Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
639 am EDT Tuesday Jul 7 2015
upper trough will open and move away tonight as ridge develops
overhead. Bermuda high pressure will bring typical summertime
heat and humidity along with a daily risk for showers and
thunderstorms through the weekend. A weak front may sag south into
Near term /through tonight/...
as of 600 am Tuesday...some patchy stratocumulus and cirrus were
around...but otherwise it was mainly sunny.
The Bermuda ridge will begin to build across the area during this
forecast period. However...precipitable water values will remain
high today...near or greater than 1.75 inches. Mixed layer cape
values will peak in the 1000-1500 j/kg range. Forcing will however
be weak with two mesoscale boundaries helping to focus moisture
and convergence...the Piedmont trough and the seabreeze. Given the
lack of support aloft...and with the warmer layer around 12 kft...
would expect thunderstorm coverage to be isolated to perhaps
widely scattered at most.
The seabreeze should make only modest inland penetration...moreso over
coastal North Carolina...given the prevailing flow in the lowest 3 kft
will be SW. The beaches and adjacent environs will have the highest
risk for a shower or thunderstorm in the vicinity late morning through
early afternoon. Inland...the risk for thunderstorms will be highest
this afternoon and into the early evening as thunderstorms develop along
the Piedmont trough...with the greatest coverage around the time of
peak heating. Overnight... thunderstorms developing across the
climatologically favored balmy Atlantic waters may briefly impinge
onto portions of the immediate coast...but the vast majority of this
convection will remain offshore.
Considerable sunshine away from any building thunderstorms will
allow temperatures to climb into the lower 90s across the majority of the
area. The warmest inland spots may reach the middle 90s. More coastal
locations will reach the upper 80s with readings at many of our
beaches stymied once they reach the middle 80s. Overnight lows will be
similar to the last many nights...lower to middle 70s.
Short term /Wednesday through Wednesday night/...
as of 300 am Tuesday...ridge will be building across the southeast
through middle week while Bermuda high and Piedmont trough remain the
dominant weather features at the surface. Building heights and
increased subsidence along with dry air aloft will limit more
widespread convection but convergence along sea breeze boundary
and Piedmont trough should produce some cumulus and localized shower/thunderstorm
activity. A shortwave riding over the top of the ridge may help to
veer winds around to a more westerly direction as it pushes trough
eastward Wednesday night into Thursday. Will leave lower end probability of precipitation in
forecast to account for some diurnally driven shower activity.
Warm and humid air mass in place along with building ridge and
rising heights will keep temperatures above normal. Day time highs will
reach between 90 and 95 most places while overnight lows will
remain in the lower to middle 70s. Heat indices will reach just above
100 each afternoon but will remain below any advisory criteria.
Long term /Thursday through Monday/...
as of 300 am Tuesday...ridge sprawled across the southeast will
continue to shift westward through the weekend. This will allow a
deep northwest flow to develop riding into the Carolinas. Models
continue to show a boundary pushing south through the weekend.
Overall expect dry air and subsidence through the middle levels but
this boundary should remain a focus for increased convective
potential. The increased northwest flow may enhance convergence closer
to the coast and allow for some shortwave energy to ride over the
top of the ridge. Overall expect an uptick of convective activity
with potential for this boundary to push south and the northwest steering
flow to drive any showers/thunderstorms that develop upstream along with
debris clouds into area and toward the coast.
Heading into early next week the ridge continues to build
westward and a broader longer wave trough over the Great Lakes
keep a deeper northwest flow over the area. It looks like the frontal
boundary will push farther south leaving a surface trough up through
the Carolinas. Expect shortwave energy to enhance diurnally driven
convection. The low to middle level flow will back to a more westerly
direction by Monday. This will help keep warm temperatures over the area
into early next week. As it looks right now heat indices will
break 100 but should remain below heat advisory criteria in most
places up through Monday. Highs should reach well into the 90s
most days with overnight lows in the low to middle 70s.
Aviation /12z Tuesday through Saturday/...
as of 12z...fairly typical Summer day with a thermal/Piedmont trough
and a sea breeze resultant that will begin to move inland around
noon. Southwest flow again today...strongest neat the coast. Look
for isolated convection to fire around 16z near the coast...a few
hours later inland on the thermal trough. Coverage warrants a thunderstorms in the vicinity
mention. Light winds tonight with little to no fog expected
Extended outlook...chance of showers and thunderstorms each
day...with brief periods of MVFR/IFR possible. Otherwise VFR.
near term /through tonight/...
as of 600 am Tuesday...typical summertime pattern with the
Bermuda ridge building across the waters. The seabreeze will make
only modest gains inland while the Piedmont trough sharpens well
inland. This will allow south-southwest to SW winds to strengthen this
afternoon and evening and then only diminish slightly as some
nocturnal jetting is expected to redevelop. Highest winds this
period will be around 15 knots. Seas will be 2 to 3 feet this
morning...otherwise 3 to 4 feet. An 8 to 10 second southeast ground swell
Short term /Wednesday through Thursday night/...
as of 300 am Tuesday...southwest winds will continue to run
around 10 to 15 knots as Bermuda high and Piedmont trough remain
dominant features driving the winds. Expect spike in winds each
afternoon due to sharpening of the Piedmont trough and sea breeze
development. Seas will remain 2 to 4 feet but will be choppier each
afternoon in sea breeze. A longer period southeast swell up to 9 second will mix
with the shorter period SW wind waves.
Long term /Friday through Saturday/...
as of 300 am Tuesday...as ridge builds westward over the Gulf
Coast states...a deeper northwest flow will develop. This will
push a boundary south Friday night into the weekend...helping to
lighten and counteract the SW flow around the Bermuda high...producing
weaker more westerly but more variable winds across the waters.
This should lower seas for the weekend down to 2 to 3 feet. Seas
will continue to blend with a longer period up to 9 seconds southeast