WLFI Video Blog Entry May 21, 2013

Forecast Discussion:

Skies are beginning to clear throughout the viewing area as drier air filters into the region following the passage of this morning’s storms system. The additional sunshine will begin to destabilize the atmosphere as the day progresses. If you take that unstable atmosphere and add a weak upper level jet to it you get slight risk for severe weather. While the environment to support inclement weather is in place over the viewing area, we still need a trigger to get the ball rolling. I’m not so sure we’ll receive that trigger. We may see a few isolated cells throughout the afternoon, but the latest models have driven most of the afternoon storms far to our south. Our best chance for precipitation won’t arrive until the evening and overnight hours. It’s possible that some showers and storms may pop over the northern half of the viewing area after dinner time. Conditions by then will not be cohesive for severe thunderstorm development; the upper level jet will have shifted and the atmosphere will have begun to stabilize. That being said, some of the storms that develop later tonight could produce gusty winds and small hail. The low pressure system that’s caused the recent rash of severe weather across the Great Plains and Mid West will finally move eastward tomorrow. Its cold front will push through the region tomorrow bringing scattered showers and thunderstorms to the viewing area. Thursday looks drier with some lingering cloud cover; afternoon temperatures will have fallen to the upper 60s. We’ll stay in the mid to upper 60s for both Friday and Saturday as well as high pressure moves in from the Great Plains. The rest of the weekend looks warmer as that high positions itself to our east and brings southerly winds to Indiana.

I am still not too concerned about any severe threat today or tonight here, but will watch.  Some additional scattered showers & a t’storms may tend to move back in with time later today-tonight, but severe threat continues to look low.

BIG thanks to all of you spotters for your help in tracking the squall line lastnight!  Your measured gusts with your weather stations & estimated wind data was instrumental in us tracking the storms.

Again, the real key in the pulsing up of the wind damage was that low-level jet nosing in.  After brief weakening trend in the line, low-level jet enhanced the squall line’s ability to produce damaging straight-line winds with some mesovortices (rotation for isolated tornado) briefly noted in the line.  One was over southeast Carroll County with others south of here in Putnam & Hendricks counties.

1:10 p.m. UPDATE:  Don’s weather station at Radnor measured gust to 61 mph just before 3 a.m.  I plotted that report on the map below.

Jim in Kentland measured a gust of 44 mph & also had penny-sized hail.  His wind report is also plotted in the map below.

1 Mile Southwest of Hillsboro   Barn Destroyed & Trees Down

New Richmond    Trees Down

Northwest Boone County    Trees Down

Flora    Trees & Powerlines Down

Tipton   Trees Down

3 miles south of Burlington  2 chicken houses destroyed.

Bringhurst     Trampoline in the field. It had been picked up, taken over our donkey’s fence and dropped in the field about 1/4 mile.

Middlefork    Trees & Limbs down

Wind Gust Map Below (M = Measured, E = Estimated by Spotter)

Larger storm report map is courtesy of NOAA’s Storm Prediction Center.

Watches & warnings have been cancelled, but rain remains in the viewing area as of 4 a.m.

Gusts 60 mph or more possible in these areas.

Measured gust to 50 mph at 2:38 p.m. at WLFI.

Other gusts:

M54 mph  Fowler

E50 mph northwest of Romney

M45 mph  Attica

 E45 mph  East of Attica

Squall line with a couple of bows is moving in.  Gusts of 35-50 mph are possible, but a few severe gusts may make it to the ground with time as low-level jet noses in more & more.

We also still need to watch isolated, brief tornado threat, especially now again as low-level jet comes in more.

Gusts (M = Measured, E = Estimated):

E50 mph  Linden

M45 mph  6 Miles Northwest of Romney

E45 mph  East of Attica

M45 mph  Attica

M41 mph  Covington

M38 mph  Morocco

M37 mph  Pine Village

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.