this is like trying to forecast where a heavy snow band sets up!!

LOT keeps extending the flood watch longer and longer and is now in effect until tomorrow afternoon which is a good idea. places in northern IL have got anywhere from 1.5 to 5 inches of rain so far with more on the way. keokuk county in southeast has recieved 11.75 inches and that report came in at 11am this morning so they should be well over a foot by now and its still coming down at a quick pace out there and should continue well into the overnight period.

synoptically we have an area of low pressure in northern MO that is barely moving with a sfc frontal boundary across central IL and a cold front extending down into OK. it has been raining all day on the north side of the frontal boundary in eastern IA and northwest IL with flood warnings out and rivers flooding very quicking and creating a dangerous situation. the sun has been out south of the front in central and southern IL and well as parts of MO closer to the sfc low. that has created some instability with SBCAPE at time approaching 2000 j/kg. cells have fired near the low and in central IL and have moved north enhancing the deformation axis band associated with old MCV/vort max.

there was even an MD out for areas near the sfc low/frontal boundary for isolated/brief tornadoes where low level shear was enhanced and instability could create a quick but strong rotating updraft, but I have not seen any good low level rotation or warnings with any of those cells. some have taken the low-topped supercell look for a scan or two but nothing special. there is still a small chance for a brief spin up with 0-1 helicity near 150 just northeast of the sfc low but should die down with the sun. best threat for any real thunderstorms looks to be from northeast MO to central IL area where cells are still firing in the better instability and there is currently a nice storm near 47,000ft just went of quincy getting ready to move into IL.

the RUC doesnt really want to move the 850 low much at all and keeps it stationary through 9z and therefore the best 850 winds/LLJ stay in eastern IA and along the mississippi. currently the defo axis is drifting south now as you can see on radar. I would say the axis for heavy rain to me looks to be from keokuk to wapello the east along and south of 88 and back around down to 80. you know how cells going up around the lincoln area where the better instability is and with better dynamics moving into the area as we get into later tonight we should see continuation of rain intensity and expanding in coverage. if the defo band can stall out for awhile somewhere it could drop alot of rain in a given area. my guess for highest totals would be where the defo band, strongest LLJ winds and dynamics intersect. so if I had to really nail it down I would say from keokuk, IA to princeton, IL for some serious heavy rain totals through tomorrow morning.

I feel like this is trying to forecast where the heavy snow band sets up cause usually when you hear deformation axis and good dynamic forcing moving into the area and even looking at the radar presentation with the true thunderstorms curling up into the colder air you think so just looking at it but its not.

http://radar.weather.gov/Conus/full_loop.php

any storm has the potential to produce heavy rain in a short period of time with dew points in the upper 60's and 70's pooling right along the frontal boundary and PWATS between 1.6 and 1.9. we could be looking at rainfall rates of 1-2 inches per hour and maybe 3 later on for a time.

also, tropical storm danny looks like crap and is completely getting sheared apart right now. really dont see it becoming a hurricane but still an outside chance once it gets near the carolinas. will depend what the through does to it and how far it pushes it off the coast. just looks like a heavy rain threat and big waves/rip current threat all along the east coast.

after all this rain moves east tomorrow evening and we begin to dry out, high pressure looks to build in over the weekend with unseasonably cold air with temperatures dipping into the 40's possibly saturday and sunday night.


Matt