Jim Martin Posted October 16, 2012 Share Posted October 16, 2012 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1230 PM CDT TUE OCT 16 2012 VALID 171200Z - 181200Z ...THERE IS A SLGT RISK OF SVR TSTMS WED ACROSS PARTS OF THE OZARK PLATEAU AND MID/LWR MISSISSIPPI VALLEY... ...SYNOPSIS... MODELS CONTINUE TO INDICATE AMPLIFICATION WITHIN THE UPPER FLOW PATTERN DURING THIS FORECAST PERIOD. A STRONG MID/UPPER JET NOW NOSING OFF THE PACIFIC INTO THE PACIFIC NORTHWEST APPEARS LIKELY TO CONTINUE INLAND...AND CONTRIBUTE TO THE EVOLUTION OF A LARGE DEEPENING MID-LEVEL LOW ENCOMPASSING MUCH OF THE CENTRAL U.S. BY LATE WEDNESDAY NIGHT. AS THIS OCCURS...A DEEP SURFACE CYCLONE ALREADY FORMING TO THE LEE OF THE CANADIAN ROCKIES IS EXPECTED TO DEVELOP SOUTHEASTWARD INTO THE GREAT LAKES REGION...WITH AN ASSOCIATED COLD FRONT ADVANCING SOUTHEASTWARD THROUGH MUCH OF THE PLAINS AND THE MISSISSIPPI/LOWER OHIO VALLEYS. STRENGTHENING OF SOUTH/SOUTHWESTERLY LOWER TROPOSPHERIC WIND FIELDS IS FORECAST AHEAD OF THE SURFACE FRONT...FROM PARTS OF THE SOUTHERN PLAINS INTO THE GREAT LAKES REGION...DURING THE DAY WEDNESDAY. HOWEVER...IN THE WAKE OF PRIOR FRONTAL PASSAGES...HIGHER MOISTURE CONTENT AIR HAS GENERALLY BECOME CONFINED TO PARTS OF THE FLORIDA PENINSULA AND WESTERN GULF COAST/LOWER RIO GRANDE VALLEY REGION. AND GUIDANCE IS GENERALLY SUGGESTIVE THAT BOUNDARY LAYER MOISTURE RETURN TO THAT PORTION OF THE WARM SECTOR MOST STRONGLY IMPACTED BY LARGE-SCALE ASCENT MAY BE LIMITED. STILL...SUFFICIENT DESTABILIZATION IS EXPECTED FROM PARTS OF THE LOWER MISSISSIPPI VALLEY INTO THE GREAT LAKES REGION WEDNESDAY FOR CONSIDERABLE THUNDERSTORM ACTIVITY...SOME OF WHICH COULD BECOME STRONG TO SEVERE. ...OZARK PLATEAU INTO LWR/MID MISSISSIPPI VALLEY... MODELS SUGGEST WEAK TO MODERATE BOUNDARY LAYER DESTABILIZATION IS POSSIBLE WEDNESDAY WITHIN AT LEAST A NARROW PRE-FRONTAL CORRIDOR ACROSS PARTS OF THE ARKLATEX INTO AREAS AS FAR NORTH AS SOUTHEAST MISSOURI OR THE MISSOURI BOOTHEEL. THIS IS WHERE A RETURN OF LOWER/MID 60S F SURFACE DEW POINTS IS EXPECTED IN THE WAKE OF A SURFACE RIDGE SHIFTING INTO THE ATLANTIC SEABOARD...BEFORE BEING CUT OFF BY THE SOUTHEASTWARD ADVANCING COLD FRONT. DISCRETE STORM DEVELOPMENT DOES NOT APPEAR OUT OF THE QUESTION AT LEAST INITIALLY...IN RESPONSE TO LIFT ASSOCIATED WITH LOWER/MID TROPOSPHERIC WARM ADVECTION...PARTICULARLY ACROSS PARTS OF CENTRAL/EASTERN ARKANSAS...IN CLOSER PROXIMITY TO HIGHER MOISTURE CONTENT AIR AND BOUNDARY LAYER INSTABILITY. IF THIS OCCURS...LOW-LEVEL SHEAR ON THE SOUTHERN FRINGE OF AN 850 JET... STRENGTHENING IN EXCESS OF 50 KT...AND DEEP LAYER SHEAR...NEAR THE EXIT REGION OF A 70-90 KT NORTHWESTERLY 500 MB