Scientific Forecaster Discussion
fxus62 krah 201329
Area forecast discussion
National Weather Service Raleigh NC
929 am EDT Wed Sep 20 2017
a weak upper level trough will move into central NC later today,
then drift sewd through Thursday. Otherwise, an upper level high
over the Ohio Valley and tropical cyclone Jose meandering off the
southern New England coast will result in warm and dry conditions
across central NC through the rest of the week.
Near term /through tonight/...
as of 929 am Wednesday...
An upper level disturbance that can be seen dropping sewd into the
southern Appalachians, will drift slowly over central NC later today
and tonight. This system interacting with a slightly unstable air
mass owing to favored diurnal timing and resultant steep low-level
lapse rates, will trigger a few showers and garden variety T-storms
late today into the evening hours.
High temperatures today will average a solid 5-8 degrees above
normal, ranging from upper 80s across the northwest Piedmont to lower 90s
across the Sandhill and southern coastal plain. For areas that hit
the 90 degree mark, this would mark the end to a 2-week sub 90
Convection will be largely diurnally driven, so expect coverage to
diminish during the evening. However, with the upper disturbance(s)
drifting slowly east-southeast across the forecast area, can't rule out a stray
shower. Min temps in the mid-upper 60s.
Short term /Thursday and Thursday night/...
as of 310 am Wednesday...
Thursday and Thursday night, our stretch of warm temperatures will
continue, with afternoon highs in the 85-90 degree range. The
heating of the marginally moist and slightly unstable air mass will
support the development of scattered showers and storms, primarily
across the sandhills into the southern coastal plain. Bulk of the
convection will dissipate with loss of heating though isolated
showers/storms still possible through midnight near the South
Long term /Friday through Tuesday/...
as of 230 am Wednesday...
Central NC will generally be under the influence of high pressure
through much of the extended forecast period, resulting in a
predominantly dry forecast. However, a weak trough over the region
could result in some showers on Friday, primarily in the southwest,
but chances are no more than slight. Also, expect skies to be mostly
sunny/partly cloudy through the weekend with highs in the mid to
upper 80s and lows in the low to mid 60s. The forecast for Sunday
Onward remains somewhat uncertain, but the medium-range models are
starting to trend closer to one another. The forecast will still
depend on the track of Maria, which will depend on what happens with
Jose. As a result, still have below average confidence in the
forecast for Monday and Tuesday.
Jose is still progged to meander off the NE U.S. Coast through the
weekend. Meanwhile, Maria will be moving through the Caribbean,
northwestward toward the Continental U.S.. as mentioned above, Maria's impacts
from Sunday Onward are still highly uncertain as they will depend
heavily on Jose and if/how the two systems interact with one
another. For now, expect increasing cloud cover across eastern
portions of central NC Monday and Tuesday. Depending on if Jose
comes back inland over Virginia and how close Maria gets to the NC coast
will determine the strength of the winds and chances for convection
Monday and Tuesday. Too much uncertainty still exists to speculate
on either at this time.
Aviation /12z Wednesday through Sunday/...
as of 735 am Wednesday...
VFR parameters are generally expected across central NC through
Sunday with a few exceptions.
Early this morning, pockets of MVFR visibility are probable through
13z. After 18z, a few showers and an isolated thunderstorm may
develop as an upper disturbance approaches from the west. The threat
for scattered convection will persist into the evening hours,
primarily in vicinity of kfay. In proximity of the heavier showers
and storms, expect brief instances of MVFR ceilings and
visibilities. On Thursday, there is a small threat for a shower or
storm near or south of kfay. Otherwise VFR parameters should persist
at the taf sites Thursday through the weekend.