Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Charleston SC
159 am EDT Sat Aug 23 2014

the region will remain between Atlantic high pressure and an
inland trough of low pressure through tonight. A backdoor cold
front will push south through the area Saturday evening into
Sunday followed by cooler and drier high pressure through the
middle of next week.


Near term /until 6 am this morning/...
overnight...the region will remain under the expansive upper ridge.
At the surface...the inland trough of low pressure will drift a bit
closer to the coast as the offshore high pressure is nudged back
to the east. A dry forecast remains in place. A few of the models
try to squeeze out isolated showers late...but this seems unlikely
given the lack of any forcing and middle level subsidence seen on 00z
soundings. Therefore the forecast remains on track with mostly
clear skies once again for what should be another warm and muggy
night. Have raised lows a couple of degrees based on the latest
trends and now expect lows in the upper 70s to around 80 across
most areas.


Short term /6 am this morning through Monday/... and humid conditions will persist ahead of a backdoor
cold front approaching the region from the north this weekend.
1000-850 mb thickness values suggest another day of near record
temperatures Saturday afternoon...with highs peaking in the upper 90s away
from the coast. We could see a few locations hit 100 degrees west of
Interstate 95 in southeast Georgia as compressional heating and a
west/northwest wind occurs ahead of the approaching front. Despite
some mixing out of middle 70 dew points during afternoon hours...heat
index values should approach 105-110 degrees over most locations
and a heat advisory should once again be needed during afternoon
hours. Little relief will be in the way of the heat as latest
model soundings indicate moisture will remain fairly shallow
before frontal passage. Have maintained no more than 20 probability of precipitation over the region
Saturday afternoon and with the timing of the front occurring
mainly during evening and overnight hours Saturday
night...shower/thunderstorm coverage should remain limited.
Saturday night lows will be mild ahead of frontal the middle to
upper 70s away from the coast.

Sunday...the backdoor cold front will continue pushing south through
southeast Georgia early with cooler high pressure building over the
area from the north. A somewhat breezy northeast flow should
occur...especially near the coast. Chances of showers/thunderstorms
will remain in the forecast throughout the day...with the highest
chances in southeast Georgia early and near the vicinity of the
front. With the front shifting further south by the evening...we
should see a fairly decent temperature gradient over the forecast
area...with afternoon high temperatures in the upper 80s to around 90 in
southeast South Carolina to low/middle 90s in southeast Georgia. Heat
index values could still be near 105 degrees across southeast
Georgia before sunset. Precipitation chances will lower considerably by
Sunday night as dryer air pushes into the area from the north.
Overnight lows should range in the upper 60s well inland to
middle/upper 70s over southern areas.

Monday...quiet and noticeably cooler conditions will occur over the
southeast as dry high pressure and northeast flow persists behind
the front to our south. Have kept mainly a dry forecast in
place...with the exception of a possible shower or two along the
coast in southeast Georgia. Overall high temperatures should range in the
middle to upper 80s over most areas...with a few temperatures around 90 away
from the coast in southeast Georgia.


Long term /Monday night through Friday/...
high pressure looks to remain in control inland through middle week.
Low pressure...possibly a weak tropical cyclone...should remain well
offshore. The main influence on our weather will be slightly higher
winds...especially along the coast. There could be a few showers
from time to time...again mostly near the coast. Another cold front
looks to approach late in the week although there is some
uncertainty regarding moisture levels and thus rain chances.


Aviation /06z Saturday through Wednesday/...
VFR conditions expected to prevail at kchs and ksav through 06z
Sunday. Increasing probabilities for showers and thunderstorms to
develop along/ahead of an approaching front from the north later
today. Have added vicinity thunderstorms at kchs from 18-23z but
just limited ksav to vicinity showers after 23z given greater
uncertainty in coverage of thunderstorms during the later part of
the forecast period.

Extended aviation outlook...extended aviation outlook...MVFR
ceilings/visibilities are then possible Saturday evening into Sunday at
either terminal as a backdoor cold front advances through the
area. VFR conditions should then prevail Sunday evening through
Tuesday...but it could be breezy each afternoon as northeast winds
develop behind the passing cold front.


overnight...the local waters will remain within a southwest gradient
between an inland trough of low pressure and high pressure to the
east. The trough will drift a bit closer to the coast and the
tighter pressure gradient will result in a modest nocturnal wind
increase into the 10-15 knots range. Seas will be 1-2 feet within 20 nm
and 2-3 feet closer to the Gulf Stream.

Saturday through Wednesday...conditions are expected to remain below
Small Craft Advisory thresholds through early Sunday. Winds/seas
should then deteriorate later Sunday when northeast winds increase
within high pressure building from the north behind a cold front
shifting south. Small craft advisories could be needed over waters
northern SC waters and offshore Georgia waters by Sunday night and
then possibly in remaining nearshore waters by daybreak Monday. Seas
should also build as high as 5-7 feet...largest over offshore Georgia
waters. Conditions look to improve below advisory levels within
20 nm Tuesday night and Wednesday in the 20-60 nm Georgia zone. The brisk
northeast winds will also cause an increase in tide levels above the
normal astronomical tide...possibly reaching close to advisory
levels during the evening high tide cycles through early week.

Low pressure near the Bahamas could possibly become a weak tropical
cyclone Sunday/Monday...but should remain well east of the area.
However...mariners are urged to pay close attention to the latest


record maximum temperatures...
ksav hit 100 degrees today...the first time since July 26 2012.

Sat 8/23...
kchs...........98 set in 1983
kcxm...........97 set in 1987
ksav...........99 set in 1987

Last time 100 degrees or higher...
kchs..........June 21 2011
kcxm..........June 20 2011


Chs watches/warnings/advisories...



Near term...
short term...dpb
long term...rjb

National Weather Service Glossary of Abbreviations