JET...PROBABLY WILL BE SUFFICIENT TO SUPPORT THE RISK FOR SUPERCELLS. THEREAFTER...LATER IN THE AFTERNOON INTO THE EVENING HOURS... DIVERGENT UPPER FLOW...COUPLED WITH FRONTAL FORCING...COULD SUPPORT AN EXPANDING STORM CLUSTER OR EVOLVING SQUALL LINE CAPABLE OF PRODUCING SEVERE HAIL AND WIND. THIS THREAT MAY PERSIST INTO THE 03-06Z TIME FRAME...WITH ACTIVITY ADVANCING SOUTHEAST OF THE MIDDLE MISSISSIPPI VALLEY...AND THROUGH THE LOWER OHIO VALLEY...BEFORE BOUNDARY LAYER INSTABILITY WANES AND BETTER MOISTURE INFLOW BECOMES CUT OFF. Link to comment Share on other sites More sharing options...
Hoosier Posted October 16, 2012 Share Posted October 16, 2012 teehee Link to comment Share on other sites More sharing options...
tornadotony Posted October 17, 2012 Share Posted October 17, 2012 Should be a pretty darn good wind threat, with decent CAPE and strong shear. Shear vectors are a bit unidirectional and winds are veered in the low-levels, but SRH should still be enough for an isolated tornado threat in a QLCS. Also, some of the high-res guidance supports a good QLCS all the way into AL. The NAM has some decent instability this far east for elevated parcels, and with the strong shear and forcing, a more eastward extent of at least a damaging wind threat for tomorrow night is something to watch. Link to comment Share on other sites More sharing options...
andyhb Posted October 17, 2012 Share Posted October 17, 2012 DAY 1 CONVECTIVE OUTLOOKNWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT WED OCT 17 2012 VALID 171200Z - 181200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE OZARKS/ARKLATEX TO LOWER/MIDDLE MS VALLEY... ...SYNOPSIS... A SOUTHEASTWARD SURGING STRONG POLAR JET /130+ KT 300 MB/ WILL CONTRIBUTE TO CONSIDERABLE LARGE SCALE TROUGH AMPLIFICATION THROUGH TONIGHT ACROSS THE CENTRAL/EASTERN CONUS...WITH THE MAIN PORTION OF THE LONGWAVE TROUGH EVOLVING OVER THE UPPER MIDWEST. MULTI-PHASED SURFACE CYCLOGENESIS WILL OCCUR TODAY ACROSS THE UPPER MIDWEST AND UPPER/MIDDLE MS VALLEYS...WITH AN EAST-SOUTHEASTWARD MOVING COLD FRONT PROGRESSIVELY INTERCEPTING AN INCREASINGLY MOIST AIRMASS TOWARD THE ARKLATEX/MS VALLEY INTO THIS EVENING...WITH SEVERE TSTMS PROBABLE AS BELOW. ...ARKLATEX/OZARKS TO LOWER/MIDDLE MS VALLEY... WHILE MOISTURE IS INITIALLY LIMITED AWAY FROM THE TX COAST EARLY IN THE OVERNIGHT...STEADY MOISTURE TRANSPORT WILL OCCUR NEAR/MORE SO ABOVE THE SURFACE EARLY TODAY IN TANDEM WITH AN INCREASINGLY STRONG SOUTHWESTERLY LOW LEVEL JET. BY MID/LATE AFTERNOON...LOWER TO MIDDLE 60S F SURFACE DEWPOINTS ARE EXPECTED TO BECOME WELL ESTABLISHED FROM THE ARKLATEX INTO THE OZARKS/MIDDLE MS VALLEY...WHERE A SURFACE WAVE