Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 250327
Area Forecast Discussion
National Weather Service Charleston SC
1127 PM EDT Mon Apr 24 2017
A low pressure system will affect the area tonight, before pulling
away Tuesday. Although a short wave could impact the area late
Thursday, high pressure will prevail most of the time into the
weekend. A cold front could affect the area early next week.
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
The Flash Flood Watch for Inland Berkeley County will be allowed
to expire at midnight. Showers will continue to diminish through
the night. Updated pops to reflect current trends.
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Tuesday: The separation between the surface low and it`s
accompanying cyclone aloft with shrink as the associated surface
warm and cold fronts occlude and the resulting vertically stacked
low pulls away to the NE. The last lobe of vorticity spinning
counter-clockwise will pull through the area in the morning, and
with considerable wrap-around moisture to continue across our
northern zones, we still have a slight chance to chance of showers
for the Charleston quad-county area through 1-3 pm. Widespread low
stratus to start the day will lift into an extensive cumulus deck,
and will be slow in diminishing in coverage until late morning south
and not until mid to late afternoon north. Depending upon this
transition, it will have huge implications on max temps. For now we
have mid 70s north of I-26 where cloud cover will last longest,
upper 70s over the rest of SC, and 80-83F across our GA counties
where insolation will b most prevalent.
Tuesday: Mid and upper level will develop and the W-NW extension of
Atlantic high pressure pokes in behind the departing stacked low
pulling through the Great Dismal Swamp and VA Tidewater to the
nearby Atlantic off the Delmarva. Winds will decouple and with
mostly clear skies south and partly cloudy north, there will be
enough radiational cooling to get lows down to the upper 50s-lower
60s inland from the warmer beaches.
Wednesday: Deep-layered high pressure with rising surface pressures
and climbing heights aloft will provide the region with plentiful
sunshine and dry conditions. Temps at 850 mb are as high as 14-16C,
or between the 75th and 90th percentile for late April, and equates
to temps reaching the mid and upper 80s. Coastal sections will
experience a resultant sea breeze, so highs will generally be held
Thursday: Sub-tropical ridging at the surface and low levels, and a
W-SW flow aloft will dominate. The resulting subsident cap around 5-
6K ft looks to keep the majority of the area rainfree, but a
dampening mid level short wave situated in the Pacific NW as of late
Monday, will skirt the region late in the day, actually taking on a
slight negative tilt. This could spark a few showers and t-storms
far inland sections before dark. Despite a little greater cloud
cover than Wednesday, similar 850 mb temps will produce highs again
the in the mid or upper 80s inland from the barrier islands.
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
A strengthening upper ridge and strong Atlantic high pressure
will maintain above-normal temperatures and mainly dry weather.
Friday and Saturday will probably reach the lower 90s across
inland southeast GA with upper 80s elsewhere. A cold front is
expected to approach next Monday, possibly bringing some rain.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Expect IFR cigs to fill in behind the upper low tonight,
especially at KCHS. KSAV is a bit more questionable as to how
low cigs will get. Latest RAP soundings suggest low-end MVFR,
but IFR is possible. Expect prevailing IFR or lower at KCHS, but
opted to limit cigs to alternate minimum thresholds for now.
Extended Aviation Outlook: No significant concerns.
Tonight: Winds expected to turn westerly behind departing low
pressure, mainly reaching 15-20 kt with seas 3-5 feet, except
up to 6 feet in the Charleston County waters and the outer
Georgia waters where an Advisory remains in effect.
Tuesday: There remains a cyclonic flow around low pressure off to
the north through the day to hold any resultant sea breeze
circulations at bay until maybe late in the day. Winds and seas will
be below any advisory levels on all waters, with one exception, the
outer GA waters, where the SCA continues into the afternoon.
Wednesday through Saturday: Atlantic high pressure will dominate
with a S-SW synoptic flow to prevail. Despite some boost from the
sea breeze, winds won`t be any higher than about 15-18 kt and seas
will be capped at 3 or 4 ft.
Astronomically high tides will prevail during the middle of the
week due to the Perigean Spring Tides, likely resulting in the
risk for shallow coastal flooding along at least parts of the
coast with the evening high tides Wednesday and Thursday.
MARINE...Small Craft Advisory until 2 PM EDT Tuesday for AMZ374.
Small Craft Advisory until 6 AM EDT Tuesday for AMZ350.