David Reimer Posted March 24, 2011 Share Posted March 24, 2011 I was surprised that a new severe weather thread wasn't already made this morning for this weekend, so here we go. The SREF is showing a substantial tornado threat on Saturday in the mid-south. Here's the latest graphic off the 09Z run. Link to comment Share on other sites More sharing options...
David Reimer Posted March 24, 2011 Author Share Posted March 24, 2011 The terrain sucks for chasing, but this is interesting never the less Link to comment Share on other sites More sharing options...
Stebo Posted March 24, 2011 Share Posted March 24, 2011 Wow at those graphics, I do have to admit this one kind of popped up on me. Certainly looks pretty good though as the flow off the gulf should be very ample. I'd like to see a little bit more shear in the 0-1km however it looks like the trend is for the shear values to be going up when comparing previous runs of the NAM. The big concern with all of this is that this could be a significant evening/nighttime event as it stands now. Link to comment Share on other sites More sharing options...
hm8 Posted March 24, 2011 Share Posted March 24, 2011 There actually is another thread...but it was made so long ago that no one really payed much attention to it Link to comment Share on other sites More sharing options...
thewxmann Posted March 24, 2011 Share Posted March 24, 2011 The 12Z NAM is going gangbusters for Sat. Not sure how much to believe it (since the GFS shows a rather docile setup by comparison), but that's probably why the SREF is so gung-ho right now. Link to comment Share on other sites More sharing options...
SluggerWx Posted March 24, 2011 Share Posted March 24, 2011 Day 4-8 sounds interesting, too: DAY 4-8 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0347 AM CDT THU MAR 24 2011 VALID 271200Z - 011200Z ...PREDICTABILITY TOO LOW TO DELINEATE A REGIONAL SVR RISK AREA... MEDIUM RANGE GUIDANCE GENERALLY INDICATES THAT THE PREVAILING BLOCKING PATTERN WILL WEAKEN...OR BECOME LESS PROMINENT...DURING THIS FORECAST PERIOD. AS THIS PROCEEDS...THE ECMWF REMAINS SUGGESTIVE THAT ONE OF THE SIGNIFICANT SHORT WAVE IMPULSES EMANATING FROM A STRONG MID-LATITUDE PACIFIC JET COULD AMPLIFY AND SUPPORT STRONG CYCLOGENESIS SOMEWHERE FROM THE LEE OF THE SOUTHERN ROCKIES INTO THE ATLANTIC SEABOARD...AT SOME POINT NEXT WEEK. IF THIS OCCURS...IT APPEARS LIKELY TO COINCIDE WITH CONTINUED MOISTENING OF THE GULF BOUNDARY LAYER...WHICH COULD SUPPORT A SEASONABLY STRONG INLAND RETURN FLOW...AND POTENTIAL FOR A SIGNIFICANT SEVERE WEATHER OUTBREAK. HOWEVER...THE RUN TO RUN VARIABILITY OF THE ECMWF HAS BEEN SUBSTANTIAL...AND THE SPREAD BEGINS TO INCREASE AMONG THE MODELS AND MODEL ENSEMBLES AS EARLY AS THE BEGINNING OF THE PERIOD. AS A RESULT...UNCERTAINTY REMAINS MUCH TOO LARGE TO CONFIDENTLY ASSESS THE SEVERE WEATHER THREAT... AND ATTEMPT TO DELINEATE A REGIONAL SEVERE RISK AREA. Link to comment Share on other sites More sharing options...
Chicago Storm Posted March 24, 2011 Share Posted March 24, 2011 Link to comment Share on other sites More sharing options...
Thundersnow12 Posted March 25, 2011 Share Posted March 25, 2011 I put this up in the last thread lol and turn off smoothing! haha Link to comment Share on other sites More sharing options...
David Reimer Posted March 25, 2011 Author Share Posted March 25, 2011 I put this up in the last thread lol and turn off smoothing! haha Link to comment Share on other sites More sharing options...
Indystorm Posted March 25, 2011 Share Posted March 25, 2011 MESOSCALE DISCUSSION 0270 NWS STORM PREDICTION CENTER NORMAN OK 0709 PM CDT THU MAR 24 2011 AREAS AFFECTED...PORTIONS OF W TX CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 250009Z - 250145Z ONE SUPERCELL IS UNDERWAY IN SCURRY CO TEXAS...WITH ADDITIONAL INITIATION POSSIBLE ALONG AND E OF THE DRYLINE IN THE NEXT 2-3 HRS. A WW IS POSSIBLE IF ADDITIONAL CELLS BECOME ORGANIZED. 23Z SFC ANALYSIS INDICATES A DRYLINE ACROSS FAR W TX...WITH CU NOTED RUNNING FROM AROUND LBB S TO NEAR AND JUST SW OF MAF. MEANWHILE...A NW-TO-SE ORIENTED WARM FRONT RUNS FROM S OF LBB TO THE NE OF MAF. WHILE MANY CELLS HAVE STRUGGLED TO SURVIVE AS THEY MOVE OFF THE DRYLINE...ONE CELL HAS INTENSIFIED AND HAS ALREADY PRODUCED SEVERE HAIL NE OF MAF. HOWEVER...THIS CELL HAS MOVED N OF THE WARM FRONT AND SHOULD BEGIN TO WEAKEN AS IT ENCOUNTERS WEAKER BUOYANCY AND STRONGER SFC-BASED INHIBITION. ADDITIONAL CELLS MAY FORM FURTHER W ON THE DRYLINE IN THE NEXT 1-2 HRS BEFORE DIABATIC COOLING STABILIZES THE BOUNDARY LAYER. VERY STEEP LAPSE RATES.../AS NOTED ON THE 00Z MAF SOUNDING/...MU CAPE OF 1000-1500 J/KG AND EFFECTIVE SHEAR OF 40-50 KTS WILL SUPPORT A LARGE HAIL THREAT WITH ANY CELL THAT BECOMES ESTABLISHED. LARGE T/TD SPREADS AND DCAPE OF AROUND 1500 J/KG WILL SUPPORT A THREAT OF ISOLATED SEVERE WIND. IF ADDITIONAL STORMS FORM FURTHER WEST ALONG THE DRYLINE AND HAVE THE OPPORTUNITY TO STAY IN THE WARM SECTOR FOR AT LEAST AN HOUR OR TWO...A WW MAY BECOME NECESSARY. CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted March 25, 2011 Share Posted March 25, 2011 The 0z GFS makes northern TX on saturday look very interesting. The CAP might be a problem but it is showing 2000 j/kg of CAPE and some sexy wind profiles/hodo's just off the dryline. Link to comment Share on other sites More sharing options...
David Reimer Posted March 25, 2011 Author Share Posted March 25, 2011 The 0z GFS makes northern TX on saturday Monday look very interesting. The CAP might be a problem but it is showing 2000 j/kg of CAPE and some sexy wind profiles/hodo's just off the dryline. Link to comment Share on other sites More sharing options...
SmokeEater Posted March 25, 2011 Share Posted March 25, 2011 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1243 AM CDT FRI MAR 25 2011 VALID 251200Z - 261200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ARKLATEX REGION TO LOWER MS VALLEY... ...SYNOPSIS... IN MIDDLE-UPPER LEVELS...SPLIT-FLOW PATTERN FCST TO PERSIST WELL BEYOND THIS PERIOD. RIDGING WILL EXTEND SWD ACROSS ND FROM ANTICYCLONE CENTERED OVER NERN SK...WHILE CONTINUOUS/QUASI-ZONAL CURRENT COVERS MUCH OF CONUS FROM MIDDLE-SRN ATLANTIC COAST WWD ACROSS CENTRAL/SRN ROCKIES. WELL-DEFINED CYCLONE -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OFFSHORE ORE -- IS FCST TO MOVE INLAND EARLY THIS PERIOD. THIS FEATURE THEN SHOULD QUICKLY DEAMPLIFY INTO WEAKENING OPEN-WAVE TROUGH OVER NRN ROCKIES...WHILE SECOND CYCLONE DEVELOPS OFFSHORE PAC NW. SHORTWAVE TROUGH -- NOW MOVING INLAND CENTRAL/NRN CA -- IS FCST TO MOVE EWD ACROSS GREAT BASIN AND CENTRAL ROCKIES TO CENTRAL HIGH PLAINS BY 26/12Z. MEANWHILE...DOWNSTREAM SHORTWAVE OVER CENTRAL PLAINS WILL MOVE EWD AND WEAKEN CONSIDERABLY ACROSS CENTRAL APPALACHIANS TODAY...AMIDST CONFLUENT FLOW ALOFT ASSOCIATED WITH CYCLONE OVER LOWER ST LAWRENCE VALLEY REGION. AT SFC...WEAK NW TX/SWRN OK LOW IS EXPECTED ALONG WARM FRONTAL ZONE EARLY IN PERIOD...WITH FRONT ESEWD ACROSS ARKLATEX TO CENTRAL/SRN LA. FRONT SHOULD LIFT NWD INTO SERN OK AND SRN AR BY 26/00Z...EXTENDING WNWWD ACROSS SRN TX PANHANDLE REGION. BY THAT TIME...DRYLINE SHOULD EXTEND FROM SERN OK SWWD ACROSS N-CENTRAL TX TO SRN HILL COUNTRY...THEN RETREAT SLIGHTLY WWD DURING EVENING. ANOTHER SFC LOW MAY DEVELOP OVERNIGHT ALONG FRONT INVOF SWRN OK/NW TX AND MOVE EWD...WITH RELATED VEERING OF SFC WINDS TO ITS S AND SW RESULTING IN EWD OSCILLATION OF DRYLINE AGAIN BEFORE 26/12Z. ...ARKLATEX REGION TO LOWER MS VALLEY... AREA OF STG-SVR TSTMS IS EXPECTED TO DEVELOP...EXPAND AND MOVE EWD FROM NE TX/SERN OK/SWRN AR AREA DURING EVENING...AMIDST INCREASING LOW-LEVEL MOISTURE AND FAVORABLE DEEP-LAYER SHEAR PROFILES TO SUPPORT SVR RISK. SUPERCELLS WITH LARGE HAIL AND SVR GUSTS ARE POSSIBLE...AND THREAT FOR TORNADOES ALSO MAY EXIST INVOF WARM-FRONTAL ZONE. PROGS ARE IN VERY STG AGREEMENT REGARDING GENERAL EVOLUTION/LOCATION OF SCENARIO...HOWEVER TIMING OF INITIATION REMAINS QUITE UNCERTAIN...ESPECIALLY POTENTIAL FOR DIURNAL/SFC-BASED DEVELOPMENT BEFORE 00Z. THIS IS BECAUSE OF STG CAPPING RELATED TO ANTECEDENT/ELEVATED MIXED LAYER...COMBINED WITH ONLY SUBTLE/SHALLOW WARM-FRONTAL LIFT AND LACK OF SIGNIFICANT MID-UPPER PERTURBATION NEARBY. THIS REGION WILL BE TOO REMOVED FROM GREAT BASIN/CENTRAL ROCKIES SHORTWAVE TROUGH TO EXPERIENCE DIRECT EFFECTS. HOWEVER...BROAD/LOW-LEVEL WAA REGIME ALREADY IN PLACE OUGHT TO STRENGTHEN OVERNIGHT ACROSS LOWER MS VALLEY REGION...RESULTING IN INCREASING THETAE WITH TIME FOR INFLOW PARCELS IN AND N OF SFC WARM-FRONTAL ZONE. TIME WINDOW FOR SFC-BASED CONVECTION SHOULD EXIST DURING EVENING NEAR WARM FRONT BEFORE SUBSTANTIAL SFC COOLING...AS LOW-LEVEL HODOGRAPH EXPANDS BENEATH STRENGTHENING LLJ. THIS WILL BOOST SRH AND TORNADO POTENTIAL FOR SEVERAL HOURS...BEFORE ACTIVITY MOVES EWD INTO MORE STABLE AIR MASS. ADDITIONAL DEVELOPMENT MAY OCCUR OVERNIGHT IN EARLIER STORM GENESIS REGION OF SERN OK/NE TX...MAINTAINING SVR THREAT BEHIND INITIAL ACTIVITY. ...WRN OZARKS REGION... CLUSTER OF SCATTERED/ELEVATED TSTMS MAY BE ONGOING EARLY IN PERIOD OVER PORTIONS NERN OK/SERN KS...ROOTED IN 750-850 MB LAYER BASED ON RUC/ETA-KF FCST SOUNDINGS. ALTHOUGH BUOYANCY IS EXPECTED TO BE RATHER UNSPECTACULAR...WITH MUCAPE 400-800 J/KG...40-50 KT EFFECTIVE SHEAR INDICATES CONVECTION MAY BE ORGANIZED ENOUGH FOR MRGL HAIL POTENTIAL. THIS ACTIVITY SHOULD WEAKEN THROUGH MID-LATE MORNING AS IT MOVES EWD OVER AR/MO OZARKS AND INITIALLY SUPPORTIVE LLJ DIMINISHES. ..EDWARDS/DEAN.. 03/25/2011 Link to comment Share on other sites More sharing options...
SmokeEater Posted March 25, 2011 Share Posted March 25, 2011 Day 2, 30% hatched. DAY 2 CONVECTIVE OUTLOOK CORR 1 NWS STORM PREDICTION CENTER NORMAN OK 0112 AM CDT FRI MAR 25 2011 VALID 261200Z - 271200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE LOWER MS VALLEY INTO THE SERN STATES... CORRECTED FOR INCLUSION OF SIG AREA ...SYNOPSIS... BELT OF PROGRESSIVE QUASI-ZONAL WLYS WILL PERSIST THROUGH SATURDAY ACROSS SRN TWO THIRDS OF THE U.S. AND SOUTH OF HIGHER LATITUDE BLOCKING PATTERN. ANOTHER IN A SERIES OF IMPULSES EMANATING FROM UPPER LOW ALONG PACIFIC NW COAST WILL LIKELY DEAMPLIFY AS IT MOVES INTO CONFLUENT FLOW REGIME OVER THE MID MS VALLEY SATURDAY EVENING. WARM FRONT WILL LIFT NWD AND LIKELY EXTEND FROM A WEAK SURFACE LOW OVER THE SRN PLAINS EWD INTO THE SERN STATES EARLY SATURDAY. NWD PROGRESSION OF FRONT SHOULD BE LIMITED BY LARGE HIGH PRESSURE AREA CENTERED OVER ONTARIO AND EXTENDING SWD INTO THE OH VALLEY REGION. AS THE IMPULSE ADVANCES EWD THROUGH THE MID-MS VALLEY INTO THE OH VALLEY SURFACE LOW WILL DEVELOP EWD ALONG WARM FRONT INTO THE SERN STATES WHILE COLD FRONT ADVANCES SWD THROUGH TX AND THE LOWER MS VALLEY. ...ERN TX THROUGH LOWER MS VALLEY AND SERN STATES... SWLY LLJ WILL STRENGTHEN FRIDAY NIGHT INTO SATURDAY FROM THE LOWER MS VALLEY INTO SERN STATES AND ADVECT MODIFIED CP AIR WITH LOW 60S DEWPOINTS NEWD THROUGH EXPANDING WARM SECTOR. WLY FLOW ALOFT WILL TRANSPORT EML PLUME EWD ABOVE MOISTENING BOUNDARY LAYER WHICH IN CONJUNCTION WITH DIABATIC WARMING SHOULD CONTRIBUTE TO 1000-1500 J/KG MLCAPE SATURDAY AFTERNOON. ELEVATED STORMS SHOULD BE ONGOING FROM PORTIONS OF AR INTO THE TN VALLEY AT START OF PERIOD. SOME OF THIS ACTIVITY COULD POSE A THREAT FOR ISOLATED HAIL. ADDITIONAL STORMS MAY DEVELOP AS THE BOUNDARY LAYER DESTABILIZES...PRIMARILY IN VICINITY OF CONVECTIVELY REINFORCED WARM FRONT OR RESIDUAL OUTFLOW BOUNDARIES. EFFECTIVE SHEAR FROM 40-50 KT WILL SUPPORT SUPERCELLS AND BOWING SEGMENTS WITH LARGE HAIL...DAMAGING WIND AND ISOLATED TORNADOES POSSIBLE. DEVELOPMENT SWWD TOWARD TX IN WARM SECTOR IS MORE UNCERTAIN DUE TO POTENTIAL FOR STRONGER CAP AND WEAKER FORCING AS THE LLJ VEERS AND WEAKENS AHEAD OF THE COLD FRONT. HAVE KEPT ERN TX THROUGH THE GULF COASTAL AREA IN 5% SEVERE PROBABILITIES GIVEN THE POTENTIAL FOR MORE ISOLATED COVERAGE. ..DIAL.. 03/25/2011 Link to comment Share on other sites More sharing options...
Thundersnow12 Posted March 25, 2011 Share Posted March 25, 2011 Wtf I swear I wrote Monday lol thanks for the fix. Link to comment Share on other sites More sharing options...
Jim Martin Posted March 25, 2011 Share Posted March 25, 2011 The significant tornado parameter is still way up there for the northern one-half of Alabama for tomorrow night. Link to comment Share on other sites More sharing options...
janetjanet998 Posted March 25, 2011 Share Posted March 25, 2011 NWS STORM PREDICTION CENTER NORMAN OK 1217 PM CDT FRI MAR 25 2011 VALID 261200Z - 271200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER MS VALLEY AND GULF COAST STATES... ..GULF COAST STATES A SUBTLE SHORTWAVE TROUGH OVER THE ROCKIES TONIGHT WILL MOVE INTO THE SRN PLAINS SATURDAY MORNING. AHEAD OF THE SYSTEM...A BROAD LOW-LEVEL JET WILL BE IN PLACE ACROSS THE LOWER MS VALLEY AND CNTRL GULF COAST STATES. ON THE NRN EDGE OF THE JET...SEVERAL CLUSTERS OF ELEVATED THUNDERSTORMS SHOULD BE ONGOING SATURDAY MORNING FROM THE SRN PLAINS EWD ACROSS ARKANSAS AND INTO THE TN VALLEY. THIS CONVECTION COULD HAVE AN ISOLATED HAIL THREAT. AT THE SFC...A COLD FRONT IS FORECAST TO MOVE SWD INTO TN VALLEY AND ERN GULF COAST STATES BY LATE AFTERNOON. AS INSTABILITY INCREASES DURING THE DAY...SFC-BASED