MAY DEVELOP IN VICINITY OF THE ADVANCING COLD FRONT THIS AFTERNOON. STRONG/STEADY HEIGHT FALLS AND A BROADLY DIFFLUENT UPPER JET EXIT REGION OVERSPREADING AN INCREASINGLY MOIST WARM SECTOR WILL LEAD TO STRONG/SEVERE SURFACE BASED TSTM DEVELOPMENT TODAY ACROSS THE REGION...PERHAPS AS SOON AS EARLY AFTERNOON OR MORE CERTAINLY BY MID/LATE AFTERNOON. SUCH DEVELOPMENT SHOULD INITIALLY OCCUR ACROSS PORTIONS OF THE OZARKS/PERHAPS FAR EASTERN OK...WHILE EXPANDING SHORTLY THEREAFTER INTO THE MIDDLE MS VALLEY VICINITY AND REMAINDER OF AR AND THE ARKLATEX VICINITY. THIS DEVELOPMENT WILL PRINCIPALLY BE NEAR THE COLD FRONT...ALTHOUGH SOME SEMI-DISCRETE DEVELOPMENT COULD OCCUR AHEAD OF IT ACROSS PORTIONS OF SOUTHERN/EASTERN AR AND NORTHERN LA/NORTHWEST MS WHERE A RELATIVELY MOIST/WEAKLY INHIBITED BOUNDARY LAYER WILL EXIST COINCIDENT WITH LOW-LEVEL CONFLUENCE. AS AN INCREASINGLY STRONG DEEP LAYER WIND FIELD OVERSPREADS THE FRONTAL ZONE/WARM SECTOR...A SEVERAL HOUR TEMPORAL WINDOW OF SEMI-DISCRETE SUPERCELLS WILL BE POSSIBLE THROUGH THE AFTERNOON...ALTHOUGH ROBUST FORCING FOR ASCENT WILL ALMOST UNDOUBTEDLY ENSURE CELL MERGERS AND RELATIVELY QUICK LINEAR EVOLUTION BY EVENING. IN A RELATIVE SENSE...SEMI-DISCRETE STORMS MAY PERSIST A BIT LONGER INTO THE EVENING ACROSS THE MID-SOUTH/LOWER MS VALLEY ON THE SOUTHERN FRINGE OF THE EVOLVING SQUALL LINE. SOME TORNADOES WILL BE POSSIBLE WITHIN A HIGHLY SHEARED LOW LEVEL ENVIRONMENT /STEADILY INCREASING 0-1 KM SRH TO UPWARDS OF 200-400 M2 PER S2/...EITHER VIA SEMI-DISCRETE SUPERCELLS OR EVOLVING QUASI-LINEAR EMBEDDED MESOVORTICES. HOWEVER...DAMAGING WINDS ARE EXPECTED TO BE THE MOST PREVALENT HAZARD. SOME HAIL IS POSSIBLE AS WELL...ESPECIALLY IN THE PRE-LINEAR EARLY CONVECTIVE CYCLE AND/OR ACROSS THE ARKLATEX TO WESTERN MS WHERE SUPERCELLS ARE MORE PROBABLE AND DESTABILIZATION WILL BE A BIT STRONGER THIS AFTERNOON. ...MIDWEST/OH VALLEY... LOWER-TOPPED CONVECTION IS LIKELY TO DEVELOP NEAR THE ADVANCING COLD FRONT THIS AFTERNOON WITHIN A KINEMATIC ENVIRONMENT CHARACTERIZED BY AMPLE FORCING FOR ASCENT/VERY STRONG SHEAR. EXPECTATIONS FOR MORE MARGINAL MOISTENING/ANEMIC DESTABILIZATION SHOULD LARGELY LIMIT THE SEVERE POTENTIAL WITH NORTHWARD EXTENT FOR AREAS SUCH AS NORTHEAST MO AND IL/INDIANA. THAT SAID...AT LEAST CONVECTIVELY ENHANCED STRONG WIND GUSTS MAY NONETHELESS BE POSSIBLE THIS AFTERNOON INTO EVENING. UNANTICIPATED LOW-LEVEL MOISTENING/DESTABILIZATION WITH NORTHWARD EXTENT...EVEN A COUPLED HUNDRED J/KG SBCAPE...WOULD WARRANT NORTHWARD-SPATIAL ADJUSTMENTS OF THE CURRENT SLIGHT RISK ACROSS MORE OF THE REGION. ..GUYER/ROGERS.. 10/17/2012 Link to comment Share on other sites More sharing options...
