DAY 3 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0230 AM CST THU NOV 14 2013 VALID 161200Z - 171200Z ...NO SVR TSTM AREAS FORECAST... ...SYNOPSIS... THE VIGOROUS SHORT WAVE IMPULSE EXPECTED TO DIG INTO THE PACIFIC NORTHWEST BY LATE FRIDAY NIGHT APPEARS LIKELY TO REMAIN PROGRESSIVE DURING THIS FORECAST PERIOD. CONSIDERABLE VARIABILITY EXISTS AMONG THE MODELS CONCERNING THE SPEED OF THIS FEATURE INTO AND THROUGH THE CENTRAL U.S...WITH THE GFS REMAINING SIGNIFICANTLY FASTER THAN THE ECMWF EAST OF THE ROCKIES AND THROUGH THE CENTRAL PLAINS. THE 14/00Z OPERATIONAL ECMWF AND THE ECMWF ENSEMBLE MEAN HAVE TRENDED A BIT FASTER...AND APPEAR IN RELATIVELY GOOD AGREEMENT WITH THE 14/03Z NCEP SREF...WHICH IS FASTER THE 14/00Z OPERATIONAL NAM. IT CURRENTLY SEEMS MOST PROBABLE THAT STRONG MID-LEVEL HEIGHT FALLS ASSOCIATED WITH THE SHORT WAVE TROUGH WILL SHIFT EAST OF THE ROCKIES INTO THE CENTRAL PLAINS SATURDAY NIGHT...SUPPORTING A DEEPENING SURFACE CYCLONE ACROSS THE CENTRAL PLAINS THROUGH THE MID MISSOURI VALLEY BY 12Z SUNDAY. IN ADVANCE OF THE PRIMARY SHORT WAVE IMPULSE...AND ASSOCIATED SURFACE CYCLONE...ANOTHER SIGNIFICANT SHORT WAVE IMPULSE AND ASSOCIATED SURFACE FRONTAL WAVE ARE EXPECTED TO RAPIDLY PROGRESS NORTHEAST OF THE CENTRAL PLAINS...INTO THE UPPER GREAT LAKES REGION...DURING THE DAY SATURDAY...BEFORE CONTINUING NORTH NORTHEASTWARD THROUGH NORTHERN/EASTERN ONTARIO. ALTHOUGH LOW-LEVEL MOISTENING WILL ALREADY BE UNDERWAY IN ASSOCIATION WITH A DEVELOPING RETURN FLOW ACROSS THE WESTERN GULF COAST...TOWARD THE UPPER MISSISSIPPI VALLEY/UPPER GREAT LAKES REGION...DEEPER BOUNDARY LAYER MOISTURE RETURN WILL BE SLOWER TO OCCUR...AND MAY NOT BEGIN INCREASING SUBSTANTIVELY ACROSS EASTERN PORTIONS OF THE CENTRAL PLAINS/OZARK PLATEAU AND MIDDLE MISSISSIPPI VALLEY UNTIL SATURDAY EVENING. DESTABILIZATION PROBABLY WILL BE SUFFICIENT TO SUPPORT INCREASING THUNDERSTORM ACTIVITY EAST OF THE MID MISSOURI VALLEY THROUGH THE UPPER MISSISSIPPI VALLEY/UPPER GREAT LAKES REGION DURING THE DAY SATURDAY...BUT ANY SEVERE THUNDERSTORM POTENTIAL STILL APPEARS LIKELY TO AWAIT BETTER MOISTURE RETURN...AND MID-LEVEL FORCING ASSOCIATED WITH THE STRONG UPSTREAM IMPULSE. ...LOWER CENTRAL PLAINS INTO UPPER MISSISSIPPI VALLEY... MODELS ARE BECOMING MORE SUGGESTIVE OF INCREASING SEVERE STORM POTENTIAL ACROSS THE CENTRAL U.S. DURING THE LATTER HALF OF THIS FORECAST PERIOD. DUE TO CONSIDERABLE LINGERING UNCERTAINTIES... ONLY SUB-SLIGHT RISK SEVERE PROBABILITIES ARE BEING INTRODUCED FOR NOW...BUT THESE COULD BE INCREASED IN LATER OUTLOOKS FOR THIS TIME PERIOD. THE AREAL DELINEATION OF THE 5 PERCENT SEVERE PROBABILITIES WAS HEAVILY INFLUENCE BY THE AFOREMENTIONED ECMWF/ECMWF ENSEMBLE AND NCEP SREF ENSEMBLE DEPICTION OF DEVELOPMENTS. INCREASING LOW-LEVEL MOISTURE/CAPE AND VERTICAL SHEAR ALONG THE WESTERN EDGE OF THE STRENGTHENING LOW-LEVEL JET /50-60+ KT AT 850 MB/ MAY PROVIDE THE FOCUS FOR SEVERE STORM DEVELOPMENT...AS THE LEADING EDGE OF STRONGER MID-LEVEL FORCING FOR UPWARD VERTICAL MOTION SHIFTS INTO THE PLAINS. THIS COULD BE AS EARLY AS LATE SATURDAY EVENING...BEFORE POTENTIAL INCREASES AND SLOWLY DEVELOPS EASTWARD OVERNIGHT. THE ENVIRONMENT MAY BECOME CONDUCIVE TO THE DEVELOPMENT OF SUPERCELLS...AND THE EVOLUTION OF A SQUALL LINE. ..KERR.. 11/14/2013
Posted on: Fri, 15 Nov 2013 04:32:08 +0000
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