RSS Mesoscale Discussions from Storm Prediction Center
No watches are valid as of Tue Jun 18 07:18:01 UTC 2013.
MD 1117 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SRN MN INTO NRN IA
MESOSCALE DISCUSSION 1117
NWS STORM PREDICTION CENTER NORMAN OK
0216 AM CDT TUE JUN 18 2013
AREAS AFFECTED...SRN MN INTO NRN IA
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 180716Z - 180915Z
PROBABILITY OF WATCH ISSUANCE...5 PERCENT
SUMMARY...ISOLATED STORMS WILL BE CAPABLE OF LARGE HAIL...BUT
COVERAGE SHOULD NOT WARRANT A WATCH.
DISCUSSION...A COMPACT SHORTWAVE TROUGH CONTINUES TO DIVE SEWD
ACROSS THE REGION WITH A POCKET OF COLD AIR ALOFT HELPING TO STEEPEN
MIDLEVEL LAPSE RATES. ALTHOUGH INSTABILITY IS MARGINAL ACROSS THE
REGION...COLD AIR ALOFT COMBINED WITH INCREASING WINDS WITH HEIGHT
WILL FAVOR A FEW CELLS CAPABLE OF LARGE HAIL. THE LACK OF LOW LEVEL
SHEAR WILL PRECLUDE ANY THREAT OF TORNADOES...ALTHOUGH SUPERCELLS
WILL BE POSSIBLE WITH LONG HODOGRAPHS. IN ADDITION...DAMAGING WINDS
ARE UNLIKELY GIVEN CELLULAR STORM MODE...AND HIGH RH BOUNDARY LAYER.
..JEWELL/MEAD.. 06/18/2013
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...ARX...MPX...DMX...FSD...
LAT...LON 44449582 44829566 45169515 45039463 44579431 44239415
43399311 42909278 42669317 42519408 42579491 42969524
43409546 44449582
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SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT TUE JUN 18 2013
VALID 181200Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EARLY
EVENING FOR SRN PARTS OF IL/IND/OH AND FAR NRN KY...
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON THROUGH TONIGHT
ACROSS SRN AND CENTRAL HIGH PLAINS INTO CENTRAL PARTS OF SD/NEB...
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
ACROSS PARTS OF CENTRAL ID INTO NWRN AND NORTH CENTRAL MT...
...SYNOPSIS...
THE NERN PACIFIC CLOSED LOW AND ATTENDANT TROUGH WILL ADVANCE EWD
INTO THE WRN STATES THIS FORECAST PERIOD TAKING ON A NEGATIVE
TILT...WITH THE LOW CENTERED ALONG THE WA/ORE COASTS AND THE TROUGH
EXTENDING SEWD THROUGH NV BY 12Z WED. AN UPPER RIDGE CURRENTLY
CENTERED OVER THE ROCKIES WILL SUBSEQUENTLY SHIFT EWD INTO THE
PLAINS. A WEAK IMPULSE IS FORECAST TO TRACK EWD THROUGH THE RIDGE
CROSSING THE CENTRAL ROCKIES AND REACHING THE CENTRAL PLAINS BY 12Z
WED. MIDLEVEL FLOW IN THE NERN STATES WILL WEAKEN TODAY AS AN
ATTENDANT SHORTWAVE TROUGH MOVES EWD FROM QUEBEC TO THE CANADIAN
MARITIMES. A PROMINENT SHORTWAVE TROUGH...CURRENTLY TRACKING SEWD
THROUGH THE ERN DAKOTAS PER WATER VAPOR IMAGERY...WILL MOVE INTO THE
LOWER OH VALLEY REGION DURING PEAK HEATING...WHILE A LOWER TN VALLEY
TROUGH SHIFTS EWD TO THE MID ATLANTIC STATES.
AT THE SURFACE...A COLD FRONT WILL MOVE SWD THROUGH THE OH
VALLEY...AND SEWD THROUGH NY/PA AND SRN NEW ENGLAND. MEANWHILE...A
COLD FRONT ATTENDANT TO THE WRN U.S. TROUGH IS EXPECTED TO MOVE INTO
THE NRN INTERMOUNTAIN WEST THIS AFTERNOON AND REACH WRN MT TONIGHT.
...OH VALLEY TO MID ATLANTIC STATES AND SRN NEW ENGLAND...
THE COMBINATION OF SURFACE HEATING ACROSS THE OH VALLEY TODAY...
SURFACE DEW POINTS AROUND 60 F AND MIDLEVEL LAPSE RATES OF 6.5 TO 7
C/KM ACCOMPANYING THE ERN DAKOTAS SHORTWAVE TROUGH SHOULD RESULT IN
A MODERATELY UNSTABLE AIR MASS FROM IL TO OH. ALTHOUGH LOW LEVEL
CONVERGENCE MAY NOT BE TOO STRONG ALONG THE SWD MOVING FRONT...
