Scientific Forecaster Discussion
fxus62 kgsp 251856
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
256 PM EDT Thu may 25 2017
a large low pressure system will lift northeast of the area tonight
allowing drier air to overspread the region and linger into early
Saturday. Moisture and unstable conditions will return to the region
over the weekend, ahead of a slow moving cold front.
Near term /through Friday/...
as of 250 PM EDT thursday: for the rest of the afternoon,
cannot rule out a few additional showers and storms, mainly over
the wrn Piedmont of the Carolinas, as cold air aloft continues
to provide for some limited sfc-based cape. Some of the stronger
cores could have small hail, as we have seen earlier. Other
showery elements may move down across the nrn mtns and nrn
foothills as they rotate around the upper low, seen in the water
vapor imagery moving into WV. Temps should remain seasonally
Over the next 24 hours, our weather should continue to unwind. The
upper low will move past across the mid-Atlantic region tonight.
Additional low level moisture and some light precip will come down
across the northern part of the fcst area, with the northwest flow forcing
additional showers along the Tennessee border into the evening hours. The
model guidance shows this gradually drying up, with precip ending by
around midnight. There is some concern for strong wind gusts across
the higher terrain as the guidance shows greater than 50kt flow at
850 mb coming around the bottom of the upper trof tonight. However,
the boundary layer remains shallow, and then decouples and keeps
that stronger flow from reaching the sfc in model fcst soundings.
Low temps will be below normal tonight, but not exceptionally cold.
On Friday, the cyclonic flow aloft will gradually be replaced by a
flat upper ridge building in from the west. This ridge will support
weak high pressure moving over the southeast. Sunny sky should
prevail that will result in a very nice and dry late Spring day with
high temps just above normal.
Short term /Friday night through Sunday/...
as of 250 PM Thu: zonal mid level flow will be in place across
the region through this period. Low level moistening will be
occurring on Friday night and Saturday. A frontal system will
move into the Tennessee vally on Saturday allowing some shower
and thunderstorm activity to move into the mountains Saturday
afternoon and Saturday night. Another round of storms should
impact most of the forecast area Sunday afternoon.
Instability will be rather high on both Saturday and Sunday
afternoons. Some storms could be rather strong especially if they
are able to organize in the westerly flow.
Long term /Sunday night through Thursday/...
as of 250 PM EDT thursday: the extended fcst picks up at 00z on
Monday with flat upper ridging over the southeast and another
broad upper trof digging down over the western Great Lakes. The
trof is slow to move eastward and is not expected to move over
the fcst area until late tues into early Wed. The long range
models have the trof axis centered to our north by Wed, however
most of the energy associated with the trof remains to our
north. As we move into Thursday, the trof lifts farther NE and
heights begin to rise a bit. At the sfc, a cold front will move
thru the County warning forecast area on Monday and stall out just to our southeast by early
tues. The front lingers over the region until another, more
robust cold front pushes thru the fcst area on Wed into early
thurs. As for the sensible fcst, no significant changes were
necessary. We still have solid chances for convection on Monday,
and slight to solid chances on Tuesday thru Thursday with the
highest pops generally over the higher terrain. Temps will start
out just above climatology and cool on Tuesday to right around
normal. They are expected to remain near normal for the rest of
Aviation /19z Thursday through Tuesday/...
at kclt and elsewhere: VFR through the period. Scattered/broken clouds
continue to develop generally with bases in the 040-050 range as
colder air aloft moves overhead. Think scattered will prevail with
temporary broken conditions. A few showers may develop, more likely
over the mtns near the Tennessee border, and over the wrn Piedmont of NC.
Have included a tempo at kclt for MVFR in passing showers through
22z. The clouds should diminish in coverage with loss of heating,
and any remaining showers after sunset should be confined to the Tennessee
border area. Wind will remain west-southwest with occasional gusts through
sunset, then diminishing overnight as the boundary layer decouples
and weak high pressure ridges up from the S. On Friday, only sct
cirrus. Wind will be SW or west-southwest again outside the mtns, with
occasional gusts beginning midday as the boundary layer deepens
again with heating.
Outlook: continued VFR Friday afternoon and night, and into the day
on Saturday. Thunderstorms and associated restrictions may develop
across NC Saturday afternoon, but will be more likely Sunday.
19-01z 01-07z 07-13z 13-18z
kclt high 100% high 100% high 100% high 100%
kgsp high 100% high 100% high 100% high 100%
kavl high 100% high 100% high 100% high 100%
khky high 100% high 100% high 100% high 100%
kgmu high 100% high 100% high 100% high 100%
kand high 100% high 100% high 100% high 100%
The percentage reflects the number of guidance members agreeing
with the scheduled taf issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link: