical June weather with scattered mainly afternoon and
evening thunderstorms and near normal temperatures.

&&

.NEAR TERM /THROUGH TONIGHT/...
Upper level and surface lows will remain west of the area
through tonight with multiple short waves rotating through the
forecast area. First batch of showers and thunderstorms
continues to move through the northern Midlands and Pee Dee
while areas which cleared late this morning in the southern
Midlands and CSRA are seeing cumulus develop. Expect showers and
thunderstorms to move into and develop over the CSRA and
southern Midlands over the next couple hours then move northward
through the late afternoon and evening hours. Instability will
remain weak to moderate today and tonight and with the heating
this afternoon expect increasing coverage in showers and
thunderstorms this afternoon. Although the potential for severe
thunderstorms is low there is some mid level dry air so stronger
thunderstorms may be capable of producing some strong and gusty
winds. With pwat values remaining aoa 1.5 inches there is also
potential for locally heavy rainfall and some localized flooding
where the ground is becoming saturated from rains over the past
couple of days. Convection will gradually diminish with loss of
heating this evening however with short waves continuing to
rotate through the region expect chance to likely pops overnight
with mainly showers and a few thunderstorms. High temperatures
today will be limited by the clouds and convection with upper
70s to low 80s at most locations and upper 60s to low 70s
tonight.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Closed low still expected to hang out across the Deep South through
Thursday, with embedded vort maxima rotating around it providing
periods of moderate to heavy rainfall. The induced deep south to
southeast flow will keep PWAT values generally between 1.75" and 2",
leading to scattered to numerous showers and thunderstorms. The
severe threat remains low, while there is still concern for locally
heavy rainfall and the potential for flash flooding. River flooding
concerns are looking more likely late this week and through the
upcoming weekend, but rainfall totals across the headwaters in the
upstate will dictate to what extent rivers will rise. WPC's
Excessive Rainfall Outlook maintains a SLGT risk for generally the
western half of our CWA on Wednesday and further across extreme
northwest areas on Thursday. Forecast QPF's Wednesday through
Thursday largely unchanged, with potentially 1.5" to 2.5" across the
area with locally higher amounts.

High temperatures will continue to be limited by cloud cover and
rain, generally in the upper 70s northwest to low 80s southeast
across the region. Diurnal swings will also be impacted, with
overnight lows expected to be in the upper 60s and low 70s each
night with conditions not conducive to radiative cooling.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Upper low looks like it will begin to lift north/northeast Friday
into the weekend. Upper level flow will start to become more
northwesterly which will bring in drier air and begin to reduce our
heavy rain chances. While deterministic guidance seems a little
extreme in terms of bringing in the drier air, ensemble means follow
a similar pattern just to a lesser extent. NBM guidance looked
reasonable with slightly lower PoPs Friday into early next week,
along with temperatures climbing back toward normal, likely due to
some increased sunshine. The low eventually moves into New England,
with the trailing trough axis pushing through the CWA over the
weekend. As such, a more typical summer pattern is expected to
return with mainly diurnally driven showers and thunderstorms.

&&

.AVIATION /19Z TUESDAY THROUGH SATURDAY/...
Periods of restrictions expected through the TAF period.

The upper and surface lows will remain west of the area through
the period keeping a very moist air mass over the region.
Showers and isolated thunderstorms have generally moved north of
the TAF sites with another round of convection developing to
the south and southwest of the terminals. This will result in
increasing coverage of showers and thunderstorms this afternoon
with slightly lower chances overnight. Confidence in timing
remains low attm in regard to terminal impacts so have remained
with TEMPO group over the next several hours with VCSH into the
early morning hours when another round of showers is expected to
move through the area. With the abundant low level moisture
stratus will again develop from the early morning and sunrise
hours into mid morning. Winds through the period will st
southeasterly to easterly at 8 knots or less.

EXTENDED AVIATION OUTLOOK...High confidence continues in
periodic restrictions in showers and thunderstorms each day
through Saturday as low pressure remains stalled over the
region. Early morning fog and stratus also possible.

&&

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

&&

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