3/13/06 FCST: IN, MI, KY, OH, PA, TN

Dan Robinson

GFS is painting 60+ dewpoints and strong 850 jet over the upper Ohio valley region for Monday. Directional shear does not look incredibly impressive and surface winds will be SSW, but strong forcing ahead of the front and the possibility of localized areas of backed surface winds (depending on the track of the low) make this setup a possible chase day in eastern Kentucky and southern/central Ohio. Degree of clearing and destabilization is the big concern.
We may have a day were storms roll through in the AM, we get some clearing and a second round of storms initiate. Nice low LCL in all that humidity.

I have sometimes witnessed good potential in second round storms. Late summer chase last year Southern Michigan for example. Of course they are hard to forecast but something to keep in mind.

The first round might be linear and cloud cover may be a problem and the second may not come at all. So there are some negatives but plenty of positives for monday in and around Ohio.

Strange day.
Almost forgot about tomorrow with everything that's been going on today.

MI looks primed for some action between 10AM and 3PM ET. BUFKIT is very impressive with speed shear and wind fields with 70-80KNTS sneaking in around 700MB. BUFKIT also generates 1250J/KG of CAPE most of which is in the 1km to 3km area... Overall, I think it is quite likely that a squall line - in some form or another - will be present along the cold front.

As if that wasn't enough, BUFKIT also shows mixing layer heights reaching up towards 700MB with just after the cold front... BUFKIT shows +60KNTS at the top of the mixing layer for a solid 9 hours, with peak values of +70KNTS... If that were to verify, we'd be talking about a damaging non-convective wind event. So if the convective event doesn't get us, the post-frontal action will... But that will be another thread in the Weather Lab.
After looking at the NAM and GFS, I have concluded that activity will get started around 1pm with the peak CAPE, LI and a 3hr pressure drop of about 5 mb. At this point, the GFS indicates a SWEAT index of around 400 which is more than enough for tornadic activity. Helicity looks superb for this kind of activity (into the 200s) and 0-6km shear is very high. Combine this with the 105kt jet overhead and we have ourselves the reasoning behind the SPC's 10% Hatched tornado risk (what I like to call a "Michigan PDS" scenario).

I'll probably set out tomorrow morning for gas to get ready for activity, come back to the house and watch the radar while talking to folks about yesterday. I hope MI can really get a piece of this action before its back to Old Man Winter's icy grip.
I think that would be in the NOW section if you added some meteorological info...

Anyways I just have a hard time seeing Michigan recover today... Still in the middle-30's when models say (along with common sense ;> ) that we should be approaching 50 at this time. I do like the clearing across IL, but don't know if we'll see enough convergence along the front to regenerate when it hits the juiced up airmass.

Sad to see such a promising day (and overnight) go flat.
Temps have shot up from about 40F to 55F as of 7:00AM. I still don't like the junk all over MI/IN/IL though. RUC has us generating some CAPE today across MI with roughly 500-1000J/KG and excellent shear, but I too am questioning SFC convergence.
I'm going to have to agree with Dewey, this morning rain and failure to recover temperatures is probably going to wind up killing this event. CAPE is still projected to be decent, but with current events, I doubt the models are accurate.

I'm probably going to hold off on my pre-chase check list until this stuff gets going.
So far, while looking at the models, most of the Convective Inhibiton is in the western parts of TN, speaking for me. If the temperatures can be sustained later this evening at the high 70's and low 80's then convection will explode while going across the Cumberlands. Helicity looks the strongest along central TN and KY, which leads me to believe that's where the main area of severity will, be shortl ived perhaps. The 850mb winds right now are more favorable along the western KY and TN areas, and as the day proceeds the winds will slowlly tilt north. It looks like supercells will be a threat tornado wise, for parts of central MI and NE IN. Dewpoints are good across all of the south. As the system moves through TN, it is expected to weaken dramtically partially because of the more complex terrain, and also because CAPE will weaken in the eevening hours and the winds aloft will move north mroe or less. I am going to target Nashville, right now and then head north from there.