Jun 21, 2015 1300 UTC Day 1 Convective Outlook
Updated: Sun Jun 21 12:51:27 UTC 2015 (20150621 1300Z Day 1 shapefile | 20150621 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20150621 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 61,039 427,208 Bismarck, ND...Aberdeen, SD...Watertown, SD...Brookings, SD...Mandan, ND...
SLIGHT 343,447 25,088,501 Kansas City, MO...Minneapolis, MN...St. Louis, MO...Pittsburgh, PA...St. Paul, MN...
MARGINAL 537,100 82,376,036 Philadelphia, PA...Indianapolis, IN...Columbus, OH...Baltimore, MD...Boston, MA...
Probabilistic Tornado Graphic
20150621 1300 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 % 52,973 940,641 Columbia, MO...St. Joseph, MO...Quincy, IL...Liberty, MO...Hannibal, MO...
2 % 264,864 12,140,514 Kansas City, MO...St. Louis, MO...Lexington-Fayette, KY...Overland Park, KS...Kansas City, KS...
Probabilistic Damaging Wind Graphic
20150621 1300 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
SIG SEVERE 44,235 265,623 Aberdeen, SD...Watertown, SD...Brookings, SD...Mitchell, SD...Pierre, SD...
30 % 44,429 263,498 Aberdeen, SD...Watertown, SD...Brookings, SD...Mitchell, SD...Pierre, SD...
15 % 356,607 25,146,828 Kansas City, MO...Minneapolis, MN...St. Louis, MO...Pittsburgh, PA...St. Paul, MN...
5 % 539,009 82,380,926 New York, NY...Philadelphia, PA...Indianapolis, IN...Columbus, OH...Baltimore, MD...
Probabilistic Large Hail Graphic
20150621 1300 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 58,223 1,396,047 Kansas City, MO...Kansas City, KS...Independence, MO...St. Joseph, MO...Bismarck, ND...
30 % 31,965 197,162 Bismarck, ND...Mandan, ND...Dickinson, ND...
15 % 327,252 19,070,907 Kansas City, MO...Minneapolis, MN...St. Louis, MO...St. Paul, MN...Lexington-Fayette, KY...
5 % 547,755 60,684,652 Philadelphia, PA...Indianapolis, IN...Columbus, OH...Baltimore, MD...Washington, DC...
   SPC AC 211251

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0751 AM CDT SUN JUN 21 2015

   VALID 211300Z - 221200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS OVER THE DAKOTAS...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN HIGH PLAINS TO
   UPPER MS VALLEY...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MO VALLEY TO
   CNTRL APPALACHIANS...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE NRN ROCKIES TO NERN
   STATES...

   ...SUMMARY...
   SEVERE STORMS CAPABLE OF VERY LARGE HAIL...TORNADOES...AND
   POTENTIALLY WIDESPREAD DAMAGING WINDS ARE PROBABLE THIS AFTERNOON
   INTO TONIGHT FROM THE NORTHERN HIGH PLAINS INTO UPPER MISSISSIPPI
   VALLEY.  ISOLATED TO WIDELY SCATTERED SEVERE THUNDERSTORMS WITH A
   RISK FOR MAINLY LARGE HAIL AND DAMAGING WINDS ARE POSSIBLE FROM THE
   LOWER MISSOURI VALLEY TO CENTRAL APPALACHIANS.

   ...SYNOPSIS...

   THE PRIMARY BELT OF POLAR WESTERLIES WILL REMAIN CONFINED TO THE NRN
   TIER OF STATES...TO THE NORTH OF A SUB-TROPICAL HIGH SHIFTING FROM
   THE SWRN DESERTS TO SRN ROCKIES.  EMBEDDED WITHIN THIS HIGH-MOMENTUM
   AIR STREAM...A SHORT-WAVE TROUGH MOVING ONTO THE PACIFIC NW COAST
   WILL PHASE WITH ANOTHER DISTURBANCE PROGRESSING SEWD FROM THE
   CANADIAN ROCKIES INTO THE SRN PRAIRIE PROVINCES TO PROMOTE
   INCREASING HEIGHT FALLS AND THE DEVELOPMENT OF A 70-80 KT MID-LEVEL
   JET STREAK OVER THE NRN PLAINS TONIGHT.  DOWNSTREAM FROM THESE
   DEVELOPMENTS...A LOW-AMPLITUDE TROUGH FROM ONTARIO INTO THE UPPER
   GREAT LAKES WILL TRACK INTO QUEBEC AND THE NERN U.S. BY TONIGHT.

