MD 1550 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR CENTRAL AND SOUTHERN IA
MESOSCALE DISCUSSION 1550
NWS STORM PREDICTION CENTER NORMAN OK
1240 PM CDT MON JUL 27 2015
AREAS AFFECTED...CENTRAL AND SOUTHERN IA
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 271740Z - 272045Z
PROBABILITY OF WATCH ISSUANCE...20 PERCENT
SUMMARY...A RELATIVELY COMPACT MCS WILL ADVANCE TO THE EAST ACROSS
CENTRAL AND PORTIONS OF SOUTHERN IA THIS AFTERNOON. ALTHOUGH MOST
OF THE WIND GUSTS ASSOCIATED WITH THIS ACTIVITY SHOULD REMAIN
SUB-SEVERE...LOCALLY STRONG WIND GUSTS /POTENTIALLY REACHING OR
EXCEEDING 50 KT/ CANNOT BE RULED OUT.
DISCUSSION...DMX RADAR TRENDS AND PERSISTENT CLOUD-TOP COOLING PER
IR SATELLITE IMAGERY INDICATED A FORWARD-PROPAGATING LINEAR MCS
ADVANCING EASTWARD ACROSS CENTRAL IA. AS THE STORMS MOVED THROUGH
THE COUNTIES OF BOONE...DALLAS...AND MADISON THE ATTENDANT OUTFLOW
BOUNDARY HAD MOVED AHEAD OF THE STRONGER BAND OF STORMS INDICATING
ANY STRONGER WIND GUSTS ATTENDANT TO THIS MCS MAY NOT BE REACHING
THE SURFACE. HOWEVER...IF THE STRONGER ACTIVITY CAN OVERTAKE THE
OUTFLOW BOUNDARY...AS MAY BE ONGOING IN NORTHEAST DALLAS COUNTY AND
PORTIONS OF WESTERN POLK COUNTY...THEN 55+ KT WLY WINDS OBSERVED
AROUND 500 FEET AGL IN THAT PORTION OF DALLAS COUNTY WILL HAVE A
GREATER POTENTIAL TO REACH THE SURFACE.
GIVEN THE ORGANIZATION OF THIS MCS WITH AN ACCOMPANYING COLD POOL
AND REAR-INFLOW JET OF 40-45 KT AT 1-2 KM AGL PER DMX RADAR
COMBINED WITH A SURFACE-BASED INFLOW REGIME THAT HAS MODERATELY
STRONG INSTABILITY...THIS COMPLEX IS EXPECTED TO PERSIST THROUGH THE
AFTERNOON...TRACKING TO EAST ALONG AN INSTABILITY GRADIENT. AN
EVENTUAL SOUTHEASTWARD TURN MAY OCCUR BETWEEN 19-20Z AS THE SOUTHERN
FLANK REACHES POWESHIEK AND MAHASKA COUNTIES WHERE THE INSTABILITY
GRADIENT IS ORIENTED NW-SE. ALTHOUGH SHORT-TERM MODELS HAVE HAD
DIFFICULTY FORECASTING THIS COMPLEX...THE HRRR /THOUGH SLOW WITH ITS
DEVELOPMENT AND PLACEMENT/ SUGGESTS THIS STORM COMPLEX SHOULD
PERSIST THROUGH THE AFTERNOON WITH AN EVENTUAL SEWD MOVEMENT. ELY
SURFACE WINDS WILL CONTINUE TO ENHANCE DEEP SHEAR FOR STORM
ORGANIZATION...WHILE FORCING FOR ASCENT ATTENDANT TO A WEAK
EWD-MOVING MIDLEVEL IMPULSE AIDS IN SUSTAINING TSTM DEVELOPMENT
WITHIN THIS MCS.
..PETERS/GOSS.. 07/27/2015
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...DVN...DMX...
LAT...LON 41909250 41849204 41549168 40999158 40909197 40899242
41129292 41339404 41629419 41869415 42029404 41909250
from SPC Mesoscale Discussions http://1.usa.gov/1U2v8tV
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