Area Forecast Discussion
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FXUS62 KRAH 261652
Area Forecast Discussion
National Weather Service Raleigh NC
1255 PM EDT FRI AUG 26 2016
An upper level ridge will extend across the region through the
.NEAR TERM /THROUGH TONIGHT/...
As of 1220 PM Friday...
Have issued a heat advisory for locations generally along and east
of highway 1 through 7 PM this evening. Afternoon temps in the upper
90s appear likely and with dewpoints in the lower 70s, heat
index values will likely reach the critical threshold of 105.
Weak sfc trough extending from the coastal plain through the
sandhills and southern piedmont will aid to pool low level moisture.
May see enough lift occur along the boundary to initiate an isolated
shower or storm, most probable over parts of the sandhills and
southern piedmont. Still, isolated nature of the convection means
that most folks will not get any relief from the intense afternoon
Tonight, expect clear to partly cloudy skies and it will feel muggy
as sfc dewpoints recover into the lower 70s. Overnight temps in the
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
As of 345 AM Friday...
With the upper ridge to our north on Saturday, northeasterly flow
will set in, though with very little change in airmass and highs
again in the mid 90s. A slight dip in 850mb temps and reduction of
the mid-level cap should allow isolated to widely scattered
convection to fire during the afternoon, mainly with an axis of
weak to moderate instability across the southern Piedmont and
coastal plain. Convection will be diurnally driven and dissipate
by early evening, with northeasterly flow supporting a chance of
some low clouds over the coastal plain by early Sunday morning.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 355 AM Friday...
Above average forecast uncertainty remains today thanks to the still
unknown, if at all, development and subsequent track of the tropical
wave located between the SERN Bahamas and Cuba. This system remains
poorly organized this morning; and the probability of subsequent
development into a tropical cyclone appears lower than previous
days. The wave will nonetheless bear watching and remain the primary
forecast concern for much of the SERN and Gulf coast states,
including central NC, as it drifts WNWWD during the next few days.
A mid to upper low developing now several hundred miles W of Bermuda
will drift W --around the SRN periphery of an initially strong sub-
tropical ridge forecast to migrate across the Central Appalachians
and Middle Atlantic states-- and consequently approach the SE U.S.
coast late Sun-Mon. The approach of this low will provide synoptic-
scale forcing for ascent atop a zone of low level convergence over
the ERN Carolinas, in association with both the sea breeze and
frictional convergence in moist ENE low level flow around surface
high pressure initially along the Middle Atlantic coast. The
presence of the surface ridge axis extending SWWD across the
interior Middle Atlantic states will cause surface dewpoints to mix
out well into the 60s Sun-Mon, while a much more humid air mass will
envelop coastal areas and the coastal plain. The forecast will
consequently be a dry one for the Piedmont, while diurnal convection
will be possible generally along and east of I-95 each afternoon.
The presence of the mid-upper low and associated height falls will
also cause the sub-tropical ridge to split, with an associated
positively-tilted trough/shear axis invof the SERN and SRN Middle
Atlantic coasts early to mid week. This weakness in the ridge will
provide a corridor through which low pressure associated with the
aforementioned tropical wave could pass, though if the wave were to
indeed remain weak/shallow, it would more likely continue a WNW
drift across the GOM.
Given continued large model spread, and doubt about any appreciable
development of the tropical wave at all, only minimal changes have
been made to the previous forecasts for mid-week.
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 1255 PM Friday...
There is high confidence that VFR conditions will persist across
central NC through Saturday night. The exception will be a threat
for isolated convection Saturday afternoon and associated MVFR
conditions/gusty sfc winds. Otherwise, an area of high pressure will
maintain dry weather with light wind conditions.
This area of high pressure is expected to maintain its influence
over our region through early next week. Circulation around the sfc
high may advect enough low level moisture to result in a period of
stratus Sunday morning and again Monday morning. Also, there will
be a threat for isolated afternoon/early evening convection Sunday
through Wednesday mainly in the vicinity of KFAY (associated with
the seabreeze), and the Triad terminals (convection drifting off the
higher terrain into the western Piedmont).
Heat Advisory until 7 PM EDT this evening for NCZ010-011-