Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 210145

Area Forecast Discussion
National Weather Service Wilmington NC
945 PM EDT Fri Apr 20 2018

Canadian high pressure will build into the Carolinas through
the weekend, bringing dry weather with chilly temperatures.
Slow-moving low pressure will cross the Southeastern U.S.
Monday through Wednesday, bringing widespread rainfall with
continued below-normal temperatures. Another system may affect
the Carolinas Thursday into Friday.


As of 945 PM Friday...Dewpoints rising quicker than forecast,
and under clear skies and light wind, this will only help the
prospects for fog overnight, and will expand this potential in
the overnight forecasts. No other significant changes.

As of 630 PM Friday...Radar wind profiler showing an easing and
backing wind column early this evening, now, 10 knots or less
in the lowest 5000 feet. GOES-East visible data showing a
cloudless sky over all of the Carolinas. Hourly temperatures
will fall through 5 AM before gradually rising, while dewpoints
climb slowly through the night, into the low 40s by daybreak. 10
meter winds should hold at 3-6 mph overnight. These factors
will lead to patchy fog along the coastal interior where
slightly higher dewpoints will reside, and away from the higher
coastal winds. The combination of low-levels near saturation
into the predawn, and chilly pockets of middle to upper 30s,
results in patches of frost over portions of Pender, central
Brunswick, and Robeson counties at first light.

As of 300 PM Friday...A 500 mb ridge over the Southern Plains will
move into Georgia and the southern Appalachians by late Saturday.
Dry northwesterly mid and upper level flow ahead of this ridge will
continue. At the surface, Canadian high pressure covering most of
the Great Lakes region will develop a secondary center along the
Virginia coast Saturday afternoon.

Light winds and clear skies tonight should promote very good
radiation cooling. My forecast lows are at the very bottom end of
guidance, ranging from the upper 30s to around 40 inland with a
sliver of mid 40s on the beaches. I`ve got mid 30s forecast across
the normally colder locations across SE North Carolina and have
added patchy frost to the forecast here as well. Blueberry growers,
whose farms are often located on the nocturnally cold peat soils,
may have some concern tonight.

Sunny skies are expected Saturday, Another weak seabreeze along the
coast should keep the beaches 5-10 degrees cooler than inland areas.
Forecast highs range from the lower 70s across the Pee Dee region to
the mid 60s near the coast.


As of 300 PM Friday...High pressure slides east of the area Saturday
night, passing by well to our north. Temperatures will be held a bit
below climatology in the NE flow with a mainly clear sky brought by
the downsloping mid level flow. Wit the high progressing further off
the MidAtlantic coast on Sunday the door will open up to moisture
influx. Cloud cover will increase from SW to NE. Some of the
guidance that has been suggesting that rain could start breaking out
soon thereafter has been discounted as being too fast. This will
eventually start to change heading into Sunday night as the
moistening deepens in response to approaching upper troughiness
tilting flow to the southwest. POPS will increase though rainfall
amounts expected to remain light and generally confined to SC zones
Sunday night.


As of 300 PM Friday...Cutoff low will continue to move east
along the Gulf Coast states Mon into Tues spreading clouds and
rain across the area from south to north. Increasing moist on
shore flow will push pcp water values up to near 1.5 inches late
Mon into Tues. The center of the low should reach the SC coast
Tues night and then track up along the Carolina Coast lifting
off to the northeast late Wed. The best moisture and lift should
come together to produce the greatest QPF Mon night through
Tues with fairly widespread amounts between a half inch and an
inch with locally higher amounts.

Some dry air should wrap in with westerly flow on the back end
of the system on Wed, but lingering upper level energy could
keep some lingering clouds and showers around. By Thurs, another
cutoff low will track across the Appalachian Mtns, with
increased potential for clouds and pcp late Thurs into Fri.
Overall a damp week ahead with a good amount of clouds and pcp
through the week.

Temps running on the cooler side on Mon will return toward
normal Tues into Wed. Overall temps will remain near or just
below climo through much of the week.


As of 00Z...Will indicate VFR in TAFS but confidence is not
high overnight. With good radiational cooling and light winds
tonight, periods of reduced visibilities due to ground fog are
possible mostly towards sunrise, but could occur as soon as late
this evening at the coastal terminals, especially fog prone KCRE.
Confidence is low however as to timing, extent and duration of any
restrictions since any ground fog will be shallow and patchy due to
very limited and shallow moisture.

Any ground fog will disperse rapidly shortly after sunrise. Winds
will be northeast to east in the morning, becoming east to southeast
by afternoon.

Extended outlook...VFR. Mon periods of MVFR/RA. Tue periods of
IFR/RA becoming MVFR. Wed VFR.


As of 630 PM Friday...Spectral plots show wave frequencies
centered near 7 seconds, from the E. Chop is decreasing and will
be light overnight. Inshore SSTs have leveled off at 62-64 deg.
The atmosphere is starved of moisture aloft, so no TSTMS or
marine showers. All in all, very manageable marine conditions
through tonight, tides are running normally, and little hazard
expected in the near term.

As of 300 PM Friday...Sprawling Canadian high pressure over the
Great Lakes will develop a secondary center along the Virginia
coast Saturday afternoon. This should maintain northeasterly
winds along our portion of the Carolina coast, with a weak
seabreeze expected to turn nearshore wind directions more
directly onshore Saturday afternoon. All models are in excellent
agreement and there is high confidence in this scenario.

Residual strong northeasterly winds most of this morning maintained
a hybrid 6-7 second northeasterly swell. Now that this wind is
diminishing, look for waves to quickly subside this evening. By 8 or
9 PM seas within 20 miles of shore should be only 1-2 feet! The
`exercise caution` headline will be allowed to expire at 3 PM, and
no advisories are needed for the next 24 hours.

As of 300 PM Friday...High pressure progressing eastward and
staying well north of the area all period. This will turn flow
onshore Saturday night with wind and seas remaining quite
light/small. This will hold true most of Sunday as well save for
a gradual increase in wind speed. Things then ramp up with the
approach of low pressure from the west Sunday night. Expect
conditions to deteriorate to near Advisory levels, though the
flags will likely go up this period to incorporate further
deterioration later on/early in the long term.

As of 300 PM Friday...Low pressure system will move east across
the Gulf Coast States to the coast of SC by Tues night and then
will track NE parallel to the Carolina coast. A strong on shore
flow will persist Mon into Tues in a tightened gradient flow
between this low pressure system and high pressure moving slowly
off the Northeast coast. Winds will diminish as they back from
E-SE to N-NE Tues night as the center of the low tracks
northeast becoming elongated just off the Carolina coast.
Eventually an off shore W-SW flow will develop late Wed as the
low exits off to the northeast.

Overall, expect this onshore push of easterly winds up to 25 to
30 kts to push seas up through Mon into Tues, from near 6 ft Mon
morning up to possibly 10 to 12 ft by Tues morning and then
subsiding slowly as winds back around further becoming off shore
Wed. Expect SCA conditions through much of the period.





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