Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
735 PM EDT Friday Aug 22 2014
a back door cold front will move into and through the northern and
central midlands Saturday...and then shift towards the csra
Sunday. This will lead to a chance of thunderstorms along and
ahead of the front...with temperatures returning to more normal
levels behind it. The front will linger south of the csra early to
middle next week...leading to generally fair weather with near normal
Near term /tonight/...
atmosphere remains capped across the midlands and airmass is
drier with dewpoint temperatures in the upper 50s to middle 60s.
County Warning Area should remain dry tonight...and this forecast agrees well
with hrrr as it shows any activity remaining north of the County Warning Area.
Surface low pressure along the Virginia coast is forecast to move
southward overnight into eastern NC. This will allow a backdoor
cold front to approach the northern midlands around daybreak
Saturday. Kept overnight lows near consensus in the lower and
Short term /Saturday through Sunday/...
main issue for Saturday and into Sunday is timing of approaching
back door front. Think pre-frontal trough sets up across southern
County Warning Area Saturday with front in eastern North Carolina shifting
southwest during Saturday evening. MOS pop guidance low but sref
and model quantitative precipitation forecast suggest scattered showers and thunderstorms ahead
and along front as air mass moderately unstable and moisture
increasing...precipitable water may rise to around 2 inches.
Warm maximum temperatures still possible Sat ahead of the front...with
warmest temperatures favoring the csra where temperatures could reach 100 again.
With NAM being slightly faster than GFS with the back door front...the
NAM MOS is slightly cooler than the GFS MOS for Sat maximum
temperature...especially north and central. Even if temperatures near 100
reached again Sat...guidance still suggests dewpoints low enough
to preclude heat index values from reaching our heat advisory
criteria of 110f.
Front expected to shift SW through the forecast area Sat night through Sun night.
Expect chance probability of precipitation near and just ahead of the front...with cooling
temperatures along and north of it. So...probability of precipitation Sun afternoon favoring the
csra where instability/low level convergence stronger. High temperatures Sunday
should be noticeably less behind the front.
Long term /Sunday night through Friday/...
models in good agreement with moving the front south of the Savannah
River with upper level ridge building in for the week. With cooler
dry air settling in will bring slightly below normal temperatures. Expect
maximum temperatures 85 to 90 early to middle week rising back into the lower 90s
later in the week. Overnight mins will be 65 to 70 rising into
the lower 70s later in the week.
Aviation /00z Saturday through Wednesday/...
VFR conditions expected through the period.
Mainly scattered middle and upper level cloudiness through the
period. Dry forecast expected overnight. Frontal boundary remains
north of the area. Winds light and variable overnight...becoming
northerly through the day Saturday. Front north of the area will
sag a little further south on Saturday...but will remain north of
all taf sites. Isolated to scattered convection may be possible
during the afternoon Saturday...but due to limited coverage will
not include in the tafs at this time. Best chance will be closer
to the midlands taf sites Saturday afternoon.
Extended aviation outlook...MVFR or IFR conditions possible in late
night and early morning fog Sunday and Monday. Isolated afternoon
and evening thunderstorms may also bring restrictions Saturday
evening and Sunday.