Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 191903

Area Forecast Discussion
National Weather Service Columbia SC
303 PM EDT Mon Mar 19 2018

A warm front will lift northward and into the area tonight
ahead of approaching low pressure. The low will be in the region
Tuesday and northeast of the area Wednesday.


A warm front which was located across southern GA earlier this
morning has lifted northward at a somewhat quicker rate than
expected. Models indicate strengthening moisture advection into
the evening as an upper level disturbance moves over the
forecast area (FA). This will lead to convective development
along the front as it advances northward towards the CSRA.
Overcast skies and relatively stable mid-levels will limit
instability. RAP LI values of -2 or more stable suggests the
convective updrafts will be weak. Thunderstorms are most likely
late this afternoon into the early evening in the CSRA but the
chance for severe thunderstorms during that period appears

Tonight: Upstream convection will push into the forecast area
from the west around midnight. MUCAPE values will be higher
tonight due to the cooler mid-levels. However a stable near-
surface layer will help to limit the severe potential. We expect
the line of thunderstorms to break up as it moves across the FA
and into the upper ridge. Although the threat of severe weather
becomes increasingly isolated through the night we cannot rule
out small hail with some of the stronger cells and a few
damaging wind gusts which manage to break through the surface

Overcast skies will help keep temperatures in the upper 50s to
the 60s for much of the area. The southern FA may reach into the
upper 60s to around 70 degrees with the warm front advancing
northward this afternoon.


A shortwave trough will move across the Southeastern US
and through the forecast area Tuesday afternoon and evening.
Models show an area of low pressure and an associated cold front
in the area shifting east. There is still some uncertainty
regarding the timing of the system and how far west into the
forecast area the moisture will be. The GFS pushes the deeper
moisture east of the area by 21Z while the NAM is slower pushing
the moisture east. A few strong to severe thunderstorms will be
possible particularly south and east of the I-20 corridor mainly
during the late morning and through the afternoon hours. The
far eastern portion of the area is in the Storm Prediction
Center`s slight risk for severe weather. The primary threats
appear to be strong to damaging winds, isolated tornadoes and
hail. Model LI values are around -5 to -7 with 0 to 6 km shear
values around 55 knots. Latest model guidance is trending warmer
further north with temperatures on Tuesday. This will
ultimately depend on the position of the warm front, but believe
northern counties will reside in the warm sector. Models show
the area becoming more stable Tuesday night. With the upper low
north of the area and wrap around moisture Tuesday night, have
continued likely pops north Tuesday night and slight chance
south. Winds will stay up Tuesday night with temperatures
forecast in the lower 40s.


The shower chance Wednesday will be greatest in the north
section closer to deeper moisture and colder air aloft. Reduced
pops some on Wednesday especially further south given that the
models are pushing the upper low northeast of the area more
quickly and moving the moisture out of the area. Wednesday
appears quite breezy with a tight pressure gradient in the area.
Dry ridging is forecast to dominate Thursday and Friday. The
GFS and ECMWF MOS have temperatures during the early morning
hours Thursday and Friday in the middle and upper 30s. It may be
cold enough for frost. The models show much of the moisture
associated with a warm front north of the forecast area Saturday
and little moisture along a cold front Sunday. The GFS and
ECMWF MOS have pops 20 to 30 percent.


Expect generally MVFR/IFR ceilings through the afternoon with a
warm front to our south. Cool surface temperatures and weak
isentropic lift will generally inhibit showers through the
afternoon with the exception of AGS/DNL where the northward
lifting warm front may bring a shower or thunderstorm late this
afternoon. But confidence in any precipitation is low during
this period. As the warm front continues to lift northward
across the FA, TAF sites should see low ceilings and some patchy
fog for a few hours.

Tonight, thunderstorms are more likely. A line of thunderstorms
will move from west to east through the forecast area after
midnight. These storms will weaken through the night but may
briefly impact the TAF sites between 05Z to 10Z. Mixing
associated with the line of convection and increasing gradient
winds should prevent fog formation through the rest of the
morning. Low level wind shear and continued IFR/MVFR ceilings
appear likely through Tuesday morning. Expect SW/W winds to pick
up shortly after sunrise with gusts up to 20 knots.

EXTENDED AVIATION OUTLOOK...Flight restrictions and precipitation
chances possible at times Tue/Wed. Breezy conditions expected




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