Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 280650
Area Forecast Discussion
National Weather Service Raleigh NC
250 AM EDT Sat May 28 2016
.SYNOPSIS...A tropical depression off the Southeast coast will drift
slowly northwest toward the South Carolina coast through Sunday,
before turning northeast and tracking off the southeast North
Carolina coast through Wednesday.
.NEAR TERM /through tonight/...
-- Changed Discussion --As of 250 AM Saturday...
What is currently TD2 (projected to become TS Bonnie) is located off
the SE coast east of JAX early this morning, and it will continue
tracking NW toward the Southeast coast today and tonight, following
a path along the weak NW-to-SE-oriented mid level shear axis now
extending across SC and SW NC. Bermuda high pressure continues to
nose westward across NC, providing subsidence and mostly clear skies
through this morning, although this will give way to the slowly
incoming cloud shield associated with TD2 later today. While the TD
is not expected to move close to shore until late Sun, the
strengthening low-fetch low level southeasterly inflow on the TD`s
north side will draw plentiful moisture into central NC starting
late this afternoon, with PW values aoa 1.5" supplanting the sub-
0.75" PW now in place over the area by this evening. The latest
model runs are slower in bringing substantial precip into central
NC, depicting little to no coverage outside of the far SE counties
until late today. Based on the stubborn nature of the Bermuda
surface ridge along with the mid level dry air noted on forecast
soundings, the current cloud trends, and the passage of the bulk of
the initial DPVA to our south within the mid level shear axis, have
delayed precip onset, will focus pops on the SE only for much of the
day. Upper divergence ramps up after nightfall along with moist
upglide, and PW values are projected to approach 2.0 inches (mainly
east half) tonight. Will retain a steady upward trend of pops from
SE to NW, reaching likely pops areawide by late tonight with an
abundance of deep moisture and improving dynamic forcing for ascent.
Expect highs today of 82-87, "coolest" over the SE given the earlier
clouds and precip arrival. Warm lows tonight of 63-69. -GIH
-- End Changed Discussion --
.SHORT TERM / /...
-- Changed Discussion --As of 325 PM Friday...
To be updated shortly.
-- End Changed Discussion --
.LONG TERM /Sunday Through Friday/...
As of 305 PM Friday...
Sunday through Tuesday: The likely tropical/sub-tropical low is
expected to be located very near the South Carolina coast Sunday
morning, shown by nearly all of model guidance. However, where the
sub-tropical/tropical/remnant low tracks after approaching/moving
onshore is still in question. Given the approaching system and
influx of tropical moisture into central NC, we should see numerous
to widespread showers and thunderstorms on Sunday as the inverted
surface trough pivots westward and into our area. This will lead to
the potential of heavy rain with any showers and storms as PW`s are
expected to surge to around/over 2 inches, along with at least some
threat of at least isolated severe storms. With regard to the severe
threat, there is still some uncertainty about how much instability
we will have and how strong the deep and low level shear will be,
with the eventual track and intensity of the system playing a major
role. High temps Sunday should be limited to around 80 degrees
thanks to the convection and mostly cloudy/overcast skies, but with
quite humid conditions.
The latest GFS and NAM shows the system lifting northward across the
coastal plain of the Carolinas on Monday night into Tuesday and
being absorbed in a passing northern stream s/w. The latest ECMWF is
hinting at this potential now as well, which differ some from its
previous run and has more of a drier solution across most of central
NC by Monday, with any heavy rain/rain generally from the I-95
corridor and eastward. However, will maintain continuity for now
with previous forecasts and still show at least likely pops across
the eastern half of the area. Chances for showers and storms are
expected to decrease further Monday night into Tuesday with any
lingering trough axis located along the coast (higher chances east
vs west for central NC). High temps on Monday and Tuesday are
expected to be in the lower to mid 80s, with lows in the mid to
Tuesday night through Friday: Will trend chances for showers and
storms more towards climo with poor run to run model continuity,
along with model differences. This will yield generally diurnal
chance pops with high temps in the lower to mid 80s and lows in the
.AVIATION /06Z Saturday through Wednesday/...
As of 123 AM Saturday...
VFR conditions are likely at all sites through today, although MVFR
conditions will begin to move into FAY then RDU/RWI starting after
21Z. Additionally, RWI is likely to see banks of dense fog this
morning which could briefly restrict vsbys there to under 2 miles.
High pressure centered well offshore continues to nose westward
across NC early this morning, yielding generally light winds and
mostly clear skies. A tropical depression located off the Southeast
coast is expected to continue tracking to the NW toward the SC coast
today, and the resulting increase in low level flow from the SE into
NC will gradually pull Atlantic moisture into our area, causing
clouds to thicken with lowering bases from SE to NW. FAY is expected
to trend to MVFR cig/vsby after 23Z, RWI after 00Z, and RDU after
02Z as patchy light rain spreads in from the SE. Surface winds will
be initially from the south then shift to be from the SE this
morning, holding under 10 kts through tonight.
Looking beyond 06z early Sun morning, cigs/vsbys are likely to
become MVFR at all central NC sites by Sun morning with areas of
rain, as the tropical system approaches the SC coast near CHS by Sun
evening. MVFR conditions will remain common through Sun with on-and-
off showers, although a period of IFR or VFR conditions may occur.
The tropical system is then expected to weak as it tracks
northeastward off the northern SC and SE NC coast through Mon, and
after areas of fog and perhaps IFR stratus Sun night, VFR conditions
should return Mon afternoon. A humid pattern will hold Tue/Wed with
IFR fog possible each morning, but otherwise VFR conditions will
dominate Tue/Wed. -GIH