Area Forecast Discussion
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FXUS62 KRAH 261931
Area Forecast Discussion
National Weather Service Raleigh NC
330 PM EDT TUE JUL 26 2016
Strong high pressure aloft will extend over the Southeast U.S.
through the work week, as weak disturbances pass by just north of
the region. A cold front will approach from the northwest on Friday,
then stall out just to our north and west next weekend.
.NEAR TERM /THROUGH TONIGHT/...
As of 330 PM Tuesday...
Scattered showers and storms have already begun to fire over the
mountains, foothills, and into the northern and western Piedmont,
where CINH has vanished and MLCAPE has already risen well over 2000
J/kg. Deep layer bulk shear still isn`t great but is better than in
the last several days, as shortwave energy tracks eastward across
the OH valley and mid-Atlantic, nudging the westerlies slightly to
the south and inducing sufficient acceleration aloft to boost values
to around 20 kts across northern NC this evening. Have retained
isolated to scattered showers and storms through the evening,
starting first over the Piedmont (better coverage north and fewer
storms south), then shifting eastward into the NE Piedmont and
northern/central Coastal Plain through the evening before weakening
and dissipating with loss of heating overnight. This scenario is
supported by the latest CAM runs. A few storms could become strong,
given the degree of instability, improving wind field aloft, and
high downdraft CAPE over 1000 J/kg, but the mid level lapse rates
remain meager with no good low level mass convergence, so widespread
strong storms aren`t expected. Persistence will be followed for lows
tonight, in the lower to mid 70s. Temps over much of the CWA won`t
drop below 80 until well after midnight, exacerbating the adverse
health effects of this ongoing hot spell. -GIH
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 325 AM TUESDAY...
Persistent mid/upper level ridge located just to the south/southeast
of central NC will continue to provide the region with hot and humid
conditions with another day of highs in the mid to upper 90s and
heat index values in the 100-107 degree range (highest east and
south again). Thus, another heat advisory will likely be needed
again on Wednesday afternoon/evening. With a similar pattern to
today, we will again see the best chance of scattered showers and
storms across the northern half of the area, with less across the
south (closer to the center of the ridge). Deep layer shear is a bit
stronger with around 20-25 KTS of 500 MB westerly flow. Thus, think
we could see a few more clusters of storms across northern portions
of the area. In addition a weak cold front will stall across
southern VA on Wednesday afternoon, helping to increase coverage near
the VA/NC border as well.
More of the same is expected on Wednesday night, with warm lows in
the mid to upper 70s and generally dry conditions. However, as will
be the case tonight, we can`t completely rule out isolated
showers/storms associated with possible weak disturbance(s) tracking
across northern portions of the area. Confidence is too low to
include any mention of precip in the forecast at this time though.
.LONG TERM /Thursday through Tuesday/...
As of 230 PM Tuesday...
Beginning Thursday, the high pressure system gets suppressed ever so
slightly to the southeast and allows the remnants of the frontal
boundary over VA to creep southward, increasing pops a bit for the
northern tier of the CWA but otherwise points south should remain
fairly dry but afternoon showers and thunderstorms will be favorable
east of the Piedmont trough. Thursday night a wave is expected to
develop just north of the area and move northeastward leaving Friday
fairly dry. Afternoon convection will be possible again Friday and
Saturday afternoons as the upper level flow turns more
southwesterly. By Sunday, central NC becomes increasingly squeezed
between a surface high to our southeast and another to our
northwest. This will set up a more active pattern over the area
which will funnel moisture into the area. This should help keep
skies cloudier and bring temps down a few degrees for the beginning
of next week. Early next week an upper trough develops to help push
the frontal boundary through the area and hopefully provide some
relief to temperatures. Until then expect continued highs in the mid
90s with heat index values approaching 105 degrees.
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
As of 100 PM Tuesday...
VFR conditions are likely to dominate through Wed afternoon,
although scattered storms may produce localized enhanced wind gusts
and brief sub-VFR conditions late today through this evening, mainly
at INT/GSO/RDU/RWI. Strong, dry, and deep ridge of high pressure in
the middle and upper levels of the atmosphere will hold overhead for
the 24 hours and beyond. Any cloudiness will be VFR, mostly
scattered except for a period of broken clouds late today into
tonight at INT/GSO/RDU/RWI, as well as in/near any storms. Light fog
(MVFR) is possible late tonight into Wed morning, mainly at RWI/FAY,
and isolated banks of shallow, more dense fog may occur, mainly near
RWI. The overall threat of sub-VFR fog is low, but places that see a
shower or storm later today will have a better chance of seeing fog
late tonight into Wed morning. Surface winds will be light from the
southwest at 6-10 kts through Wed.
Looking beyond 18z Wed: Mostly VFR conditions are anticipated,
although late night and early morning MVFR fog is possible each day
through Fri, with a better chance of sub-VFR fog/stratus Sat/Sun.
Scattered showers/storms are again expected Wed afternoon, mainly at
the northern TAF sites. Storm chances will drop once again for Thu
and Fri, before rising again over the weekend. -GIH
Heat Advisory from noon today to 8 PM EDT this evening for