Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
644 am EST Sat Nov 22 2014
cool and dry high pressure continues to build into the area this
morning and will continue through much of the day. Moisture will
return to the region later tonight through Sunday night...with
plenty of rainfall expected to occur Sunday into Sunday night. A
front will move into the region Monday and is expected to stall
near the coast Tuesday.
Near term /until 6 PM this evening/...
WV loop this morning shows some weak middle/upper level ridging
building eastward into the region ahead of digging short wave across nm/West Texas.
At the surface...cool and dry high pressure centered across eastern
Virginia/northestern NC will dominate the weather across the midlands and csra
through the day. Guidance temperatures fairly consistent for
afternoon highs and will stay close to consensus.
Short term /6 PM this evening through Monday night/...
tonight...short wave across nm/Texas continues to progress eastward and middle/upper
level riding begins to push off the coast. Surface high pressure
moves off the NC/Virginia coast but continues to ridge into the area. By
Sunday...short wave will be across the lower MS River Valley. Low
pressure developing across the Southern Plains. A warm front to
our south will begin to try and push northward through the day on
Sunday/Sunday night. Looking a model Li fields along with some
weak surface riding and surface winds from the NE/east for much of the
day on Sunday. This indicates at least some weak wedge conditions
across much of the County Warning Area...especially across the northern/central
midlands along with the northern csra. With increasing isentropic lift
and moisture flux into the region. Any rainfall should help
sustain wedge conditions. However...by late in the day Sunday and
Sunday night...surface flow will increase from the southeast and S as 50
to 60 knots low level jet approaches. Precipitable water values will rise
dramatically through the period from less than one half inch this
evening to well above 1.5 inches...approaching nearly 2.0
inches...by Sunday afternoon. This is much higher than
climatology for middle/late November. With such impressive isentropic
lift and moisture flux...the rain will be heavy at times during
the afternoon and evening hours Sunday/Sunday night. As the warm
front tries to move north/northwest across the area late Sunday
into Sunday night...the airmass across the area will become more
unstable. This is especially true across the eastern portion of
the County Warning Area south of I-20. Storm Prediction Center day two has the southeastern half of the
Palmetto state in a slight risk for severe thunderstorms. This is
where the best shear and instability will develop. Have mentioned
isolated to chance of thunderstorms from late Sunday afternoon
into Sunday across much of the area developing first in the southeastern
portion of the County Warning Area and then north/northwest into the remainder of
the County Warning Area. Rainfall amounts from 1 to 2 inches will be possible by
Sunday night. On Monday...the cold front associated with the low
in the plains will try to push eastward across the area...but by
afternoon/evening becomes parallel to the upper flow and will
likely slow/stall along the coastal plain or near the coast. This
is where models begin to disagree on how far the front will push
eastward. At this time...have continue to keep a chane of
rain showers/thunderstorms and rain through Monday with front in the vicinity. As for
temperatures...fairly straight forward tonight with increasing
clouds and have stayed close to consensus. However...they will be
very tricky on Sunday with wedge and approaching warm front from
the south. Have stayed well below most of the guidance for Sunday
with a tight temperature gradient from northwest to southeast. The high for
Sunday will most likely occur during the evening hours as the warm
front pushes northward. Temperatures will be dramatically warmer on
Monday with breezy south/southwest winds ahead of the cold front
with all of the guidance in the middle/upper 70s.
Long term /Tuesday through Friday/...
uncertainties in the forecast for Tuesday through Wednesday of
next week. Both the GFS/European model (ecmwf) models begin to shift the main upper
trough axis eastward as energy drops into the base of the trough
across the Southern Plains by Tuesday/Tuesday night. By Tuesday night...both
models begin to develop low pressure in the Gulf of Mexico and
bring a system up along the East Coast. This looks slightly more
westward with precipitation shield than 12z/18z runs. Due to this
have increase probability of precipitation a bit on Wednesday across the County Warning Area. By Thursday and
Friday...both models have trofiness across the eastern half of the
country...with high pressure building into the region at the
surface. Expect temperatures to remain below normal through the
Aviation /12z Saturday through Wednesday/...
high confidence VFR conditions through 06z then possible MVFR ceilings
developing through the end of the 24 hour forecast period.
High pressure over the Carolinas and middle-Atlantic coast will
provide light northeast winds through the day with mostly clear
skies through 18z. Winds will pick up a bit after 15z and shift
more to the east around 5 to 10 knots. High clouds will increase
late in the afternoon and into the evening along with some
possible middle level clouds.
Developing low level southeasterly flow will increase moisture
tonight and lower ceilings will develop with possible MVFR ceilings
arriving after 06z from the south tonight.
Extended aviation outlook...ceiling and visibility restrictions
are likely in rain showers late Sunday through Monday as
a low pressure system affects the region.
SC...Flash Flood Watch through Monday evening for scz030.