Hoosier Posted October 9, 2012 Share Posted October 9, 2012 Pretty typical fall system on the way for the weekend. SPC has an area outlined for possible severe weather... generally where the best instability is currently being shown. As is often the case with these fall systems, the low level/deep level flow looks strong with models showing 850 mb winds ramping up to 50-70 kts and 500 mb winds of 70-80 kts. The shear will be there. We'll have to see about instability but you usually don't need as much at this time of year. This looks like it could be a substantial event. How far east the threat gets is in question, but with the current scenario I think there would probably be at least a low end threat lingering into overnight Saturday/early Sunday simply due to the strength of the wind fields. Link to comment Share on other sites More sharing options...
Stebo Posted October 9, 2012 Share Posted October 9, 2012 Pretty typical fall system on the way for the weekend. SPC has an area outlined for possible severe weather... generally where the best instability is currently being shown. As is often the case with these fall systems, the low level/deep level flow looks strong with models showing 850 mb winds ramping up to 50-70 kts and 500 mb winds of 70-80 kts. The shear will be there. We'll have to see about instability but you usually don't need as much at this time of year. This looks like it could be a substantial event. How far east the threat gets is in question, but with the current scenario I think there would probably be at least a low end threat lingering into overnight Saturday/early Sunday simply due to the strength of the wind fields. I fully agree with everything you mention here, especially the bold part. The key here is that we could end up having a dynamically driven squall line racing ENE with this type of shear, won't take much instability to maintain it then. Link to comment Share on other sites More sharing options...
Powerball Posted October 9, 2012 Share Posted October 9, 2012 12z EURO looks better for the GL/OV region on Sunday as it slowed down the system. It definitely has the potential to be a decent event, depending on how fast the GOM moisture can advect northward and cloud cover.. Link to comment Share on other sites More sharing options...
Hoosier Posted October 10, 2012 Author Share Posted October 10, 2012 I fully agree with everything you mention here, especially the bold part. The key here is that we could end up having a dynamically driven squall line racing ENE with this type of shear, won't take much instability to maintain it then. I probably shouldn't do this, but if I had to guess at this early juncture, I'd say that if you draw a line along the IL/IN state line and northward along the western shore of LM... 50 miles either side of there will be the zone where this starts to run out of gas. Better hope I'm wrong for your sake. Link to comment Share on other sites More sharing options...
wisconsinwx Posted October 10, 2012 Share Posted October 10, 2012 I probably shouldn't do this, but if I had to guess at this early juncture, I'd say that if you draw a line along the IL/IN state line and northward along the western shore of LM... 50 miles either side of there will be the zone where this starts to run out of gas. Better hope I'm wrong for your sake. I agree, and it's called climo around here. Seriously, is it really that likely a scenario that you go into the specifics several days out? I would think given the likelihood of rain associated with the initial WAA Saturday morning, ongoing rain would prevent a massive squall line from even forming. Link to comment Share on other sites More sharing options...
Hoosier Posted October 10, 2012 Author Share Posted October 10, 2012 I agree, and it's called climo around here. Seriously, is it really that likely a scenario that you go into the specifics several days out? I would think given the likelihood of rain associated with the initial WAA Saturday morning, ongoing rain would prevent a massive squall line from even forming. If that rain is an all day event then it would be a problem. The way it looks now, there should be a break to allow a nice line to form to the west. On another subject, the CAPE/LCL parts of the SREF sigtor ingredients have been changed to 500 J/kg and 1.5 km, which means that those maps will be looking more bullish in the future. Link to comment Share on other sites More sharing options...
Hoosier Posted October 10, 2012 Author Share Posted October 10, 2012 On another subject, the CAPE/LCL parts of the SREF sigtor ingredients have been changed to 500 J/kg and 1.5 km, which means that those maps will be looking more bullish in the future. Here is a prime example. 50 probs on the old sigtor ingredients more than 72 hours out would lead to mass hysteria. Given that this is a low instability/high shear setup, this one is particularly sensitive to the CAPE change. Link to comment Share on other sites More sharing options...
trapperman Posted October 10, 2012 Share Posted October 10, 2012 Here is a prime example. 50 probs on the old sigtor ingredients more than 72 hours out would lead to mass hysteria. Given that this is a low instability/high shear setup, this one is particularly sensitive to the CAPE change. I looked at the map without reading anything prior and nearly pissed my pants. What happens when a "real" set up comes along? Link to comment Share on other sites More sharing options...
