Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 280659
Area Forecast Discussion
National Weather Service Raleigh NC
259 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/...
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
.SHORT TERM / /...
As of 325 PM Friday...
To be updated shortly.
.LONG TERM /Monday Through Friday/...
-- Changed Discussion --As of 300 AM Saturday...
Monday and Tuesday: Tropical Depression Two will continue to spin
along the Carolina coast on Monday somewhere in the vicinity of
Myrtle Beach and heading northeastward towards the NC/SC border by
Monday night. The storm should be in a weakening mode possibly
moving from tropical storm strength back down to tropical depression
strength sometime during the day on Monday. Regardless of the
strength...models point to a large amount of moisture across the
eastern half of the state. Will keep pops in the high chance to
likely range with slight chance of thunder Monday afternoon. The
depression will shift slightly eastward on Tuesday as surface high
pressure builds in over the Ohio Valley. This will quickly move
northward though and weaken and is unclear how much of an effect it
will have on precipitation. Therefore expect lower chances Tuesday
but still a good chance for wet weather east of I-95. Highs during
this period in the low 80s with lows in the mid 60s.
Models diverge on Wednesday as the handling of Tropical Depression
Two becomes more uncertain. The ECMWF keeps the storm lingering off
of the coast while the GFS breaks it down. Either way a low pressure
system over the northern plains with a frontal system extending down
the Mississippi Valley will start to work eastward but will be very
slow in doing so. This will leave a very moist and warm airmass in
place, but a stagnant one without much forcing. Therefore expect
diurnal chances for rain and possibly thunder as well Wednesday and
Thursday. Highs and lows remain steady in the mid 80s and mid 60s
There is very good agreement in the models regarding the frontal
system finally making it to the area on Friday as an upper trough
digs out of the Great Lakes. This will increase the chances for
precipitation on Friday closer to 50 percent and may cool
temperatures a few degrees into the lower 80s, at least across the
-- End Changed Discussion --
.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