Bow approaching Fountain County produced gust to 48 mph at Danville, Illinois.

Morocco has gusted to 38 mph. 

40-50 mph gusts possible Newton, Benton, Warren & Fountain counties.

Squall line with several rather large bows continues to race north & eastward.  Right now, the two most intense bows are north & south of the viewing area, where Severe T’Storm Warnings are in effect.

However, bow west of Newton & Benton counties & bow southwest of Covington needs to be monitored.

Gusts of 40-50 mph are possible in these two bows.

Tornado Watch has been issued by SPC until 6 a.m. Eastern for south half of viewing area until 6 a.m. Eastern & Severe T’Storm Watch now in effect for north half until 5 a.m. Eastern.

Squall line is surging north-northeastward at 50-60 mph & will gradually make its way eastward with pockets of damaging straight-line wind & a brief, isolated tornado threat.  Some small hail cannot be ruled out.

Line of storms in south-central Illinois is exhibiting areas of damaging straight-line winds & occasionally, a meso-vortex in the line (see first image), showing bits of rotation for brief tornadoes.

Pockets of damaging wind & an isolated brief tornado still look possible for our area, likely requiring watch issuance. 

SPC explains there is an 80% chance of watch issuance for area.  This is after 60% chance of watch issuance this afternoon.  Chance of a tornado watch bit higher now.

Line of storms will pass tonight with wind/isolated tornado threat……….

Supercells in central Illinois have congealed with developing squall line, which is producing corridors of damaging straight-line winds.  Supercells have been confined to central Illinois this evening, but we have been storm-free for several hours in our viewing area.  Any forcing for supercells from outflow boundary to gravity wave to MCV have pulled away.  So, it appears the squall line will be the main wave of storms for the day-night.

Squall line will pass here as we get into the overnight with a wind, but also isolated tornado threat.  Tornadoes of EF0-EF1 strength would occur in LEWPs or “S”-shapes in the line as eddies/meso-vortices.

Stratified rain behind the squall line will likely linger into Tuesday morning.

SEVERE NORTHEAST & WEST & SOUTHWEST OF US TODAY & RIGHT NOW………….

We had severe weather outbreak to our northeast in Michigan (widespread wind damage with large hail [roofs off homes & at one country club 40 large trees were uprooted]) & to our southwest from Missouri to Texas today (widespread severe weather outbreak [large, violent tornadoes & very large hail to softball size]), but in-between we are faring well, so far.

NOW-TONIGHT TO EARLY TUESDAY…………….

Have have had scattered storms popping on outflow boundaries, gravitiy waves & MCV since 2 p.m.  However, they have all now collapsed.  Of note, the May EF0 tornado near New Ross & Yeddo last year was spawned by an MCV-induced supercell t’storm.

Behind the present collapse is 1) lack of good dynamics (pretty much staying north & west & southwest of the area) & recent capping (despite nice surface instability).

HOWEVER, I am still watching for a few supercells to develop this evening, namely with enhanced cumulus field just south of storm that just collapsed over Fountain & Montgomery counties & in enhanced cumulus field running from near Morocco to Wheatfield & over to Starke County.  Nice mid-level winds are spreading into Illinois, initiating supercells that are forming in central Illinois.

For the overnight, I have concerns regarding the developing squall line to our west as supercells merge & morph.  I think we still need to watch any random supercell(s) that can develop ahead of the line not only this evening, but overnight.  As low-level jet begins to nose in, the capping issues this evening will be overcome & the main area of storms with its better dynamics will move in.  This will be moving in after dusk with a wind/isolated tornado threat.

Broken line of non-severe showers/t’storms is runing from Bunker Hill to Forest to Lebanon & Ladoga.  Best shear & dynamics are north & southwest of us, so these don’t have much shear to go on but they are tapping some decent instability.

Firing on gravity wave/outflow boundary, these continue to push east.

Meanwhile MCV is pivoting through Illinois, but is encountering a pocket of drier, more stable air, inhibiting development.

Current thinking is that current showers/t’storms will exit, then as better shear & mid-level wind fields overspread area, storms may really pulse up with side-swiping MCV & diffust outflow boundary southwest of here.

Thinking as this stronger mid-level flow overspreads area, watch may be issued.  Scattered supercells will tend to gell into one or more clusters with time.

We will then need to watch for another round of storms tonight-early Tuesday morning as a squall line passes.

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MCV with outflow boundary/gravity wave & strong mid-level winds will likely trigger some storms over the next several hours in our area.  Watches are already in effect to our northeast & southwest.

Some debri cloudiness from collapsed t’storms to our west overnight is passing right now.  However, this will exit & skies will rapidly clear this afternoon with highs of 85-90 with dew points near 70.

Outflow boundary, subtle gravity wave & MCV will act as trigger for some scattered supercell t’storms late today with a large hail, wind & isolated EF0-EF2 tornado threat.  The best low-level winds for more tornadoes & large EF3-EF4 tornadoes will likely reside in Oklahoma & Missouri to northern Arkansas, however.  Any supercells would likely tend to congeal into one or more clusters before exiting the viewing area.

Projected surface instability per HRRR Hi-Res model at 4 p.m. shows very impressive 2500-5000 J/kg of CAPE.  I think 3000-4000 J/kg is definitely reasonable as a forecast number.  This is energy for storms to feed upon.  Such number promote very strong updrafts & with bulk shear, promote growth & accretion of large hailstones.

Tonight, developing squall line to our west will approach & pass late tonight-early Tuesday morning with a wind & perhaps isolated EF0 tornado threat.

Stay tuned as small changes to the forecast & timing are still possible as the small-scale details continue to emerge this afternoon & tonight.

WLFI Video Blog Entry May 20, 2013

Forecast Discussion:

With plenty of sunshine throughout the first part of our day, afternoon temperatures are expected to once again reach the upper 80s. When you pair our well above average temperatures along with the muggy air mass settled in over the Midwest, it makes for an unstable atmosphere. Our first round of severe weather will come as early as this afternoon as a line of thunderstorms makes its way across the viewing area. The main threats from our potential severe weather over the next 48 hours will be hail larger than an inch in diameter and strong straight line wind gusts in excess of 60 mph; however, we can not count out isolated EF0 – EF2 tornados either. The second round of possibly severe storms will arrive late tonight into early tomorrow morning. It will come in the form of a squall line, and though it will have lost a lot of its steam by the time it reaches our boarders, it may still pack a hefty punch. Even though temperatures will only climb into the mid to low 80s tomorrow, that risk for volatile weather will remain. Multiple semi organized lines of storms may develop ahead of a cold front that will kick to our east by Wednesday morning. There may be some lingering rainfall on both Wednesday and Thursday as this cold front positions itself to our east. High pressure will then take control for the holiday weekend. Afternoon high temperatures will have fallen to 69° by Friday before they begin to bounce back come Saturday. Conditions for the Around the Fountain Art Fair this Saturday are looking picture perfect; it will be 72° and Sunny that day. If you’re headed to the race this weekend, you may be in fro a treat! If the current trends hold, it will be 74° and mostly sunny at the track! That’s a heck of a lot better than the 91° high temperature that was measured last year.