Scientific Forecaster Discussion
fxus62 kilm 072316
Area forecast discussion
National Weather Service Wilmington NC
715 PM EST Sat Dec 7 2019
cool, dry high pressure will build down from the north this
weekend. A coastal warm front will lift north Sunday night,
leading to warming temperatures Monday into Tuesday. A cold
front will cross the coast Tuesday night and early Wednesday,
bringing a cool down through mid-week and drying. Low pressure
migrating from the Gulf late week, may bring wet weather next
Near term /through Sunday night/...
clear and cold overnight, but most localities to hold above the
freezing mark with a tight NE pressure gradient in the boundary
layer. Lesser isotach values near I-95 will promote brief freezing
temperatures early Sunday morning from near Maxton to Bennettsville
to Hartsville, and known cold spots inland, for several hours.
Veering low-level wind profile to direct a coastal warm front onto
our coast late Sunday, with a good batch of marine showers lining up
Sunday afternoon, pushing inland middle to late afternoon. Model
reflectivity become more robust Sunday night, as convergence in the
low levels intensifies. By this time, dewpoints have surged to
around 60 degrees, with pronounced southerly moisture advection
through 15,000 feet. This to warrant isolated tstms over the 0-20nm
waters westward across the coastal interior Sunday night, the severe
threat however appears low.
Potentially a solid rainfall from myr to Wampee to Grissettown to
Shallotte to Leland to ilm to Castle Hayne to Burgaw to Surf City,
where a few spots are likely to exceed an inch of rainfall Sunday
night. Through Sunday night our current quantitative precipitation forecast projections bring the
highest rain totals over Brunswick and New Hanover counties, and
including eastern Horry, and southeast Pender County.
Short term /Monday through Monday night/...
deep layer southwesterly flow this period will keep plenty of clouds
socked in across the area. Forcing for precipitation however will
largely be lacking save for Monday morning/midday along the coast
where some shear vorticity provides some ascent. The WRF is a bit of
an outlier with its heavier quantitative precipitation forecast (and there are enough models that
don't show much rain at all) and so it's values were curtailed
considerably. Temperatures will be elevated significantly above
climatology in the moisture-laden flow regime.
Long term /Tuesday through Saturday/...
cold front pushes through Tuesday night bringing a good chance for
rain though the lack of good dynamics indicates that it will be a
low quantitative precipitation forecast event. The Wedge that sets up thereafter will do little to
remove the copious moisture in place and the area appears to be in
for an extended period of cloudy skies. The latter part of the
period appears to turn quite unsettled though forecast confidence is
a bit low. Models are showing an active southern branch that will
interact with moisture from Tuesday night's front sitting offshore.
A front running disturbance may lead to a weak area of low pressure
that affects the area on Friday. The main southern branch feature
could bring a bigger rain locally as early as Saturday whereas other
guidance like the ec are more cutoff and therefore much slower.
Aviation /00z Sunday through Thursday/...
high confidence in VFR conditions prevailing tonight through Sunday
morning as a ridge of high pressure lingers across the Carolinas.
Isentropic lift at 300k will likely produce some -ra at the coastal
terminals generally after 21z Sunday, especially as the warm front
approaches the coast. During this time there is a potential for MVFR
cigs at kilm, kcre, and kmyr.
Extended outlook...tempo MVFR conditions possible at times Sun night
into Mon as the warm front moves through. MVFR conditions also
possible again Tuesday as the next cold front approaches.
a difficult period for smaller craft, as 25 kt gusts tonight and
Sunday morning has advisory flags raised. Numerical wave height
guidance shows Frying Pan Shoals reaching 7 feet after midnight
tonight for several hours. 25 kt gusts Sunday offshore and 4-6 foot
seas has the advisory through Sunday afternoon at this time. NE
waves tonight and early Sunday 4-6 feet every 6-7 seconds. This will
transition to east to east-southeast waves 3-6 feet every 7-8 seconds late in the
day Sunday. Scattered marine showers Sunday afternoon will become
more widespread Sunday night, and heavier, and as a result marine
visibilities will suffer and become much reduced Sunday night, this
includes the icw as well, mainly from Myrtle Beach northward.
Though SW flow will gradually diminish on Monday as a cold front
approaches guidance is hesitant to allow seas to subside below
advisory thresholds especially for northern zones. Tuesday night's
cold frontal passage will bring a sharp wind shift to the north
steepening wave wave faces. A cool air wedge of high pressure over
land Wednesday and Thursday will keep north to NE gradient winds strong
enough to warrant an advisory on their own, pushing seas more
solidly into advisory criteria.
Marine...Small Craft Advisory until 6 PM EST Sunday for amz250-252-