Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 181605
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1105 AM EST Wed Jan 18 2017

.SYNOPSIS...
A cold front will slide slowly south across South Carolina late this
afternoon, reaching the southern Savannah River Valley tonight. Weak
high pressure will build across the region tonight. A front will
then waver across the area through the weekend followed by a stronger
cold front Monday which will keep the weather unsettled through
then. Drier high pressure will then return into the middle of next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Visible satellite shows stratus over a decent portion of our
CWA, moving towards the SE. Adjusted the sky grids a little bit
to reflect the current trend. Temperatures may remain a few
degrees cooler under these clouds, but should rebound quickly
once the stratus clears out. In addition, the backdoor cold
front is expected to remain north of the CWA until ~21Z. Given
this pattern, high temperatures should range from the mid to
upper 70s inland to low to mid 70s along the coast. Despite the
near record temps, instability along and ahead of the front
will remain low. The thermal profiles support cumulus, but deep
convection is not expected.

Tonight, weak high pressure will build southward across the CWA
behind the backdoor cold front. Dewpoints will steadily lower through
the overnight hours, reaching the low 40s across Berkeley County by
12Z Thursday. Decreasing sky cover, light north winds, and weak H85
CAA should yield low temps in the upper 40s north to the low to mid
50s within the southern Savannah River Valley. These temps will feel
cool, but will be 10 to 15 degrees above normal.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
High pressure centered north of the area Thursday will shift
offshore Thursday night as a stalled front lingers across the area.
The front will shift north of the area as a warm front as low-level
southerly flow increases ahead of an approaching upper shortwave
trough and associated weak surface cold front. This cold front will
then either remain just north of the area or even push south into at
least SC Friday night before it lifts northward as as warm front
Saturday ahead of another trough near the Southern Plains/western
Gulf Coast.

Rain chances will begin Thursday night with a bit of a break Friday
morning before increasing again from the southwest later Friday. The
best chances and amounts should come Saturday when deeper moisture,
more instability and better synoptic forcing from shortwave energy
and the upper jet move into the area. Some thunderstorms will be
possible, mainly on Saturday in Georgia, although severe weather is
not anticipated given the limited instability. Temperatures will
remain well above normal through the period.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Unsettled weather expected into Monday as a deeper upper closed low
near Texarkana shifts east through the Deep South. Very unseasonable
amounts of deep moisture will likely advect into the region from the
south and with strong synoptic forcing occurring we think conditions
will be favorable for high rain chances and some heavy rainfall with
several inches possible through early Monday. There is also a slight
chance of strong to possibly severe storms later Sunday as a warm
front shifts northward across the area.  Shear/helicity look
favorable but as usual the amount of instability doesn`t look as
favorable. Conditions should improve Monday night and especially by
Tuesday as the upper low lifts north and high pressure builds into
the region and then continues into Wednesday with dry weather.
Although cooler conditions are expected starting Monday,
temperatures will likely remain above normal.

&&

.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
Visible satellite shows an area of stratus moving SE, across our
area. Ceilings with the stratus range from MVFR to just barely
IFR. The TAFs reflect the stratus moving through the airports,
and improving to prevailing VFR by late in the afternoon. The
combination of a tightening pressure gradient and increased
mixing with result in strengthening WSW winds during the
daylight hours, remaining until sunset. In addition, the
backdoor cold front is timed to slide south across the terminals
this evening. Winds will veer from the NW during the evening
hours, NE at KCHS late, speeds should remain 5 kts or less.

Extended Aviation Outlook: Flight restrictions are likely Friday
into Monday as a front wavers across the area. Breezy/gusty
winds likely Sunday/Monday.

&&

.MARINE...
No significant concerns regarding winds/seas. SW winds across the
Charleston County waters should see gusts into the low 20 kts today.
Winds will veer from the NW to NE as a backdoor cold front pushes
south across the SC waters, becoming nearly stationary off the GA
coast by sunrise Thursday. Seas should favor values between 2 to 3
feet.

Thursday through Monday: A front is expected to waver across the
area through Sunday with a stronger cold front Monday. No
significant concerns regarding winds/seas until early next week,
although fog could reduce visibilities, especially over the near
shore waters starting Friday.

&&

.CLIMATE...
Record highs for Wednesday, 18 January:
KCHS: 77/1952.
KCXM: 79/1928.
KSAV: 81/1937.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$
NEAR TERM...
SHORT TERM...
LONG TERM...RJB
AVIATION...
MARINE...
CLIMATE...



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