Jim Martin Posted October 17, 2012 Author Share Posted October 17, 2012 Here are a few soundings from the 12z NAM... Greenville, MS at 7pm CDT this evening... Monroe, LA at 7pm CDT... Monticello, Arkansas at 7pm CDT tonight... Is there an outside chance an upgrade to moderate risk would occur on the next day 1 from SPC at 1630z? Link to comment Share on other sites More sharing options...
SmokeEater Posted October 17, 2012 Share Posted October 17, 2012 1st warnings of the day coming out in MO. Damage already reported. Link to comment Share on other sites More sharing options...
andyhb Posted October 17, 2012 Share Posted October 17, 2012 MESOSCALE DISCUSSION 2065 NWS STORM PREDICTION CENTER NORMAN OK 0344 PM CDT WED OCT 17 2012 AREAS AFFECTED...PARTS OF CENTRAL AND ERN AR/FAR NERN LA/FAR NWRN MS/FAR WRN TN/MO BOOTHEEL CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 172044Z - 172145Z PROBABILITY OF WATCH ISSUANCE...80 PERCENT SUMMARY...SHORT TERM MODEL TRENDS CONTINUE TO SUGGEST TSTMS WILL DEVELOP ALONG A PRE-FRONTAL TROUGH/DIFFERENTIAL HEATING BOUNDARY EXTENDING FROM NORTH CENTRAL-NERN AR TO SOUTH CENTRAL AR BETWEEN 22-23Z. ADDITIONAL STORMS SHOULD ALSO FORM ALONG THE COLD FRONT AS IT REACHES CENTRAL AR LATE THIS AFTERNOON/EARLY EVENING. A MOISTENING BOUNDARY LAYER AND STRENGTHENING...VERTICALLY VEERING WINDS WILL SUPPORT A TORNADO THREAT...IN ADDITION TO DAMAGING WINDS. DISCUSSION...18Z SOUNDINGS AT LZK/SHV BOTH INDICATED MOISTENING OF THE BOUNDARY LAYER BENEATH A CAP BASED AROUND 850 MB WHICH FOR NOW IS MAINTAINING SURFACE-BASED INHIBITION. ADDITIONAL MOISTURE RETURN INTO THE NRN EXTENT OF THE LOWER MS VALLEY COMBINED WITH SURFACE HEATING...WHICH HAS BEEN STRONGEST ACROSS SRN/ERN AR PER VISIBLE SATELLITE IMAGERY AND SURFACE OBSERVATIONS...WILL FURTHER DESTABILIZE THE AIR MASS /MLCAPE APPROACHING 1000 J/KG OVER SRN-SERN AR LATE THIS AFTERNOON/. THE 18Z SOUNDINGS ALSO INDICATED 850-700 MB LAYER WINDS HAD BACKED SOME SINCE 12Z AND STRENGTHENED...WITH AN INCREASE IN WLY MIDLEVEL WINDS ALSO NOTED. THESE KINEMATICS ARE SUSTAINING LOW LEVEL HODOGRAPH CURVATURE WITH SURFACE-1 KM SHEAR AROUND 40 KT FOR A TORNADO THREAT AND EFFECTIVE BULK SHEAR OF 40-50 KT FOR STORM ORGANIZATION. UNCERTAINTIES REMAIN ABOUT THE DEGREE OF DESTABILIZATION AND AMOUNT OF FORCING FOR ASCENT ATTENDANT TO A DIGGING NWLY MID-UPPER LEVEL JET AND TROUGH TO SUPPORT TSTM DEVELOPMENT ACROSS THE DISCUSSION AREA. HOWEVER...TRENDS IN SHORT TERM MODELS /HRRR AND 12Z 4 KM WRF-NMM/NSSL/ CONTINUE TO SUGGEST FACTORS WILL BECOME JUXTAPOSED ACROSS CENTRAL AR BETWEEN 22-23Z...WITH ADDITIONAL STORM DEVELOPMENT ALONG THE COLD FRONT BY EARLY EVENING ACROSS CENTRAL AR. ..PETERS/THOMPSON.. 10/17/2012 Link to comment Share on other sites More sharing options...
