ACUS11 KWNS 281617
SWOMCD
MESOSCALE DISCUSSION 1415
NWS STORM PREDICTION CENTER NORMAN OK
1116 AM CDT THU JUL 28 2016
AREAS AFFECTED...PORTIONS OF NRN IL AND FAR SRN WI
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 281616Z - 281845Z
PROBABILITY OF WATCH ISSUANCE...5 PERCENT
SUMMARY...PORTIONS OF NRN IL AND FAR SRN WI ARE BEING MONITORED FOR
A WEAK/BRIEF TORNADO POTENTIAL THROUGH THE AFTERNOON. SUCH RISK
SHOULD REMAIN MARGINAL...AND WW ISSUANCE IS NOT EXPECTED.
DISCUSSION...SFC MESOANALYSIS PLACES A QUASI-STATIONARY BOUNDARY
FROM THE CHICAGO AREA THROUGH ROCKFORD AND THEN WWD TO SFC LOW
PRESSURE ANALYZED NEAR DUBUQUE. A WEAK COLD FRONT ARCHES SWWD FROM
THE SFC LOW NEAR THE MS RIVER AND SWWD INTO N-CNTRL MO...WHILE A SFC
TROUGH/OUTFLOW BOUNDARY INTERSECTS THE QUASI-STATIONARY BOUNDARY
NEAR CHICAGO AND EXTENDS SWD INTO CNTRL IL. THE AIR MASS IN
PROXIMITY TO THE SFC TROUGH/OUTFLOW BOUNDARY AND QUASI-STATIONARY
BOUNDARY...AND WITHIN THE WARM SECTOR...CONTINUES TO DESTABILIZE AS
INSOLATION CONTRIBUTES TO DIABATIC HEATING OF A MOIST BOUNDARY
LAYER. WITH SFC DEWPOINTS GENERALLY IN THE LOWER TO LOCALLY MIDDLE
70S...MLCAPE HAS INCREASED TO AROUND 1000-2000 J/KG.
WITH ADDITIONAL DIURNAL HEATING...AN INCREASE IN CONVECTIVE
COVERAGE/INTENSITY IS EXPECTED ACROSS THE REGION THROUGH THE
AFTERNOON. THIS IS ANTICIPATED GIVEN THE LARGELY UNCAPPED/MOIST
ENVIRONMENT...AND MODEST ASCENT AROUND THE SFC LOW AND
AFOREMENTIONED BOUNDARIES.
POOR MID-LEVEL LAPSE RATES WILL CONTINUE LIMITING THE DEGREE OF
NORMALIZED CAPE AND STORM-SCALE UPWARD ACCELERATIONS. HOWEVER...THE
MOIST BOUNDARY LAYER IS CONTRIBUTING TO DIURNALLY INCREASING
LOW-LEVEL BUOYANCY...WITH AROUND 100-150 J/KG OF 0-3-KM MLCAPE
ACROSS THE WARM SECTOR.
THE COMBINATION OF THIS LOW-LEVEL BUOYANCY IN THE MOIST
ENVIRONMENT...AND AMBIENT SFC VERTICAL VORTICITY IN PROXIMITY TO THE
RELATIVELY COMPACT SFC LOW...QUASI-STATIONARY BOUNDARY...AND SFC
TROUGH/OUTFLOW BOUNDARY...WILL SUPPORT THE POTENTIAL FOR A FEW
STORM-SCALE CIRCULATIONS WITH TSTM CELLS THROUGH THE AFTERNOON
HOURS. LOCALLY BACKED SFC WINDS N OF THE QUASI-STATIONARY BOUNDARY
AND RELATED STREAMWISE VORTICITY MAY ALSO ENCOURAGE SUCH POTENTIAL.
A WEAK/BRIEF TORNADO CANNOT BE RULED OUT WITH THIS ACTIVITY.
HOWEVER...GIVEN THE RELATIVELY WEAK LOW-LEVEL FLOW...LACK OF ANY
SALIENT MID-LEVEL WAVE/PERTURBATION ENHANCING LARGE-SCALE UPWARD
MOTION...AND POOR MID-LEVEL LAPSE RATES...A MORE SUBSTANTIAL SVR
RISK IS NOT ANTICIPATED.
..COHEN/DIAL.. 07/28/2016
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LOT...ILX...MKX...DVN...
LAT...LON 41848772 41208816 40818895 40988973 41389008 41729014
42559009 42708933 42608821 42408780 41848772
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