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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

                            
000
FXUS62 KCHS 212017
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
417 PM EDT Thu Mar 21 2019

.SYNOPSIS...
A cold front will move offshore tonight. High pressure will
build over the region on Friday and will linger through this
weekend. Low pressure may move across the region on Monday
night through Tuesday night. 

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
This Evening and Tonight: The area will remain along the southern 
base of a mid-lvl trough of low pressure shifting over the Southeast 
United States this evening, helping maintain a westerly flow 
across the area. Mixing profiles continue to support wind gusts 
generally up to 15-20 mph, but winds should gradually decrease 
as diurnal heating is loss this evening. A dry cold front is 
expected to continue shifting over the area this evening, then 
offshore early tonight, helping maintain modest low-lvl mixing 
and winds generally around 5 mph through the night. There 
should be a brief period of mid clouds shifting over the area 
this evening, but skies are expected to become clear overnight 
as dry air continues to advect into the region behind the cold 
front and mid-upper lvl trough aloft. In general, temps should 
dip into the low/mid 40s, coldest well inland. 

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A elongated area of high pressure sourced from central Canada will 
begin to build over the region on Friday. The center of the high is 
forecast to settle over the forecast area Saturday and Saturday 
night. The high will slide off the Carolina coast on Sunday. The 
weather through the period will be dry with clear to mostly clear 
sky conditions. Daytime temperatures will peak around 70 with 
morning lows in the 40s, warmest conditions on Sunday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A broad low pressure system is forecast to track across the region 
Monday night through Tuesday night. I will increase PoPs during the 
period and will introduce SCHC for thunderstorms Tuesday afternoon 
and evening. Cold air advection in the wake of the low may result in 
upper 30s inland early Wednesday morning. Sfc high pressure is 
expected to dominate the region Wednesday and Thursday.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
VFR conditions will prevail at both CHS and SAV terminals through 
18Z Friday. West-southwest winds could up to around 15-20 kt at 
both terminals this afternoon.

Extended Aviation: VFR through Sunday. Flight restrictions are 
possible Tuesday and Tuesday night. VFR conditions return on 
Wednesday.

&&

.MARINE...
This Evening and Tonight: West-southwest winds will peak near
15-20 kt at times this evening ahead of a dry cold front 
approaching the waters by early evening. Winds should be highest
across northern South Carolina waters. Seas will generally peak
near 3-4 ft in nearshore waters and up to 4-6 ft in offshore 
Georgia waters this evening. Jetting and surging is expected 
behind the front with west-southwest winds turning more northwest
during the second half of the night. Cold air advection along 
with 1000mb Geostrophic flow near 30-35 kt will likely support 
Small Craft Advisory level conditions over offshore Georgia 
waters through the night and for roughly a 4-6 hour window 
across northern South Carolina waters beyond 10 nm from the 
coast. Given the setup, a Small Craft Advisory is now in effect 
for northern South Carolina waters starting at 11 PM tonight, 
mainly for wind gusts near 25 kt and seas up to 6 ft closer to 
20 nm offshore. A Small Craft Advisory will remain in effect for
offshore Georgia waters through the night. Weaker low-lvl 
mixing near the coast and south, should keep winds just below 
advisory criteria over remaining waters. 

Extended Marine: High pressure will build over the marine zones 
Friday through Saturday, yielding winds generally below 15 kts. A 
short window of gusty winds are possible Friday evening. Seas are 
expected to range between 2 to 4 ft. Low pressure is forecast to 
track near the region on Tuesday and Tuesday night. In the wake of 
the low, gusty NE winds are expected across the marine zones. Small 
Craft Advisory conditions may begin on Tuesday and remain through 
Wednesday.

Rip Currents: A moderate risk for rip currents will continue along 
the beaches through Friday evening. Surf is forecast to feature
2 ft with 10 second periods. Northwest winds are expected during
the morning Friday, then will shift from the west. 

&&

.FIRE WEATHER...
A dry cold front will move across Southeast Georgia late afternoon 
into early evening. Winds are expected to remain elevated with gusts 
up to around 15-20 kt early evening. In addition, RH values will 
remain near critical for the next couple hours away from the coast. 
Fuels across Southeast Georgia are the lowest in our forecast area, 
but values appear marginal. Per collaboration with SPC Fire Weather, 
all of Southeast Georgia is in an elevated potential for fire danger 
through late afternoon. A Fire Danger Statement remains in place for 
this region into early evening.

Friday: RH values as low as 25-30 percent and elevated offshore
winds could also cause fire concerns, especially if partners 
report low fuel moisture.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until noon EDT Friday for AMZ374.
     Small Craft Advisory from 11 PM this evening to 6 AM EDT 
     Friday for AMZ350.

&&

$$
NEAR TERM...DPB
SHORT TERM...NED
LONG TERM...NED
AVIATION...DPB/NED
MARINE...DPB/NED
FIRE WEATHER...