Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
300 am EDT Tuesday Sep 2 2014
high pressure will extend into the forecast area from the Atlantic
through Thursday. A persistent upper ridge will help maintain the
Near term /through tonight/...
nocturnal cooling and high low-level moisture should result in
areas of stratus and fog early this morning. However...weak instability
and deep moisture should help prevent dense fog.
The surface ridge will remain east and south of the forecast area
with weak Lee-side troughing in the area. Strong heating plus
convergence into the trough should help support thunderstorms.
Thunderstorm coverage should be limited by the upper ridging and
slow storm movement. The high-resolution models display scattered
coverage. The guidance consensus support probability of precipitation around 30 percent.
Precipitable water will be around 2 inches. This moisture plus a
slow storm motion signals a possibility of localized flooding. The
models indicate strong instability. The NAM has surface-based Li/S
near -8 today. This instability plus heavy precipitation loading
indicates a possibility of damaging wind with the thunderstorms.
Recent verification favors the warmer temperature guidance.
Short term /Wednesday through Wednesday night/...
the surface ridging east and south of the forecast area will
continue to dominate. A weakening front approaching from the
northwest should stall before reaching the area. However...strong
heating with deep moisture plus some convergence associated with
Lee-side troughing should help support thunderstorms. Coverage
should be limited because of continued upper-level ridging and
slow storm movement. The guidance consensus supports probability of precipitation around
30 percent. Heavy rain may occur with any thunderstorms because of
slow storm movement and precipitable water near 2 inches. Recent
verification favors the warmer temperature guidance.
Long term /Thursday through Monday/...
the GFS and European model (ecmwf) show ridging extending into the area from the
Atlantic dominating early in the medium-range period. Sufficient
moisture combined with heating should support scattered mainly
diurnal thunderstorms. The models display a cold front in the area
Sunday and Monday supporting an increased chance of showers and
thunderstorms. The GFS...ECMWF...and ekd MOS have probability of precipitation 20 to 30
percent early increasing to 30 to 40 percent by the end of the
period. Above normal temperatures should lower to near normal
toward the end of the period because of increased cloudiness
associated with the front.
Aviation /07z Tuesday through Saturday/...
VFR conditions through the next several hours with MVFR/IFR
possible during the early morning and around sunrise.
Convection has dissipated across the area early this morning. Main
concern for the taf period remains fog and stratus threat...however
much of the threat is diminished by convective debris across the
region. As such have remained with IFR conditions for ags and MVFR
elsewhere. Fog and stratus which develop will erode with sunrise
and mixing with the remainder of the period VFR. Expect cumulus to
again develop during the late morning through afternoon
hours...confidence remains too low to include mention of
convection at this time.
Extended aviation outlook...restrictions possible in late night
and early morning stratus and fog. Scattered mainly afternoon
showers and thunderstorms Monday through Friday.