Hoosier Posted October 10, 2012 Author Share Posted October 10, 2012 I looked at the map without reading anything prior and nearly pissed my pants. What happens when a "real" set up comes along? Well, there will be high probs over a huge area I guess. The old one wasn't ideal by any means but not a big fan of this change. Just gonna have to use with even more caution than before. Link to comment Share on other sites More sharing options...
andyhb Posted October 11, 2012 Share Posted October 11, 2012 I loathe that change to SREF sig-tor ingredients, to say the least. Link to comment Share on other sites More sharing options...
Hoosier Posted October 11, 2012 Author Share Posted October 11, 2012 00z runs seem to be leaving more energy behind farther south. Link to comment Share on other sites More sharing options...
Geos Posted October 11, 2012 Share Posted October 11, 2012 00z runs seem to be leaving more energy behind farther south. I noticed that the low is quite a bit farther south. Low passes over Milwaukee about. Severe weather threat area more likely in IL, IA, and MO. - not WI probably. Link to comment Share on other sites More sharing options...
cyclone77 Posted October 11, 2012 Share Posted October 11, 2012 00z runs seem to be leaving more energy behind farther south. Indiana/Michigan/Ohio looking more likely for severe on the 14th to me. As far as on Saturday the best threat looks to stay west of I-35 to me. East of there will get late night leftovers. If I had a dime for every time this type of setup skips over the DVN area and impacts areas to the east I'd have lots of dimes. Link to comment Share on other sites More sharing options...
hm8 Posted October 11, 2012 Share Posted October 11, 2012 DAY 3 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0228 AM CDT THU OCT 11 2012 VALID 131200Z - 141200Z ...THERE IS A SLGT RISK OF SVR TSTMS SAT INTO SAT NIGHT ACROSS PARTS OF THE MID/UPPER MISSISSIPPI VALLEY INTO THE UPPER GREAT LAKES...SOUTHWARD INTO THE SOUTHERN PLAINS... ...SYNOPSIS... MODELS INDICATE THAT SPLIT BELTS OF STRONGER WESTERLIES WILL BEGIN TO CONSOLIDATE ACROSS NORTH AMERICA DURING THIS FORECAST PERIOD...AS THE REMNANT SOUTHERN STREAM CLOSED LOW CONTINUES ITS EAST NORTHEASTWARD ACCELERATION OUT OF THE SOUTHWEST. VARIABILITY IS INCREASING AMONG THE MODEL DATA CONCERNING THE EVOLUTION OF THIS FEATURE...FROM WHICH A COUPLE OF MORE DISTINCT SMALLER SCALE IMPULSES COULD EMERGE AS IT PROGRESSES EAST OF THE ROCKIES INTO THE PLAINS/MISSISSIPPI VALLEY REGION. NAM/SREF APPEAR TO MAINTAIN THE INITIAL CIRCULATION FORECAST TO REACH THE CENTRAL HIGH PLAINS BY 12Z SATURDAY AS THE PRIMARY UPPER IMPULSE...AND ACCELERATE IT EASTWARD INTO THE UPPER GREAT LAKES BY 12Z SUNDAY...MUCH AS GENERALLY HAS BEEN INDICATED BY MEDIUM RANGE GUIDANCE THE PAST FEW DAYS. HOWEVER...THE GFS SUGGESTS THAT A DISTINCT SECONDARY IMPULSE...TRAILING TO THE SOUTHWEST...MAY BECOME THE MORE PROMINENT IMPULSE SATURDAY...AS IT LIFTS EAST OF THE SOUTHERN ROCKIES...ACROSS THE SOUTH CENTRAL HIGH PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY. ECMWF ALSO NOW IS MORE SUGGESTIVE THAT STRONGER MID-LEVEL FORCING MAY DEVELOP SOUTH OF THE INITIAL IMPULSE...BUT NORTH OF