Area Forecast Discussion Issued by NWS Wilmington, NC
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000
FXUS62 KILM 182333
AFDILM
Area Forecast Discussion
National Weather Service Wilmington NC
733 PM EDT Mon Mar 18 2024
.SYNOPSIS...
Dry weather and below normal temperatures will continue through
Tuesday night. Milder and continued dry through Thursday. Rain
chances return Friday into Saturday as Gulf coast low pressure
moves northeastward up the Southeast Atlantic coast.
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.UPDATE...
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A mid-level shortwave trough is beginning to produce cloud
cover across west-central NC/SC. Additionally, low-level
frontogenesis is maximized ahead of what appears to be a surface
trough or secondary cold front. Shortwave energy will catch the
surface boundary tonight and these two will work to produce
lowering cloud bases and a light shower or sprinkle. The latest
update advertises a slight increase in PoPs where LCL-LFC RH
will be nearly saturated: southern and eastern NC. Dry air
beneath the LCL and a shallow warm cloud layer should keep the
intensity at a sprinkle. Weaker echos on radar are unlikely to
reach the ground all together.
Forecast wind gusts have been increased with the latest update
as well due to deep mixing behind the boundary. Dry adiabatic
momentum transfer of 25-30 knots is possible before cooler air
arrives and a surface inversion knocks surface winds back to
around 10 knots.
Observed dew points in western NC/SC are currently in the upper
teens. While this exceptionally dry air pushes eastward tonight,
the late night surface inversion will pause advection briefly.
Therefore, I made an adjustment to daytime dew points and RH to
more accurately reflect tomorrow`s mixing potential based on
these initial observations. Tonight`s dew points seem OK,
assuming dew point advection pauses briefly after 9Z.
For this discussion: the routine aviation section has been
updated for 00Z issuance and a Fire Weather section has been
added to provide details on the Fire Danger Statement issued
earlier.-- End Changed Discussion --
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.NEAR TERM /THROUGH TUESDAY/...
Latest surface analysis shows the old frontal boundary well
offshore, while weak low pressure lingers across Appalachia and
the Piedmont. The frontal passage from earlier this morning has
allowed for very dry air to settle at the surface. Dewpoints
this morning were in the mid 50s, and have now dropped into the
upper 20s to lower 30s. Ironically enough, clouds aloft have
filled in over the last couple of hours, as a potent shortwave
aloft starts to drop into the area from the northwest.
Said shortwave will quickly sweep through the area tonight.
Cloud cover will continue to thicken aloft, despite the very
dry air at the surface. There`s a subtle hint of moisture
convergence north of Cape Fear after 10 PM, and the atmosphere
will try to squeeze out whatever water it can. However, the
saturation is very thin, lingering at around 700mb. Surface
dewpoints continue to plummet into the lower 20s, so whatever
falls out of the cloud may dry out before it hits the surface
("virga" being the technical term for that phenomena). Some
folks may see a couple sprinkles at best before 2 AM tonight
across the coastal regions of southeast NC.
Elsewhere, lows tonight bottom out in the mid-to-upper 30s. The
temperatures meet Frost Advisory criteria inland, but tonight
looks looks much too dry and windy to actually issue one.
Probabilistic guidance suggests a modest chance (30-50%) of
temperatures actually near or even just below freezing across
certain parts of Darlington and Marlboro Counties. I`m not so
confident on that idea, given the elevated winds, and if anybody
does hit the freezing mark, it probably would only be for an
hour or so. Therefore, holding off on a Freeze Warning tonight.
Plenty of sunshine on the way for Tuesday, but it`ll be on the
chilly side, with high pressure from the Midwest having an
influence. Highs only reach the mid-to-upper 50s in what looks
to be the coolest day of the week.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Not much of note this period with the region under the
influence of weak sfc high pressure, allowing for continued dry
weather over the local area. Some moderation of temps noted as
thicknesses increase...highs in the 60s/70s unlike the 50s
forecasted for Tuesday. A weak front moving through Wednesday
night will lead to slightly cooler temps Thursday than
Wednesday, but still near normal.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Focus in the long term period will be on developing Gulf of
Mexico sfc low pressure tracking northeastward. In general
guidance seems a bit more progressive with this southern stream
system now, however there remains large differences in timing.
Enough confidence to retain likely PoPs for Friday and Friday
night, with the rain moderate to heavy at times and a slight
chance of thunder. A drying trend ensues over the weekend, but
it remains unclear how long the rain will linger especially on
Saturday should the mid-level trough slow down. Temps fairly
close to normal for late March this period.
&&
.AVIATION /23Z MONDAY THROUGH SATURDAY/...
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VFR. Gusts this evening behind a surface boundary could peak
around 30-35 knots before cooler air initiates a surface
inversion prior to morning flights. Upper trough may squeeze out
a couple of sprinkles in NC, but no VIS/CIG issues expected.
Clear tomorrow with winds gradually shifting from NW to SW
during the afternoon. SW winds could be gusty prior to sunset.
Extended Outlook... VFR expected through the rest of the
period.-- End Changed Discussion --
&&
.MARINE...
Through Tuesday...Pressure gradient increases tonight with an
upper level system moving through, bringing stiff northwesterly
winds into the fold. These winds will initiate a Small Craft
Advisory at 11 PM EDT tonight, going through noon EDT Tuesday.
Wouldn`t be surprised to see a few gusts hit gale criteria
tonight, particularly over the northeast SC coastal waters, but
it`s not quite consistent enough to upgrade these to a Gale
Warning at this time. These offshore winds cause wind waves to
poke up at 3-4ft. After the upper level disturbance moves
through, winds eventually decrease to 10-15kts from the
southwest by Tuesday afternoon. Seas decrease to 1-2ft.
Tuesday Night through Saturday...Couple more SCA headlines
expected this period. First is Tuesday night as the pressure
gradient increases in SW flow ahead of the next weak front.
Somewhat improving conditions then for Wednesday and Thursday,
before winds and seas ramp up Friday into Saturday in
association with developing low pressure sliding up the SE
coast. By early Saturday expect seas up to 8-9 ft and winds
gusting to ~25 kt.
&&
.FIRE WEATHER...
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A Fire Danger Statement has been issued for all of southeastern
North Carolina. Minimum relative humidity tomorrow afternoon
will fall to 15-25% across the area. Northwest and west winds
will hover around 10-15 mph early in the day, but southwest
winds will increase during the afternoon, becoming gusty later
in the day. Gusts up to 25 mph are possible during the late
afternoon and just prior to sunset. The combination of dry
fuels, low relative humidity, and gusty winds will lead to
increased fire danger on Tuesday.-- End Changed Discussion --
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
NC...None.
SC...None.
MARINE...Small Craft Advisory from 11 PM this evening to noon EDT
Tuesday for AMZ250-252-254-256.
&&
$$
SYNOPSIS...ILM
UPDATE...21
NEAR TERM...IGB
SHORT TERM...MAS
LONG TERM...MAS
AVIATION...IGB
MARINE...MAS/IGB
FIRE WEATHER...ILM