Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 300843
Area Forecast Discussion
National Weather Service Charleston SC
443 AM EDT MON MAY 30 2016
Tropical Depression Bonnie will meander over or near the coast of
South Carolina through Monday before slowly lifting northeast away
from the area through mid week. A cold front will then approach the
region late week and stall over or near the area.
.NEAR TERM /THROUGH TONIGHT/...
Pre-dawn: TD Bonnie has undergone trachoidal motions since stalling
out over the Charleston Tri-County region Sunday morning. The alignment
of the deep layered ridge over the western Atlc and detachment of
the steering flow to the nw have resulted in a stagnant system that
still has a pool of deep tropical moisture locked in over se South
Carolina. Through daybreak, banding mainly light to moderate showers
should continue to spiral around the low pres center. widespread
clouds and very moist low levels keep temps elevated around 70 degrees
many areas this morning.
Today: The meandering low will likely continue to linger across the
central and and upper South Carolina Coast as the mid level reflection
and vort maxima remain generally parked over the Low Country and
Pee Dee. Pwats are forecast to to be at least 2 inches today over
the Charleston Tri-County area; climatalogically top of the charts
for this time of year.
00Z model consensus is good agreement on major synoptic features
today including TD Bonnie. The main forecast concern today continues
to revolve around heavy rain potential and the risk for localized
flooding. The region and timing of concern falls across Colleton...
Berkeley...Charleston...and Dorchester Counties this afternoon and
evening. We think the slight bit of warming or breaks in the clouds
will enhance a diurnal convective maximus of rain across this region.
Convective rains buoyed by a depiction of upper forcing on the left
exit region of a 50 kt 200 mb jet that is arcing into Southeast
North Carolina. A combination of dynamics and deep tropical moisture
with a good amount of coastal convergence is a significant concern;
especially for locations that have seen 3-5 inches of rain in the
past 24 hours. Showers and tstms should be locally heavy in the
Charleston quad county region this afternoon and early evening but
convective evolution remains very uncertain given the vast mesoscale
complexities. We continue to highlight localized flooding potential
in our hazardous weather outlook.
Further south, deep moisture is expected to wane across southeast
Georgia and this will limit rain chances as the day wears on. We
maintained a slight chance pop for most areas today with diurnal
instability fairly poor and only isolated tstms at best expected.
It will be warmest in this region today; mid to a few upper 80s to
the south of I-16.
Tonight: Upper level features and what is left of Bonnie nudge slowly
away and convective rains should wane across se South Carolina later
in the evening with scattered showers possible after midnight. Low
temps will be in the 65 to 70 degree range...coolest inland Georgia
where some skies should be mainly clear by then.
.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Remnants of the tropical system will be located somewhere near the
coast of the SC/NC border at daybreak Tuesday. Through the day,
models indicate that the low will make very little northeast
progress, mainly just meandering in the general vicinity. Deepest
moisture will have shifted north of the area, but precipitable water
values around 1.7 inches will keep rain chances in the forecast,
highest across the northern zones.
Wednesday into Thursday the low will slowly track along the NC
coast, while a rather weak pressure pattern remains in place over
the local area. Sea breeze and sufficient moisture will help kick
off afternoon showers thunderstorms each afternoon, with decreasing
coverage in the overnight hours. Deep layered shear will be lacking,
but forecast surface based CAPE of around 2500 J/kg could support a
few stronger storms. Mid level ridge building over the southeast
will result in a warming trend through the period.
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Models are in fairly good agreement through the long term period.
Weak high pressure will give way to a cold front approaching from
the west Friday into Saturday. The front will then likely stall over
or near the area through weekend, before eventually dissipating.
Rain chances will stay in the forecast each day, peaking in the
afternoon when instability is greatest. Temperatures will be near
or slightly above normal.
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
MVFR or possible IFR conditions to impact the terminals tonight
into Monday, due to the proximity of the meandering region of
surface low pressure, which will be in the vicinity of KCHS
tonight, finally starting to pull away later today and tonight.
This should allow for at least some improvement back to VFR at
KSAV later Monday.
EXTENDED AVIATION OUTLOOK...Low ceilings could linger into Tuesday
morning, mainly at KCHS. Thereafter, low risk for flight
restrictions from mainly afternoon showers/thunderstorms and early
We have managed to lower all Small Craft Advisories this morning.
Most of the waters will see an offshore flow on the s and sw
flanks of the poorly defined depression. Speeds through tonight
will mainly be 15 kt or less and seas 2 to 4 ft, highest off the
Charleston County coast. Any Convection may produce higher wind
gusts but we expect conditions on the waters to less turbulent
than on Sunday. The depression will slowly drift ne tonight...
winds and seas will continue to slowly come down.
Tuesday through Saturday: Marine conditions expected to be fairly
quiet through the period. Remnants of the tropical system will
linger north of the waters much of Tuesday before slowly lifting
northeast along the North Carolina coast through mid-week. In wake
of the low, a rather weak pressure pattern will be in place. Winds
will generally be 10 knots or less, with seas 2 to 3 feet on
average. A cold front will then approach from the west Friday into
Saturday providing some increase in winds/seas, but conditions will
still stay well below small craft advisory criteria.
Rip Currents: An enhanced risk of rip currents is expected at all
beaches through at least Monday.