Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
1044 am EDT Tuesday Aug 4 2015
dry high pressure will weaken today as a weak cold front drops south
toward our region. Low level moisture will gradually return through
the work week as this cold front approaches from the area from the
Near term /through tonight/...
as of 1030 am EDT...there remains little to no convective activity
along the frontal zone draped to the north this morning...but recent
hrrr runs still feature convection forming mainly along the northern Blue
Ridge and expanding eastward across the NC Piedmont through late
day. Will continue to shade probability of precipitation below MOS and cam guidance since
the profiles remain fairly dry. Morning sbcapes on the laps analysis
are already showing some 1200 to 2500 j/kg values...but these may
drop a touch in the afternoon with dewpoints mixing into the lower
60s in many areas. The potential for strong thunderstorms appears limited
with persistent negative energy areas in the profiles this afternoon. The
maximum temperature forecast appears on track through middle morning...with heat
index values capped below 100 given the expected dewpoint mixing.
Otherwise...the broad trough extending from eastern Canada through the southeast
United States will continue to lift today with heights rising and
flow becoming more westerly. At the surface...a low pressure center will move
NE along a frontal boundary near the southeastern coast. Moisture and
forcing associated with this low will remain well to our east...with
a cold front dropping south toward the area having a greater effect
on our sensible weather. 850 to 500 mb lapse rates should steepen to 6.5
degree c or better. The low level convergence associated with the front
could be enough to act on the developing instability to create
isolated to scattered diurnal convection across the mountains the westerly flow
could drive any convection eastward over the NC Piedmont through
late day. Have gone isolated there...with a continued dry forecast
across the upstate and NE Georgia. Convection should diminish during the
evening...but more mesoscale convective system activity could drop toward the mountains again
overnight. However...chance too low to include at this time. Lows tonight will
be up to 5 degrees above normal.
Short term /Wednesday through Thursday night/...
at 230 am EDT Tuesday...on Wednesday morning an upper trough will be
over The Rockies...and and upper trough east of the MS river. The
pattern largely deamplifies by Thursday. A well defined shortwave is
expected to approach the southern Appalachians on Thursday...
crossing the area on Thursday night.
At the surface...a cold front will stall over our area on
Wednesday...while moisture from the Gulf of Mexico moves north
toward the boundary. The models even show a weak low spinning up
along the front near the eastern portion of our area. The models
disagree on how much instability will be present near the
front...but agree on increasing moisture. Although precipitation
coverage is expected to increase...low level flow will generally be
southwesterly...limiting upslope flow into high terrain.
Temperatures will run above normal.
Long term /Friday through Monday/...
at 230 am EDT Tuesday...on Friday morning a low amplitude upper
ridge will be over the plains...and a trough will be over the east.
This pattern slowly progresses such that the trough moves off the
East Coast on Saturday. The upper ridge amplifies over the center of
the nation on Sunday...and builds east across the Gulf states. The
upper trough persist just off the East Coast through Monday.
At the surface...a nearly stationary front will be in our vicinity
on Friday...and moves slowly south into Saturday. This system will
serve as a focusing mechanism for precipitation as moisture spreads
east along it...and model sounding show enough instability to support
convection. The boundary is expected to stall well to our south by
Sunday...while another front approaches from the northwest. The second front
is expected to stall near the coast on Monday...with ostensibly drier
air arriving in its wake. Temperatures will run near normal.
Aviation /15z Tuesday through Saturday/...
at kclt...VFR will continue with any morning stratus layer lifting
and scattering well to the east. Winds remain the primary concern
through the day...with circulation around the coastal low providing
more of a northwest surface component which should persist through the
afternoon hours. Any isolated to scattered convective triggering
along the Blue Ridge is expected to remain mainly north of the
airfield this afternoon/evening. Winds will become variable tonight.
No overnight restrictions will be featured...but once again low
stratus to the east could develop in the nearby Piedmont.
Elsewhere...expect VFR through the period at all locations.
Kavl/khky have the best chance of seeing any convection this
afternoon...but the chances are too low to include in the tafs at this time.
Otherwise...expect developing cumulus through the day with broken cirrus. Light
S to SW winds expected through the day with near calm winds overnight.
Kavl is the exception with northwest winds. Anticipate little to no chance of
Outlook...gradually increasing precipitation/restriction chances are
expected through the week as moisture returns and a front stalls in
our vicinity...with a disturbance then moving along it.
14-20z 20-02z 02-08z 08-12z
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% medium 66%
khky high 100% high 100% high 100% high 95%
kgmu high 100% high 100% high 100% high 100%
kand high 98% 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)