Scientific Forecaster Discussion
fxus62 kilm 230946
Area forecast discussion
National Weather Service Wilmington NC
546 am EDT Tue may 23 2017
waves of low pressure will develop along stalled cold front
producing a good chance of showers and thunderstorms through mid
week. A cold front trailing from a deep low pressure system
over the Ohio Valley on Thursday will push through, bringing the
final round of storms to the area. High pressure will build in
on Friday maintaining quieter weather for much of the weekend.
Near term /through tonight/...
as of 3 am Tuesday...moisture laden broad southwest flow will
continue to impact the area through the near term period.
Guidance has been somewhat consistent in showing another wave of
showers and thunderstorms across the coast this morning and
another more potent feature later this afternoon and evening.
With some areas, albeit somewhat isolated showing 3-6 inches of
storm total qpf already, it is prudent to issue a Flash Flood
Watch beginning this morning and lasting through 2 am tonight.
Based on the events of Monday we could easily see another 2-4
inches of rain with isolated higher amounts. Fortunately we
haven't seen a lot of rain the past couple of weeks so this will
mitigate the situation to a certain degree. Severe threat
remains in place but with very warm and obviously moist profiles
it will take some doing for precipitation loading to manifest
itself into severe gusts. Storm Prediction Center has most of the area in a marginal
risk. Highs in the lower 80s with overnight lows in the middle
to upper 60s.
Short term /Wednesday through Thursday night/...
as of 3 am Tuesday...unsettled weather continues into the short
term as a very slow moving frontal system tracks across the
eastern Carolinas. Model disparities makes precip timing an
issue for Wednesday so have opted for categorical pops,
indicating widespread convection, through that 24 hour period.
Although confidence is high that all locations will see
measurable precip, if not a substantial amount for most places,
confidence is low as to actual timing of the event. Thursday is
a little more clear cut in that the front will be moving
offshore early in the period, so bulk of remaining precip will
be during the daytime, likely early, with a dry overnight.
Long term /Friday through Monday/...
as of 3 PM Monday...deep frontal moisture to be offshore by the
start of the period. However the main trough axis and strongest
shortwave will be crossing the area and this should manage to
squeeze a few light and short-lived showers. Continued dry
advection and the lifting of the trough Thursday night should
keep US dry despite one last final and moderately strong
vorticity center streaking by. Zonal flow will keep the weekend
dry and fairly seasonable with only gradually increasing surface
Aviation /12z Tuesday through Saturday/...
as of 12z Tuesday...challenging conditions for pilots today,
with periods of showers and thunderstorms, the possibility of
heavy rain and gusty winds from convection. This applies to all
taf sites for today and tonight. Expect all locations will see
some IFR conditions for lowered cigs and vsbys in rain and fog,
with MVFR for the same conditions common for all sites.
Extended outlook...reduced flight categories will be possible
in periodic showers and thunderstorms into Thursday. The
strongest convective activity should occur Wednesday.
near term /through tonight/...
as of 3 am Tuesday....somewhat distorted wind fields across the
waters this morning due to earlier and current convection. A
good southwest flow should reemerge in just a few hours however.
Winds speeds increase to 15-20 knots later today and increase
even further tonight leading to some marginal small craft seas
of 5-7 feet. Will go ahead and raise an advisory for the
afternoon and overnight hours.
Short term /Wednesday through Thursday night/...
as of 3 am Tuesday...the overall trend during the short term
will be one of gradually increasing SW winds and building seas
in advance of a slowly moving cold front. The front will be over
or near the waters on Thursday morning, at which point we will
likely see some loosening of the gradient and a subsequent
decrease in winds and seas during the afternoon. Until then,
though, it is likely that Small Craft Advisory conditions will
be breached on Wednesday or Wednesday night. Expect frequent
period of shower and thunderstorm activity Wednesday and
Wednesday night, with improving conditions on Thursday.
Long term /Friday through Saturday/...
as of 3 PM Monday...Small Craft Advisory will be in effect on
Thursday just ahead of a cold front that will pinch the
gradient. Within the agitated wind field of the pinched gradient
a strong upper disturbance will traverse the area possibly to
enhance wind gusts. In the wake of this boundary there will be
west winds to round out the period of gradually diminishing
speed. Wave heights will similarly abate somewhat slowly.
SC...Flash Flood Watch through late tonight for scz017-023-024-032-
Beach hazards statement through this evening for scz054-056.
NC...Flash Flood Watch through late tonight for ncz087-096-099-
Beach hazards statement through this evening for ncz106-108.
Marine...Small Craft Advisory from 2 PM this afternoon to 6 am EDT
Wednesday for amz250-252-254-256.