Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 220230

Area Forecast Discussion
National Weather Service Wilmington NC
930 PM EST Tue Feb 21 2017

Temperatures will remain well above normal this week. A week
trough may bring spotty showers to the region Wednesday and
Thursday. Near record highs are possible Friday. A cold front,
approaching from the west, will bring a slight chance of
showers Saturday. Much cooler and drier air will build into the
area Saturday night into early next week.


As of 9 PM Tuesday...Closed upper low and surface reflection
over the Mid-South and Gulf Coast states will drift southeast
overnight, while surface high pressure off the New England coast
drops south. 00Z soundings from MHX and CHS reveal a dry airmass
from about 850 mb up to 400 mb. However high cloud cover will be
extensive overnight, and low-level moisture will continue to
increase in onshore flow. Few adjustments needed to forecast
this period, however have adjusted temps up a tad as they are
falling a little slower. As a result, the dewpoint depression is
not as supportive for fog development, so forecast coverage has
been trimmed back.


As of 3 PM Tuesday...The center of high pressure Wed will be
offshore of the Mid-Atlantic states and will drift further
offshore as it ridges back across the eastern Carolinas through
Thu night. At the same time, slow moving low pressure will be
vertically stacked as it moves across the Florida peninsula and

Still looks like there will be too much dry air to support showers
on Wed. Yet there will be some shortwave energy migrating from W to
E across the area, so hard to rule out an isolated shower although
all the guidance has backed off on any showers across the Forecast
Area Wed and Wed eve. Therefore, since we can not rule a shower out,
will leave the smallest of POPs in the forecast Wed afternoon and
early eve. Model soundings and moisture profiles support the
development of late night fog late Wed night.

Columnar moisture is a little greater Thu, but there are no obvious
triggers and transport of deeper moisture to our S will be cutoff by
the large circulation center across FL and the Bahamas. Will include
a small POP as the seabreeze may provide sufficient lift to support
shallow showers. Any afternoon showers Thu should quickly dissipate
early in the eve with loss of heating.

Highs will be mainly in the mid 70s away from the cooling impacts of
the ocean both days, with Thu likely slightly warmer. Near and along
the immediate coast, highs will be in the upper 60s to around 70
with lower to mid 60s at the beaches. Lows will be in the mid and
upper 50s.


As of 3 PM Tuesday...Period begins with the forecast area between
filling 5h low off the east coast of FL and high amplitude 5h trough
moving east across the center of the country. Although a strong cold
front will move across the area late Sat there is unlikely to be
much in the way of convection along the front. The environment ahead
of the front is very dry, due to a combination of limited moisture
return and strong mid level subsidence. Cannot rule out a few
isolated showers but do not feel anything more than a slight
chc/silent pop is warranted. Despite low level northeast to east
flow ahead of the front Fri into Sat, as a weak surface low passes
well off the coast, temperatures will be well above climo with highs
approaching 80 each day and lows in the 50s. Sat could end up
slightly warmer than Fri as low level flow becomes southwest once
the low exits northeast. Following the passage of the front, 850
temps drop as much as 12C. Despite the impressive drop, temperatures
Sun will be right around climo. Mid level trough exits Mon and warm
advection begins as the surface high shifts off the coast and
pattern aloft becomes progressive. Temperatures will jump back above
climo Mon, remaining above climo through the end of the period.


As of 00Z...Patchy areas of MVFR fog possible late overnight
into the early morning hours. Otherwise expect VFR.

Widespread cirrus cigs along with SCT/BKN mid clouds continue
to move across the area this evening, with easterly winds around
5 kts or less. Expect this trend to continue overnight, with
latest guidance continuing to suggest the potential for areas of
MVFR due to fog to develop late overnight. After daybreak on
Wednesday, expect any fog to disperse, giving way to VFR through
the rest of the valid TAF period. East- southeasterly winds
will increase to 5 to 10 kts throughout the day, with BKN/OVC
mid to high clouds expected.

Extended Outlook...Isolated showers late Wednesday through
Thursday. Showers possible Saturday with a cold front. Otherwise
expect VFR.


As of 9 PM Tuesday...E to ESE winds will prevail tonight as
high pressure drifts south along the Mid-Atlantic coast. Wind
speeds will be 10 to 15 kt most of the time. Seas will remain 2
to 3 ft.

As of 3 PM Tuesday...The center of surface high pressure along
the Mid-Atlantic coast Wed will drift further offshore as it
ridges back across the Carolina waters through Thu night. A
vertically stacked area of low pressure will slowly move across
FL and the Bahamas during the period. This will tighten the
pressure gradient to our S. The wind direction will be mainly E
or ESE Wed through Thu with a tendency to back slightly Thu
night. Wind speeds during this forecast period will be no higher
than 10 to 15 kt. Seas will build gradually, reaching 3 to 4 ft
Wed and Wed night and 3 to 5 ft Thu. Small Craft Advisory seas
may develop Thu night, from S to N, as seas build to 4 to 6 ft.

As of 3 PM Tuesday...Weak low pressure moving northeast, well
off the coast, and weak high to the west will both contribute to
northeast flow around 10 kt Fri into Sat. Winds back to
southwest Sat as the low exits and front approaches from the
west. Pinched gradient ahead of the front may lead to speeds in
excess of 20 kt late Sat into Sat night. Offshore flow behind
the front will remain a solid 20 kt, possibly bumping 25 kt
early Sun, with cold advection developing. Offshore flow
continues Sun but weakens during the day as both gradient and
cold advection relax. Seas well away from shore will flirt with
6 ft for at least the first half of the period, a mix of wind
wave and swell. Swell component decreases Sat and Sun while the
wind component increases a bit Sat before offshore flow Sun
knocks seas within 20 nm down for the later half of the period.
Headlines will likely be required for Fri and Sat but have low
confidence as to which headline will be needed.




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