FORCING FOR ASCENT ATTENDANT TO THE PROGRESSIVE TROUGH IS EXPECTED
TO SUPPORT TSTM DEVELOPMENT. MLCAPE TO AT LEAST 1000 J/KG AND
EFFECTIVE BULK SHEAR OF 35-40 KT PARALLEL TO THE FRONT SUGGEST LINE
SEGMENTS SHOULD BE THE PRIMARY STORM MODE...THOUGH A FEW SUPERCELLS
WILL BE POSSIBLE. DAMAGING WINDS AND HAIL WILL BE THE PRIMARY
THREATS...WITH ACTIVITY DIMINISHING IN INTENSITY DURING THE EVENING
AS THE BOUNDARY LAYER STABILIZES.
FARTHER EAST ACROSS PA TO SRN NEW ENGLAND...TSTMS WILL BE POSSIBLE
THROUGH THE AFTERNOON WITH A FEW ORGANIZED STORMS GIVEN 35-40 KT OF
EFFECTIVE BULK SHEAR. HOWEVER...WEAKER INSTABILITY SHOULD LIMIT THE
OVERALL SEVERE WEATHER THREAT...AND PRECLUDES HIGHER PROBABILITIES
AND THE EWD EXTENSION OF THE SLIGHT RISK.
FORCING FOR ASCENT ATTENDANT TO THE LOWER TN VALLEY TROUGH WILL
SPREAD ACROSS VA/MD THIS AFTERNOON/EARLY EVENING...AND SHOULD
SUPPORT SOME TSTM DEVELOPMENT. MODEL DIFFERENCES IN THE DEGREE OF
DESTABILIZATION PRECLUDES THE ISSUANCE OF A CATEGORICAL SLIGHT
RISK...THOUGH 30-40 KT WLY MIDLEVEL WINDS ACCOMPANYING THE TROUGH
COULD PROMOTE SOME STORM ORGANIZATION. THUS...THIS OUTLOOK WILL
EXTEND LOW SEVERE WIND/HAIL PROBABILITIES SWD ACROSS MD/VA.
...CENTRAL AND SRN HIGH PLAINS TO CENTRAL SD/NEB...
SELY LOW LEVEL WINDS ARE EXPECTED TO STRENGTHEN TO 20-25 KT ACROSS
THE FULL EXTENT OF THE HIGH PLAINS. TSTM DEVELOPMENT IS EXPECTED
WITHIN THIS UPSLOPE FLOW REGIME FROM ERN NM TO ERN WY BY MID-LATE
AFTERNOON WHERE THE AIR MASS WILL BE MODERATELY UNSTABLE. EFFECTIVE
BULK SHEAR UP TO 35-40 KT WILL SUPPORT ORGANIZED STORMS WITH
SUPERCELLS POSSIBLE RESULTING IN THREATS FOR HAIL AND DAMAGING
WINDS. A NON-ZERO TORNADO THREAT IS FORECAST ACROSS MAINLY THE
CENTRAL HIGH PLAINS...WHERE MODELS SUGGEST AN INCREASE IN LOW LEVEL
SHEAR DURING THE EARLY EVENING. THERE IS SOME CONFIDENCE FOR AN MCS
TO DEVELOP THIS EVENING INTO THE PART OF THE OVERNIGHT PERIOD ACROSS
THE WRN HALF OF NEB/SD AS LOW LEVEL WAA INCREASES ALONG THE NOSE OF
A STRENGTHENING/VEERING LLJ. DAMAGING WINDS AND HAIL WILL BE THE
PRIMARY THREATS WITH THE MCS.
...PART OF CENTRAL ID/WRN AND NORTH CENTRAL MT...
SURFACE DEW POINTS IN THE MID-UPPER 40S TO LOWER 50S COMBINED WITH
SURFACE HEATING AND STEEP LAPSE RATES WILL RESULT IN MLCAPE OF AT
LEAST 1000 J/KG ACROSS THE SLIGHT RISK AREA THIS AFTERNOON INTO THE
EVENING. HEIGHT FALLS SPREADING EWD INTO THIS REGION IN THE
AFTERNOON/EVENING WILL SUPPORT TSTM DEVELOPMENT WITH THE THREAT FOR
HAIL AND DAMAGING WINDS...AS INCREASING BULK SHEAR SUPPORTS STORM
ORGANIZATION INCLUDING A FEW SUPERCELLS.
..PETERS/ROGERS.. 06/18/2013
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SPC 0600Z Day 2 Outlook
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT TUE JUN 18 2013
VALID 191200Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS MOST OF MT INTO WRN ND WED
AFTERNOON TO WED NIGHT...
...SYNOPSIS...