THUNDERSTORM SHOULD INITIATE ALONG THE BOUNDARY AND MOVE ESEWD ACROSS THE REGION. MODEL CONSENSUS SUGGESTS THE GREATEST COVERAGE OF THUNDERSTORM ACTIVITY WILL BE ALONG THE BOUNDARY FROM NRN MS ESEWD ACROSS NCNTRL AL INTO CNTRL GA. THIS CORRIDOR IS ALONG THE NRN EDGE OF MODERATE INSTABILITY AND ON THE SRN EDGE OF BROAD BAND OF STRONG MID-LEVEL FLOW. FORECAST SOUNDINGS ACROSS NRN MS AND NRN AL AT 21Z SATURDAY SHOW MLCAPE CAPE AROUND 2000 J/KG WITH 50 KT OF DEEP LAYER SHEAR AND STEEP MID-LEVEL LAPSE RATES. THIS ENVIRONMENT SHOULD BE SUPPORTIVE OF SUPERCELL DEVELOPMENT WITH LARGE HAIL ACCOMPANYING THE MORE DOMINANT STORMS. IN ADDITION...TORNADOES MAY OCCUR AS SUPERCELLS MATURE AND THE LOW-LEVEL JET STRENGTHENS SATURDAY EVENING. THE BIRMINGHAM FORECAST SOUNDING EARLY SATURDAY EVENING SHOWS 0-3 KM STORM RELATIVE HELICITIES AROUND 400 M2/S2 SUGGESTING A THREAT FOR STRONG TORNADOES WILL BE POSSIBLE. A CLUSTERING OF TORNADOES MAY OCCUR ACROSS NRN MS AND NCNTRL AL WHERE INSTABILITY...SHEAR AND LIFT IS FORECAST TO BE MAXIMIZED. FURTHER EAST SOUTHEAST ALONG THE BOUNDARY IN CNTRL GA...MODEL FORECASTS ARE ALSO IN AGREEMENT WITH THUNDERSTORM DEVELOPMENT SATURDAY AFTERNOON. FORECAST SOUNDINGS AROUND MACON AT 21Z SATURDAY SHOW MLCAPE VALUES OF 1000 J/KG WITH 50 KT OF DEEP LAYER SHEAR. THIS SHOULD BE SUFFICIENT FOR A SEVERE THREAT WITH SUPERCELL DEVELOPMENT POSSIBLE. LARGE HAIL AND AN ISOLATED TORNADO THREAT MAY ACCOMPANY THE STRONGER CELLS ESPECIALLY IF STORMS REMAIN DISCRETE. HOWEVER...THERE IS A POSSIBILITY THAT A LINEAR MCS COULD DEVELOP WHICH WOULD MAKE WIND DAMAGE THE PRIMARY THREAT. ..LOWER MS VALLEY/ARKLATEX A SHORTWAVE TROUGH WILL APPROACH THE ARKLATEX SATURDAY AS A COLD FRONT ADVANCES SEWD INTO THE SRN PLAINS AND SRN OZARKS. AS SFC TEMPS WARM AHEAD OF THE BOUNDARY...MODERATE INSTABILITY IS FORECAST TO DEVELOP BY MIDDAY. FORECAST SOUNDINGS SHOW A STRONG CAPPING INVERSION IN PLACE UNTIL MID-AFTERNOON WHEN INCREASING CONVERGENCE ALONG THE BOUNDARY COULD RESULT IN THUNDERSTORM INITIATION ACROSS SRN AR...NRN LA AND EAST TX. THE MODELS DISAGREE ON HOW MUCH CONVECTION WILL FORM BUT THE GFS IS MORE AGGRESSIVE...DEVELOPING SCATTERED STORMS BY EARLY SATURDAY EVENING. FORECAST SOUNDINGS AROUND GREENVILLE AR AT 03Z SUNDAY SHOW MLCAPE VALUES OF 1200 TO 1500 J/KG WITH 0-6 KM SHEAR IN THE 40 TO 50 KT RANGE. THIS COMBINED WITH STEEP MID-LEVEL LAPSE RATES SHOULD RESULT IN AN ISOLATED LARGE HAIL THREAT. A FEW DAMAGING WIND GUSTS WILL ALSO BE POSSIBLE. THE SEVERE THREAT SHOULD BE INCREASINGLY ISOLATED WITH SWWD EXTENT WITH JUST A MINIMAL THREAT ACROSS SE TX. Link to comment Share on other sites More sharing options...
SmokeEater Posted March 25, 2011 Share Posted March 25, 2011 From James Spann's blog, from ABC 33/40 in Birmingham. Significant Severe Weather Threat SEVERE WEATHER THREAT: SPC maintains their standard “slight” risk of severe weather for the northern two-thirds of Alabama, but they continue to show an enhanced 30 percent chance of severe weather within 25 miles of a given point for North Alabama, and are now mentioning strong tornadoes as a possibility. They indicate the best combination of instability, shear, and lift will be over North-Central Alabama, so we will all have to be on our toes. All modes of severe weather are likely, including hail, damaging straight line winds, and tornadoes. While we could see severe weather as early as 3:00… it really looks like the core threat will come from about 6:00 p.m. tomorrow through 4:00 a.m. Sunday. Everybody will need to be close to a good source of weather information so you won’t miss any warnings. Link to comment Share on other sites More sharing options...