THAT OF THE GFS. REGARDLESS...ALL GUIDANCE INDICATES THE CONTINUED DEVELOPMENT OF A SUB-1000 MB SURFACE LOW...GENERALLY EAST OF THE MIDDLE MISSOURI VALLEY TOWARD THE GREAT LAKES REGION. WITHIN THE WARM SECTOR OF THIS FEATURE...AND SOUTHWARD AHEAD OF THE TRAILING COLD FRONT/DRY LINE ADVANCING EASTWARD THROUGH THE SOUTHERN PLAINS...A BROAD SOUTHERLY 850 MB JET IS FORECAST TO STRENGTHEN FROM 50-70 KT...BENEATH A 70+ KT SOUTHWESTERLY 500 MB JET. THIS WILL CONTRIBUTE TO THE NORTHWARD ADVECTION OF SEASONABLY HIGH MOISTURE CONTENT AIR /PRECIPITABLE WATER UP AROUND 1.5+ INCHES/...WITH 60F+ SURFACE DEW POINTS AS FAR NORTH AS PORTIONS OF THE UPPER MISSISSIPPI VALLEY. DESTABILIZATION SHOULD BE SUFFICIENT TO SUPPORT WIDESPREAD CONVECTIVE DEVELOPMENT...INCLUDING PERHAPS CONSIDERABLE POTENTIAL FOR SEVERE THUNDERSTORMS FROM PORTIONS OF THE UPPER MISSISSIPPI VALLEY SOUTHWARD THROUGH THE SOUTHERN PLAINS. Link to comment Share on other sites More sharing options...
Hoosier Posted October 11, 2012 Author Share Posted October 11, 2012 Went ahead and extended it into Sunday as it looks like there could be continuation/regeneration but details are a bit sketchy. Link to comment Share on other sites More sharing options...
Stebo Posted October 11, 2012 Share Posted October 11, 2012 Went ahead and extended it into Sunday as it looks like there could be continuation/regeneration but details are a bit sketchy. I am thinking more so continuation, whatever forms should be dynamically driven as it moves ENE into the Lakes, although the NAM does not drop off instability as much as to be expected overnight Saturday so things could be rocking well after dark. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted October 11, 2012 Share Posted October 11, 2012 from LOT.. SATURDAY EVENING AND NIGHT ARE ANOTHER STORY. THE COLD FRONT SWINGS THROUGH SATURDAY EVENING/NIGHT. IF SEVERE WEATHER OCCURS IT WILL BE ALONG THE COLD FRONT. 0-6 KM SHEAR WILL STILL BE PLENTIFUL THROUGH THE FROPA...AND 0-1 KM SHEAR SPIKES TO ARND 40 KT AHEAD OF THE COLD FRONT. THEREFORE AREAS OF ROTATION AND TORNADOES ARE POSSIBLE ALONG THE COLD FRONT. THE MAIN QUESTION IS WHAT KIND OF ATMOSPHERE WILL THE COLD FRONT MOVE INTO. IF SOME OF THE AREA CLEARS OUT AND IS ABLE TO WARM/DESTABILIZE...WE COULD SEE A STRONG SQUALL LINE/DERECHO MOVE THROUGH THE CWA. HOWEVER...IF THE CLOUD COVER DOES NOT DISSIPATE...WHICH IS THE MORE LIKELY SITUATION RIGHT NOW...THE COLD FRONT AND ASSOCIATED LINE OF PRECIP WILL BE MOVING INTO A WORKED OVER ENVIRONMENT. LOCALIZED SPIN UPS AND ISOLATED SEVERE WEATHER WOULD BE FAVORED IN THIS SECOND ENVIRONMENT. GUIDANCE IN GENERAL IS FAVORING THE SECOND SCENARIO WITH CAPE DWINDLING TO 500 J/KG OR LESS AS THE COLD FRONT MOVES THROUGH. WILL NOTE HOWEVER...THAT THE LOW PRESSURE WILL BE DEEPENING AS IT PASSES BY SO FORCING FROM THE LOW ITSELF MAY PROVIDE SYNOPTIC ASCENT. Link to comment Share on other sites More sharing options...
PatrickSumner Posted October 11, 2012 Share Posted October 11, 2012 Interesting AFD from LOT. If a derecho did materialize, it would certainly hold together as it went east/southeast into Michigan and Indiana. Link to comment Share on other sites More sharing options...
