Hoosier Posted November 3, 2015 Share Posted November 3, 2015 At least it's an interesting system to try and forecast if not frustrating. We have terrible lapse rates keeping instability down, but strong dynamics including 30+ kts of 1km shear. It looks like there could be strong synoptic scale lift owing to the vorticity max sweeping through, but also mesoscale lifting mechanisms owing to some mid level frontrogenesis to drive us all insane as well. At least we'll all have the opportunity to hone our skills! I thought the SPC outlook was good for starters, though I'd say that the isolated/spinup tornado threat could exist farther north toward the Lakes especially if the somewhat more unstable NAM is right. Still gotta iron out some synoptic scale details though, like how fast the surface low bombs, as that will affect low level wind fields. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted November 3, 2015 Author Share Posted November 3, 2015 I thought the SPC outlook was good for starters, though I'd say that the isolated/spinup tornado threat could exist farther north toward the Lakes especially if the somewhat more unstable NAM is right. Still gotta iron out some synoptic scale details though, like how fast the surface low bombs, as that will affect low level wind fields. Would you agree with the SPC doing an upgrade to Slight tomorrow, across most of our northern forum area? Link to comment Share on other sites More sharing options...
Hoosier Posted November 3, 2015 Share Posted November 3, 2015 Would you agree with the SPC doing an upgrade to Slight tomorrow, across most of our northern forum area? I tend to think it would wait until Thursday to get an upgrade that far north. I could see them expanding the current day 3 slight risk northward into some of the area on the day 2 outlook later tonight. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted November 3, 2015 Author Share Posted November 3, 2015 IWX's new AFD mentions the increased cape on the NAM... so they added a thunder mention to the grids No Severe Mention. Link to comment Share on other sites More sharing options...
wxdudemike Posted November 3, 2015 Share Posted November 3, 2015 If we can manage 65kt plus at 850mb ahead of the cold front, I'm not as worried about frontal timing. The 6z GFS held steady with the frontal timing but ramped up wind fields some. The NAM does have a few hundred J/KG of CAPE getting into OH FWIW. I'd probably lean on the NAM for instability over the GFS in situations like this. My main concern is getting the low to really strength before the cold front pushes through, or else the wind fields won't suffice for a severe QLCS.While the GFS does tend to underestimate CAPE, the NAM goes CAPE happy especially in these cool season situations. So if lean towards it but adjust downward. Sent from my XT1060 using Tapatalk Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted November 3, 2015 Author Share Posted November 3, 2015 Now that I thought of it, it's a better idea for the CWA's not to mention severe yet, too conditional. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted November 3, 2015 Author Share Posted November 3, 2015 18Z GFS is more windy, more amped. Link to comment Share on other sites More sharing options...
OHweather Posted November 3, 2015 Share Posted November 3, 2015 Now that I thought of it, it's a better idea for the CWA's not to mention severe yet, too conditional.It needs to be mentioned in AFDs at least, maybe it's a bit too soon to mention in the HWO, although it's close to time for that too. Link to comment Share on other sites More sharing options...
Stebo Posted November 3, 2015 Share Posted November 3, 2015 It needs to be mentioned in AFDs at least, maybe it's a bit too soon to mention in the HWO, although it's close to time for that too. I agree, even if it is conditional, the wind fields are such that any instability or strong showers would bring down significant winds. Link to comment Share on other sites More sharing options...
Hoosier Posted November 3, 2015 Share Posted November 3, 2015 Looks like the record November dewpoint for Chicago is 65, back on November 2, 1971. A dewpoint of 63 has happened several times, most recently on 11/17/2013. Could approach those levels Thursday night/Friday morning. Edit: scratch that. Found a 66 on November 17, 1958 (MDW) Link to comment Share on other sites More sharing options...
Hoosier Posted November 4, 2015 Share Posted November 4, 2015 Cute pencil thin line Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted November 4, 2015 Author Share Posted November 4, 2015 0Z update: GFS supports the pencil line idea this run. Winds: GFS has widespread wind advisory level winds, with medium sized pockets of High Wind Warning criteria Link to comment Share on other sites More sharing options...
Hoosier Posted November 4, 2015 Share Posted November 4, 2015 Tried to post a gif earlier and it came out weird, but anyway, like the 100-105 kt mid level speed max accompanying the cold front. Link to comment Share on other sites More sharing options...
Hoosier Posted November 4, 2015 Share Posted November 4, 2015 Slight risk expanded into the southwestern fringes of the region. DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1253 AM CST WED NOV 04 2015 VALID 051200Z - 061200Z ...THERE IS A SLGT RISK OF SVR TSTMS SRN GREAT PLAINS TO LOWER OH VALLEY... ...THERE IS A MRGL RISK OF SVR TSTMS LOWER MO/UPPER MS VALLEY AND MIDWEST... ..SUMMARY SCATTERED SEVERE STORMS ARE POSSIBLE ACROSS THE SOUTHERN GREAT PLAINS ON THURSDAY INTO THE LOWER OHIO VALLEY EARLY FRIDAY. ISOLATED SEVERE STORMS...MAINLY IN THE FORM OF DAMAGING WIND...ARE POSSIBLE OVER THE LOWER MISSOURI VALLEY TO THE UPPER MISSISSIPPI VALLEY AND MIDWEST. ..SYNOPSIS POSITIVE-TILT SHORTWAVE TROUGH FROM THE CNTRL HIGH PLAINS TO AZ/NM AT 12Z/THU SHOULD TAKE AN INCREASINGLY NEUTRAL TILT AS IT RAPIDLY EJECTS TOWARDS THE UPPER GREAT LAKES. A SURFACE CYCLONE WILL DEEPEN ACROSS THE UPPER MIDWEST AS IT TRACKS INTO NRN ONTARIO. A COLD FRONT SHOULD ACCELERATE E AND EXTEND FROM THE MIDWEST TO SE TX BY 12Z/FRI. ..SRN GREAT PLAINS CONVECTION SHOULD BE ONGOING ACROSS PARTS OF W TX AT 12Z/THU AS THE COLD FRONT IMPINGES ON THE PERIPHERY OF THE MARITIME TROPICAL AIR MASS THAT WILL BE PREVALENT ACROSS S/E TX. ADDITIONAL PRE-FRONTAL CONVECTION SHOULD FORM THROUGH THE MORNING WITHIN THE WARM CONVEYOR AS THE LEADING EDGE OF MID-LEVEL HEIGHT FALLS OVERSPREAD THE REGION. THE NET RESULT WILL LIKELY BE ABUNDANT MORNING/EARLY AFTERNOON ACTIVITY THAT SHOULD LIMIT THE AMPLITUDE AND SPATIAL EXTENT OF DIABATIC DESTABILIZATION. NEVERTHELESS...DEEP-LAYER SHEAR WILL BE FAVORABLE FOR ORGANIZED LINE SEGMENTS AND EMBEDDED SUPERCELL STRUCTURES CAPABLE OF ALL HAZARDS...ALTHOUGH INCREASINGLY VEERED LOW-LEVEL WINDS WITH SRN EXTENT SHOULD TEMPER THE LATTER RISK IN TIME. THE TORNADO THREAT SHOULD BE MOST PROMINENT ACROSS CNTRL/NERN TX...WITH HAIL MOST LIKELY CONFINED TO THE WRN/SRN PORTIONS OF THE SLIGHT RISK. ..MID-SOUTH/LOWER OH VALLEY ON THE NRN EXTENT OF THE RICHER WRN GULF AIR MASS AND SRN PERIPHERY OF STRENGTHENING LOW-LEVEL SWLYS...A NOCTURNAL TORNADO AND DAMAGING WIND RISK MAY DEVELOP. INSTABILITY WILL LIKELY BE LIMITED WITH WEAK TROPOSPHERIC LAPSE RATES BUT PRESENCE OF 65-68 DEG F SURFACE DEW POINTS COULD SUPPORT MEAGER SURFACE-BASED INSTABILITY IN THE PRESENCE OF AN ENLARGED LOW-LEVEL HODOGRAPH. ..LOWER MO/UPPER MS VALLEY LOW-LEVEL MOISTURE WILL BE MODEST AHEAD OF THE COLD FRONT AND DEEPENING SURFACE CYCLONE...LARGELY CHARACTERIZED BY MIDDLE 50S SURFACE DEW POINTS N TO LOWER 60S S. STILL...A CONFINED CORRIDOR OF WEAK DIURNALLY ENHANCED DESTABILIZATION MAY DEVELOP FROM ERN MN TO ERN KS. WHILE VERY STRONG DEEP-LAYER SHEAR WILL BE PRESENT...THE STRONGEST FORCING FOR ASCENT SHOULD BE ACROSS THE UPPER MIDWEST. HERE A THIN QLCS MAY FORM DURING THE AFTERNOON WITH A RISK FOR ISOLATED DAMAGING WINDS AND PERHAPS MARGINALLY SEVERE HAIL. WEAK LOW-LEVEL LAPSE RATES/COOL BOUNDARY-LAYER TEMPERATURES MAY DETER A MORE SUBSTANTIAL THREAT. ..MIDWEST FRONTALLY FORCED DIURNAL CONVECTION SHOULD EVENTUALLY MERGE WITH PRE-FRONTAL WARM CONVEYOR ACTIVITY THU NIGHT AS THE COLD FRONT ACCELERATES. SURFACE-BASED INSTABILITY WILL LIKELY BE MINIMAL N OF THE LOWER OH VALLEY WITH MOIST-ADIABATIC THERMODYNAMIC PROFILES AND NEUTRAL LAPSE RATES NEAR THE SURFACE. STRENGTHENING LOW-LEVEL SWLYS BENEATH A 100-KT 500-MB SPEED MAX COULD SUPPORT A FAST-MOVING SQUALL LINE /THAT MAY HAVE LITTLE LIGHTNING/ WITH SOME RISK FOR DAMAGING WINDS. HOW MUCH MOMENTUM TRANSFER IS REALIZED AT THE SURFACE IS QUITE UNCERTAIN GIVEN THE DEARTH OF INSTABILITY. ..GRAMS.. 11/04/2015 Link to comment Share on other sites More sharing options...
WxDanny Posted November 4, 2015 Share Posted November 4, 2015 I am not real impressed by this. I was tempted just to stay down in OKC and chase, but even that looks marginal to me. Poor lapses rates will be sure to limit the overall thunder potential up here, but I can't rule out some wind right along the front. Given the warm and moist airmass there should be at least SOME favorable thermodynamics to work with. My eyes are focused on next week. Sent from my SM-G925V using Tapatalk Link to comment Share on other sites More sharing options...
Indystorm Posted November 4, 2015 Share Posted November 4, 2015 Hopefully this first system will prime the pump for next week. Link to comment Share on other sites More sharing options...
Hoosier Posted November 4, 2015 Share Posted November 4, 2015 12z NAM has an area of SBCAPE of 500 J/kg in N IL at 9z Friday. GFS is less of course. Here is a forecast sounding from west of ORD. Flow is unidirectional by this time with very impressive speed shear but this isn't a bad look considering the dynamics/strong shear. Link to comment Share on other sites More sharing options...
chase_stormz Posted November 4, 2015 Share Posted November 4, 2015 12z NAM has an area of SBCAPE of 500 J/kg in N IL at 9z Friday. GFS is less of course. Here is a forecast sounding from west of ORD. Flow is unidirectional by this time with very impressive speed shear but this isn't a bad look considering the dynamics/strong shear. 12_NAM_045_42.06,-88.32_skewt_ML.gif That's not a bad look at all. And dew points into the low 60s by this time as well. Link to comment Share on other sites More sharing options...