   AT THE SURFACE...A LEE TROUGH OVER CNTRL MT EARLY THIS MORNING WILL
   SHIFT EWD TODAY AHEAD OF A COLD FRONT WHICH WILL UNDERGO
   CONSIDERABLE STRENGTHENING WHILE SWEEPING SEWD FROM THE NRN INTO
   CNTRL HIGH PLAINS AND MOST OF THE DAKOTAS BY 12Z/MONDAY.  A
   DEEPENING LEE CYCLONE WILL DEVELOP ALONG OR AHEAD OF THIS COLD FRONT
   FROM CNTRL WY TO SERN SD/SWRN MN BY THE END OF THE FORECAST PERIOD. 
   FARTHER EAST...THE REMNANT OF T.D. BILL MOVE FROM THE MID ATLANTIC
   COAST TO THE GULF OF MAINE AHEAD OF A WEAK COLD FRONT ADVANCING
   THROUGH THE NERN STATES AND OH VALLEY.  THE WRN EXTENSION OF THIS
   BOUNDARY FROM NEAR THE IA-MO BORDER INTO NRN KS WILL WEAKEN TODAY
   WHILE DEVELOPING NWD INTO THE MID MO VALLEY.

   ...NRN HIGH PLAINS TO UPPER MS VALLEY THIS AFTERNOON THROUGH
   TONIGHT...

   STRENGTHENING SLY LOW-LEVEL FLOW AHEAD OF THE DEEPENING LEE CYCLONE
   WILL ENHANCE THE POLEWARD FLUX OF AN INCREASINGLY MOIST BOUNDARY
   LAYER THROUGH WRN PARTS OF NEB AND THE DAKOTAS.  THIS PROCESS WILL
   OCCUR BENEATH AN EWD-ADVECTING EML...YIELDING AFTERNOON MLCAPE
   VALUES OF 1500-3000 J/KG.  INITIAL STORM DEVELOPMENT IS ANTICIPATED
   BY MID TO LATE AFTERNOON ALONG THE LEE TROUGH AND/OR COLD FRONT OVER
   NERN MT INTO WRN ND WITH A QUICK EVOLUTION INTO SUPERCELLS GIVEN
   DEEP-LAYER SHEAR OF 50-60 KT.  ADDITIONAL STORMS ARE EXPECTED TO
   DEVELOP LATE THIS AFTERNOON INTO EVENING ALONG FAVORED TERRAIN...THE
   LEE TROUGH AND/OR COLD FRONT OVER SERN MT...NERN WY AND WRN SD WHERE
   SUPERCELLS ALSO APPEAR LIKELY.  IN BOTH AREAS...THE INITIAL STORMS
   WILL BE CAPABLE OF VERY LARGE HAIL AND A FEW TORNADOES.

   DYNAMIC CONTRIBUTIONS TO THE DIURNAL OSCILLATION WILL RESULT IN THE
   DEVELOPMENT OF A BROAD AND INTENSE LLJ OVER NRN PLAINS TONIGHT WHICH
   WILL SUPPORT RAPID AIR MASS DESTABILIZATION INTO LOWER ELEVATIONS OF
   THE DAKOTAS AND THE UPPER MS VALLEY.  A RESULTANT CONSOLIDATION OF
   DAYTIME STORMS INTO ONE OR MULTIPLE MCSS WILL LIKELY OCCUR WITH THIS
   ACTIVITY ACCELERATING EWD INTO THE UPPER MS VALLEY LATE
   TONIGHT/EARLY MONDAY ON THE NOSE OF THE STRENGTHENING MID-LEVEL JET
   STREAK.  VERY STEEP LAPSE RATES ALOFT...MUCAPE OF 2000-4000+ J/KG
   AND INTENSE VERTICAL SHEAR WILL SUPPORT ELEVATED SUPERCELLS CAPABLE
   OF LARGE HAIL AND THE POTENTIAL FOR BOW ECHO FORMATION WITH
   ATTENDANT RISK FOR SIGNIFICANT WIND DAMAGE.