SmokeEater Posted October 17, 2012 Share Posted October 17, 2012 Multiple reports of structural, tree and powerline damage from the line earlier, in and around Springfield, MO. Link to comment Share on other sites More sharing options...
NaoPos Posted October 17, 2012 Share Posted October 17, 2012 Check out the new "draw" feature on radar scope. Pretty useful: Link to comment Share on other sites More sharing options...
earthlight Posted October 17, 2012 Share Posted October 17, 2012 Dude on Fox just said "St Louis is actually under a severe thunderstorm watch until 6:15pm Central time which means strong winds, potential for lightning and thunder, and isolated tornadoes". And we wonder why people don't understand the difference between a watch and a warning. Link to comment Share on other sites More sharing options...
Buckeye05 Posted October 17, 2012 Share Posted October 17, 2012 ...20Z UPDATE... VIGOROUS CONVECTIVE DEVELOPMENT IS UNDERWAY ACROSS PARTS OF SOUTHWEST MISSOURI. THIS APPEARS TO BE WHERE AGEOSTROPHIC FORCING IN THE EXIT REGION OF A 70-90+ KT 500 MB JET...DIGGING SOUTHEAST OF THE CENTRAL ROCKIES THROUGH THE SOUTH CENTRAL PLAINS...IS ENHANCING LOW-LEVEL FRONTOGENETIC FORCING FOR UPWARD VERTICAL MOTION IN THE PRESENCE OF WEAK DESTABILIZATION. THIS FORCING IS EXPECTED TO SPREAD EASTWARD INTO THE LOWER OHIO VALLEY...AND SOUTHWARD THROUGH THE OZARK PLATEAU...TENNESSEE AND LOWER MISSISSIPPI VALLEYS BY LATE EVENING...BEFORE WEAKENING OVERNIGHT. HIGHER TORNADO PROBABILITIES ACROSS EASTERN ARKANSAS AND THE MISSISSIPPI DELTA REGION ARE LARGELY CONTINGENT ON MORE SUBSTANTIVE BOUNDARY LAYER DESTABILIZATION OCCURRING IN THE PRESENCE OF STRONGER PRE-FRONTAL LOWER/MID TROPOSPHERIC WARM ADVECTION DEVELOPING EASTWARD THROUGH THE LOWER MISSISSIPPI VALLEY LATE THIS AFTERNOON AND EVENING. IT IS INCREASINGLY UNCERTAIN WHETHER LIFT AND DESTABILIZATION WILL BECOME SUFFICIENT FOR SUBSTANTIVE DISCRETE PRE-FRONTAL STORM DEVELOPMENT NECESSARY TO SUPPORT THESE PROBABILITIES. HOWEVER...THE POTENTIAL FOR A STRONG TORNADO OR TWO IS NOT NEGLIGIBLE...AND IT SEEMS MOST PRUDENT TO MAINTAIN THE CURRENT OUTLOOK AS IS...AT LEAST UNTIL THE EVENING /01Z/ OUTLOOK UPDATE. We shall see... Link to comment Share on other sites More sharing options...
Buckeye05 Posted October 17, 2012 Share Posted October 17, 2012 Storm just north of Coy, AR is starting to grab my attention. Link to comment Share on other sites More sharing options...
SouthernNJ Posted October 17, 2012 Share Posted October 17, 2012 The storm NW of Stuttgart AR is trying to get active. Link to comment Share on other sites More sharing options...
Ellinwood Posted October 17, 2012 Share Posted October 17, 2012 Storm just north of Coy, AR is starting to grab my attention. The storm NW of Stuttgart AR is trying to get active. Definitely looking like a nice supercell now... just got severe-warned but circulation is tightening: Link to comment Share on other sites More sharing options...
