MESOSCALE DISCUSSION 0729 NWS STORM PREDICTION CENTER NORMAN OK 0327 PM CDT MON MAY 20 2013 AREAS AFFECTED...NERN MO...CNTRL IL...W-CNTRL IND CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 202027Z - 202130Z PROBABILITY OF WATCH ISSUANCE...60 PERCENT SUMMARY...PROSPECTS FOR TSTM DEVELOPMENT ARE SOMEWHAT UNCERTAIN ACROSS W-CNTRL IND WWD INTO NERN MO...BUT THE ENVIRONMENT IS FAVORABLE FOR DMGG WINDS AND HAIL GIVEN STRONG HEATING/DESTABILIZATION. CONVECTIVE TRENDS ARE BEING MONITORED FOR A POSSIBLE WW...PARTICULARLY ACTIVITY DEVELOPING NEWD FROM SWRN MO TOWARDS THE MID-MS VALLEY. DISCUSSION...RADAR/SATELLITE TRENDS SHOW A DECAYING TSTM CLUSTER/MCV MOVING ACROSS N-CNTRL IL...WITH AN INCREASE IN SHALLOW BOUNDARY LAYER CU NOTED ACROSS E-CNTRL IL. THIS APPEARS TO BE DEVELOPING WITHIN A WEAK CONFLUENCE AXIS WHICH EXTENDS FROM 30 SE MMO TO 20 SSW SPI. BOTH MODIFIED 12Z RAOBS AND 12Z NAM FORECAST SOUNDINGS SUGGEST MLCAPE VALUES HAVE INCREASED TO 1000-1500 J/KG. WHILE THERE IS STILL SOME UNCERTAINTY TO WHAT DEGREE TSTMS WILL INTENSIFY/ORGANIZE OVER IL...A THREAT FOR DMGG WINDS AND LARGE HAIL COULD DEVELOP GIVEN STEEP LOW-LEVEL LAPSE RATES AND MODERATELY STRONG DEEP-LAYER SHEAR. ADDITIONALLY...TSTMS CURRENTLY DEVELOPING OVER WRN MO SHOULD EXPAND/DEVELOP NEWD TOWARDS E-CNTRL MO THROUGH LATE AFTERNOON. IT IS UNCERTAIN WHETHER A WW WILL BE REQUIRED WITHIN THE NEXT 1-2 HRS...BUT CONVECTIVE TRENDS CONTINUE TO BE MONITORED. ..ROGERS/KERR.. 05/20/2013
What a incredible photo from our friend Lorraine Mahoney! This tornado occurred near Rozel, Kansas.
Tornado outbreaks are known for their devastation and for peculiar stories which accompany them. Here's one: This paper was blown 80 miles from near Shawnee, OK to the Tulsa area in part of the mammoth EF-4 intensity twister which ripped across that section of the country. Larry Gordon Wilson took this photo and tells us magazines, newspapers and photos fell to earth in his area, having traveled, near as he can tell, near 80 miles from the point of origin.
Last night's thunderstorms, which were most pronounced over western sections of the metro area, produced lightning like the discharges photographed in the Wauconda area by Dirk Leahy.
This Victoria, Kansas wall cloud and emerging tornado from storm chaser Brad Hruza. More than 500 severe weather reports, including 29 tornado reports, were filed Sunday and Sunday night with the Storm Prediction Center. Wall clouds like this one are region’s of the thunderstorm where air is rising quickly. Tornadoes often spin up beneath wall clouds, which appear as an isolated lowering of the base of thunderstorm clouds—often in the rear southwest quadrant of the thunderstorm.
Cool temperatures and the absence of high humidity have suppressed severe thunderstorm activity across much of the Midwest this Spring. Locally, the quiet severe weather season is expected to come to an abrupt end late this afternoon and this evening as clusters of strong to severe thunderstorms rake across much of Illinois, northern Indiana and southern Wisconsin.
Storms could fire anytime this afternoon, however the highest probability will be between 6PM and 1AM.
Type of severe weather
All thunderstorms that develop later today will produce lightning, gusty winds and periods of heavy rain. A few of these storms are expected to turn "severe".
A thunderstorm is not considered "severe" unless it is producing damage via wind, hail or a tornado. Damage begins to occur when:
-Hail size reaches or exceeds 1.00" in diameter.
-Wind gusts reach or exceed 58mph.
BELOW: One possible storm scenario is depicted by our in house RPM model indicating several strong to severe thunderstorms roaming portions of northeast Illinois around 9PM tonight.
It won't be a washout but the week will start out stormy at times. Clusters of thunderstorms fueld by warm, moist air from the Gulf of Mexico could reach severe limits with the help of strong jet stream winds. The Storm Prediction Center has us outlooked for a slight risk of severe weather for both today (top image below) and tomorrow (bottom image below).
SPC forecasters say there is a potential for tornadoes:
There were at least 20 states this weekend that reported severe weather. Yesterday alone there were 28 reports of tornadoes across 4 states. That brings the total number of preliminary reports of tornadoes to 251 so far this year with 9 deaths. While the 2013 severe weather season is getting more active it still pales in comparison to last year when 617 tornadoes were reported through May with 66 deaths.
A center of low pressure will be moving east through Minnesota today while a warm front extends east across northern Wisconsin and the associated cold front sweeps east into Iowa. Illinois rests in the “warm sector” of this system with southerly winds pulling warm moist unstable air out of the central plains into the Midwest and western Great Lakes.
A band of showers and a few thunderstorms will work northeast through central into northern Illinois this morning with stronger – potentially severe storms expected to develop over northeast Illinois, southeast Wisconsin, northwest Indiana into southern Lower Michigan later this afternoon into tonight.
As this weather system advances east, the cold front should sweep through the Chicago area later Tuesday. The threat of strong potentially severe storms here could carry-over from Monday night into Tuesday morning.
In the severe weather outlook map below, much of illinois, Indiana, Wisconsin and Lower Michigan are in the slight risk areas for later today and tonight. The slight risk is approximently a 15 percent chance of damaging hail and winds in excess of 58 mph as well as a 5 percent chance of tornadoes within 25 miles of a given point.