NZUS99 KLSX 241947 RRA
WRKAFD

.Key Messages...

-The warm-up will continue with temperatures at or near records on
Thursday.

-Showers and thunderstorms are expected along and behind Thursday's
front, mainly Thursday evening through Friday morning.

...WRKSRD...

Mainly dry weather is expected through tomorrow as the temperatures
will continue to warm up.  We are about 10 degrees warmer than
yesterday as we have seen low level warm air advection and sunshine
today.  Lows tonight will only fall off into the low to mid 40s
given the light southerly winds.  Winds will then turn south to
southwesterly on Wednesday as the HREF shows high pressure moving
off the East Coast at the same time low pressure moves into the
Plains.  This will help to increase the warm air advection across
Missouri and Illinois tomorrow pushing highs up another 15 to 20
degrees, ranging from the mid 70s over south central Illinois to the
lower 80s over central Missouri.

...WRKAFD...

High temperatures by Thursday will be in record territory (see Climo
Section) with 850mb temperatures near 20C which are near max climo
for late March.  With surface winds turning out of the southwest and
increasing ahead of a cold front and some additional sunshine during
the day, high temperatures will be in the upper 80s to around 90
degrees which will challenge record temperatures.

There is reasonably good agreement in the global models showing that
a trough will move across the upper Midwest late this week that will
push a cold front south through Missouri and Illinois late Thursday
and Thursday night.  While model guidance continues to show that the
atmosphere will continue to become unstable (MLCAPES >1000 J/kg)
ahead of the front with deep layer shear of 40-50 knots, forecast
soundings continue to show notable low level capping which will
likely limit convection ahead of the front.  The more likely
scenario is that showers and thunderstorms will develop behind the
front where there is best combination of frontogenetical and jet
streak forcing to overcome the capping.  This is where the soundings
are showing potential for some elevated storms capable of producing
some hail.

Much colder air will move into the area behind the front on Friday.
A surface high will move across the area on Saturday and pass off to
out east causing us to be in southwesterly flow by Sunday allowing
for temperatures to start another warm-up.  By early next week we
will be in a warm and unsettled weather pattern as the LREF is
showing 30-40% of its members producing rain by Tuesday with 850mb
temperatures in the 90th percentile of normal.