Severe Storm Outlook Narrative (AC)
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872
ACUS11 KWNS 281617
SWOMCD
SPC MCD 281616
ILZ000-WIZ000-281845-

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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