Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 140502
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1202 AM EST Thu Dec 14 2017

.SYNOPSIS...
High pressure will persist across the region through Thursday.
A mainly dry cold front will then push through later Friday and
Friday night before high pressure returns Saturday and Sunday.
Another cold front will move through Monday into Tuesday before
high pressure returns during the middle of next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
No major changes were made for the early morning update.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY/...
Pretty high confidence this period with no significant weather
expected. Surface high pressure will prevail, although a generally
dry cold front will move through later Friday and Friday night.
Temperatures will be above normal Thursday in the mid 60s aided by
the downslope westerly flow ahead of the approaching cold front,
then return closer to normal Saturday, then below normal Saturday
when most places should stay in the mid to upper 50s. Low
temperatures will be near freezing Saturday morning well inland.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
High pressure centered over the area Saturday night will lead to
strong radiational cooling and temps that dip into the mid/upper 30s
inland to low/mid 40s near the coast. Conditions will then become
noticeably warmer on Sunday as a light southerly wind develops on
the west side of high pressure shifting offshore. Temps should
approach the mid 60s Sunday afternoon before clouds develop as
moisture and isentropic ascent increase late. The next chance of
showers should begin Sunday night and increase in coverage on Monday
as a plume of moisture characterized by PWATs near 1.75-2.0 inches
advects over the Southeast along/ahead of a cold front approaching
from the west. Temps could peak into the upper 60s to near 70
degrees on Monday before fropa occurs. Models insist that mid-lvl
energy will traverse over the Southeast before the main mid-lvl
trough axis passes over the area on Tuesday. For this reason, at
least slight chances of showers will be possible Monday night into
Tuesday before dry high pressure returns mid week.

&&

.AVIATION /05Z THURSDAY THROUGH MONDAY/...
VFR. Could see some marginal low-level wind shear at KCHS, but
current data suggest levels will remain just shy of criteria.

Extended Aviation Outlook:  No significant concerns through Sunday
but restrictions are likely Monday as moisture increases the risk
for low clouds and rain ahead of an approaching cold front.

&&

.MARINE...
Early this evening: Have increased winds in the Charleston
Harbor with the strengthening southwest flow. Therefore, a Small
Craft Advisory is now in effect through 10 am Thursday. Previous
discussion continues below.

Tonight: A secondary surge of CAA is expected to push across the
southern Appalachians early this evening. The primary CAA is
expected to remain across the mid Atlantic states. However, H85
winds are forecast to veer from the northwest and increase to 50 kts
across the higher terrain of the western Carolinas. The downsloping
flow should result in a well defined sfc wave/lee trough over the
adjacent foothills. The marine area will remain between the lee
trough to the west and sfc high pressure centered over FL. As a
result, the pressure gradient should range between 3-4 mbs. Forecast
sounding over the Edisto buoy 41004 indicates that the mixed layer
will remain above 3 kft, resulting in average momentum transfer of
low 30 kts gusts. This supports gusts in the mid 20 kts across outer
GA waters and the majority of the near shore zones. Tonight, wave
heights will increase to 5-6 ft across AMZ350 and 374 and 3-4 ft
across the near shore waters south of the Edisto River. A Small
Craft Advisory will be in effect starting at 10 PM.

Thursday through Monday: Small Craft Advisories will continue into
Thursday morning for the coastal waters outside Charleston Harbor.
Winds/seas will then improve until reaching close to Advisory levels
again late Friday/Friday night as a generally dry cold front moves
through, mainly over the Charleston County nearshore waters and
offshore Georgia waters. No concerns then until possibly Monday when
another cold front approaches.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 10 AM EST this morning for AMZ330-
     352-354.
     Small Craft Advisory until 1 PM EST this afternoon for AMZ350-
     374.

&&

$$



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