Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
1003 am EDT Thursday Sep 3 2015
above normal temperatures are expected today through Friday. A weak
trough will linger in the area through early Friday. A ridge of high
pressure will build in from the north behind a cold front this
weekend...bringing unsettled weather and cooler temperatures through
the first part of next week.
Near term /through tonight/...
as of 1000 am Thursday...shortwave was exiting the Hatteras
coast this morning with a trough extending back to another
shortwave over KY/TN. Winds through the lower levels were more
northerly with drier air to the north of this boundary over NC/Virginia
border this morning. South of the trough winds will remain more
westerly which will help to produce a greater downslope push and
warmer temperatures for our area today. Higher dewpoint air remains in
place with readings up above 70 most places. This trough oriented
more west to east will sink south through this afternoon and
should provide some added convergence along and ahead of it to
enhance convection. The westerly component to the flow should also
keep sea breeze closer to the coast and expect this to be a player
in convective development later this afternoon as it pushes slowly
inland. Although there still remains some drier air through the
middle levels...the moisture through the column has increased with
pcp water levels up to 1.9 inches. This drier air could be a
player in better downdraft potential and wind gusts in showers/thunderstorms
this afternoon. Sounding parameters point to a moderately unstable
atmosphere with ml cape up to 2800 and Li -9...k index 36 and
dcape up to 1100.
Overall expect greater chance of scattered diurnal shwers/thunderstorms through
this afternoon in localized convergence along this trough and sea
breeze boundary along with any other outflow boundaries. Steering
flow will shift from more northwest to north pushing any development toward
the south and closer to the coast. Temperatures up into the 90s most
places inland of beaches will combine with dewpoint temperatures in the
70s to produce another day of heat indices up close to 100.
Diurnally driven convection will fade with the sunset with
diminishing cloud cover. Above normal temperatures this afternoon will drop
to the upper 60s inland to middle 70s along the coast.
Short term /Friday through Saturday night/...
as of 230 am Thursday...500 mb ridge axis is shown to extend from the
Southern Plains and lower MS valley into the middle west and Great
Lakes region early Friday with a weak trough oriented nearly east-
west from the middle-Atlantic region toward the Ohio Valley. The 500 mb
trough will drift south across the southeastern states with some
during Saturday as high pressure aloft evolves across New England.
At the surface...a ridge will build south across the forecast area
Friday night into Saturday bringing an end to the atypically warm
temperatures. The precipitable water does not stand out as it is
expected to average a little over an inch and a half each day. An
increase in low-level convergence on Saturday in northeasterly flow
translates to slightly higher probability of precipitation compared to Friday in an
environment that is unsettled...but devoid of a significant lifting
Long term /Sunday through Wednesday/...
as of 230 am Thursday...weak/broad area of low pressure noted in
500mb forecasts will linger over the southeast United States Sunday
resulting in a continuation of unsettled weather through Tuesday as
it gradually weakens over the region. The surface ridge weakens
across the Carolinas as well during the period with lower pressure
lingering off the coast. Although the precipitable water is expected
to increase to just under two inches by Monday the highest
precipitable water will continue to be suppressed offshore to the
southeast and south of the area. Expecting scattered showers and a
few thunderstorms each day with the best chances Monday coincident with the
highest precipitable water. Maximum temperatures each day will range
within a couple degrees of climatology while the mins remain a
couple categories above normal.
Aviation /12z Thursday through Monday/...
as of 12z...confidence is high MVFR visibilities will rise to VFR by
13z. Otherwise terminals will likely be VFR through 18z. Any
potential shower activity will be northwest-east of kilm and well S of kmyr.
Winds will be light and variable or light west-northwest this
morning...becoming S-SW at the coastal terminals by late morning.
Predominate VFR into the afternoon and evening hours. Scattered
showers and isolated thunderstorms will develop this afternoon. Best
locations for development will be just inland of the coastal
terminals along a pinned sea breeze...along and north of an outflow
boundary from convection earlier this morning lying roughly S of
kilm to near klbt...and along a weak front north of klbt/kilm.
Steering flow is from the northwest thus there will be an increased
chance the coastal terminals could be affected by any convection.
Expected coverage suggests at worse tempo conditions. Will
continue to indicate vcsh/thunderstorms in the vicinity in tafs for now... and update to
add tempo groups if needed at 18z.
With a front slipping slowly S across the terminals overnight there will
continue to be a chance of showers. With lack of heating think the chance
of thunderstorms will be low. With light winds and slightly cooler air
there is a chance of fog especially at terminals that receive rainfall
today. At this time think klbt would have the best chance of IFR especially if rain
Extended outlook...predominately VFR with brief morning fog and
isolated/scattered afternoon showers and thunderstorms.
near term /through tonight/...
as of 1000 am Thursday...a weak pressure pattern over the
western Atlantic will maintain a westerly flow of 10 kts over the
coastal waters early today...increasing to 10 to 15 kts with
higher gusts near shore this afternoon. Winds will decrease back
to around 10 kts or less overnight while becoming more
southwesterly. Seas will stay in the 2 feet range through the
Short term /Friday through Saturday night/...
as of 230 am Thursday...light/variable winds expected with a weak
pressure gradient across the waters Friday through Friday evening.
As ridge of high pressure builds south into the Carolinas early
Saturday morning the wind will veer to the northeast and increase to
10 to 15 knots...possibly closer to 15 knots across the Cape Fear
waters for a bit Saturday afternoon/evening. Seas will increase to
around 3 feet or a little higher as the northeast winds increase.
Long term /Sunday through Monday/...
as of 230 am Thursday...northeast winds will begin to weaken during
Sunday as the ridge weakens. Could see another period of
light/variable winds during Monday with a weak pressure gradient
returning to the area. Seas around 3 feet Sunday will subside to 2-3
feet during Monday.