Jim Martin Posted March 25, 2011 Share Posted March 25, 2011 685 ACUS11 KWNS 252044 SWOMCD SPC MCD 252043 ARZ000-LAZ000-TXZ000-OKZ000-252315- MESOSCALE DISCUSSION 0271 NWS STORM PREDICTION CENTER NORMAN OK 0343 PM CDT FRI MAR 25 2011 AREAS AFFECTED...NCNTRL/NERN TX...SCNTRL/SERN OK...SWRN AR AND EXTREME NRN LA CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 252043Z - 252315Z LATEST VISIBLE SATELLITE IMAGERY DEPICTS A DEEPENING CUMULUS FIELD ACROSS THE WARM SECTOR OVER SCNTRL/SERN OK AND NCNTRL TX. HOWEVER...RIDGE/ANTICYCLONIC CHARACTER TO HIGH-LEVEL CLOUDS MOVING OVER THE REGION AND LACK OF SUBSTANTIAL LOW-LEVEL CONVERGENCE WILL PROBABLY BE DETRIMENTAL TO SURFACE-BASED CONVECTIVE INITIATION UNTIL AFTER 23Z OR SO. THEREAFTER...WEAK HEIGHT FALLS ASSOCIATED WITH AN UPSTREAM TROUGH AND THE PRE-EXISTING WARM BOUNDARY LAYER MAY BECOME SLIGHTLY MORE FAVORABLE FOR INITIATION. THERE APPEARS TO BE ENOUGH EVIDENCE TO SUPPORT LATEST RUC/GFS/NAM SOLUTIONS FOR AT LEAST ISOLATED THUNDERSTORMS NEAR THE TRIPLE POINT AND SWD ALONG THE DRYLINE FROM SCNTRL OK INTO NCNTRL TX NEAR SUNSET WHERE NRN-EXTENT OF 1000-1500 J/KG MLCAPES WILL EXIST. SHOULD A STORM FORM...ROUGHLY 45-50 KTS OF LARGELY UNIDIRECTIONAL DEEP-LAYER SHEAR AND MID-LEVEL LAPSE RATES IN EXCESS OF 7 DEG C PER KM WILL BE FAVORABLE FOR SPLITTING SUPERCELLS CAPABLE OF LARGE HAIL. A SUSTAINED SURFACE-BASED STORM EVOLVING ALONG/N OF THE RED RIVER NEAR A WARM FRONT COULD PRODUCE A TORNADO OR TWO...BUT THE HAIL RISK WILL DOMINATE. OTHERWISE...ADDITIONAL ACTIVITY IS EXPECTED TO EVOLVE AND/OR DEVELOP ALONG/N OF THE WARM FRONT AS ELEVATED ENTITIES OVER ERN OK AND CNTRL AR LATER THIS EVENING WITH POSSIBLE LARGE HAIL. ..RACY.. 03/25/2011 Link to comment Share on other sites More sharing options...
thewxmann Posted March 25, 2011 Share Posted March 25, 2011 My concern for tornado potential tomorrow is two-fold: 1) That the frontal zone might shift southward more than currently progged, and 2) That the edge of the capping inversion might nudge northward. I have seen both happen on severe weather days, and tomorrow is no exception, with a shortwave allowing early convective development to reinforce the front, and the usual NAM bias in underestimating the cap. I just *feel* like tomorrow's one of those days when everything elevated develops north of the front, and no surface-based convection develops south of it... alas, fine details will need to be sorted out tomorrow on frontal placement and capping strength. Otherwise, on paper, this looks like a decent (MDT-risk sized) event. Link to comment Share on other sites More sharing options...
Ed Lizard Posted March 25, 2011 Share Posted March 25, 2011 Re: Mesoscale Discussion above. Latest SPC RUC based analysis, the cap is almost gone along what appears to be a diffuse dry line South of DFW. DFW late afternoon looks like maybe a candidate for some hailers based on real good midlevel instability. Light low level winds and a high LFC, not so good tornado wise, but a spread T to Td might enhance downdrafts Link to comment Share on other sites More sharing options...
Ed Lizard Posted March 25, 2011 Share Posted March 25, 2011 Maybe... Finally... Link to comment Share on other sites More sharing options...
