Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 282040
SWOMCD
SPC MCD 282040
IAZ000-MOZ000-NEZ000-282245-

MESOSCALE DISCUSSION 1564
NWS STORM PREDICTION CENTER NORMAN OK
0340 PM CDT TUE JUL 28 2015

AREAS AFFECTED...SOUTHEAST NEB/PARTS OF WESTERN...CENTRAL AND
SOUTHERN IA/EXTREME NORTHERN MO

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 282040Z - 282245Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...THE POTENTIAL FOR NEW TSTM DEVELOPMENT IS EXPECTED TO
INCREASE THROUGH THE AFTERNOON ACROSS SOUTHEAST NEB INTO PORTIONS OF
WESTERN...CENTRAL AND SOUTHERN IA...WITH ACTIVITY EVENTUALLY
SPREADING INTO FAR NORTHERN MO.  WW ISSUANCE IS BEING CONSIDERED.

DISCUSSION...TRENDS IN MOSAIC RADAR IMAGERY AND SURFACE OBSERVATIONS
SHOWED A COLD FRONT ADVANCING EASTWARD INTO NORTHWEST IA AND EASTERN
NEBRASKA...AND AT 20Z THIS BOUNDARY EXTENDED FROM WRN MN SSWWD
THROUGH NORTHWEST IA /30 W SPW/ TO 30 ESE OLU TO 15 WNW CNK.
MEANWHILE...AS INDICATED IN THE RECENT SWODY1...AN OUTFLOW BOUNDARY
HAS RETURNED NWD THIS AFTERNOON FROM THE LATE MORNING POSITION ALONG
THE MO/IA BORDER.  THIS BOUNDARY CURRENTLY EXTENDS FROM THE
INTERSECTION WITH THE COLD FRONT IN DODGE COUNTY NEB EWD THROUGH
WESTERN IA /ALONG AND NORTH OF I-80/ TO NEAR DSM...AND THEN INTO
SOUTHEAST IA.

STRONG SURFACE HEATING ACROSS THE WARM SECTOR HAS BOOSTED AFTERNOON
TEMPERATURES TO AROUND 90 F...WHILE SLY WINDS AND EVAPOTRANSPIRATION
HAVE RESULTED IN SURFACE DEW POINTS RISING INTO THE MID-UPPER
70S...RESULTING IN RECENT REDUCTION IN SURFACE-BASED INHIBITION.
THIS COMBINED WITH A PLUME OF STEEP MIDLEVEL LAPSE RATES /7-7.5 C
PER KM/ IS CONTRIBUTING TO VERY STRONG INSTABILITY /MLCAPE 2000-3500
J PER KG/.  VERTICALLY VEERING WIND PROFILES WITH SWLY 500-MB FLOW
OF 35 KT HAS ALLOWED FOR BULK SHEAR TO BECOME SUPPORTIVE FOR
ORGANIZED STORMS.  DESPITE FAVORABLE THERMODYNAMICS/KINEMATICS...
RECENT TRENDS IN THE CU FIELD ACROSS ERN NEB AND WEST-CENTRAL/SWRN
IA DO NOT INDICATE STRONG VERTICAL DEVELOPMENT PER VISIBLE SATELLITE
IMAGERY.  THIS MAY BE DUE TO SUBSIDENCE IN THE WAKE OF THE EARLIER
MCS AND APPARENT SHORTWAVE RIDGING PRESENT ACROSS ERN NEB/WRN IA PER
WATER VAPOR IMAGERY.  MEANWHILE...SOME INCREASE IN CONVECTIVE
DEVELOPMENT ACROSS CENTRAL NEB MAY BE INDICATING AN INCREASE IN
LARGE SCALE ASCENT AHEAD OF A WEAK MIDLEVEL IMPULSE ADVANCING NEWD
FROM NERN CO.  ALTHOUGH MOST SHORT-TERM MODELS LACK ROBUST
CONVECTIVE DEVELOPMENT IN THE SHORT-TERM...THE APPROACHING
DEEP-LAYER ASCENT MAY PROVE SUFFICIENT FOR NEW STORM DEVELOPMENT
ACROSS SOUTHEAST NEB INTO SWRN IA BY 22-23Z.

..PETERS/GOSS.. 07/28/2015

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

ATTN...WFO...DVN...DMX...EAX...OAX...

LAT...LON   40909663 41559618 41829528 41859380 41569246 41009175
            40659179 40349301 40239443 40089522 40049591 40099655
            40309697 40909663




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