Scientific Forecaster Discussion
fxus63 ksgf 211914
Area forecast discussion
National Weather Service Springfield MO
214 PM CDT Sat Oct 21 2017
Short term...(this evening through tonight)
issued at 121 PM CDT Sat Oct 21 2017
As of 2 PM, a cold front extended from eastern Nebraska through
central Kansas and into the Oklahoma Panhandle. Gulf moisture
continued to advect north into the plains and Ozarks ahead of the
front with a fairly uniform area of lower to middle 60s dew
points. Upper 60s dew points are starting to impinge on the I-40
Low-level water vapor imagery and morning soundings indicate that
an expansive elevated mixed layer remains in place over the
region. This has suppressed deep convection up to this point.
However, the combination of vigorous short wave energy and
increased frontal forcing are really beginning to work on the
capping inversion. It should be noted that visible and infrared
satellite trends along with modification of short term soundings
indicate that the cap may become weak enough over the next hour or
two for convective initiation along the front from central Kansas
into northern Oklahoma. This is backed fairly well with short term
convective allowing models (cams).
Convection that fires across Kansas and Oklahoma will grow quickly
upscale late this afternoon and early this evening due to
extensive low and mid-level forcing. Thus, a line of strong to
severe storms appears quite likely to move into our southeastern
Kansas counties initially in the 7-9 PM time frame. This line of
storms will then March east across western Missouri and the
Missouri Ozarks overnight tonight.
Short term models have actually increased the amount of
instability that will be available this evening and overnight
ahead of the front. This should allow the line of storms to remain
more robust farther to the east across the Ozarks. We therefore
agree with the Storm Prediction Center in the eastward expansion
of both the elevated and slight risk areas.
Damaging wind gusts remain the main potential severe weather
hazard with this line of storms. However, cams continue to
indicate bowing structures embedded within the line. With 0-3 km
bulk shear vectors expected to increase into the 30-35 knot range
towards the northeast starting this evening, any bows which surge
in a northeasterly fashion will have mesovortex tornado potential.
There may be an initial hail risk over southeastern Kansas and
western Missouri with any stronger embedded cores.
Long term...(sunday through saturday)
issued at 121 PM CDT Sat Oct 21 2017
The cold front will be in the process of moving through the
Ozarks during the first half of day Sunday. Convection will be
well southeast of the by lunch time however, light rain and
showers will linger across the area into the afternoon.
The front will slow up significantly Sunday night which may allow
for light rain to continue across portions of the Southeastern
Ozarks mainly east of an Ava to Rolla line.
Temperatures will be on a downward trend behind the front through
the middle of the week. A deep upper level trough will slide
across the center of the country with models cutting of and upper
low over the bootheel region Monday night. This will help to slow
up the exit of the colder airmass and keep upper level troughing
across the region into Wednesday morning which may bring an
airmass with the potential for frost to portions of the area.
A brief period of northwesterly upper level flow will occur for
the end of the week before another deep upper level trough moves
towards the region for the weekend with another chance for a frost
or light freeze Saturday and Sunday mornings.
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1238 PM CDT Sat Oct 21 2017
MVFR ceilings are expected for much of this afternoon around the
Branson area with VFR expected elsewhere across southern Missouri.
Brisk and gusty southerly surface winds will persist into this
evening with gusts approaching 30 knots. Low level wind shear
conditions will then develop this evening.
A line of thunderstorms will then pass through the region
overnight in association with a passing cold front. MVFR and IFR
conditions can be expected with these storms along with gusty
IFR and MVFR ceilings will then hang on behind the front into
early Sunday morning. Winds will be somewhat brisk out of the
northwest with gusts around 20 knots.