Jun 18, 2015 1630 UTC Day 1 Convective Outlook
Updated: Thu Jun 18 16:23:39 UTC 2015 (20150618 1630Z Day 1 shapefile | 20150618 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20150618 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 259,666 29,858,263 Indianapolis, IN...Columbus, OH...Baltimore, MD...Washington, DC...Pittsburgh, PA...
MARGINAL 870,630 88,100,453 Detroit, MI...Charlotte, NC...Denver, CO...Nashville, TN...Kansas City, MO...
Probabilistic Tornado Graphic
20150618 1630 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 24,081 143,426 Gillette, WY...Sheridan, WY...Spearfish, SD...Belle Fourche, SD...
2 % 415,606 44,607,164 Detroit, MI...Indianapolis, IN...Columbus, OH...Baltimore, MD...Washington, DC...
Probabilistic Damaging Wind Graphic
20150618 1630 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 249,636 29,652,239 Indianapolis, IN...Columbus, OH...Baltimore, MD...Washington, DC...Pittsburgh, PA...
5 % 876,775 88,244,730 Detroit, MI...Charlotte, NC...Denver, CO...Nashville, TN...Kansas City, MO...
Probabilistic Large Hail Graphic
20150618 1630 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 15,079 179,155 Billings, MT...Laurel, MT...Lewistown, MT...
15 % 129,135 981,881 Billings, MT...Rapid City, SD...Great Falls, MT...Bozeman, MT...Helena, MT...
5 % 602,353 74,381,625 Detroit, MI...Indianapolis, IN...Columbus, OH...Baltimore, MD...Denver, CO...
   SPC AC 181623

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1123 AM CDT THU JUN 18 2015

   VALID 181630Z - 191200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON INTO
   TONIGHT ACROSS PARTS OF THE NORTHERN ROCKIES AND ADJACENT NORTHERN
   HIGH PLAINS...

   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON ACROSS PARTS OF
   THE CENTRAL AND SOUTHERN HIGH PLAINS...

   ...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS PARTS OF THE LOWER
   GREAT LAKES AND UPPER OHIO VALLEY INTO THE MID ATLANTIC COAST
   REGION...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
   ROCKIES AND PLAINS...THE OZARK PLATEAU AND MIDDLE MISSISSIPPI
   VALLEY...THE LOWER OHIO AND TENNESSEE VALLEYS AND APPALACHIANS...

   ...SUMMARY...
   A FEW SEVERE THUNDERSTORMS ARE EXPECTED LATE THIS AFTERNOON AND
   EVENING ACROSS PARTS OF THE NORTHERN ROCKIES AND ADJACENT HIGH
   PLAINS...AND PORTIONS OF THE CENTRAL INTO SOUTHERN HIGH PLAINS. 
   THUNDERSTORM ACTIVITY CAPABLE OF GENERATING LOCALLY DAMAGING WIND
   GUSTS AND SOME HAIL IS ALSO POSSIBLE ACROSS MUCH OF THE LOWER GREAT
   LAKES REGION...AND THE UPPER OHIO VALLEY INTO THE MID ATLANTIC
   COAST.

   ...SYNOPSIS...
   MID/UPPER SUBTROPICAL RIDGING WILL REMAIN PROMINENT ACROSS MUCH OF
   THE CENTRAL AND SOUTHERN TIER OF THE U.S. THROUGH THIS PERIOD. 
   WITHIN THE SOUTHERN BRANCH OF SPLIT MID-LATITUDE WESTERLIES...A
   SIGNIFICANT CLOSED LOW IS EXPECTED TO CONTINUE GRADUALLY MIGRATING
   INLAND ACROSS THE BRITISH COLUMBIA/PACIFIC NORTHWEST COAST. 
   DOWNSTREAM SHORT WAVE RIDGING ACROSS THE NORTHERN ROCKIES/PLAINS MAY
   BE SUPPRESSED BY THE EASTWARD PROGRESSION OF A SMALLER SCALE
   IMPULSE...AND THE SOUTHEASTWARD PROGRESSION OF ANOTHER IN A SERIES
   OF NORTHERN STREAM SHORT WAVE TROUGHS DIGGING THROUGH THE CENTRAL
   CANADIAN PROVINCES.  A MUCH MORE VIGOROUS NORTHERN STREAM
   IMPULSE...NOW OVER HUDSON/JAMES BAYS AND ONTARIO...IS FORECAST TO
   TURN EAST NORTHEASTWARD ACROSS QUEBEC.  AT THE SAME TIME...IN LOWER
   LATITUDES...THE REMNANTS OF TROPICAL STORM BILL LIKELY WILL CONTINUE
   SLOWLY AROUND THE NORTHWESTERN PERIPHERY OF THE SOUTHWESTERN
   ATLANTIC SUBTROPICAL HIGH CENTER...FROM THE LOWER SOUTH CENTRAL
   PLAINS INTO THE OZARK PLATEAU.

