Area Forecast Discussion
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FXUS62 KRAH 230651
Area Forecast Discussion
National Weather Service Raleigh NC
251 AM EDT SAT JUL 23 2016
An area of high pressure aloft will expand from the central U.S.
across the mid-Atlantic states and Carolinas through early next
week. This will bring a period of hot temperatures to central NC.
.Near Term /Overnight/...
As of 720 pm Friday...
Central NC lies on the eastern periphery of a deep upper level ridge
(centered over the lower Midwest) and on the western periphery of an
upper level trough stalled offshore the Southeast coast. Similar to
yesterday, diurnal destabilization this afternoon has been strongest
in the W/SW Piedmont (1000-2000 J/kg MLCAPE) and weakest (500-1000
J/kg MLCAPE) in eastern/coastal NC where subsidence prevails on the
backside of the upper level trough stalled offshore. Small amplitude
disturbances /DPVA/ rounding the NE periphery of the 300 mb ridge
over the central Appalachians could track into western NC this
eve/tonight, however, the `sphere of influence` of such disturbances
should remain west of central NC as they track S/SSW along the
eastern periphery of the H3 ridge. As a result, forcing for ascent
this evening will be confined to shallow convergence attendant a
weak Piedmont trough and convective outflow. With the above in mind,
expect scattered convection to largely remain confined along/west of
Highway 1 and to gradually weaken/dissipate within a few hours after
the loss of heating/insolation. Expect lows generally in the lower
70s, though a few rural/low-lying areas in the N/NW Piedmont may
fall as low as 68-70F. -Vincent
.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
As of 345 PM Friday...
The environment on Saturday should be similar to today, although PW
values are expected to rise steadily, with thicknesses continuing to
climb. We`ll also be on the anticyclonic side of MCVs dropping
southward through the southern Appalachians, with no other dynamic
forcing mechanisms evident. So we`ll be relying on purely
thermodynamic lift, it appears, focused on differential heating in
the higher terrain as well as subtle boundaries, a few of which may
be leftover from the current convection over western NC. Will expand
the low shower/storm chances a bit from today`s pops, but still
expect coverage and upscale growth to be limited by warm and
somewhat dry mid levels. Thicknesses and new guidance indicate highs
of 94-98, and with dewpoints dropping no further than around 70 over
much of the area, heat index values should peak in the 99-104 range
for a couple of hours. This is below advisory criteria, so will
stick with a mention in the HWO for now, but this will certainly be
revisited tonight. Lows Sat night in the low-mid 70s, not allowing
much recovery from the heat stress. -GIH
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 245 AM Saturday...
Additional s/w energy is expected to track across
Southern/Southeastern Canada and the Great Lakes and Northeast U.S.
next week, which will allow a weak cold front to approach the region
(likely stalling to the north of the area though). This will allow
the mid level ridge to dampen across our region early next week and
relocated to the south and southeast of central NC. This should
place central NC on the southern fridge off potential disturbances
tracking atop/around the ridge, which should lead to a better chance
of mostly diurnal scattered showers and storms each
afternoon/evening. Given the predictability of such hard to time
features this far out in the forecast, will go with around 30-35
percent chance for showers and storms each day (generally climo).
This additional associated cloud cover is expected to lead to temps
a bit cooler, though highs are still expected to at least be in the
lower to mid 90s.
.Aviation /06Z Saturday through Wednesday/...
As of 140 AM Saturday...
VFR conditions expected to prevail across central NC through Monday
as an area of high pressure aloft builds over the region. While
isolated thunderstorms will be possible each late afternoon-early
evening through Monday, probability of convection affecting a
specific TAF site is too low to mention in the terminal forecast at
this time. Patchy MVFR fog will be possible early each morning,
primarily between the hours of 10Z-12Z.
While VFR conditions will likely dominate through Wednesday, there
will be periods of MVFR conditions associated with either early
morning fog, or late afternoon/early evening convection.
Record high temperatures and the year in which the record was most
recently set at Raleigh, Greensboro, and Fayetteville.
Sat Jul 23 Sun Jul 24 Mon Jul 25
RDU 105/1952 101/2011 102/2010
GSO 99/1952 99/1914 101/1914
FAY 103/2011 105/1952 103/1914