A VIGOROUS SHORTWAVE IMPULSE EMBEDDED WITHIN THE BASAL PORTION OF
THE AMPLIFIED WRN CONUS UPPER-LEVEL TROUGH WILL TAKE ON A NEGATIVE
TILT AS IT EJECTS NEWD FROM THE NWRN GREAT BASIN TO THE NRN ROCKIES
BY EARLY THU. THIS WILL INDUCE WEAK HEIGHT RISES ACROSS MUCH OF THE
GREAT PLAINS AS A MID-LEVEL RIDGE CONTINUES TO SLOWLY SLIDE EWD. AT
THE SURFACE...A LEE CYCLONE SHOULD BECOME CENTERED OVER SERN MT WED
EVENING WITH A COLD FRONT ACCELERATING EWD ACROSS THE NRN HIGH
PLAINS WED NIGHT. FARTHER S...THE DRYLINE WILL MIX E OVER THE
CNTRL/SRN HIGH PLAINS.
...NRN ROCKIES/HIGH PLAINS...
PRECEDING DAYS OF LOW-LEVEL MOIST ADVECTION SHOULD YIELD
PREDOMINATELY 50S SURFACE DEW POINTS ACROSS MOST OF THE LEE OF THE
NRN ROCKIES AT PEAK HEATING WED. WITH STEEP LAPSE RATES THROUGHOUT
THE TROPOSPHERE...AIR MASS SHOULD BECOME RATHER UNSTABLE WITH MLCAPE
LIKELY REACHING 1500-2500 J/KG TO THE E OF THE COLD FRONT. MID-LEVEL
HEIGHT FALLS AND DCVA DOWNSTREAM OF THE APPROACHING SHORTWAVE TROUGH
WILL OVERSPREAD SWRN MT DURING THE AFTERNOON AND EARLY
EVENING...WITH ISOLATED TO SCATTERED TSTM DEVELOPMENT LIKELY
OCCURRING OVER THE HIGHER TERRAIN. INITIALLY MERIDIONAL
MID/UPPER-LEVEL WIND PROFILES WILL FAVOR N/NELY STORM
MOTIONS WITH A FEW SUPERCELLS PRIMARILY PRODUCING LARGE HAIL /SOME
OF WHICH MAY BE SIGNIFICANT OVER CNTRL MT ALONG THE PERIPHERY OF
GREATER BUOYANCY/. DURING THE EVENING/NIGHT...THE LLJ WILL
STRENGTHEN AND MORE PRONOUNCED VEERING OF WIND PROFILES WITH HEIGHT
SHOULD EXIST WITH ERN EXTENT. SETUP SHOULD YIELD UPSCALE GROWTH AND
MAY RESULT IN A SEVERE WIND-PRODUCING MCS PROPAGATING E/NEWD ACROSS
NERN MT. GIVEN CONTINUED MAINTENANCE OF LARGE INSTABILITY...ENHANCED
BY ADVECTION OF LOWER TO MIDDLE 60S SURFACE DEW POINTS...A FEW
SIGNIFICANT SEVERE WIND GUSTS MAY OCCUR AS WELL.
...GREAT PLAINS...
ALTHOUGH MODERATE TO STRONG BUOYANCY SHOULD EXIST ACROSS THE BULK OF
THE PLAINS...OVERALL PATTERN STILL APPEARS NEBULOUS FOR WARRANTING
SLIGHT RISK PROBABILITIES ATTM. WITH MID-LEVEL HEIGHTS SLOWLY RISING
IN RESPONSE TO THE NORTHWEST SHORTWAVE TROUGH AND MODERATE 700 MB
WINDS BECOMING PREDOMINATELY SWLY...THE WRN PERIPHERY OF THE
PERSISTENT MOISTURE PLUME SHOULD MIX E OF THE CNTRL/SRN ROCKIES.
WITH A STRENGTHENING EML/CAPPING INVERSION...ANY DRYLINE-INDUCED
CONVECTION SHOULD STRUGGLE TO DEVELOP EWD AND LIKELY REMAIN ISOLATED
IN COVERAGE.
FARTHER E...CONVECTIVELY-PARAMETRIZED GUIDANCE IS HIGHLY CONSISTENT
THAT A CONVECTIVE CLUSTER WILL BE ONGOING ACROSS PARTS OF NEB/KS AT
12Z/WED. THIS GUIDANCE SUGGESTS CONVECTION MAY PERSIST THROUGH THE
DIURNAL HEATING CYCLE WITH ACTIVITY DEVELOPING E OR S...WHICH WOULD
PROBABLY YIELD AN ISOLATED SEVERE WIND/HAIL THREAT.
HOWEVER...CONVECTION-ALLOWING GUIDANCE IS MUCH LESS EMPHATIC ABOUT
THIS OCCURRING...BREEDING SUBSTANTIAL UNCERTAINTY IN DELINEATING A
SLIGHT RISK. WED NIGHT...A FEW ELEVATED TSTM CLUSTERS MAY FORM ALONG
THE LEADING EDGE OF THE CAP AS THE LLJ STRENGTHENS. SOME OF THIS
ACTIVITY MAY POSE A RISK FOR MARGINALLY SEVERE HAIL/WIND.
..GRAMS.. 06/18/2013
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