Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Highlight Changed Discussion --
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FXUS62 KRAH 261445
Area Forecast Discussion
National Weather Service Raleigh NC
1045 AM EDT FRI AUG 26 2016
An upper level ridge will extend across the region through the
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 1045 AM Friday...
Little change/adjustment required to the near term forecast.
Strong mid/upper level anti-cyclone overhead will result in hot
conditions this afternoon across central NC. Observed temperature
trends this morning support high temps solidly in the mid 90s with a
few upper 90s possible in the coastal plain and sandhills. The hot
temperatures combined with the humidity will create heat index
values this afternoon between 102 and 105 degrees generally along
and east of highway 1. Have updated the HWO to reflect this.
Still a potential for an isolated shower or storm late this
afternoon over the southern piedmont where weak convergence along a
surface trough may be enough to initiate lift. Elsewhere expect
subsidence associated with the anti-cyclone to inhibit convective
Tonight, expect clear to partly cloudy skies and it will feel muggy
as sfc dewpoints recover into the lower 70s. Overnight temps in the
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.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 /12Z FRIDAY THROUGH TUESDAY/...
As of 650 AM Friday...
Strong high pressure over the region will lead to light/variable
predominately VFR conditions today anD tonight, with just some
scattered clouds above 4k ft drifting east across the Piedmont this
morning. There has been some low level moisture bleeding southeast
off the Blue Ridge into the northwest Piedmont. The only impact
would be a brief period of MVFR vsbys at KINT and KGSO prior to
123z. Any storms this afternoon will be very isolated and well
southwest of TAF sites.
Outlook: This area of high pressure is expected to maintain its
influence over our region through early next week. A weak backdoor
cold front early Saturday will be followed by a northeast wind that
could lead to some sub-VFR ceilings across the coastal plain on
Sunday morning. Otherwise, VFR conditions are expected to prevail.