HillsdaleMIWeather Posted November 4, 2015 Author Share Posted November 4, 2015 New Day 2 stresses one thing for Thursday night/Friday morning. Wind damage will easily occur without any accompanying Lightning. Link to comment Share on other sites More sharing options...
Hoosier Posted November 4, 2015 Share Posted November 4, 2015 I'm just going to turn this thread into a catch-all to include other aspects of this storm. Link to comment Share on other sites More sharing options...
andyhb Posted November 4, 2015 Share Posted November 4, 2015 Hopefully this first system will prime the pump for next week. Moisture trajectories with that one aren't looking so good either. Link to comment Share on other sites More sharing options...
OHweather Posted November 4, 2015 Share Posted November 4, 2015 Moisture trajectories with that one aren't looking so good either.I'd have to imagine getting dew points in the mid-60s into the Ohio Valley in November is about as "good" as you can realistically expect with just a few exceptions. This low is going to deepen too far north to get a higher end event with this system...although I can still see the SPC expanding the slight risk farther north tomorrow at some point. Link to comment Share on other sites More sharing options...
bdgwx Posted November 4, 2015 Share Posted November 4, 2015 Yeah, so the 12Z NAM does support a secondary risk area in IA and northern MO and IL. It is showing frontogenesis forcing a pencil thin line through IA in front of a negatively tilting shortwave. The frontogenesis eases off as the boundary approaches IL, but at this point the low level nocturnal jet is ramping up and the mid level speed max is racing past MO so that might help reinforce convective activity. It looks like there's enough synoptic lift in the presence of sufficient moisture out ahead of the boundary to produce scattered showers and at least cloudy conditions most of the day. That'll definitely keep instability down. The GFS is showing some similar stuff big picture-wise, but with differences in the timing and location of the forcing mechanisms and the extent of the instability. Link to comment Share on other sites More sharing options...
Hoosier Posted November 4, 2015 Share Posted November 4, 2015 Moisture trajectories with that one aren't looking so good either. Yeah...at this point, it looks worse than this impending system, and we are still struggling to generate much instability with the poor lapse rates. Link to comment Share on other sites More sharing options...
andyhb Posted November 4, 2015 Share Posted November 4, 2015 Yeah...at this point, it looks worse than this impending system, and we are still struggling to generate much instability with the poor lapse rates. 2015 just sucks. Edit: 12z Euro came in slower (more time for moisture return) and less pos tilt on ejection. Link to comment Share on other sites More sharing options...
Hoosier Posted November 4, 2015 Share Posted November 4, 2015 2015 just sucks. We need a shakeup with ENSO...this hanging around either side of neutral for 3 years hasn't done much good. I'd take my chances with a Nino plummet next year... Link to comment Share on other sites More sharing options...
csnavywx Posted November 4, 2015 Share Posted November 4, 2015 Too much shear vs instability. That BRN of 2.1 on Hoosier's forecast sounding is a red flag. Updrafts are going to get sheared apart pretty quickly. It will lead to short updraft lifetimes, so almost everything will be associated directly with the frontal forcing. Link to comment Share on other sites More sharing options...
Hoosier Posted November 4, 2015 Share Posted November 4, 2015 18z NAM has a bit more instability than the 12z run.... Link to comment Share on other sites More sharing options...
IllinoisWedges Posted November 4, 2015 Share Posted November 4, 2015 WRF models seem to agree with the line as well. Good to see some instability as well! Link to comment Share on other sites More sharing options...
Hoosier Posted November 5, 2015 Share Posted November 5, 2015 NAM forecast sounding a little northwest of Madison at 6z Friday. A little bit of a veer-back profile. Link to comment Share on other sites More sharing options...
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