Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
1115 am EDT sun Mar 16 2014
Synopsis...a frontal system will remain near the southeast coast
through Tuesday. High pressure moving from the Great Lakes region
into New England will push cold air southward and into the
forecast area. The front will begin to move farther offshore late
Near term /through tonight/...
rain has overspread the forecast area associated with strong
isentropic lift north of warm front. The NAM surface-based Li
pattern indicates the front will remain south of the area. The NAM
and GFS show isentropic lift diminishing late as low pressure
approaching from the west becomes less dominate as cyclogenesis
occurs near the Carolina coast. Cooling will occur as high
pressure centered well to the north wedges into our area. All of
the NAM and GFS MOS support temperatures remaining above freezing.
Elevated thunderstorms are possible but the chance appears low
based on satellite trends. The stronger convection will likely
remain south of the forecast area.
Short term /Monday through Tuesday night/...
active weather continues this period with the positively tilted
upper trough moving through the southeastern states culminating in
the development of a coastal low off the Carolina coast which will
shift northeastward away from the area on Tuesday. Leaned toward a
preferred blend of GFS/European model (ecmwf) as the NAM solution continues to be an
outlier showing upper trough become negatively tilted contributing
to a much slower timing and lifting the coastal low northward over
inland eastern North Carolina late Tuesday. The NAM solution has
also continued to be much colder than the other operational models
regarding the lowest levels and surface temperatures...showing
possible freezing rain in the northern midlands on Monday morning
and again Monday night into Tuesday morning.
The upper low at the base of the upper trough will track eastward
across the northern Gulf of Mexico on Monday and Monday night before
opening up and accelerating northeastward across southern Georgia
and eastern South Carolina on Tuesday. Persistent
north-northeasterly low level flow across the area during this
period will keep The Wedge locked into place further supported by
the overrunning of moist southwesterly flow atop the cad layer.
While there is expected to be a break in the heavier precipitation
Monday into Monday afternoon with the main baroclinic zone east of
the forecast area...areas of drizzle are possible along with patches
of light rain. The next wave of precipitation will move up with the
upper trough Monday night and Tuesday...and expect the best rainfall
to occur across the eastern midlands into the coastal plain where
better deeper moisture will exist. Bumped up probability of precipitation to
categorical/likely Monday and Monday night with decreasing probability of precipitation
Tuesday through the day as the system departs to the northeast.
Temperatures during this period will be well below normal...with
highs some 20-25 degrees below normal with highs on Monday ranging
from the lower 40s northern midlands to middle 50s in the southern csra.
Long term /Wednesday through Saturday/...
little change made to the extended forecast. Generally a dry weather
pattern forecast Wednesday-Friday with surface high pressure building over
the area and zonal westerly flow aloft. Temperatures expected to
moderate during the period back to near or slightly above normal
values by the end of the week. A cold front may move into the
region on Saturday bringing another chance for rain.
Aviation /15z Sunday through Thursday/...
all models indicate VFR at the beginning of the taf period with
conditions deteriorating to MVFR by 15z as the airmass becomes
saturated and rain continues over the taf sites. High confidence
for IFR after 18z with widespread rain and fog. IFR/LIFR expected
to continue tonight as cold air damming develops.
Extended aviation outlook...a prolonged period of rain with IFR/LIFR
conditions into Tuesday as a cold air damming event persists.