MnWeatherman Posted October 17, 2012 Share Posted October 17, 2012 This supercell is about to get nasty! Inflow near 55 knots! Link to comment Share on other sites More sharing options...
MnWeatherman Posted October 17, 2012 Share Posted October 17, 2012 Tornado warning just got issued for that cell Link to comment Share on other sites More sharing options...
Ellinwood Posted October 17, 2012 Share Posted October 17, 2012 Aaaand now it's TOR warned: BULLETIN - EAS ACTIVATION REQUESTED TORNADO WARNING NATIONAL WEATHER SERVICE LITTLE ROCK AR 648 PM CDT WED OCT 17 2012 THE NATIONAL WEATHER SERVICE IN LITTLE ROCK HAS ISSUED A * TORNADO WARNING FOR... SOUTHERN PRAIRIE COUNTY IN CENTRAL ARKANSAS... WEST CENTRAL MONROE COUNTY IN EASTERN ARKANSAS... EAST CENTRAL LONOKE COUNTY IN CENTRAL ARKANSAS... * UNTIL 730 PM CDT * AT 645 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A FUNNEL CLOUD. NATIONAL WEATHER SERVICE DOPPLER RADAR ALSO INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS SEVERE STORM WAS LOCATED NEAR PARKERS CORNER...OR 13 MILES SOUTHWEST OF HAZEN. DOPPLER RADAR SHOWED THIS SEVERE STORM MOVING EAST AT 35 MPH. Link to comment Share on other sites More sharing options...
Disc Posted October 17, 2012 Share Posted October 17, 2012 Keep posting screen caps of these storms.I'm stuck in class. Gonna have a hard time focusing now. Link to comment Share on other sites More sharing options...
Buckeye05 Posted October 17, 2012 Share Posted October 17, 2012 The one just north of Fredonia bears watching as well imo. Link to comment Share on other sites More sharing options...
SouthernNJ Posted October 17, 2012 Share Posted October 17, 2012 The tornado-warned storm over Sheridan AR has a better g2g signature at the 654 PM CDT scan than the Stuttgart storm. It could get close to Pine Bluff if it can gain some strength. Link to comment Share on other sites More sharing options...
MnWeatherman Posted October 18, 2012 Share Posted October 18, 2012 My GR2 radar is stuck at 23:41z, anybody else? Link to comment Share on other sites More sharing options...
MnWeatherman Posted October 18, 2012 Share Posted October 18, 2012 Here you go Disc, Level 3 Link to comment Share on other sites More sharing options...
NaoPos Posted October 18, 2012 Share Posted October 18, 2012 Hey now: Link to comment Share on other sites More sharing options...
andyhb Posted October 18, 2012 Share Posted October 18, 2012 Those cells in Southern AR have up to 500 m2/s2 Effective SRH to work with, per mesoanalysis. Link to comment Share on other sites More sharing options...
MnWeatherman Posted October 18, 2012 Share Posted October 18, 2012 Brief Tornado? Link to comment Share on other sites More sharing options...
NaoPos Posted October 18, 2012 Share Posted October 18, 2012 This needs a warning: Lots of the cells in the area have the textbook supercell look to them. Link to comment Share on other sites More sharing options...
andyhb Posted October 18, 2012 Share Posted October 18, 2012 It's got a warning now. Link to comment Share on other sites More sharing options...
andyhb Posted October 18, 2012 Share Posted October 18, 2012 Cells moving right into this... Link to comment Share on other sites More sharing options...
Ellinwood Posted October 18, 2012 Share Posted October 18, 2012 This needs a warning: Lots of the cells in the area have the textbook supercell look to them. 4-minute gap between expired warning and the new one, with no question at the expiration of the old one that another warning was needed. Link to comment Share on other sites More sharing options...
SouthernNJ Posted October 18, 2012 Share Posted October 18, 2012 Two circulations about 8 miles apart nearing Clarendon AR, with a couple of funnel cloud reports. The storm near Marvel in the Memphis CWA is close to requiring a TOR. Link to comment Share on other sites More sharing options...
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