Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 220140

Area Forecast Discussion
National Weather Service Wilmington NC
840 PM EST Sun Jan 21 2018

The risk for showers and perhaps a rumble of thunder will be on
the increase ahead of a cold front which will move across the
eastern Carolinas on Tuesday. Temperatures will cool to seasonable
levels Wednesday through Friday. Weekend temperatures will warm
again ahead of a cold front along with the risk for more showers,
especially on Sunday.


As of 800 PM Sunday...SKies were clear this eve with nearest
cloud cover offshore and not making any inroads closer to the
coast. High clouds across GA and AL were increasing and this
trend will continue with the clouds expanding across the
Carolinas overnight and Mon morning.

After a warm day by late January standards, temps have cooled
into the 40s and have had to adjust hourly temps down to account
for the temp drop this eve. For the remainder of the night, the
temp curve will flatten and likely not deviate but a degree or
two toward morning as the higher clouds begin to increase and
thicken. Forecast lows are within a couple degrees of 40.

A challenging forecast develops Monday as the surface high
slips further offshore ahead of a cold front approaching from
the west. The NAM and Euro indicate a weak coastal trough will
develop and lift onshore during the aftn with some showers,
while the GFS is dry despite increasing cloudiness. There
appears to be a weakness in the pressure field already
developing off the FL/GA coast, so this trough seems likely.
However, profiles indicate moisture will be quite shallow, below
700mb, even during maximum saturation. Given weak forcing and
relatively low PWAT, have kept shower chances to SCHC, favored
along the Grand Strand and into Cape Fear during the aftn and
into the evening. This enhanced cloud cover combined with
southerly winds will keep highs along the coast in the mid 60s,
warming to near 70 inland where more sunshine will allow the
strong WAA to be realized.

Very late in the period the front will approach and may spawn a few
showers west of I-95, but the guidance has slowed and expect the
bulk of the shower and potential tstm activity to occur overnight
Monday into Tuesday.


As of 300 PM Sunday...Mid-level low moving from the Upper
Mississippi Valley Mon night into Tue will drag a cold front
into and across the area Tue morning. Convection ahead of the
front is likely to be limited. Deeper moisture and best dynamics
pass north of the area and both the GFS and ECMWF suggest the
mountains may take a little bit out of convection as it moves
east. Also in play will be convection along and south of the FL
Panhandle. Convective activity in this area in these kind of
setups always seems to lead to reduced coverage in the eastern
Carolinas. Convection ahead of and with the front will be
associated with some elevated instability. Cannot rule out some
isolated thunder, but it may be difficult to get the bulk of
the convection that does develop deep enough to generate
sufficient charge separation given the abundance of dry air
aloft. Still will continue to carry isolated thunder Tue
morning. Strong low level jet (50+ kt) does warrant mentioning
the low possibility of an isolated damaging wind gust, but
overall this is unlikely given the low level stability. If the
front/convection were delayed until later in the day
strong/severe storms could become more of a concern. Total
rainfall will be limited, likely under a quarter of an inch area
wide, given the broken coverage and storm motions approaching
50 kt.

Front moves off the coast during Tue but a lack of cold advection
and clearing skies in the afternoon will keep highs well above
climo, especially given Tue morning lows in the mid 50s. Clouds may
linger through midday or so, slightly longer at the immediate coast,
but then skies should clear out. Combination of sun and deep
westerly flow(downslope) in the afternoon will push high into the
upper 60s to low 70s (even to the coast). Strong winds just above
the surface will likely lead to a breezy day, especially once the
sun does come out. Winds start to drop off overnight as surface high
builds in from the west. Weakening gradient and lack of cold
advection/boundary layer mixing coupled with clear skies will allow
for good radiational cooling. This should drop lows back close to
climo for late January, mid to upper 30s.


As of 300 PM Sunday...High pressure will be building in from the
west on Wednesday while mid level flow will be zonal and confluent;
normally a recipe for sunny and seasonable weather. The surface and
upper air pattern will be both progressive and amplifying through
Saturday with the ridge developing in the east. Once surface return
flow gets established locally we should start to see warmer
temperatures. It appears this happens on Saturday. Cloud cover and
rain chances then rise quickly on Sunday with the approach of the
cold front and strengthening upper trough from the west.


As of 00Z...Except for tempo MVFR vsbys due to BR around
sunrise at KFLO/KLBT, VFR expected all terminals into Monday
morning. By mid-morning MVFR cigs are likely to develop.
Confidence is low on IFR in the afternoon at KFLO/KLBT due to
differences in expected precipitation. There is higher
confidence of sea fog/IFR/LIFR at the coastal terminals towards
the end of the TAF period, however there is a question whether
dewpoints will get high enough above water temperatures in the
late afternoon.

Extended Outlook...VFR. MVFR/IFR/LIFR Mon evening/early Tue


As of 800 PM Sunday...Large elongated high pressure across the
waters was producing an extremely weak gradient as evidenced by
winds at the buoys of 5 kt or less, and seas just around 1 ft.

The surface high will remain overhead overnight producing light
and variable winds, before it shifts offshore during Monday.
This will be followed by slowly increasing return flow with
winds becoming south at 10-15 kt by the end of the period. Seas
will be slow to respond, but a SE swell and subtly amplifying
southerly wind wave will push seas up to 2-3 ft late Monday.

As of 300 PM Sunday...Southerly flow will increase Mon night
with winds veering to southeast by daybreak as gradient becomes
more defined. Cold front moves off the coast and across the
waters as Tue morning turns into Tue afternoon. Winds gradually
veer to westerly later Tue and Tue night as high pressure
expands east. Gradient slowly weakens during the second half of
the period as the surface high expands. Weakening gradient
coupled with the lack of cold advection will allow for steadily
decreasing offshore flow Tue night. Strong southerly flow may
create a brief period of SCA seas late Mon night into Tue
afternoon before development of offshore flow and weakening wind
speeds drops seas under 6 ft late Tue afternoon.

As of 300 PM Sunday...Winds out of the NW on Wednesday as high
pressure well to our west approaches. AS the anticyclone
approaches Thursday flow veers to N then NE, possibly becoming
light and variable for a time Thursday evening or early Thursday
night as it moves nearly overhead. E or ESE winds should then
increase Friday as this high begins to share a center with one
moving off the New England coast.





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