   A COLD FRONT ASSOCIATED WITH THE EASTERN CANADIAN SHORT WAVE TROUGH
   HAS ALREADY ADVANCED THROUGH PORTIONS OF THE UPPER GREAT LAKES AND
   NORTHERN PLAINS...AND IS EXPECTED TO CONTINUE SOUTHEASTWARD TODAY. 
   THIS WILL REINFORCE A STALLED SURFACE FRONTAL ZONE NOW ARCING FROM
   THE MID ATLANTIC COAST INTO THE SOUTHERN GREAT LAKES/OHIO VALLEY
   REGION.  THIS FRONT EXTENDS INTO THE MIDDLE MISSISSIPPI VALLEY AND
   CENTRAL PLAINS...BUT IS BECOMING INCREASING OBSCURED DUE TO THE
   INFLUENCE OF PRECIPITATION ASSOCIATED WITH THE REMNANTS OF
   BILL...AND CONVECTIVE OUTFLOW FROM AN OVERNIGHT MCS.  THE CONVECTIVE
   OUTFLOW IS ADVANCING STEADILY SOUTHWARD THROUGH THE CENTRAL HIGH
   PLAINS...AND MAY CONTINUE TO DO SO AS FORCING ALONG ITS LEADING EDGE
   SUPPORTS RENEWED CONVECTION.

   ...NORTHERN ROCKIES/ADJACENT HIGH PLAINS....
   BOUNDARY LAYER MOISTENING ON EASTERLY POST-FRONTAL LOW-LEVEL FLOW
   PROBABLY WILL CONTRIBUTE TO CAPE ON THE ORDER OF 1000-2000
   J/KG...WITH DAYTIME HEATING BENEATH RATHER STEEP MID-LEVEL LAPSE
   RATES.  IN THE PRESENCE OF STRONG DEEP LAYER SHEAR BENEATH WESTERLY
   500 MB FLOW STRENGTHENING TO 40-50+ KT...THE ENVIRONMENT IS EXPECTED
   TO BECOME CONDUCIVE TO ORGANIZED SEVERE STORM DEVELOPMENT. 
   SUPERCELLS MAY INITIATE OVER THE MOUNTAINS OF SOUTHWEST/CENTRAL
   MONTANA...BEFORE CONVECTION CONSOLIDATES INTO AN ORGANIZING
   MESOSCALE CONVECTIVE SYSTEM ACROSS SOUTH CENTRAL INTO SOUTHEASTERN
   MONTANA THIS EVENING.  ACTIVITY MAY REMAIN STRONG ENOUGH TO MAINTAIN
   THE RISK FOR SEVERE WEATHER ACROSS PARTS OF SOUTHWESTERN NORTH
   DAKOTA/WESTERN SOUTH DAKOTA AND NORTHEAST WYOMING OVERNIGHT.

   ...CENTRAL/SOUTHERN HIGH PLAINS...
   THE TENDENCY FOR WARMING MID-LEVEL TEMPERATURES COULD ACT TO
   SUPPRESS RENEWED CONVECTIVE DEVELOPMENT...WITH MID/UPPER SUPPORT FOR
   CONVECTIVE DEVELOPMENT UNCLEAR.  HOWEVER...FORCING ON THE SOUTH
   SOUTHWESTWARD SURGING PORTION OF THE CONVECTIVE OUTFLOW MAY BE
   SUFFICIENT TO SUPPORT CONVECTIVE RE-INTENSIFICATION ACROSS PARTS OF
   SOUTHWEST KANSAS INTO THE TEXAS/OKLAHOMA PANHANDLE REGION...AS IT
   ENCOUNTERS A RATHER STRONGLY DESTABILIZING ENVIRONMENT.  MID-LEVEL
   LAPSE RATES ARE FAIRLY STEEP...AND WITH CONTINUED STEEPENING OF
   LOW-LEVEL LAPSE RATES...SEVERE HAIL AND WIND GUSTS PROBABLY WILL
   ACCOMPANY STRONGEST STORMS.  WEAK TO PERHAPS MODEST SHEAR...DUE TO
   PRONOUNCED VEERING WITH HEIGHT OF LOW TO MID-LEVEL WIND
   FIELDS...COULD ENHANCE LATE AFTERNOON AND EARLY EVENING ACTIVITY.

   ...LOWER GREAT LAKES/UPPER OHIO VALLEY INTO MID ATLANTIC...
   THE LATEST CONVECTION ALLOWING MODEL OUTPUT DOES NOT ADD ANY MORE
   CLARITY CONCERNING POTENTIAL CONVECTIVE EVOLUTION AND THE EXTENT OF
   THE SEVERE WEATHER RISK TODAY.  IT CURRENTLY SEEMS THAT THE RISK FOR
   MAINLY POTENTIALLY DAMAGING WIND GUSTS MAY REMAIN RATHER LOCALIZED
   WITH STRONGEST CONVECTION.  HOWEVER...CONSIDERABLE THUNDERSTORM
   DEVELOPMENT DOES APPEAR PROBABLE AS THE PRE-FRONTAL MOIST BOUNDARY
   LAYER BECOMES MODERATELY UNSTABLE THIS AFTERNOON.  AND DOWNWARD
   MIXING OF 30+ KT LOWER/MID TROPOSPHERIC FLOW MAY CONTRIBUTE TO THE
   POTENTIAL FOR PEAK CONVECTIVE GUSTS AT LEAST APPROACHING...IF NOT
   BRIEFLY EXCEEDING...SEVERE CRITERIA.

   ..KERR/PICCA.. 06/18/2015

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