Area forecast discussion
National Weather Service Greenville-Spartanburg SC
422 PM EDT Wednesday Jun 19 2013
Synopsis...
cooler high pressure centered near New York state will ridge
southward tonight and Thursday. This high will drift to near Bermuda
and into next week as an upper ridge builds in from the west as
temperatures slowly rise.
&&
Near term /through Thursday/...
2030 UTC update...probability of precipitation were adjusted in the the northern NC
mountains and the upper Savannah River valley the latest per radar
trends.
As of 215 PM...a weak short wave trough is forecast to move through
the area from northwest to southeast late this afternoon and early tonight. The
best forcing will be over the far eastern areas. Hence...the models
show some light quantitative precipitation forecast response there. The latest hrrr shows the most
shower coverage from the northern mountains...east through the
northern NC Piedmont. Will make a last minute adjustment on the pop
field to reflect that idea. Widely scattered showers/thunderstorms are
expected elsewhere through the mountains during the middle to late
afternoon hours due to weak upslope flow. Convective available potential energy should generally
stay below 1000j as somewhat lower dewpoints continue to advect into
the region...so no severe threat. The showers are expected to
dissipate during evening.
Otherwise...the overnight should be quiet. Model time heights Show
Low level moisture increasing toward sunrise as moisture from
Atlantic advects into the area. Therefore...expect a period of low
cloudiness early Thursday...especially east of I-26. On Thursday...high
pressure located off the New England coast will remain ridged into
the area producing an easterly wind flow in the southern
Appalachians. The upslope flow in the mountains should produce
scattered showers and thunderstorms during the afternoon hours.
Using a blend of models produces maximum temperatures about a category below
average on Thursday.
&&
Short term /Thursday night through Saturday/...
as of 210 PM EDT Wednesday...short range models agree that the region will
remain under a weak middle level trough...with ridging across the
Southern Plains and Atlantic. At the surface...a stationary front and
possible frontal wave will remain across the coastal plain of the
Carolinas. Weak surface ridging may remain across the southern
appalachian region. Given the surface pattern...I will indicate
persistent NE winds across the foothills and Piedmont for Friday and
Saturday. A blend of model guidance indicates that sky cover will
remain partly to mostly cloudy through the period. The combination
of NE winds and cloud cover should yield temperatures 3 to 5 degrees
below normal. Overall...the chances of rain showers and thunderstorms and rain appears
unfavorable within the corridor of deep NE flow. In fact...model
cape fields indicate little to no values for surface based parcels
between the east facing mountain slopes to the western Piedmont. I will
indicate schc probability of precipitation for ts across the extreme western NC mountains on Friday
and Sat. By Sat...low level winds may veer NE...possibly allowing weak
instability across NE Georgia and the eastern Piedmont during the late
afternoon.
&&
Long term /Saturday night through Wednesday/...
as of 240 PM EDT Wednesday...a 591 dm 500 mb ridge will remain dominant over
the southeast through the medium range period. Anticipate a mainly diurnal
trend of isolated to scattered afternoon probability of precipitation through the period...with
the mountains being the primary focus. The GFS is the most aggressive in
bringing an inverted coastal trough back inland along the Savannah
on Saturday...but the other operational and ensemble mean solutions
keep the system along the immediate coast with the ridge persisting
over the western Carolinas. The diurnal pattern of isolated to scattered showers
and thunderstorms should thus continue sun through Tuesday...with
temperatures steadily warming under the upper ridge. Expect maxes to
reach climate normals by Sunday and then exceed them Monday and Tuesday.
The upper ridge will break down in middle week as a upper trough forms
over the East Coast for the second half of next week. The GFS is a
bit more progressive in bringing the trough in sooner by late Wednesday or
Wednesday night as opposed to Thursday or Friday on the European model (ecmwf). Temperatures are expected
to cool some as this trough sets up with more clouds and higher probability of precipitation.
&&
Aviation /21z Wednesday through Monday/...
at kclt...sct-bkn cumulus is expected through the afternoon. Convective
chances still seem too low to mention in the taf. Some rain showers
associated with a weak backdoor front will probably be noted on
radar well to the north of the field late this afternoon. Most
guidance suggests that stratus will arrive from the east-NE late
tonight. Hence...have introdcued a bkn016 beginning at 11z. The
stratus should then scattered by 15z.
Elsewhere...it appears convective chances will be mostly limited to
widely scattered showers/thudnerstorms over the mountains and NC
foothills. However...chances too low to mention except for a vcsh at
kavl late this afternoon. Broken VFR cumulus will scattered this evening. Guidance
is advertising a stratus deck to arrive from the east-NE late tonight
and is expected to affect all airfields with at least MVFR ceilings for
several hours early Thursday...except kand.
Outlook...increasing moisture towards the end of the work week will
allow diurnal convection to develop each afternoon....mainly over
the mountains. Genrally VFR conditions are expected except some
early morning stratus is possible each day. Deep Atlantic moisture
will arrive this weekend promoting more widespread showers and
thunderstorms and more restrictions.
Confidence table...
20-02z 02-08z 08-14z 14-20z
kclt high 100% high 100% high 89% high 95%
kgsp high 100% high 100% high 86% high 95%
kavl high 100% high 94% high 89% high 91%
khky high 100% high 100% medium 72% high 96%
kgmu high 100% high 100% high 86% high 98%
kand high 100% high 88% high 81% high 98%
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...deo
near term...jat/lg
short term...Ned
long term...deo
aviation...lg
