SPC 2000Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0251 PM CDT TUE AUG 06 2013 VALID 062000Z - 071200Z ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT ACROSS PARTS OF THE UPPER MISSISSIPPI VALLEY SOUTHWESTWARD INTO THE MID MISSOURI VALLEY...AND ACROSS THE CENTRAL PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY... ONLY 2 MINOR ADJUSTMENTS HAVE BEEN MADE TO THE PREVIOUS FORECAST. 1...SHIFTED THE 5 PERCENT TORNADO PROBABILITY AREA NORTHWARD ACROSS S-CNTRL AND CNTRL MN TO ACCOUNT FOR THE POSSIBILITY OF A TORNADIC SUPERCELL TRACKING EWD ALONG A WARM FRONTAL ZONE. 2...INCLUDED THE CO/KS BORDER REGION IN THE 15 PERCENT HAIL/WIND PROBABILITY AND CATEGORICAL SLIGHT RISK TO ENCOMPASS AREAS ON THE WRN EDGE OF GREATER MOISTURE AND ONGOING STORM ACTIVITY. ..SMITH/KERR.. 08/06/2013 .PREV DISCUSSION... /ISSUED 1115 AM CDT TUE AUG 06 2013/ ...SYNOPSIS... MID/HIGH LEVEL SUBTROPICAL RIDGING...NOW CENTERED OVER TEXAS...APPEARS LIKELY TO REMAIN STRONG ACROSS MUCH OF THE CENTRAL AND SOUTHERN PLAINS INTO THE SOUTHEASTERN U.S. THROUGH THIS FORECAST PERIOD. HOWEVER...FLOW IS BECOMING INCREASINGLY CYCLONIC ACROSS THE NORTHERN ROCKIES AND PLAINS...INTO THE UPPER MISSISSIPPI VALLEY...TO THE SOUTH OF SIGNIFICANT CLOSED LOW CENTERED JUST SOUTHWEST OF HUDSON BAY. A COUPLE OF SHORT WAVE PERTURBATIONS ARE EMBEDDED WITHIN THIS LATTER REGIME...INCLUDING ONE SHEARED IMPULSE NOW DEVELOPING EAST SOUTHEASTWARD INTO THE DAKOTAS. THIS FEATURE IS FORECAST TO CONTINUE THROUGH THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES REGION LATER TODAY/TONIGHT...ACCOMPANIED BY A 50+ KT WEST NORTHWESTERLY 500 MB JET STREAK...THE SOUTHEASTWARD PROGRESSION OF A STRENGTHENING COLD FRONT ACROSS THE PLAINS/UPPER MISSISSIPPI VALLEY...AND AT LEAST ONE WEAK FRONTAL WAVE ACROSS CENTRAL MINNESOTA INTO NORTHWEST WISCONSIN LATE THIS AFTERNOON AND EVENING. WHILE A NORTHWARD RETURN OF LOW-LEVEL MOISTURE FROM THE MIDDLE MISSOURI VALLEY IS EXPECTED AHEAD OF THE FRONT TODAY...HIGHER MOISTURE CONTENT AIR CHARACTERIZED BY SURFACE DEW POINTS IN THE 70S AND PRECIPITABLE WATER NEAR 2 INCHES LIKELY WILL LINGER ALONG/NORTH OF A RESIDUAL FRONTAL ZONE FROM PARTS OF THE SOUTHEAST INTO THE LOWER MISSOURI VALLEY. THIS IS NEAR THE PERIPHERY OF THE SUBTROPICAL RIDGING...ALONG WHICH A NUMBER OF WEAK PERTURBATIONS HAVE AND CONTINUE TO EMERGE FROM THE MONSOONAL REGIME ACROSS THE SOUTHERN PLATEAU/GREAT BASIN INTO THE ROCKIES. STEEPEST MID-LEVEL LAPSE RATES...ASSOCIATED WITH WEAK COOLING ABOVE ELEVATED MIXED LAYER AIR EMERGING FROM THE PLATEAU REGION...HAVE BECOME FOCUSED IN A CORRIDOR ALONG AND SOUTH OF THE NORTHERN PLAINS MID-LEVEL JET STREAK. THIS MAY DEVELOP AS FAR EAST AS PORTIONS OF THE UPPER MISSISSIPPI VALLEY LATER TODAY. OTHERWISE...MID/UPPER TROUGHING NOW DEVELOPING NORTHWARD FROM BAJA/NORTHWEST MEXICO APPEARS LIKELY TO CONTINUE INTO THE FOUR CORNERS STATES TODAY...AS WEAK UPPER TROUGHING SLOWLY APPROACHES THE CALIFORNIA COAST AND CONTRIBUTES TO LARGE-SCALE ASCENT ACROSS THE NORTHERN SIERRA NEVADA AND ADJACENT GREAT BASIN INTO THE SOUTHERN CASCADES. ...UPPER MISSISSIPPI VALLEY INTO MID MISSOURI VALLEY... WITH STEEPENING MID-LEVEL LAPSE RATES...PRE-FRONTAL MOISTENING IS EXPECTED TO BE SUFFICIENT TO SUPPORT MODERATELY LARGE CAPE BY LATE AFTERNOON. COUPLED WITH THE STRENGTHENING DEEP LAYER SHEAR ...THE ENVIRONMENT WILL BECOME CONDUCIVE TO SEVERE STORM DEVELOPMENT WITHIN THE WARM SECTOR OF THE SURFACE WAVE...SOUTHWESTWARD ALONG THE DEVELOPING SURFACE FRONT. CONFIDENCE IS HIGHEST THAT THIS WILL OCCUR ROUGHLY FROM PARTS OF CENTRAL MINNESOTA INTO NORTHEASTERN NEBRASKA...ON THE NORTHERN EDGE OF THE WARMER MID-LEVEL AIR...BEFORE SPREADING SOUTHEASTWARD INTO WESTERN WISCONSIN AND NORTHERN/WESTERN IOWA THIS EVENING. A FEW SUPERCELLS ARE POSSIBLE INITIALLY...AND LOW-LEVEL HODOGRAPHS ACROSS EAST CENTRAL MINNESOTA INTO WEST CENTRAL WISCONSIN MAY BECOME STRONG ENOUGH TO SUPPORT A RISK FOR TORNADOES. OTHERWISE ...THE EVOLUTION OF ONE OR MORE ORGANIZED MESOSCALE CONVECTIVE SYSTEMS APPEARS POSSIBLE...ACCOMPANIED BY THE RISK FOR SEVERE WINDS AND HAIL...BEFORE DIMINISHING OVERNIGHT. ...CENTRAL PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY... BOUNDARY LAYER CAPE IS EXPECTED TO BECOME LARGE ONCE AGAIN WITHIN THE MOIST ENVIRONMENT ALONG AND NORTH OF THE REMNANT...CONVECTIVELY ENHANCED FRONTAL ZONE. IT IS POSSIBLE THAT FORCING ASSOCIATED WITH ANOTHER IMPULSE EMERGING FROM THE MONSOONAL FLOW COULD HELP OVERCOME MID-LEVEL INHIBITION ACROSS PARTS OF KANSAS LATE THIS AFTERNOON. OTHERWISE...IT APPEARS STRONGEST LOW-LEVEL WARM ADVECTION WILL SHIFT FROM PARTS OF SOUTHEAST KANSAS/SOUTHWEST MISSOURI INTO SOUTH CENTRAL MISSOURI ...WHERE ANOTHER LARGE STRONG/SEVERE STORM CLUSTER MAY FORM BY LATE THIS EVENING.
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_2000.html
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