Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
1014 am EST sun Feb 14 2016
cold high pressure will remain in control today. A low pressure
system will then impact the region late Monday into early Tuesday
followed by high pressure through the remainder of the week.
Near term /through tonight/...
Arctic surface high pressure will continue to wedge down the
eastern Seaboard today...maintaining a cold northeast flow. Clear
skies begin the day though some cirrus will overspread from the
west at times and late day stratocumulus expected to develop as
the flow becomes more onshore. High temperatures will top out in the middle
to upper 40s in most areas with a chilly wind keeping wind chill
readings several degrees lower.
A complex and tricky forecast tonight as warm air advection
builds across the region. Low temperatures in some areas may occur this
evening if clouds are not present and may fall to around freezing
northern zones if this is the case. Otherwise lower clouds should
expand and temperatures will likely remain steady or slowly rise
overnight. The surface pattern will remain wedged as the Arctic
air retreats to the north and a coastal trough moves toward the coast
late. The NAM is an outlier breaking out light measurable precipitation in
southeast Georgia not long after sunset. Given the lack of moisture depth
and high condensation pressure deficits we maintained a dry forecast
all areas through most of the night although a few sprinkles are
certainly possible. The nose of the coastal trough nearing the
upper South Carolina coast late may produce a few showers along southeast
South Carolina late tonight. Build down stratus decks over southeast
Georgia may result in some patchy fog late tonight as forecast
soundings suggest but opted to not mention in the forecast until
trends are more definitive.
Short term /Monday through Wednesday/...
Monday...high pressure will quickly erode as a coastal trough lifts
north along the southeast coast. Most areas will be dry early...but
a few showers are possible along the Charleston County coast. Strong
isentropic ascent will then develop Monday afternoon...helping
produce chances of showers over many areas as a southerly flow helps
advect higher moisture levels to the southeastern United States.
Afternoon highs should peak late afternoon under mostly cloudy
skies...with locations reaching the upper 50s in northern areas and
low/middle 60s in southeast Georgia.
Monday night into early Tuesday...greater precipitation coverage is
expected as a cold front pushes through the area after midnight.
Given strong forcing associated with the passing low pressure system
along with modest middle level lapse rates and weak instability...have
added a slight chance of thunderstorms over all areas until daybreak
Tuesday. At this time...severe weather potential remains low. In
general...low temperatures will range in low/middle 50s.
Tuesday afternoon through Wednesday...deepening low pressure will
track over New England...while dry high pressure shifts into the
area from the west. Expect most precipitation to shift north/northeast of
the area by Tuesday afternoon...followed by dry high pressure
through Wednesday. Clearing skies within a west flow will support
afternoon temperatures in the middle 60s on Tuesday...then low/middle 60s on
Wednesday as the surface flow slowly turns to the north.
Long term /Wednesday night through Saturday/...
dry high pressure will build over the area...resulting in a light
northerly wind through Thursday. In general...afternoon highs should
peak near 60 degrees on Thursday...then modify into the middle/upper
60s on Friday as an onshore wind develops in response to high
pressure slowly shifting off the eastern Seaboard. Overnight lows
will be in the upper 30s to around 40 Wednesday night...before
returning to the low/middle 40s Thursday night. Dry high pressure will
then become more established over the western Atlantic...setting up
slightly warmer conditions within a light southerly flow. In
general...temperatures will peak near 70 degrees Saturday and Sunday.
Aviation /15z Sunday through Thursday/...
VFR at kchs/ksav through 00z Monday. Stratocumulus should develop
this afternoon and lower/thicken tonight. MVFR ceilings are possible
by sunset at ksav and mainly later this evening at kchs. MVFR/IFR
ceilings are expected after 06z at both terminals along with a chance
of a few sprinkles. Forecast soundings indicate strong warm air
advection aloft wedge clouds lower overnight and at this time our
confidence in stratus/IFR ceilings late tonight would be at the ksav
Extended aviation outlook...flight restrictions are likely Monday
night into early Tuesday as widespread showers and/or isolated
thunderstorms occur with a passing low pressure system. A strong low
level jet could also support some gusty winds...especially over the
chs terminal around daybreak Tuesday.
a complicated coastal waters forecast through tonight as very
strong thermal and moisture gradients are noted during the next 24
hours. Cold high pressure is wedging down the eastern Seaboard
with a fairly tight gradient across our waters. Solid 15-20 knots
winds occurring over all of our waters minus The Harbor with
frequent gusts at or above 25 knots. We expanded the Small Craft
Advisory into the nearshore waters given these observation...both from
buoys as well as the Charleston pilot boat at 9 am. The advisory
runs through the daytime hours...after which winds should relax as
the parent high shifts offshore.
Monday through Thursday...a coastal trough will lift north along the
southeast coast early Monday...followed by deteriorating conditions
Monday afternoon and Monday night as a strengthening low pressure
tracks inland and to the northeast coast. Strong low level winds
associated with the system will likely result in a period of Small
Craft Advisory level winds/seas for most waters Monday night into
early Tuesday. Widespread showers and a few thunderstorms will also
be possible until a cold front pushes through the waters late
Tuesday morning. Conditions will then improve Tuesday afternoon as
high pressure builds over the coastal waters from the west. West
winds at or below 10 kts will slowly shift to north/northwest on
Thursday as high pressure continues to build along/over the eastern
Marine...Small Craft Advisory until 6 PM EST this evening for amz350-
Small Craft Advisory until 5 PM EST this afternoon for amz374.