Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
101 PM EST Tuesday Mar 3 2015
considerable day to day changes expected over the next several days.
A weak surface front will stall just south of the forecast area
tonight behind a back door front...with some patchy light rain
and drizzle. The front will return north as a warm front early
Wednesday providing a return to warm temperatures. Another cold
front will come through the region on Thursday. High pressure with
colder temperatures will settle into the region behind the front
for Thursday night into Friday.
Near term /through tonight/...
this afternoon...center of the surface high will continue to move
into the mid-Atlantic. Back door front is moving through the
southern midlands and is close to the csra. This front is expected
to stall out across the southern County Warning Area late this afternoon. Northeasterly
flow is setting up across the County Warning Area at this time. Winds should turn
more easterly again late this afternoon as the surface high moves
off the middle-Atlantic coast. A weak upper impulse moving through
central Georgia will lead to some isentropic lift...allowing some light
drizzle and rain to remain over our region through the afternoon.
Models do trend to push the precipitation further north and west late in
the afternoon...and this may leave the area with just some light
drizzle. Temperatures generally falling slowly through early afternoon
then steady late.
Tonight...surface high will be off the coast...while the weak
upper ridge shifts towards Florida. The main surface boundary will
begin to slowly move northward back into the County Warning Area late tonight.
Still expect that the weak wedge will hold across most of the County Warning Area
overnight. As the warm front begins moving through the County Warning Area...will
expect to see steady or slowly rising temperatures...along with patchy
drizzle and areas of fog. Bigger issue late tonight and towards
morning will be the fog. Expect areas of fog to develop along and
north of the surface boundary as it begins moving northward.
Guidance is indicating widespread fog development...with some
dense fog developing across the County Warning Area. At this time do not plan on
issuing any advisory due to semi-low confidence level. However would
not be surprise if later shifts would need to issue a dense fog
advisory. This will need to be monitored late tonight.
Short term /Wednesday through Wednesday night/...
warm front to traverse north through the forecast area Wednesday morning.
Deep SW flow to provide warm temperatures Wednesday. Guidance suggests
temperatures could reach 80 central and south forecast area...which would be first
time since early Nov. Next approaching front will move slowly and
remain to our north through Wednesday nt due to SW flow aloft...nearly
parallel to the front.
Long term /Thursday through Tuesday/...
northern stream upper energy to shift east from the middle miss valley
into the NE and Middle Atlantic States...while southern stream trough
remains near the SW Continental U.S.. upper flow to remain generally west-southwest over
our region. Cold front to come slowly through Thursday....latest
models trending a tad slower with it. Best precipitation coverage and
amounts appear will remain just to our north and NE due to main upper
energy remaining just to our north. Instability appears weak. Cannot
rule out isolated thunder in the afternoon mainly central and south
along and ahead of the front...but not enough confidence to warrant
mention at this time.
Models indicate upper flow to remain generally west to west-southwest and
indicates the front stalling to our south...while Canadian high
center builds into the middle Atlantic Thursday nt into Friday. Air mass behind
front is of polar Canadian origin and a significant drop in temperatures is
expected Thursday nt into Friday.
Saturday into early next week...SW Continental U.S. Upper low to open and shift
east. It along with some leading impulses appear to shift east along
the Gulf Coast into our region...leading to a wave or two of low
pressure developing along the stalled front. Significant differences
remain between the models with regards to specifics...severely
reducing confidence for this time frame. Continued to accept HPC
guidance...providing slight chance to chance probability of precipitation.
Aviation /18z Tuesday through Sunday/...
surface wedge flow has set up across the County Warning Area with most ceilings overcast
and below 1kft...with many sites around 500 feet. Ceilings are
expected to remain there through the afternoon and overnight
period as isentropic lift continues bring moisture over The Wedge.
Bigger issue overnight will be the possible development of
IFR/LIFR visibilities as areas of dense fog develop late tonight.
Guidance indicating visibilities below 1/2sm in many areas by
07z...lasting through 14z. Ceilings and visibilities should begin
to lift and break out Wednesday morning as The Wedge lifts and
breaks. Precipitation overnight should mainly be dz...with some rain mixed
in at times. Winds east to northeast around 8 to 10 miles per hour. Some
low level wind shear will become possible later tonight as low-level jet develops
near the Top of the Wedge. This will last until The Wedge breaks
Extended aviation outlook...widespread IFR or MVFR conditions will
be possible again on Thursday