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fxus63 ksgf 220007 

Area forecast discussion
National Weather Service Springfield MO
607 PM CST sun Jan 21 2018

..mesoscale and updated aviation discussion...

Mesoscale discussion...
issued at 528 PM CST sun Jan 21 2018

At this point, this "event" is going as planned. A broad corridor
of convection has developed from northeastern Texas into eastern
Oklahoma and southwestern Missouri. This convection is developing
over an area of 0 to 0.5 km above ground level convergence on the eastern
periphery of increasing 500 mb height falls.

Instability remains weak with the ongoing 00z sgf radiosonde observation measuring
117 j/kg of MLCAPE. The lower level capping inversion present on
the 21z sounding has been removed, however a secondary (higher)
inversion remains in place and is resulting in the presence of
some inhibition.

Instability farther south across the arklatex into the I-40
corridor is a bit better, with MLCAPE values on the order of 500
to 900 j/kg. We have seen some low-topped supercells with decent
low-level rotation along with qlcs mesovortex structures down
south across this region.

As we head throughout the evening, it will be very difficult for
this better instability to reach the Missouri Ozarks as convection
will continue to develop and impede its progress northward. We
will see cooling mid-levels which may offset this slightly. Deep
layer and low-level shear will remain robust as mid/upper level
jet cores impinge on the region and a low level jet strengthens
and noses into southern Missouri.

With all of that said, we are going to maintain a limited severe
weather risk as this broad area of convection slowly shifts east
with time across the Missouri Ozarks. Despite the lack of
instability, these setups can be conducive to line segments with
mesovortex potential. Mesovortices will be more favored with
bowing structures towards the east, northeast, or north. We may
also see some low-top supercell structures early this evening over
far southwestern Missouri.

One other item of note will be the potential for a few additional
cells to develop back to the west closer to I-49 corridor late
this evening as even stronger height falls overspread an
accelerating dry line/surface trough. Instability may briefly
increase as this happens as strong mid-level cooling takes place.
If these cells can develop, they may have a limited hail risk.


Short term...(this evening through monday)
issued at 130 PM CST sun Jan 21 2018

A deep closed upper low will track from The Rockies into the
Central Plains this evening while a surface low pressure system
tracks from eastern Kansas into northern Missouri. A trailing
surface trough then cold front will push across the Ozarks region
this evening. Strong synoptic lift and moisture advection along
with at least ample instability will ignite numerous showers and
thunderstorms from late afternoon into tonight.

While instability will be rather modest the shear profiles will be
favorable to support intense updrafts and possibly supercells.
Shear vectors will also support surging line segments and bowing
structures. This all adds up to a risk of severe storms with the
potential of damaging winds and possibly a couple of tornadoes.
While a low risk the primary area of concern for tornadoes would
be across far southern Missouri.

The showers and storms will end from the west late this evening
into the overnight hours. Expect some clearing overnight as a dry
slot wraps around the upper low.

The true cold front will sweep across the area early Monday as the
upper low transitions eastward. This will bring steady or falling
temperatures and increased cloud cover. Also expect showers mainly
across central Missouri. Some potential that some snow will mix
with the rain before ending.

Long term...(monday night through sunday)
issued at 130 PM CST sun Jan 21 2018

Colder temperatures settle back into the region through mid week
before upper level ridging and southerly winds return by late

The next upper trough and associated front will move into the
region heading into later Friday and this weekend. This will
bring another good chance for precipitation. Colder weather will
again follow this system this weekend.


Aviation...(for the 00z tafs through 00z Monday evening)
issued at 528 PM CST sun Jan 21 2018

Showers and a few thunderstorms can be expected across the region
this evening as a strong storm system approaches from the west.
MVFR and brief IFR conditions can be expected around storms.

Meanwhile, low level wind shear conditions can be expected along
with brisk and gusty southerly surface winds.

Most of the shower and thunderstorm activity will then shift east
of the area for the overnight period with predominantly VFR
conditions then expected.

MVFR ceilings will then settle back into the region on Monday as
the upper level portion of this storm system tracks into the
region. Strong and gusty surface winds will also continue with
southwesterly gusts exceeding 35 knots.


Sgf watches/warnings/advisories...


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