   ...CNTRL PLAINS INTO LOWER MO AND MID MS VALLEYS TODAY INTO THIS
   EVENING...

   ISOLATED SEVERE STORMS HAVE PERSISTED OVERNIGHT ACROSS PORTIONS OF
   N-CNTRL/WRN NEB...AIDED BY LOW-LEVEL WAA TO THE NORTH OF THE STALLED
   SURFACE FRONT...AND THE POSSIBLE INFLUENCE OF A WEAK MID-LEVEL
   PERTURBATION TRACKING SEWD ACROSS THE REGION.  IT REMAINS UNCERTAIN
   AS TO WHETHER THESE STORMS WILL CONTINUE TO POSE A SEVERE WEATHER
   THREAT THIS MORNING FARTHER TO THE SE OVER CNTRL/SERN NEB AND NERN
   KS.  HOWEVER...IT DOES APPEAR MORE LIKELY THAT THESE FORCING
   MECHANISMS WILL CONTRIBUTE TO THE DEVELOPMENT OF ADDITIONAL STORMS
   BY AFTERNOON ALONG THE SYNOPTIC FRONT AND/OR OUTFLOW BOUNDARY
   PRESENT OVER NRN MO AND PERHAPS NERN KS.

   STRONG INSTABILITY /MLCAPE OF 2000-3000 J/KG AND AMPLE VERTICAL
   SHEAR WILL SUPPORT SUPERCELLS CAPABLE OF VERY LARGE HAIL AND PERHAPS
   A TORNADO OR TWO BEFORE STORMS CONGEAL INTO CLUSTERS OR AN MCS...AT
   WHICH POINT...THE RISK FOR DAMAGING OUTFLOW WINDS WOULD INCREASE.

   OVER THE MID MS VALLEY...SOME PORTION OF THE NOCTURNAL MCS PRESENT
   OVER E-CNTRL MO/W-CNTRL IL COULD PERSIST THIS MORNING AND INTENSIFY
   BY AFTERNOON...WITH OTHER STORMS FORMING ALONG THE ASSOCIATED
   OUTFLOW BOUNDARY.  FORECAST SOUNDINGS SUGGEST THAT BOTH SHEAR AND
   INSTABILITY WILL BE WEAKER THAN THAT TO THE NW...THOUGH SEVERE HAIL
   AND/OR LOCALLY DAMAGING WINDS WILL BE POSSIBLE WITH THE STRONGEST
   STORMS.

   ...OH VALLEY INTO CNTRL PA THIS AFTERNOON/EVENING...

   WEAK PERTURBATIONS EMBEDDED WITHIN THE CYCLONIC FLOW ALOFT WILL ACT
   IN CONCERT WITH THE SEWD-MOVING COLD FRONT AND RESIDUAL OUTFLOW
   BOUNDARIES TO FOSTER WIDELY SCATTERED STORMS THIS AFTERNOON AMIDST A
   MOIST AND MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF 1000-2000
   J/KG.  12Z SOUNDINGS AND REGIONAL VAD DATA INDICATE RATHER STRONG
   WLY/WNWLY FLOW IN THE 700-500-MB LAYER WHICH WILL BE SUPPORTIVE OF
   ORGANIZED STORM MODES AND AN ASSOCIATED RISK FOR SEVERE HAIL AND
   DAMAGING WINDS INTO THIS EVENING.

   ..MEAD/MOSIER.. 06/21/2015

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z