Scientific Forecaster Discussion
fxus62 kchs 261010
Area forecast discussion
National Weather Service Charleston SC
610 am EDT sun Mar 26 2017
Atlantic high pressure will weaken early this week. A
weak cold front will stall over the area during the middle of the
week, then shift back north as a warm front Friday. Another cold
front should move through Saturday or Saturday night followed by
drier high pressure Sunday.
Near term /through tonight/...
as of 6 am: composite radar showed a weak line of showers from
the SC foothills south to the Georgia/Florida border. These showers have
been weakening as they move east into a less supportive
environment. It still appears likely that a weak line or
clusters of showers will move across the inland Georgia counties
today. I will update the forecast update the near term sky
trends to recent satellite images.
As of 325 am, regional radar composite indicated a weak band of
showers near the Alabama/Georgia border, sliding slowly east. Coastal
Georgia/SC will remain of the western edge of 500 mb ridging this
morning, slowly weakening as a broad 500 mb short wave ripples over the
lower Savannah River valley this afternoon. Forecast soundings
indicate that a significant inversion will remain across the
forecast area, centered around h75. In addition, afternoon
dewpoint depressions are forecast to remain greater than 20
degrees. Given the thermal and moisture profiles, sbcapes values
will remain limited to around 500 j/kg across inland GA, to
less than 100 j/kg near the SC coast. The fading band of showers
will likely move close to the southern Savannah River valley,
then gradually dissipating. Pops will remain limited to schc and
the mention of thunderstorms will be removed from all zones.
High temperatures are forecast to range from the low 80s across
inland Georgia to the low to mid 70s across the beaches.
Tonight, the axis of a weak sfc ridge will pivot west over the Georgia/SC
coast. The sfc pattern will support light southeast onshore flow across the
forecast area through the night. At the mid levels, heights should
slowly increase in the wake of the shallow short wave. I will keep pops
limited to the single digits. Low temperatures are forecast to range
in the upper 50s to around 60.
Short term /Monday through Wednesday/...
Atlantic high pressure will weaken through the period, especially by
Wednesday when a weak cold front is expected to push offshore around
the mid-Atlantic but struggle to move all the way through southeast
Georgia. Expect a decent chance of showers and thunderstorms Monday and
Tuesday when instability will be greatest and the sea breeze and
upper shortwave energy will be present. However, no appreciable
rainfall and/or severe weather is anticipated at this time.
Temperatures should push into the lower to mid 80s inland each
afternoon, likely warmest across interior southeast Georgia. Wouldn't be
surprised if upper 80s occurred Wednesday, mainly interior GA, due
to compressional heating with the front and offshore winds. Onshore
winds will keep beach areas much cooler, mainly in the 60s.
Long term /Wednesday night through Saturday/...
the stalled front should shift north as a warm front Friday followed
by a cold frontal passage Saturday or Saturday night. Drier high
pressure should then return later in the weekend. Showers and
thunderstorms will be possible, mainly Thursday through Friday
night, with temperatures running above normal through at least
Aviation /10z Sunday through Thursday/...
flight conditions are forecast to remain VFR through 6z taf
period. As of 520z, infrared satellite showed an expanding area of the
cooling cloud tops across the coastal plain. I will indicate at
least scattered mid level clouds over kchs and ksav through
early Sunday morning. Onshore flow will likely result in
increasing moisture on top of the mixed later during the
daylight hours, I will mention sct050 from late morning through
most of the afternoon. Winds should remain between 130-150
degrees through the taf period, peaking between 10-15 kts during
Extended aviation outlook: mainly VFR. Brief restrictions possible
in any showers/thunderstorms, mainly Mon/Tue/Thu/Fri. Low
probability of restrictions due to early morning low clouds and/or
a sfc ridge will remain off the Georgia/SC coast through today and
tonight. Steady southeast winds should remain over the marine zones through
the near term. Wave heights are forecast to persist between 2 to 3
feet within 20 nm, 3 to 4 feet across amz374.
Monday through friday: no significant concerns with Atlantic high
pressure generally in control until a weakening cold front moves
into the area Wednesday. The front will transition into a warm front
as it moves back north Friday. Seas could reach 6 feet near the Gulf
Stream through Tuesday due to swells from low pressure well
offshore. Advisories will be possible across the outer Georgia waters
through Tuesday and then for more of the area Thursday night/Friday
as strengthening southerly winds build seas to 6 feet again.