Jim Martin Posted March 25, 2011 Share Posted March 25, 2011 STORM INITIATION IS STILL EXPECTED ACROSS THE ARKLATEX EARLY THIS EVENING AS THE CAPPING INVERSION WEAKENS. HOWEVER...STORM COVERAGE REMAINS THE GREATEST UNCERTAINTY DUE TO THE LACK OF LARGE-SCALE ASCENT. THE ENVIRONMENT SHOULD BE CHARACTERIZED BY MODERATE INSTABILITY...STRONG DEEP LAYER SHEAR AND STEEP MID-LEVEL LAPSE RATES. THIS SHOULD SUPPORT SUPERCELL DEVELOPMENT WITH EFFICIENT HAIL PRODUCTION SO WILL KEEP THE 30 % HAIL PROBABILITY IN PLACE ACROSS FAR NE TX...SE OK AND SW AR. OVERALL...THE OUTLOOK IS IN GOOD SHAPE AND NO CHANGES ARE MADE FOR THE 20Z ISSUANCE. From the day 1 outlook from SPC. Link to comment Share on other sites More sharing options...
thewxmann Posted March 25, 2011 Share Posted March 25, 2011 To be honest, I find it very unlikely that any storms will form today without a decent forcing mechanism, which is not to be found attm. Link to comment Share on other sites More sharing options...
Ed Lizard Posted March 25, 2011 Share Posted March 25, 2011 I thought I was finally seeing something on satellite, but thewxmann may be correct. Obs at DFW and the FWD radar show the dryline is retreating. Winds back to the South after being SW, and dewpoints rising. I think the Lubbock F-5 of years back formed on a retreating dryline, but in general observation, it seems like it works out more often the other way. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted March 25, 2011 Share Posted March 25, 2011 To be honest, I find it very unlikely that any storms will form today without a decent forcing mechanism, which is not to be found attm. Yep, all you need to look at is H7 temps and its not happening. Link to comment Share on other sites More sharing options...
Ed Lizard Posted March 26, 2011 Share Posted March 26, 2011 Yep, all you need to look at is H7 temps and its not happening. I blame a diffuse and retreating dryline myself. It shouldn't take much of anything to initiate storms. Link to comment Share on other sites More sharing options...
Fred Gossage Posted March 26, 2011 Share Posted March 26, 2011 You can have a cap, and no convective inhibition present on the plot.... and you can also have convective inhibition present.... but no capping inversion present. CIHN is basically "anti CAPE" and happens when the environmental temperature is greater than the theoretical parcel temperature in a certain layer (temperature line goes to the right of the parcel lapse rate on the skew-T). This can happen right at the surface with no inversion at all present..... but would keep any storms that form from being surface based. In the same manner, there can be a moderate or even strong cap in place, but no CIHN, as long as there is a layer where the temperature increases with height.... but the temp curve doesn't go to the right of the parcel lapse rate line on the skew-T. CIHN does not instantly = capping inversion. Link to comment Share on other sites More sharing options...
Jim Martin Posted March 26, 2011 Share Posted March 26, 2011 /ISSUED 339 PM CDT FRI MAR 25 2011/ A DRY LINE WILL MOVE INTO THE NORTHWEST PORTION OF NORTH TEXAS THIS EVENING BUT WILL STALL/RETREAT AFTER SUNSET UNTIL A COLD FRONT MOVES THROUGH THE REGION SATURDAY MORNING. SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE TONIGHT AS LARGE SCALE LIFT AND INSTABILITY INCREASE AHEAD OF AN APPROACHING SHORT WAVE. THE BEST STORM CHANCES WILL BE IN THE NORTH/NORTHEAST. HOWEVER...WITH A LACK OF GOOD FORCING EXPECTED...WE WILL KEEP POPS LOW. IF ANY STORMS DO FORM TONIGHT THEY WILL HAVE A POTENTIAL TO BRIEFLY BECOME SEVERE WITH HAIL/DAMAGING WIND. THE SHORT WAVE WILL QUICKLY TRANSLATE ACROSS THE REGION SATURDAY MORNING AND ALLOW A COLD FRONT SLIDE SOUTH. A FEW SHOWERS AND STORMS WILL BE POSSIBLE WITH THE FRONT...MAINLY SATURDAY MORNING. THE COLD FRONT IS PROGGED TO STALL OVER SOUTH TEXAS SATURDAY NIGHT WITH SOME ISENTROPIC LIFT EXPECTED OVER THE SOUTHERN ZONES. THEREFORE...WE WILL CARRY SOME LOW POPS. RAIN CHANCES WILL WILL END SUNDAY WITH DRIER AND COOLER AIR EXPECTED. This is from the Area Forecast Discussion from the NWS Dallas/Fort Worth office. Link to comment Share on other sites More sharing options...
