Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
236 PM EDT Tuesday Aug 4 2015
an area of surface low pressure will move generally north across
southeast NC overnight...exiting to the NE Wednesday. Warmer and drier
weather is expected through middle week. An area of low pressure and
its associated cold front will cross the area Friday into Saturday.
Weak high pressure is expected to follow Sunday and Monday.
Near term /through tonight/...
as of 236 PM Tuesday...latest radar and satellite suggest the
center of the low that had been off the northeast SC coast this
morning has now moved over land. So while the low had been
showing some signs of becoming better organized it may not develop
much more beyond its current state. The influx of low level
moisture and convergence ahead of the low continues to manifest as
light to moderate showers across portions of coastal North
Carolina. This will continue into the late afternoon hours as the
low slowly moves north...along a weak surface trough axis.
Abundant moisture...precipitable water in the 12z chs radiosonde observation was
over 2 inches...combined with deep warm cloud layer...about 12k
feet...will create high rainfall rates within the best convection.
However storm motion approaching 10 miles per hour should keep single storms
from creating a flooding issue. There will be a window of time
when training storms will be possible but the flooding threat
overall appears to be on the low side.
As the low lifts north the pinched gradient on the east side of
the low will move into coastal NC...with potential for winds to
briefly gust to 30 miles per hour during the later afternoon hours. By this
evening the low will be north of the area with low level dry air
spreading in from the south and southwest. This should end any
precipitation chances by evening. Subsidence in the wake of the low along
with dry air aloft will help clear skies overnight. Southerly
boundary layer flow will help keep lows a little above climatology. Do
think winds will be light enough for at least some fog
development...especially those areas that have received
significant rainfall in the last 2 days.
Short term /Wednesday through Thursday night/...
as of 236 PM Tuesday...primary weather headline this period
includes a wave of heat after a couple rain-cooled days along the
coast and coastal interior ... an abrupt uptick in daytime
maximums tomorrow compared to today on the order of 10-20 degrees
warmer across the eastern zones of NE SC and southeast NC. Deeper inland
where rain remains sparse...maximums will run several degrees
warmer into the middle and upper 90s. The low-level downslope
component of wind Wednesday will aid in very warm to hot maximums
An increase in middle-level moisture Thursday from the west accompanied
by weak disturbances aloft warrants an increase in pop
values...and moreso into Thursday night. In general a weak area of
low pressure over the region will help with low-level lift
Thursday. Clouds and a southerly wind flow regime will result in
cooler maximums Thursday by 4-8 degrees f.
Long term /Friday through Tuesday/...
as of 236 PM Tuesday...overall the middle level pattern will
continue to feature a ridge basically stationary over Texas with
troughing on either side of this feature. A very weak Omega
pattern that is. A decent cold front will move across Friday and
into early Saturday. There appears to be enough of a push to bring
the front well south of the area slowly by Sunday morning as high
pressure across the middle Atlantic gets a couple of reinforcements
from weak middle level ridging across the Midwest. Probability of precipitation remain in the
forecast for Friday and Saturday but Sunday should be pleasant and
dry which will extend into the new work week.
Aviation /18z Tuesday through Sunday/...
as of 18z...low pressure is currently moving north into southeast NC.
Expect intermittent moderate to heavy showers at ilm through
around 21z...with diminishing showers later in the afternoon
as the low begins to pull to the north. Gusty winds in the
convection...perhaps as high as 30 kts. Intermittent IFR
conditions are expected in the heaviest activity. This
evening...things will calm down as the gradient weakens as the
low tracks into Morehead city's area. Some light fog is
likely...particularly along the coast. Subsidence returning on
Wednesday with VFR conditions expected.
Extended outlook...scattered convection on Thursday with increasing
chances for showers and storms Friday and Saturday. Scattered storms
near term /through tonight/...
as of 236 PM Tuesday...strong southerly flow on the east side of
the low along the coast has pushed winds close to 25 knots with gusts
around 30 knots. This has also built seas to 9 feet in some areas. The
strongest winds and highest seas are along a corridor
extending south-southeast from Southport. This is coincident with
the tightest gradient east of the low. The low will continue
slowly moving north-northeast this afternoon and evening...with
the gradient over the waters gradually weakening. Small Craft Advisory continues
for all zones and at this point do not plan on upgrading to a Gale
Warning. Sustained winds should remain under 30 knots...especially
since the center of the low now appears to have moved inland and
the organization of the system is not expected to improve anymore.
Winds and seas will gradually fall through the evening and
overnight hours with winds dropping under 20 knots around midnight
and seas following a similar trend. Current headlines may extend
a little too far into the future but given the higher than
forecast seas this afternoon do not want to trim headline end
Short term /Wednesday through Thursday night/...
as of 236 PM Tuesday...a recovery day for seas expected Wednesday
and likely still elevated from the wind fetch occurring at this
time...so it is possible a Small Craft Advisory may still be
needed very early Wednesday. Advisories are expected to be
dropped sometime on Wednesday as seas subside. This will be
followed by west-southwest to SW winds...which will increase to 10-20 knots
into Thursday as weak low pressure along the coastal interior
keeps the pressure gradient tighter offshore. Exercise caution
conditions may unfold Thursday. Seas this period mainly 3-4 feet
with areas of 5 feet seas into late Thursday as winds approach 20
Long term /Friday through Sunday/...
as of 236 PM Tuesday...southwest winds will be in place ahead of
a front slated to cross the waters early Saturday. Speeds will be
10- 15 knots. The front moves across by Saturday morning and as is
typical this time of year a slow transition to west then
northwest/north winds takes place. This flow gets reinforced early
Sunday but overall wind speeds will remain in a 10-15 knot range.
Seas will be 2-3 feet.
Marine...Small Craft Advisory until 3 am EDT Wednesday for amz254-256.
Small Craft Advisory until 6 am EDT Wednesday for amz250-252.