Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 241018

Area Forecast Discussion
National Weather Service Wilmington NC
618 AM EDT Wed May 24 2017

Waves of low pressure will continue to move along a slow-moving
cold front, producing a good chance for showers and
thunderstorms today and tonight. Another cold front trailing
from a deep low pressure system over the Ohio Valley on Thursday
will cross the area, bringing the final round of showers to the
area. High pressure will build in late Thursday into Friday
maintaining quieter weather for much of the weekend. Low
pressure may affect the area early next week producing more
unsettled weather.


As of 3 AM Tuesday...Post wave subsidence has helped dry out the
mid levels overnight, leading to a lull in rainfall. Sizable area of
dry air, evident in water vapor imagery, will work its way northeast
through the morning hours. Not only do forecast soundings show the
increasing mid level dry air but they also depict weakening of the
850 to 500 mb lapse rates, another sign of increasing subsidence.
There is a weak shortwave currently moving across GA, heading
northeast that could generate some isolated elevated convection in
the area a few hours either side of daybreak. Front continues to
linger in or just northwest of the area and will gradually weaken

Mid level dry air and subsidence will linger in the area through
much of this morning before next slug of deep moisture, with
precipitable water values exceeding 1.9 inch, starts moving into the
region. Increase is not instant but will be steady from late
morning, peaking in the evening. Heights start to fall in the
afternoon, just as surface based instability peaks. Although the GFS
is riddled with feedback this afternoon it is possible to discern a
shortwave moving northeast from the Gulf coast later this morning.
PVA ahead of the wave arrives coincident with the other favorable
factors. While there is a 110 kt+ 300 mb jet the wind max ends up
passing northwest of the area. Although limited by less than
favorable jet location there will still be some divergence aloft.
Deep warm cloud layer continues to be a theme in this environment,
forecast soundings suggest a depth around 11k ft, which will aid
precipitation efficiency and keep flooding a concern, especially in
areas that have received 3+ inches of rain in the last day or so.
Storm motions will be high enough that a single storm is unlikely to
be a concern but training storms will pose a significant flood risk
and so the flash flood watch will remain in effect. Temperatures
today will be in the upper 70s to lower 80s but with potential for
localized areas where highs run several degrees warmer if the late
May sun is able to break out for a brief period of time.

Widespread convection continues into the evening and first part of
the overnight. Low level jet strengthens to a solid 45 kt this
evening, although shear is somewhat limited. Still a strong or
severe storm cannot be ruled out and SPC has marginal risk for the
region. Dry slot wrapping around the 5h trough spreads over the area
around midnight, bringing an end to significant rainfall. The cold
front will still be west of the area at this point, likely just
entering the western Carolinas. The 5h trough axis continues to be
slow moving and it is the strong shortwave rounding the base of the
trough the ultimately pushes the cold front into the forecast area
as the period ends. Although the mid levels dry out rapidly and the
forcing exits to the northeast by midnight, lingering low level
moisture will keep skies cloudy. Temperatures will range from mid
60s west to around 70 along the coast.


As of 3 AM Tuesday...Cold front will be in process of moving
offshore Thursday morning, and along with it, much of the deep
moisture associated with our recent wet period. However, a
potent upper disturbance will swing through on Thursday
afternoon behind FROPA, and this combined with residual moisture
should be enough to kick off a scattered round of daytime
convection. Rapid improvement will follow as the short wave
lifts northeast of the area and weak surface ridging builds in
from the west. Expect dry weather and clearing skies for
Thursday night through Friday. Relatively cool temperatures
following FROPA on Thursday will give way to seasonal readings
on Friday.


As of 3 PM Tuesday...Plenty of dry air will move in with deep
westerly flow on the back end of exiting low pressure system on
Fri. Pcp water values drop down to .75 inches or below early Fri
but do creep back up over an inch by late Friday. Overall
expect a sunny dry day on Friday with temps reaching into the
mid 80s.

High pressure ridge to the south will reach up into the
Carolinas maintaining pleasant weather through much of the
weekend. A shortwave rides across the top of the ridge over the
weekend mainly remaining north of the forecast area. This could
produce some clouds or a spotty shower late Sat into Sat night,
mainly over NC. The GFS builds the ridge a little farther north
and therefore holds any weather farther to the north with a deep
warm southerly flow and sunnier weather overall all weekend. A
deeper mid to upper trough digs down late in the weekend and
could produce an increase of clouds and showers Sun through Tues
timeframe. Will have to see how the models evolve. For now,
will keep chc of shwrs north of area through Sat night but will
include Pops for Sun through Tues.

The building ridge and westerly downslope flow through the mid
levels will produce above normal temps through much of the
period with temps reaching above 90 in spots especially over
the weekend.


As of 12Z Wednesday...Primary concern today and tonight are low
cigs and vsbys due to scattered to widespread convection.
Although confidence in exact timing is low, confidence is high
that all terminals will see at least short periods of IFR
conditions due to shower and thunderstorm activity. Best chances
for reduced vsbys and cigs this afternoon into early evening.

Extended Outlook...VFR anticipated Thursday through Sunday.


As of 3 AM Tuesday...Small craft advisory remains in effect for
all zones through tonight. Southwest winds around 15 kt this morning
will increase to 20 to 25 kt today and 25 to 30 kt tonight as
gradient becomes pinched ahead of advancing cold front. Front will
remain west of the waters through the period, keeping wind direction
southwest. Exception would be thunderstorm outflow which would be
capable of producing winds in excess of 34 kt from any direction.
Seas will build from 4 to 6 ft this morning to 5 to 7 ft this
afternoon and evening with potential for 10 ft tonight.

As of 3 AM Tuesday...Expect Small Craft Advisory criteria to be
breached Thursday and Thursday night as a cold front passes
across and then moves east of the waters. Have extended the SCA
into Thursday as a result. Gradually improving conditions on
Friday as high pressure builds in from the west means we will
likely be advisory-free for the end of the work week.

As of 3 PM Tuesday...A stronger off shore westerly flow on
Friday will diminish and back around to the W-SW through the day
as low pressure system exits farther off to the east and high
pressure builds up from the south. Seas of 3 to 5 ft will
diminish to 2 to 4 ft through Friday and down below 3 ft by Fri
night in weakening offshore flow.

High pressure south of the area waters will shift east through
the weekend into early next week producing a persistent SW
return flow. Initially winds will only be 10 kts or so but low
pressure moving by to the north Sat night into Sun and an
approaching cold front late in the weekend into early next week
may produce an increase in SW winds. Seas less than 3 ft
Saturday in lighter winds will rise up to 3 to 5 ft in
increasing SW winds Sat night into Sun.


SC...Flash Flood Watch through this evening for SCZ017-023-024-032-
     Beach Hazards Statement through this evening for SCZ054-056.
NC...Flash Flood Watch through this evening for NCZ087-096-099-
     Beach Hazards Statement through this evening for NCZ106-108.
MARINE...Small Craft Advisory until 6 PM EDT Thursday for AMZ250-252-


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