Area forecast discussion
National Weather Service Lincoln Illinois
issued by National Weather Service St Louis MO
110 am CDT Tuesday may 21 2013
Discussion...
issued 845 PM CDT Monday may 20 2013
Updated the forecast tonight to expand the Tornado Watch until 1
am from McLean...DeWitt...Macon and Christian counties west.
Increased to categorical probability of precipitation of 80-100% from I-55 west through 1
am including risk of tornadoes...large hail...damaging wind gusts...
heavy rains and frequent lightning. Have chance of showers and
thunderstorms developing over eastern Illinois late this evening and
continue likely chances of showers and thunderstorms overnight
where strong to severe storms possible as well after midnight over
eastern Illinois.
996 mb low pressure over NE South Dakota with warm front over northern WI/Michigan
and its cold front over SW Minnesota...western Iowa into southeast Kansas and central OK.
Strong 556 dm 500 mb low was also over NE South Dakota. Scattered to
numerous strong to severe thunderstorms was southeast of this large low
pressure system from the Illinois River valley through central MO into southeast
OK and central Texas. Convection was as far east as I-55 and racing
NE at 40 to 50 miles per hour. Short wave ejecting NE from OK and Ozarks of
northwest Arkansas and SW MO into central Illinois during tonight to produce
widespread convection across central and eventually eastern Illinois by
overnight. Much of Illinois remains in slight risk of severe storms
tonight through Tuesday while moderate risk of severe storms tonight
over southern MO. There is 30% risk of large hail and damaging
wind gusts over central Illinois tonight especially from I-57 west and
5-10% risk of tornadoes with supercells. Storm Prediction Center said mesoscale convective system to evolve
into qlcs during this evening and continue risk of severe storms
into central Illinois tonight. Increase quantitative precipitation forecast tonight over central Illinois with
average half to 1 inch amounts and locally 1-2 inch amounts with
stronger storms. Lows in the middle to upper 60s by dawn.
07
&&
Aviation...
issued 109 am CDT Tuesday may 21 2013
Most intense convection along outflow boundary has weakened
considerably as its moved into southeast sections of County Warning Area...and over the
next few hours elevated...and generally light...convection will be
tapering off along and east of a bmi-Dec line. Some lighter
elevated showers working into eastern Missouri should return to the
area during the predawn hours...and will also need to keep an eye on
some elevated convection refiring as low level S flow intensifies
and taps residual instability but for now have held these out of the
tafs. Once the heavier convection exits east tafs by 08z...VFR
conditions should prevail with ceilings at or above 8kft...with perhaps a bit of
St forming during the predawn hours and have hinted at that with scattered
3kft. Not many changes made to forecasts for later today...with scattered
cumulus forming by middle morning. Due to uncertainty of timing/location of
convective initiation...will let next shift monitor trends before
introducing next round of storms.
Truett
&&
Ilx watches/warnings/advisories...
none.
&&
$$
