Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
1205 PM EDT Sat Oct 10 2015
a Flash Flood Watch is in effect through tonight. A strong upper
level system will bring moderate to occasionally heavy rain and
thunderstorms today and tonight. Light rain may linger along the
coast into Monday. A dry cold front will move across the area
Tuesday. Dry autumn weather is expected next Wednesday through
Friday as high pressure settles into the region.
Near term /through tonight/...
as of 1215 PM Saturday...the surface cold front has moved south
to a line extending from Lake City to just north of Conway...to North
Myrtle Beach to near Southport. The boundary should slowly slip
southward through the day...making it into Myrtle Beach and
Georgetown by early and middle afternoon respectively. In the upper
levels a fairly strong 500 mb disturbance will begin to cut off
across South Carolina this afternoon. This closed 500 mb will then
slowly move eastward...reaching the coast Sunday.
Light to moderate rain continues along the Interstate 95 corridor.
A Flood Warning was issued earlier for Darlington and Marlboro
counties through 115 PM. New convection has recently developed
near Florence and Marion out ahead of a strongly forced convective
line extending from Sumter southward to Savannah Georgia. This
line has rainfall rates estimated by the Charleston SC radar to be
0.5 to 0.8 inches per hour. Its slow movement means an additional
1-2 inches of rain should fall over the next 6 hours across much
of eastern South Carolina...with new flood or flash flood warnings
Sunshine has boosted temperatures in the upper 70s from just
north of Charleston across the grand strand and into parts of
Brunswick County NC. This could ignite new surface-based
convection ahead of the main line...or at least will help
intensify the incoming elevated convective band.
The heaviest rain should shift eastward to the South Carolina
coast late this afternoon and this evening just ahead of the upper
level low. 500 mb temperatures as cold as -13c will contrast quite
strongly with subtropical air near the surface...with elevated
convection likely continuing into tonight either on the coast and
Short term /Sunday through Monday night/...
as of 330 am Saturday...as a cold front remains just offshore and a
closed upper low skirts along the Carolina coast...anticipate
showers along the immediate coast to begin Sunday morning. Shower
activity should remain light in nature as wrap around moisture
gradually becomes limited. Per latest guidance...the upper level low
finally cuts ties with the Carolina coast on Monday as another front
makes its way towards the forecast area. Cooler temperatures on
Sunday around 70 degrees will increase to middle 70s on Monday.
Overnight lows will hover in the middle 50s inland to lower 60s along
Long term /Tuesday through Friday/...
as of 330 am Saturday...broad upper trough sets up across much of
the eastern US as another cold front makes its way towards the
forecast area on Tuesday. Latest guidance keeps a majority of the
moisture offshore...thus do not anticipate any precipitation with
this feature. This brings good news to those areas still recovering
from the recent flooding event. Wednesday through
Saturday...guidance continues to support dry conditions with another
shortwave pushing through late in the week before high pressure
finally settles in. Pleasant fall-like temperatures expected through
the period with highs in the middle to upper 70s and overnight lows in
the middle 50s to upper 60s.
Aviation /18z Saturday through Thursday/...
as of 18z...convection will reach The Myrtles around taf issuance time.
Rainfall could be heavy with some thunder. Intermittent LIFR conditions
possible. Ilm will be in the more stable air...however due to the
nature of the elevated convection...still could get some heavy downpours.
Most of the heaviest convection will come to an end around nightfall...with
conditions becoming more stratiform with IFR ceilings and perhaps visibilities
with fog. Sunday...slowly improving conditions as the low and upper low
begin to weaken. Continued northeast flow.
Extended outlook...becoming VFR Monday with a slight chance for showers
Tuesday. VFR Wednesday and Thursday.
near term /through tonight/...
as of 1215 PM Saturday...with northerly winds both ahead of and
behind the front the actual boundary is becoming difficult to
locate. Based on barometric pressure and temperatures it appears
to lie from Southport to near North Myrtle Beach and then inland
just south of Florence SC. Light winds ahead of the front will
become northeasterly and increase to 10-15 knots by late
afternoon/early evening...then could increase to near 20 knots
just offshore tonight as low pressure develops along the front.
Radar shows heavy rain and thunderstorms inland across South
Carolina. This activity should make its way down to the beaches
this afternoon...spreading offshore. Visibility will occasionally be
reduced to one mile or less in heavy rainfall late this afternoon
Seas are currently only 1-2 feet and won't begin to build
appreciably until the stronger NE winds arrive late this afternoon
or this evening.
Short term /Sunday through Monday night/...
as of 330 am Saturday...as of 330 am Saturday...north-northeast
winds around 15 knots will continue on Sunday through the evening as
upper level low moves near the area. With persistent
flow...anticipate seas on Sunday to be 2 to 3 feet...with 4 footers
likely in the northern waters. On Monday...northeasterly flow will
continue with winds decreasing to around 10 knots early as
aforementioned system starts to move off to the
northeast...becoming southwest into the afternoon hours with the
sea breeze. Seas will hold steady around 2 to 3 feet.
Long term /Tuesday through Thursday/...
as of 330 am Saturday...pressure gradient begins to tighten again
ahead of an approaching cold front from the west on Tuesday.
Southwest winds will increase to 15 to 20 knots throughout the
day...with a shift to the west- northwest late Tuesday night as
the cold front moves through. Sustained winds will decrease to
around 10 knots or less...continuing through the rest of the period.
Anticipate seas of 2 to 4 feet on Tuesday...with occasional 5 fters
possible in the extreme outer waters. Wednesday...seas will drop
to around 2 to 3 feet behind the front.
SC...Flash Flood Watch through late tonight for scz017-023-024-032-
NC...Flash Flood Watch through late tonight for ncz087-096-099-