SmokeEater Posted March 26, 2011 Share Posted March 26, 2011 MESOSCALE DISCUSSION 0272 NWS STORM PREDICTION CENTER NORMAN OK 0731 PM CDT FRI MAR 25 2011 AREAS AFFECTED...NCNTRL/NERN TX...SCNTRL/SERN OK...SWRN AR AND NWRN LA CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 260031Z - 260200Z CURRENT POTENTIAL FOR A WW ISSUANCE ACROSS NCNTRL/NERN TX... SCNTRL/SERN OK AND EWD TO SWRN AR/NWRN LA REMAINS CONDITIONAL BASED ON TSTM DEVELOPMENT. HOWEVER...GIVEN THE AVAILABLE WARM SECTOR INSTABILITY/SHEAR PARAMETERS...STORMS WILL LIKELY BE SEVERE ONCE INITIATION OCCURS. THUS...THIS REGION WILL CONTINUE TO BE MONITORED FOR GREATER REFLECTIVITY DEVELOPMENT AND THE NEED FOR A SEVERE WEATHER WATCH THIS EVENING. ...ANALYSIS AND THREATS... EARLY EVENING SURFACE ANALYSIS SHOWED AN AREA OF LOW PRESSURE LOCATED OVER SOUTH CENTRAL OK /INVOF ADM/ WITH A DRY LINE TRAILING SWWD /TO THE NW-W OF DALLAS-FT WORTH METROPLEX/ THROUGH SRN MONTAGUE TO STEPHENS COUNTIES TX. MEANWHILE...A QUASI-STATIONARY BOUNDARY EXTENDED ESEWD FROM THE SURFACE LOW THROUGH EXTREME SERN OK TO FAR SRN AR AND WEST CENTRAL MS. LATEST VISIBLE SATELLITE IMAGERY AND REGIONAL RADARS INDICATED MORE PERSISTENT AND LIKELY DEEPER CU/TCU ALONG THE DRY LINE FROM WISE AND MONTAGUE COUNTIES TX TO LOVE COUNTY OK...WITH A SECOND AREA OF GREATER CU FORMATION ALONG AND NORTH OF THE STATIONARY FRONT...JUST EAST OF THE SURFACE LOW. 00Z FWD SOUNDING SHOWED A WEAK CAP REMAINS AROUND 700-800 MB WITH MLCAPE CLOSE TO 1000 J/KG. THIS INSTABILITY WHICH WAS SIMILAR WITHIN THE WARM SECTOR ACROSS NCNTRL/NERN TX INTO NWRN LA COMBINED WITH EFFECTIVE BULK SHEAR AROUND 50 KT IS SUFFICIENT FOR ORGANIZED STORMS. A STRAIGHT HODOGRAPH WITH THIS SOUNDING SUPPORTS SPLITTING STORMS. GIVEN THE FAIRLY SUBSTANTIAL DRY SUB-CLOUD LAYER...STRONG WIND GUSTS AND HAIL WOULD BE THE INITIAL PRIMARY THREATS. HOWEVER...ANY STORM THAT CAN TRACK ALONG THE STATIONARY FRONT WOULD HAVE A GREATER POTENTIAL TO PRODUCE A TORNADO. ...STORM INITIATION POTENTIAL... GIVEN THE WEAK CAP YET EVIDENT ON THE 00Z FWD SOUNDING AND OVERALL WEAK UPPER FORCING ACROSS THIS REGION...STORM INITIATION IS UNCERTAIN DURING THE NEXT 1-2 HOURS...WHICH IS MORE CONSISTENT WITH THE RECENT RUNS OF THE EXPERIMENTAL HRRR MODEL. TRENDS IN LOW LEVEL FLOW STREAMLINE ANALYSIS INDICATED DIFFLUENT FLOW ACROSS THE DISCUSSION AREA WITH WINDS OVER NWRN TX BEGINNING TO BACK IN RESPONSE TO PRESSURE FALLS WITH THE LEE TROUGH OVER THE CENTRAL/SRN HIGH PLAINS AND MORE VEERED SSWLY WINDS ALONG THE SABINE RIVER. THIS WOULD TEND TO LIMIT LOW LEVEL CONVERGENCE ALONG AFOREMENTIONED BOUNDARIES. THUS...DESPITE THE MORE PERSISTENT CU/TCU DEVELOPMENT...STORM INITIATION MAY NOT OCCUR UNTIL AFTER SUNSET ALONG THE RED RIVER VALLEY OF NERN TX/SERN OK WHEN THE STRENGTHENING LLJ INTO THIS REGION RESULTS IN AN INCREASE OF WAA/ASCENT AND MOISTENING. THESE LATTER FACTORS WOULD SUPPORT BOTH A TORNADO THREAT AND HAIL/DAMAGING WINDS. ..PETERS.. 03/26/2011 Link to comment Share on other sites More sharing options...
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