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Area forecast discussion 
National Weather Service Greenville-Spartanburg SC
653 am EDT Wednesday Jul 23 2014

Synopsis...
weak high pressure across the area today will move away tonight. A
surface front will approach from the northwest tonight and is
expected to move across the Carolinas and north Georgia Thursday
afternoon and evening. High pressure will build in behind the front
for Friday and the weekend. Another front is expected to pass on
Monday.

&&

Near term /through tonight/...
as of 6 am...latest 11u-3.9u satellite images indicated an expanding
area of low clouds across the Piedmont and west to the southern NC
foothills. Surface observations show a wide range of
visibilities...ranging from m1/4sm at kmrn to 10sm across the
Greenville/Spartanburg/Anderson areas. The lowest visibilities are
generally across the I-77 corridor and within the mountain valleys. All
preferred guidance indicates that the fog will dissipate during the
two hours following sunrise. I will update the forecast to adjust
fog and visibilities to the latest observations and thinking. In
addition...latest MOS has trended warmer for this afternoon...I will
warm forecast highs a click. Otherwise...the current forecast is in
good shape.

As of 320 am...early morning fog is expected to develop and expand
across the I-77 corrdior and within the mountain valleys. The hrrr
condensation pressure deficits indicates that the lowest values
will exist across the southeastern half of the Charlotte metropolitan areas
and within the mountain valleys. Fog should dissipate during the first
two hours of sunlight. In addition...early mixing should yield a
light southwest wind. Greater insolation and southwest winds should
result in steadily warming temperatures from sunrise to middle
afternoon. I will forecast highs to range from the l80s within the
mountains valleys to u80s to near 90 east of I-85.

Recent west/v loop indicated that the middle level low was drifting west
across the Mississippi River Delta...as another trough will digging
over the Ohio River valley. At the surface...a weak Lee trough may
develop across the Piedmont during the afternoon. A cold front will
approach from the northwest today...reaching the southern Appalachians late
tonight. Cams indicate that rain showers and thunderstorms and rain will favor the mountains and
adjacent foothills as early as middle morning today. Coverage will
increase through the heat of the afternoon...becoming scattered across the
Piedmont. Convection should generally dissipate east of the mountains one
to two hours after sunset. However...I will maintain chance to likely
probability of precipitation across the Tennessee border counties to cover the arrival of pre
frontal convection. Low temperatures tonight are forecast to range
from the middle 60s across the mountains to low 70s east.

&&

Short term /Thursday through Friday night/...
as of 230 am EDT Wednesday...the model guidance has come into better
agreement with the passage of a surface front more or less during
peak heating on Thursday. The front will be driven across the forecast
area by a fairly strong short wave in the presence of some upper
divergence in the entrance region of the jet over the northeast.
Plenty of low level moisture will remain ahead of the front as well.
Thus...with the timing a bit more in focus...feel it appropriate to
bump the precipitation probability up into the likely range across the
entire forecast area in the afternoon. Might be a bit too early to talk
too much about severe weather potential...but the front should focus
storms in an air mass with 1500-2500 j/kg of cape...so the day2
outlook seems appropriate. Suspect we will have to contend with
several severe thunderstorms. The front will drop southeast during the
evening hours ending the precipitation chance by the early morning hours on
Friday.

Behind the front...the air mass will not really be much cooler...but
it should be a bit drier on Friday. High pressure should move in
during the day. Not really seeing much to support any showers in the
afternoon so the precipitation chances were lowered. Friday night should be
dry as well with seasonal temperatures.

&&

Long term /Saturday through Tuesday/...
as of 315 am Wednesday...still expecting the mean upper trough over
the east to fill over the weekend as a short wave ridge moves
through. This will support weak high pressure for Saturday and into
Sunday. Think convection will be limited to the ridgetops Saturday
afternoon and have cut back the already meager pop a bit more.
Earlier runs of the models showed the potential for upstream mesoscale convective system
development on Saturday night...and that could still happen...but
the main focus looks like it will be more like the Ohio Valley and
central Appalachians. So...Saturday night was kept dry across the
mountains as well. Expect more of a return to diurnal thunderstorms
for Sunday. Another in a series of fairly strong short waves will
once again carve out an upper trough over the east early next week. It
still looks like this wave will drive another cold front over the
region on Monday. Unlike the earlier front...this one should usher
in a noticeably different air mass for next Tuesday as a cool
Continental high moves down over the northern plains...then modifies and
builds in from the west. That should drop temperatures a category or more
below normal.

&&

Aviation /12z Wednesday through Sunday/...
at kclt and elsewhere...latest 11u-3.9u satellite images indicated an
expanding area of low clouds across the Piedmont and west to the
southern NC foothills. Surface observations show a wide range of
visibilities...ranging from m1/4sm at kavl/kmrn to 10sm across the
Greenville/Spartanburg/Anderson areas. The lowest visibilities are
generally across the I-77 corridor and within the mountain valleys. All
preferred guidance indicates that the fog will dissipate during the
two hours following sunrise this morning. By 14z...SW winds should
develop with VFR cloud cover. Scattered Piedmont coverage of late
afternoon thunderstorms and rain are possible 18z to 24z. Thunderstorms and rain coverage will be
significantly greater across the mountains...highlighted with a tempo
18z-21z. Another round of LIFR fog/ceilings are possible across the mountains
late tonight...patchy MVFR over wet ground east.

Outlook... showers and thunderstorms Thursday with the passage of a
cold front. Scattered showers and thunderstorms mainly during the
afternoons and evenings through the end of the week.

Confidence table...

11-17z 17-23z 23-05z 05-11z
kclt high 86% high 100% high 100% high 100%
kgsp high 95% high 100% high 100% high 100%
kavl medium 62% high 99% high 91% medium 77%
khky high 85% high 100% high 100% high 100%
kgmu high 81% high 99% high 100% high 100%
kand high 88% 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: (must be lower case)

Www.Weather.Gov/gsp/aviation_tables

&&

Gsp watches/warnings/advisories...
Georgia...none.
NC...none.
SC...none.

&&

$$
Synopsis...PM
near term...Ned
short term...PM
long term...PM
aviation...Ned

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