Scientific Forecaster Discussion
fxus62 krah 202338
Area forecast discussion
National Weather Service Raleigh NC
735 PM EDT Wed Jun 20 2018
an upper level disturbance will move east across the central
Appalachians and Middle Atlantic States through tonight. A surface
trough will linger over NC, ahead of a back-door cold front that
will drift southward and stall near the Virginia and NC border late
Thursday through Friday.
Near term /through tonight/...
as of 735 PM Wednesday...
Heat advisory through 800 PM...
The isolated pulse severe thunderstorms are weakening over central
NC as of 735 PM. There were numerous outflow boundaries over the the
region; however the latest meso-analysis indicated the northern
Piedmont east to the sounds and Outer Banks is the most unstable
area this evening. We will have to watch this region and the
isolated storms over the SW Piedmont near Badin and High Point for
development. Otherwise, hot and humid with a 20-30 percent chance of
thunderstorms. Lows in the 70s.
Short term /Thursday and Thursday night/...
as of 410 PM Wednesday...
A mid-upr level low over the nrn/cntl plains will amplify across the
mid MS valley by 12z Fri. Preceding, and influenced by that low, a
portion of a mid level low over srn Texas will eject/shear shear newd
across the Tennessee Valley Thu, and srn and cntl Appalachians/Carolinas
Thu night. A preceding shortwave ridge aloft will build/extend
across the Carolinas for much of the day Thu.
The models suggest the pre-frontal trough will redevelop over nrn-
cntl NC on Thu, while the synoptic frontal zone settles slowly swd,
and reaches the vicinity of the NC/Virginia border Thu night.
The presence and influence of the aforementioned ridge aloft will
likely limit convective coverage in the warm sector, with scattered
development focused over nrn NC and srn VA, then continuing in those
areas through at least early Thu night. It will also be hot once
again in the warm sector, with temperatures mostly in the lwr to mid
90s, with a few upr 90s possible over the sandhills and srn coastal
plain. When combined with dewpoints in the upr 60s to lwr 70s, heat
index values are expected to range between 100 and 105 degrees from
afp to rdu to rwi, and points ewd. While these values are short of
the 105 degree criteria for two or more hours for a heat advisory,
local policy allows (re-issuance) of an advisory for three or more
consecutive days of 102-105 degree heat index values. This criteria
will likely be met in the current advisory area, so another heat
advisory may be issued for those rah counties for Thu. Lows, again
mostly in the lwr 70s, with some Post-frontal stratus over the nrn
Long term /Friday through Wednesday/...
as of 230 PM Wednesday...
A frontal boundary will be lifting north out of the area early
Friday as a closed low over the Ohio Valley edges slowly east before
lifting northeast into the Great Lakes Friday night. Showers and
storms should be ongoing at the onset of the extended period, with
likely chances on Friday on Friday, especially across the north
nearer the frontal zone. Highs will vary from the mid 80s across the
northern tier counties to the lower 90s in the south.
Storm chances will decrease on Saturday and Sunday with weak forcing
in a warm advection regime as a westerly-flow induced Lee trof sets
up over the area through the weekend. Highs will be in the low to
mid 90s with climatological 30-ish pops tied to the diurnal cycle.
A front will be approaching on Monday, increasing the chance of
convection Monday afternoon into Monday night as highs again reach
low and mid 90s. Cooler and drier high pressure will build in behind
this front, and the coolness looks to linger into Wednesday to keep
highs nearer normal, mostly upper 80s with small chances of diurnal
Aviation /19z Wednesday through Monday/...
as of 300 PM Wednesday...
Mainly VFR. Scattered thunderstorms, some in clusters with strong
wind gusts, will move generally ewd across cntl NC through 22-00z.
Patchy stratus and fog will be possible late tonight-early Thu,
mainly at Fay, where low level moisture and convergence are likely
to be maximized.
Scattered showers and storms are expected to develop once again
along a pre-frontal surface trough and then back-door cold front,
both focused near the Virginia border, Thu aft, then continue into the
early nighttime hours Thu night. The greatest concentration of
convection is consequently likely to occur from near and north of
the Piedmont sites, ewd to rwi. IFR-MVFR conditions will develop on
the cool side of that front, over nrn and nern NC and va; and some
of these conditions may edge as far swd as rwi Fri morning.
Outlook: mainly VFR.
Max temperature and high-minimum temperature records...
day maximum yr min yr
06/21 100 1933 75 1924
06/22 100 1914 75 1981
day maximum yr min yr
06/21 101 1933 75 1933
06/22 100 1981 78 1933
day maximum yr min yr
06/21 105 1933 84 1928
06/22 101 1990 84 1928
heat advisory from 11 am to 8 PM EDT Wednesday for ncz041>043-