Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
1039 PM EDT Friday Mar 14 2014
a warming trend will continue into Saturday as high pressure moves
offshore of the Carolinas. Low pressure approaching from the Gulf
states will bring a good chance of rain late Sunday into Monday.
Drier. Slightly cooler weather can be expected Tuesday into midweek.
A cold front will cross the area late on Wednesday or Thursday of
Near term /through tonight/...
as of 1030 PM Friday...adjustments to the forecast late this evening
mainly concern hourly temperatures and sky cover. The first batch of
high clouds has arrived from the west...and satellite loops suggest
cloud cover should increase from this point forward through early
Saturday morning. This means temperatures may actually rise along
the coast as the radiational inversion partially mixes out. Farther
inland for the Pee Dee region and Lumberton...temperatures will
probably flat-line through 4-5 am then fall in the last couple of
hours before sunrise as low-level winds turn more westerly. Previous
discussion from 730 PM follows...
1028 mb high pressure off the North Carolina coast will scoot east
and out to sea overnight. A positively tilted shortwave will move
east from Kentucky/Tennessee and across the eastern Carolinas
overnight...spreading high clouds overhead but with little change in
sensible weather down here at the surface.
Behind the departing high the pressure gradient has fueled wind
gusts in the 20-25 miles per hour range. A developing nocturnal inversion
should help surface winds to diminish to 10 miles per hour or less away from
the beaches this evening...but this momentum will simply become
shifted up above the stable boundary layer...fueling a nocturnal low
level jet with 1000 foot wind speeds increasing to 25-30 knots by
03z/11 PM EDT. Increasing high clouds will impede good radiational
cooling and lows should fall into the middle 40s inland...with upper
40s to near 50 at the coast. This is a bit higher than MOS consensus.
Short term /Saturday through Sunday night/...
as of 3 PM Friday...after some morning clouds...high pressure should
result in a nice Spring day Saturday...though clouds could increase
again late in the day ahead of the next system. Maximum temperatures
Saturday look to range from 70 to 75 though cooler temperatures are
expected at the beaches.
Increasing clouds are expected Saturday night as low pressure
approaches from the south and west. There is a slight chance of
showers late. Mins will fall to the upper 40s to lower 50s.
Scattered showers Sunday morning will become numerous Sunday
afternoon and continue Sunday night. Maximum temperatures will be in
the middle 60s Sunday with lows in the upper 40s to lower 50s. At this
time...thunder potential looks limited to to weak instability. For
now...thunder is not in the forecast but it is not impossible that
thunder might be heard over the coastal counties Sunday afternoon
Long term /Monday through Friday/...
as of 330 PM Friday...cold front will be making its way off shore as
the associated low pressure system will be lifting off to the
northeast on Monday. The middle to upper low will trail behind it
finally making its way across the Carolinas through Monday night. The
heaviest pcp and best convection will be making its way off the
coast Monday morning remaining more aligned with vicinity of the cold
front. The cold front at the surface will bring shallow cooler air
through the day while winds aloft will continue out of the west-SW
until middle to upper shortwave finally exits the area Monday night. This
will lead to period of isentropic lift Monday but as the vorticity swings
through later in the day...there will be a greater chance for heavier
pcp with greater upper level support and possibly renewed
development along remnant frontal boundary. Therefore will keep
clouds and increased chance of pcp through Monday into early Tuesday until
entire system makes its way off to the east-NE on Tuesday.
As potent shortwave lifts off to the east-NE on Tuesday...subsidence and
dry air on the back end will end pcp by afternoon but there may be
some residual low level moisture to produce some lingering clouds
into Tuesday night. High pressure will build in behind this system Tuesday
night through Wednesday.
Northern stream system may push a trailing cold front through the
area on Wednesday night...but looks like main effects will be some clouds
and a reinforcing shot of cooler air. Otherwise...as one high
pressure system shifts off shore another one will build in behind
this dry front through latter half of the week. Another shortwave
may produce some passing clouds as it passes through Thursday night.
Temperatures will take a dip on Monday in clouds...pcp and northerly flow
behind front on Monday recovering through middle week back to
seasonable levels. But...a fair amount of clouds and cold air advection
through the first half of the week will help to keep afternoon temperatures
a bit lower.
Aviation /00z Saturday through Wednesday/...
as of 00z...VFR conditions will prevail through this taf period.
Regional satellite imagery shows middle and upper clouds spreading over
the Carolinas this evening in association with an upper disturbance.
Middle-level VFR ceilings will develop after midnight across the County Warning Area...but
otherwise its impacts will be negligible. Although dewpoints will
climb overnight...increasing clouds and southwest winds 4-8 kts will
inhibit fog formation. Saturday will be VFR with scattered high clouds and
west-SW winds around 10 kts.
Extended outlook...expect showers with tempo MVFR conditions Sunday
into early Monday. Rain with MVFR/IFR ceilings will likely persist on
Monday through early Tuesday. VFR late Tuesday through Wednesday.
near term /through tonight/...
as of 1030 PM Friday...I reduced sea height forecasts for the next
few hours by about 1 foot based on current observations from our two
data buoys...otherwise no significant changes were made to the
forecast. Previous discussion from 730 PM follows...
High pressure a couple hundred miles off the North Carolina coast
will move east and out to sea tonight. Low pressure moving across
the eastern Great Lakes into northern New England tonight is too far
away for any direct impact on the area...but it is helping to
compress the pressure gradient behind the departing high with
southwest winds the result.
There is an interesting pattern evident in wind speeds currently:
15-20 knot winds exist well offshore over the warm water beyond 30
miles out...and also inland over the warm ground. Much lighter 10
knot winds exist over the nearshore waters. This is because the cold
nearshore water temperatures are creating very stable conditions
preventing stronger winds from mixing down from above. This should
remain the case through the night...with nearshore winds veering
more westerly with time but probably not increasing beyond 15 knots.
Seas currently 2 feet will probably build to 3 or potentially 4 feet
away from shore due to stronger offshore winds developing larger
Short term /Saturday through Sunday night/...
as of 3 PM Friday...high pressure offshore leaves SW return flow
across the waters on Saturday. The gradient never becomes very
strong...and weakens through the day...so SW winds will fall from
10-15 kts early...to around 5 kts by Sunday morning. Coastal
trough/warm front will lift towards the area ahead of a
significant low pressure system Sunday morning...turning winds to
the southeast with speeds increasing again to 10-15 kts...before a cold
front crosses the waters...veering winds all the way around to the
northwest at the end of the period. Seas will diminish to 2 feet by Saturday
afternoon and continue Saturday night...but will rise quickly on
Sunday and may reach 6 feet just ahead of the cold front Sunday night.
Long term /Monday through Wednesday/...
as of 330 PM Friday...low pressure system will affect the local
waters Monday through Tuesday. Trailing cold front will make its way off
the Carolina coast on Monday but may linger through Tuesday before
entire storm system lifts off to the east-NE away from area waters
through early Wednesday. Southerly flow on the front end of this system
should be just beyond our area waters with northerly flow up to 15
kts developing behind it through Monday. This will knock down near
shore waters but will keep outer waters with Small Craft Advisory conditions through
Monday and possibly into early Wednesday before entire low pressure system
moves away. Northerly flow will increase up to 15 to 20 kts in cold air advection
and pinched gradient Monday night into Tuesday but will lighten through
late Tuesday into Wednesday and may become variable as a dry front approaches
the waters from the northwest late Wednesday.