Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 211901
SWOMCD
SPC MCD 211900
ILZ000-IAZ000-WIZ000-MNZ000-MOZ000-SDZ000-212100-

MESOSCALE DISCUSSION 1726
NWS STORM PREDICTION CENTER NORMAN OK
0200 PM CDT WED SEP 21 2016

AREAS AFFECTED...SERN MN/NERN AND ERN IA/NRN IL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 211900Z - 212100Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...STORMS DEVELOPING INVOF A NW-SE OUTFLOW ACROSS ERN IA/NRN
IL MAY POSE ISOLATED SEVERE RISK.  SUBSEQUENT STORM DEVELOPMENT MAY
OCCUR FARTHER W/NW AS THE AFTERNOON WEARS ON...WITH POTENTIALLY MORE
SUBSTANTIAL RISK.  EVENTUAL WW ISSUANCE MAY BE NEEDED.

DISCUSSION...LATEST VISIBLE SATELLITE LOOP IN CONJUNCTION WITH
RECENT SURFACE ANALYSIS SHOWS A NW- TO SE-ORIENTED OUTFLOW BOUNDARY
MOVING SWWD ACROSS ERN IA AND NRN IL ATTM...WITH CONVECTION
INCREASING ALONG -- AND JUST AHEAD OF -- THIS BOUNDARY.  STRONGEST
CELLS ATTM ARE OCCURRING OVER THE IL PORTION OF THE BOUNDARY...WHERE
FLOW ALOFT REMAINS RELATIVELY WEAK.  THE MODEST SHEAR IN THIS REGION
SUGGESTS THAT STORMS SHOULD REMAIN ONLY WEAKLY ORGANIZED -- AND
ASSOCIATED SEVERE RISK THUS LIKELY TO REMAIN LOCALIZED.

FARTHER W...TOWERING CU IS INDICATED ALONG THE OUTFLOW ACROSS
NRN/ERN IA...WITH SOME INCREASE IN VERTICAL DEVELOPMENT OF THE CU
FIELD ALSO INDICATED W OF THE OUTFLOW -- PARTICULARLY INTO CENTRAL
IA.  STORMS DEVELOPING ON THE IMMEDIATE BOUNDARY WILL LIKELY BE
UNDERCUT QUICKLY...AS WLY MEAN FLOW ALOFT SUGGESTS EWD STORM MOTION
ACROSS/TO THE COOL SIDE OF THE BOUNDARY.  AS SUCH...THE COMBINATION
OF THESE STORMS BECOMING SLIGHTLY ELEVATED WITH TIME...AND MOVING
OUT OF THE ZONE OF GREATER LOW-LEVEL VORTICITY...SUGGESTS LIMITED
SEVERE RISK ALONG THE OUTFLOW IN THE SHORT TERM.

GREATER SEVERE RISK MAY POSSIBLY EVOLVE FARTHER W/NW...WITH CU
DEVELOPING OVER CENTRAL IA AND -- LATER -- INTO SRN MN AHEAD OF A
WEAK SURFACE LOW/ALONG THE W-E WARM FRONT.  HERE...AN ENVIRONMENT
FEATURING MODERATE INSTABILITY /MIXED-LAYER CAPE IN THE 3000 TO 3500
J/KG RANGE PER OBJECTIVE ANALYSES/ AND FLOW VEERING AND INCREASING
WITH HEIGHT MAY EVENTUALLY SUPPORT AMPLE RISK FOR DAMAGING
WINDS/LARGE HAIL OR EVEN AN ISOLATED TORNADO SO AS TO WARRANT
POSSIBLE WW ISSUANCE.

..GOSS/THOMPSON.. 09/21/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LOT...ILX...LSX...DVN...ARX...MPX...DMX...FSD...

LAT...LON   41868988 41838821 40968783 39919070 40809267 43209529
            43619692 44419665 44709311 44129197 42559081 41868988




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