Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service Springfield MO
731 PM CDT Tue Apr 21 2015

..updated mesoscale and aviation discussions...

Mesoscale discussion...
issued at 731 PM CDT Tuesday Apr 21 2015

Scattered thunderstorms continue along and ahead of a mid level
shortwave trough that is moving southeast through the area. For
early this evening, this activity will be focused on areas
along/east of Hwy 65 and along/south of Hwy 60.

00z ksgf sounding was in proximity to the incoming storms and it
indicates 0-6km bulk shear of around 40kt along with mixed layer
cape of 400 j/kg and most unstable cape around 700 j/kg. We have
mixed to about 675mb, which is a little unusual for the area this
time of year, resulting in a large sub cloud layer in the low
levels. Evaporative cooling in this layer will produce gusty
winds as these storms move to the southeast. If these cells can
get organized into a linear structure and Bow to the southeast,
there is the potential for mesovortex production. If this were to
occur in would be in the next hour. As this activity continues to
the southeast, it is running into a slightly more hostile
environment with decreasing cape values. Hail will continue to be
common with these storms, with most reports in the pea to nickel
size range. The occasional quarter sized stone is possible from
time to time.

We should have a break in the action during the mid to late
evening hours, with regeneration of scattered showers and storms
along a cold front that will move in from the northwest during the
overnight hours. Given lower instability values, we are only
expecting cloud to ground lightning and small hail with any
stronger storms overnight.

&&

Short term...(this evening through wednesday)
issued at 248 PM CDT Tuesday Apr 21 2015

Gusty west to southwesterly winds will continue through the reminder
of the afternoon hours...but will gradually weaken into this
evening.

Scattered thunderstorms are starting to develop across portions of
west central MO into the Eastern Ozarks. These storms are developing
as lift from an upper level low over the Great Lakes region
interacts will weak instability that is developing with day time
heating and low level moisture advection. The upper level low is
spreading increased wind shear and colder temperatures in the mid
levels. So, it won't take much of an updraft to get a small hail out
of storms. Instability will remain on the weak side and wide spread
severe weather is not expected, but a few of the stronger storms
could produce hail up to the size of quarters and winds over 50 mph.
These storms will generally occur along and northeast of a Lamar to
Springfield to West Plains MO line and will push southeast of the
area this evening.

Later this evening into tonight additional isolated to scattered
storms will be possible as a cold front sags south through the area.
Instability will remain on the weak side with small hail and cloud to
ground lightning strikes being the main risk with these storms.

On Wednesday 500mb low lifts northeast of Lake Superior but
cyclonic flow continues over Missouri. At the surface high pressure
noses southward into northern Missouri while residual boundary slips
south into Arkansas. This will keep the area with below normal
temperatures with highs only in the 50s and 60s. Models consistent
in weak isentropic lift north of the boundary into southern Missouri
at least early on Wednesday with enough lift for some
showers/storms, especially over far southern Missouri. Best
instabilities remain south of the forecast area with only 300 j/kg
of most unstable cape early in the day along the Arkansas border.
Tapered probabilities from north to south. There could be some
showers across far southern Missouri Wednesday night, otherwise dry
conditions will be seen.

Long term...(wednesday night through tuesday)
issued at 248 PM CDT Tuesday Apr 21 2015

Shortwave ridging builds across the area Thursday suppressing any
showers to the south near the Arkansas border during the morning
hours. The next shortwave will lift out of the Desert Southwest
into the central/Southern Plains Friday and across Missouri on
Saturday. Although there are some model differences with respect
to the track of the surface low, the Friday time frame looks to be
the best chances for showers and storms, with Saturday more
showery as system begins to pull east of the area. Weak high
pressure will move in Saturday night and into Sunday giving
everyone a break from the rainy weather. However, next shortwave
will drop across the plains around another deep 500mb low over the
Great Lakes. This will bring rain chances back into the forecast
for late Sunday into Sunday night and then pushes east Monday.
Some low probability rain chances on Monday and Tuesday with hard
time shortwave energy in fast flow aloft.

Temperatures look to remain on the cool side through much of the
period with highs in the 60s and lows in the 40s. At this point it
looks like there is minimal frost potentials.

&&

Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 731 PM CDT Tuesday Apr 21 2015

Scattered thunderstorms will continue to move southeast through
southern Missouri early this evening. At this time it appears that
this activity will miss bbg to the east, but will closely monitor
over the next hour or so. Otherwise, there will be a break in the
action until the overnight hours when scattered showers and storms
will redevelop along a cold front moving in from the northwest.
Coverage again looks scattered and will hone in on timing of this
activity with future updates. Winds will shift to the north late
tonight with the frontal passage. Overall, mainly VFR conditions
are expected, with mainly mid/high level clouds expected.

&&

Sgf watches/warnings/advisories...
MO...none.
Kansas...none.
&&

$$

Mesoscale...gagan
short term...raberding/wise
long term...raberding
aviation...gagan

National Weather Service Glossary of Abbreviations