Area Forecast Discussion
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FXUS62 KRAH 250743
Area Forecast Discussion
National Weather Service Raleigh NC
343 AM EDT THU AUG 25 2016
High pressure will extend across the region through the remainder of
the week, as a strong upper level ridge builds overhead.
.NEAR TERM /THROUGH TONIGHT/...
As of 345 AM Thursday...
On the eastern periphery of a 596m ridge at 500mb, water vapor
imagery and dynamic trop maps depict a compact tropopause
disturbance diving south across the area this morning. This has
only resulted in a few extra clouds and will go mostly unnoticed.
the aforementioned ridge will build eastward over the TN Valley
today, continuing the warming trend and dry conditions over
central. Some CAMs suggest convection over the higher terrain
will progress southeast into the Piedmont late this afternoon,
but limited moisture and instability will make it hard for much
more than an isolated storm to reach the northwest Piedmont. Highs
The surface ridge axis will shift east tonight, favoring a little
better cooling over the coastal plain, with lows ranging from the
upper 60s to around 70 east to west.
.SHORT TERM / FRIDAY THROUGH FRIDAY NIGHT/...
As of 345 AM Thursday...
The center of the upper ridge -forecast at 594dm- will shift
east and be centered over southwest VA on Friday, bringing the
850mb thermal ridge across northwest NC and southern VA. 850mb
temps around 21C favor highs in the upper 90s, and while mixing
may not be quite that deep, highs should be on the upper end of
guidance, 93-96. dew points creeping back into the lower 70s area
while will spell a return of humid conditions and heat indices
back around 100F. A weakening cold front is forecast to drop into
VA Friday evening, but ahead of the front lows on Friday night
will be in the lower 70s for most areas.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 240 PM Wednesday...
Fri-Sun: Quite warm to start this period, followed by moderating
temps, and very low precip chances throughout. Strong mid level
ridging will remain the dominant weather feature heading into the
weekend, with its center drifting slowly from the western Carolinas
early Fri ENE to over eastern VA/NE NC by Sun, all the while
maintaining dry and stable mid-upper levels over our area. A surface
cold front approaching from the NW Fri will drop into and through NC
over the weekend, causing a dip in thicknesses from much above
normal Fri/Sat to near or just slightly above normal starting Sun.
With a weakening low level wind field and no opportunity for
moisture influx at any level, any convection ahead of or with the
front will be feeble and very isolated, likely limited to a few
cells drifting slowly off the higher terrain (extreme NW CWA) and
along an inland-drifting sea breeze (far SE CWA) late in the day
Fri, with perhaps a bit better (but still low) coverage Sat
afternoon over the southwest CWA near weak upglide and low level
mass convergence near the Piedmont trough. The front settles to our
south Sun with a high pressure ridge centered off New England nosing
narrowly to the SW through central NC, supporting a drop in max
temps from the mid 90s Fri/Sat to around 90 or the lower 90s
Mon-Wed: Starting Mon, the mid level ridge weakens and flattens yet
continues to extend W-E across the region. Low level flow from the
east or ENE may be sufficiently strong and onshore-directed to boost
low level moisture profiles and increase diurnal sea-breeze
convection chances in the SE CWA on Mon, although the limited deep
moisture should keep coverage low. Models still vary quite a bit
with the tropical wave now over the northern Leeward Islands which
may be driven toward the WNW by the mid level ridge and may affect a
portion of FL and/or the Gulf Coast by early to mid week. Model
solutions continue to range widely, with the GFS remaining weak with
an erratic motion and the so-far-strongest ECMWF solution showing a
slowing trend with the 12z/24 run, which all results in reduced
confidence in any details this far out. At the very least, the
increasing easterly low-mid level component should draw increasing
amounts of Atlantic moisture into the eastern Carolinas, and we
should see an increase in daily showers and a few storms mainly east
as we head into midweek. We will, of course, continue to monitor the
tropical wave, although by all accounts it will not be a direct
factor in our weather through at least Wed. With thicknesses holding
a bit above normal, temps are expected to peak around 90 to the
lower 90s Mon-Wed, with lows mostly in the lower 70s. -GIH
.AVIATION /07Z THURSDAY THROUGH MONDAY/...
As of 145 AM Thursday...
High confidence in predominately VFR conditions through the TAF
period, as strong high pressure remains in control of the region.
As was the last last night, there will likely be a period of IFR
or LIFR vsby after 08z at RWI, with MVFR vsbys more likely at RDU
AND FAY. Confidence is much higher at RWI. All terminals will
return to VFR by around 12z.
Outlook: Persistence of high pressure over the region will
continue to promote VFR conditions, with early morning fog
possible each morning.