A-L-E-K Posted October 11, 2012 Share Posted October 11, 2012 Interesting AFD from LOT. If a derecho did materialize, it would certainly hold together as it went east/southeast into Michigan and Indiana. not so certainly...threat is going to decrease rapidly east of RFD Link to comment Share on other sites More sharing options...
Thundersnow12 Posted October 11, 2012 Share Posted October 11, 2012 not so certainly...threat is going to decrease rapidly east of RFD I'm not so sure about that. If something good can get going...moisture/theta-e advection impressive from 18-3z and mid-level flow/LLJ only increase as the evening goes on. I guess it all depends on how much sfc heating we see here and points west. Link to comment Share on other sites More sharing options...
Hoosier Posted October 11, 2012 Author Share Posted October 11, 2012 I'm not so sure about that. If something good can get going...moisture/theta-e advection impressive from 18-3z and mid-level flow/LLJ only increase as the evening goes on. I guess it all depends on how much sfc heating we see here and points west. The factors you mentioned will work toward countering any significant nocturnal cooling, so it would help to have a good starting point. Wind fields are pretty impressive late Saturday into Sunday so it won't take much in the way of robust convection to mix some of that down toward the surface. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted October 12, 2012 Share Posted October 12, 2012 The factors you mentioned will work toward countering any significant nocturnal cooling, so it would help to have a good starting point. Wind fields are pretty impressive late Saturday into Sunday so it won't take much in the way of robust convection to mix some of that down toward the surface. Here is a wind profile and hodograph for DVN for 0z Saturday evening off the 18z GFS. Obviously supportive of strong tornadoes but probably won't have but if we were to see more sun than thought it's something to watch as those wind fields only increase. Link to comment Share on other sites More sharing options...
Stebo Posted October 12, 2012 Share Posted October 12, 2012 I'm not so sure about that. If something good can get going...moisture/theta-e advection impressive from 18-3z and mid-level flow/LLJ only increase as the evening goes on. I guess it all depends on how much sfc heating we see here and points west. Agree 100% the wind shear and mean flow are going to be substantial, if something were to form it won't run out of gas when it hits Lake Michigan Link to comment Share on other sites More sharing options...
A-L-E-K Posted October 12, 2012 Share Posted October 12, 2012 I'm just not seeing much sun the cards...this looks like a low end squall event....much better action towards the quad cities. Link to comment Share on other sites More sharing options...
Stebo Posted October 12, 2012 Share Posted October 12, 2012 I'm just not seeing much sun the cards...this looks like a low end squall event....much better action towards the quad cities. Not going to need a ton of sunshine. 2-4 hours will easily do the job. Link to comment Share on other sites More sharing options...
Geos Posted October 12, 2012 Share Posted October 12, 2012 I'm just not seeing much sun the cards...this looks like a low end squall event....much better action towards the quad cities. I agree with the lack of sun deal too. Looks to be quite a bit of rain moving in early with the warm front. I'm expecting a line of storms and not so much of a derecho! Clouds seem to like to linger around lately! Link to comment Share on other sites More sharing options...
A-L-E-K Posted October 12, 2012 Share Posted October 12, 2012 Not going to need a ton of sunshine. 2-4 hours will easily do the job. I would consider 4 hours a lot...I think 2 would be enough for a low end event. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted October 12, 2012 Share Posted October 12, 2012 18z NAM is progging 80 degrees up to PIA by 21z Saturday, that would be more than enough juice if something were to get going. And that nice theta-e air will continue northward into the evening. Link to comment Share on other sites More sharing options...
Stebo Posted October 12, 2012 Share Posted October 12, 2012 I agree with the lack of sun deal too. Looks to be quite a bit of rain moving in early with the warm front. I'm expecting a line of storms and not so much of a derecho! Clouds seem to like to linger around lately! Yeah up that far north I am not expecting much. Link to comment Share on other sites More sharing options...
tornadotony Posted October 12, 2012 Share Posted October 12, 2012 not so certainly...threat is going to decrease rapidly east of RFD Doubtful if a major serial derecho does get going. Link to comment Share on other sites More sharing options...
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