Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 270545

Area Forecast Discussion
National Weather Service Wilmington NC
145 AM EDT Fri Apr 27 2018

Low pressure will pass across northern North Carolina late
tonight bringing a good chance of showers. A pair of cold fronts
will push offshore late Friday and Saturday night, bringing
unseasonably cool temperatures for Sunday and Monday. Canadian
high pressure will push offshore late Monday, and temperatures
should warm rapidly Tuesday and Wednesday, with dry weather


As of 900 PM Thursday...Have re-adjusted overnight POPS,
Skycover thru 15Z Fri, using the latest 88D trends, HRRR and
18Z Superblend models respectively. All of this to take into
account the latest band of mainly showers with embedded
thunderstorms associated with the upper low that will affect the
ILM CWA late this evening thru the overnight and exiting NE-E
of the area by daytime mid-morning. QPF was also updated using
the latest WPC guidance. Some tweaking of temps/dewpts using
current trends applied to 18Z Superblend model guidance.

As of 300 PM Thursday...Combination water vapor imagery and
regional radar mosaic show a large spin across northern AL into
GA representative of both a closed upper low and surface
reflection. These will slowly eject to the NE tonight to become
over VA on Friday. As this occurs, 500mb diffluence increases as
the flow spreads out ahead of the mid-level low, in conjunction
with 300mb divergence in the RRQ of an exiting upper jet. At
the same time, moist advection peaks in the warm sector ahead of
the associated weak cold front, and this combination of
moisture and lift suggest precip chances will increase from west
to east and this is echoed by all available high res guidance.
However, despite mins expected to remain around 60 tonight,
diurnal instability will wane significantly and this will limit
both coverage and intensity of showers overnight. Have
maintained high CHC showers with SCHC tstms since elevated
instability is progged to remain 300-500 J/kg which could
support a few lightning strikes in any stronger updrafts, aided
additionally by a robust 30-40 kt LLJ. Most of this activity
will occur after midnight, moving from SW to NE and leaving the
area by daybreak on Friday.

Another very nice day forecast Friday with a ridge of high
pressure building in from the west while yet another weak cold
front pushes down from the NW. This front is driven by another
spoke of vorticity moving through the longwave eastern CONUS
trough, and will exit offshore just beyond this period. Despite
temps climbing into the mid 70s once again, do not anticipate
convection Friday even with the added lift of the FROPA thanks
to very dry air aloft keeping PWATs around 0.75 inches. There
should be rather extensive diurnal Cu Friday however as
soundings saturate at the LCL beneath a pronounced subsidence


As of 300 PM Thursday...Quiet, rain-free, and seasonable
weather expected through the short term period. The area will
find itself between two cold fronts and under a broad mid level
trough. The second cold front will come through Saturday night
with far too dry an antecedent airmass to bring any weather. It
will mark the turn to slightly cooler weather.


As of 300 PM Thursday...Model differences are very small
through the extended portion of the forecast and have only
minor impacts on sensible weather. Confidence is rather high.

The tail-end of an upper trough will pass over the Carolinas
Sunday as high pressure, centered over the Midwest, builds
southeastward toward the area. Chilly air beneath the upper
trough (850 mb temps only +2C to +3C Sunday) should give us
another unseasonably cool day despite nearly full sunshine:
highs only 69-72. The upper trough pushes offshore Monday,but a
lobe of that chilly low-level air remains behind with highs not
expected to be warm much from Sunday.

Nighttime lows early in the week should be quite chilly for this
late in the year. Diminishing winds and clear skies Sunday night
should allow lows to fall into the low-mid 40s, and it wouldn`t
surprise me if a few of the typical cold spots get into the
upper 30s. We`re not expecting a freeze, but it`s interesting
that the latest freeze on record in Elizabethtown, NC was May 2,
1963, and for Lumberton was May 10, 1980.

By Tuesday, the surface high should push offshore with upper
level ridging building across the Carolinas. Our high and low
temperatures should quickly warm as 850 mb temps rise to +12C
Tuesday and +14C Wednesday and Thursday. The orientation of the
mid and upper level ridge should prevent any inflow of moisture,
and skies should remain very clear through the extended
forecast period. Dewpoints dipping into the 30s Sunday and
perhaps Monday should moderate through the week, finally
reaching 55-60 by Thursday which may develop the first flat
cumulus we will have seen all week!


As of 06Z...A mid-level wave moving northeast this morning is
spreading showers across the area. Thus far ceilings have not
dropped into the MVFR category, but this will be possible
closer to daybreak. At this time IFR ceilings seem unlikely. The
wave will help pull a cold front across the area later this
morning, leading to a drying trend during today. Winds from the
west-southwest around 20 kt at 4k ft will mix to the surface
from late morning through early afternoon. Scattered afternoon
clouds are expected but skies will clear out in the evening with
widespread VFR expected overnight.

Extended outlook...VFR.


As of 900 PM Thursday...Winds likely at their lowest for the
night, 5 kt or less. Should see an increasing trend as well as
a veering trend during tonight. And by daybreak, winds should be
from the SSW-SW at 10 to possibly 15 kt. Significant seas will
continue to be governed by the ESE ground swell at 9 second
periods. Along with a noteworthy increase in wind chop by
morning. Could see vsby briefly reduced to 1 to 3 nm from
showers associated with the rotating band of pcpn extending out
from the upper low and associated with the cold front.

As of 300 PM Thursday...Light S/SE winds this eve will veer
gradually to the SW as a weak cold front moves across the waters.
Wind speeds will generally increase to 10-15 kts tonight, and
then slightly higher towards 15-20 kts Friday as the gradient
becomes more pinched ahead of another weak cold front which will
approach late on Friday. Seas this even will remain 2-3 ft, but
a gradual amplification to 3-5 ft is expected as the winds
increase to drive a growing 6 sec wind wave, which will combine
with the 8-9 sec SE swell.

As of 300 PM Thursday...West to southwest flow to dominate
through the period as the area spends most of the time in
between two cold fronts. The second boundary is slated for
passage near the end of the period, and it may bring a sharp
turn to the north towards daybreak. Swell energy will be quite
minimal, seas will be comprised of a series of fairly diminutive
wind waves.

As of 300 PM Thursday...High pressure will build southeastward
behind Saturday night`s cold front, finally reaching the
eastern Carolinas Monday afternoon or evening. Northerly winds
as strong as 15-20 kt at daybreak Sunday should subside to
around 10 kt Sunday afternoon. An upper level disturbance
passing just to our north late Sunday night should bump winds
back up toward 15 knots, but winds should diminish again as the
high pressure area approaches later Monday. Westerly winds
behind the high Monday night will turn more southerly along the
beaches Tuesday afternoon with the daily seabreeze circulation.




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