WXALERT: Severe Risk Increasing for Today

From: Nick Weig
Area under consideration for SVR Watch on Friday, May 8, 2009

Area under consideration for SVR Watch on Friday, May 8, 2009

I admit I did not expect any severe weather risk so I am certainly caught off guard by this latest development.  A low pressue system is tracking into the state this afternoon and bringing with it a wave of energy that could spark severe weather in Iowa this afternoon.  Although a risk of tornadoes is there, the greatest threat appears to be large hail and damaging winds.  Will try to update as best I can this afternoon on here and our facebook page.

Here is the text from the Storm Prediction Center on the possibility of severe weather today:

SEVERE THREAT WILL INCREASE ACROSS IA AHEAD OF A VIGOROUS SHORT WAVE TROUGH APPROACHING FROM THE NRN PLAINS. ALTHOUGH INSTABILITY SHOULD REMAIN MODEST…INTENSE MID-LEVEL FLOW WILL SUPPORT TSTM ORGANIZATION AND PROBABLE HAIL DEVELOPMENT INITIALLY. A SEVERE TSTM WATCH WILL LIKELY BE NEEDED BY 20Z. LATEST SUBJECTIVE SURFACE ANALYSIS PLACED A 1004 MB CYCLONE NEAR TQE DOWNSTREAM OF A POTENT SHORT WAVE TROUGH OVER THE NRN PLAINS /PER WATER VAPOR IMAGERY/. A QUASI-STATIONARY FRONT WAS DRAPED EWD FROM THE LOW ALONG THE US-20 CORRIDOR…WITH A COLD FRONT SWWD INTO NRN KS. STRONGLY FORCED ASCENT SHOULD RESULT IN TSTM COVERAGE INCREASING INVOF THESE BOUNDARIES OVER IA. INSTABILITY AND LOW-LEVEL FLOW BOTH APPEAR WEAK IN THE WAKE OF LARGE-SCALE MCS CENTERED OVER THE MID-MO RIVER VALLEY. HOWEVER…CONTINUED DAYTIME HEATING MAY RESULT IN MLCAPES APPROACHING 1000 J/KG BY LATE AFTERNOON. ALTHOUGH LOW-LEVEL WINDS SHOULD REMAIN MODEST…MODEL FORECASTS ARE QUITE CONSISTENT ON STRENGTHENING 500 MB WINDS TO AOA 80 KT OVER MUCH OF NEB THIS AFTERNOON AND ACROSS THE MO RIVER VALLEY BY 00Z. THIS INCREASE IN SPEED SHEAR ALONG WITH NEARLY STRAIGHT-LINE HODOGRAPHS SHOULD INITIALLY FAVOR SPLITTING CELLS PRODUCING SEVERE HAIL. WITH TIME…UPSCALE GROWTH AMIDST THE STRONG ASCENT MAY LEAD TO A FORCED LINE WITH STRONG/SEVERE WIND GUSTS.

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