Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
123 PM EST Thursday Mar 5 2015
a strong cold front will move through the forecast area this
afternoon. Temperatures twill drop later this afternoon. High
pressure ridge behind the front will extend through the area
Friday night and Saturday.
Near term /through tonight/...
the cold front will move through the forecast area this afternoon.
Convergence associated with the front will support showers.
Confidence is low with the temperature forecast today as it will
be very trick with precipitation/clouds moving across the area and
timing of frontal passage. Rain moving into the area and cold
advection behind the front should limit the temperature rise from
late morning into the early afternoon hours. However...we did get
off to a warm start this morning with temperatures ranging from
the middle 60s west to the middle 70s east. The models are
typically too fast moving the very dense colder air over the
mountains. Have continued with the warmer guidance for the first
part of the afternoon...then expect temperatures to fall from northwest
to southeast through the late afternoon. The NAM indicated weak
instability ahead of the front with surface-based Li/S near -2 in
the southeast section this afternoon. Based on mixing associated
with this instability and the low-level jet with 850 mb winds 40 to
50 knots believe gusty winds will occur. Vwp shows 25 kts at 1k
feet and 45 kts at 3k feet. With the relatively Cool Lakes...water
temperatures in the middle/upper 40s...winds should limit
mixing...but still believe a lake Wind Advisory is needed for
areas surrounding the lakes. The NAM BUFKIT momentum Transfer
tool and GFS lamp support gusts around 25 to 30 knots.
Thunderstorms are not out of the question this afternoon across
the eastern half of the County Warning Area. Have left any mention out...but an
isolate rumble of thunder possible.
The models show moisture lingering behind the front and rain may
continue into the evening. The NAM and GFS time-height displays
and sref probabilities indicate precipitation will end before
temperatures fall below freezing. Lingering shallow low-level
moisture could possibly support freezing drizzle late...but we
believe the chance is too low to include in the forecast at this
time. The risk of black ice also appears low. Breezy conditions
behind the front should help dry wet roads plus temperatures
Short term /Friday through Sunday/...
the main front is forecast to be of the East Coast by Friday
morning. There may be a few lingering showers closer to the coast
early in the day...but for the midlands and csra conditions will be
dry...and cold. The center of the Arctic high is forecast to remain
of the the west of the area...although a portion of the high will
eventually push eastward towards the southeastern U.S. By Sunday.
Forecast is for dry conditions through the weekend. Coldest day
through the short term should be Friday and Friday night as the
Arctic air tries to settle over the area. Some modification may
begin to take place on Saturday...which would allow for slightly
warmer but below normal temperatures. Then by Sunday...reading
will be back closer to normal...with readings in the lower to
middle 60s. Overnight lows through the period generally around
Long term /Sunday night through Thursday/...
moisture and slightly warmer temperatures will begin to reenter the
region beginning Sunday night...lasting through Thursday. Good
southwest flow aloft will bring moisture northward from the Gulf.
There remains some uncertainty in the longer term with probability of precipitation.
However with weak shortwaves moving through the region...along with
the added moisture...can not rule out at least a slight
chance/change pop through much of the period. Generally kept a
blend of previous forecast with the HPC guidance.
Aviation /19z Thursday through Tuesday/...
MVFR/IFR ceilings this morning as a cold front approaches from the
Southwest winds increase through the afternoon as cold front
approaches from the west. Good mixing with initial heating and
increasing surface pressure gradient. MVFR conditions expected by
the afternoon. Vcsh later this morning. Bulk of showers will move
into the taf sites 18z-23z time-frame. The cold front will cross
the taf sites in the 19z-22z time-frame...with winds shifting to
the north...then northeast. The chance for rain will linger
through the evening. The precipitation will end by late evening
with gusty surface winds shifting to the northeast by 04z Friday
in wake of the front with conditions becoming VFR.
Extended aviation outlook...no restrictions expected Saturday
through Monday. Ceiling/visibility restrictions possible Monday night into
Tuesday as a wedge pattern develops.
SC...lake Wind Advisory until 4 am EST Friday for scz015-016-018-
Georgia...Lake Wind Advisory until 4 am EST Friday for gaz040-063>065-