WXALERT: Watch Likely for Parts of Iowa

mcd920

The Storm Prediction Center is anticipating a watch for a large portion of central and southwest Iowa for Saturday Evening.  All modes of severe weather will be possible. Eastern Iowa will be on the lookout for overnight severe weather and potential for heavy rains.

Here is the raw text from SPC…

TRENDS ARE BEING MONITORED FOR AN INCREASING SEVERE THREAT. UNCERTAINTIES STILL EXIST…BUT A WW COULD BECOME NECESSARY PRIOR TO 22-23Z. STRONG LOW-LEVEL CONVERGENCE/WARM ADVECTION APPEARS FOCUSED NEAR AND JUST EAST OF A FRONTAL WAVE ACROSS THE MID MISSOURI VALLEY… WHERE SURFACE HEATING AND INCREASING DEW POINTS ARE CONTRIBUTING TO BOUNDARY LAYER DESTABILIZATION. RUC GUIDANCE SUGGESTS MIXED LAYER CAPE IS NOW IN EXCESS OF 1500 J/KG…WITH INDICATIONS OF WEAKENING MID-LEVEL INHIBITION…PARTICULARLY FOR BOUNDARY LAYER PARCELS NEAR THE OMAHA AREA. THIS APPEARS LIKELY TO WEAKEN FURTHER DURING THE NEXT FEW HOURS…WITH THE SUPPRESSION OF THE THERMAL RIDGE NEAR 700 MB…ASSOCIATED WITH PASSAGE OF A WEAK MID-LEVEL IMPULSE WITHIN THE STRONG SOUTHWESTERLY MID/UPPER FLOW ACROSS THE REGION. AT THE SAME TIME…THE APPROACH OF ANOTHER LOW AMPLITUDE WAVE WILL MAINTAIN LOW-LEVEL WARM ADVECTION…AND THIS FORCING MAY SUPPORT THE INITIATION OF AT LEAST ISOLATED STORM DEVELOPMENT TOWARD THE 23-00Z TIME FRAME. IN THE PRESENCE OF STRONG DEEP LAYER SHEAR BENEATH 50+ KT 500 MB FLOW…THE ENVIRONMENT WILL BE FAVORABLE FOR SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL. THE PRECISE LOCATION OF STORM INITIATION IS STILL NOT CLEAR…BUT IT SEEMS MOST PROBABLE EAST OF THE OMAHA AREA INTO THE DES MOINES VICINITY. WHILE THIS ACTIVITY MAY INITIALLY FORM ABOVE A SHALLOW WEAK NEAR-SURFACE STABLE LAYER…SIZABLE CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS NEAR A 30-40 KT SOUTHERLY LOW-LEVEL JET WILL SUPPORT POTENTIAL FOR TORNADOES AND DAMAGING WIND GUSTS.

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