Potentially Severe Convection Crossing the Appalachian Mountains Tonight?

Impressive squall line moving across the Tennessee and Ohio Valleys this afternoon producing lots of severe weather reports. High resolution WRF simulations (shown below) indicate this system may the cross the Appalachian Mountains around midnight. Timing of this system will be problematic and simulations are already slower then radar observations indicate. In very general terms, the NMM appears to be slightly faster and maintains the system more, at least into the very early morning hourse. Local experience has shown that the reflectivity products from the NMM runs are often times stronger then those forecast by the ARW. It will be interesting to see how well this system maintains intself overnight.

This event relates to a recent paper in Weather and Forecasting from a recent CSTAR project.
Forecasting the Maintenance of Mesoscale Convective Systems Crossing the Appalachian Mountains
Casey E. Letkewicz, Matthew D. Parker

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One Response to Potentially Severe Convection Crossing the Appalachian Mountains Tonight?

  1. Steve Keighton says:

    Good comments Jonathan. Some prelim work we did with SPC is available in an extended manuscript at:

    http://www.erh.noaa.gov/rnk/Research/MCS_Appalachians_Manuscript_final.pdf

    While the climatology of severe MCS’s crossing strongly favors daytime into early evening, this is largely because of the warm season dominance and role of instability. The few that crossed severe overnight tended to either be associated with anomalously high instability, or these very strong dynamical systems in the Fall with a narrow line of convection (perhaps not even thunder but just enough updraft to support accelerating downdrafts with some dry air and obviously strong momentum in mid levels). While some high res models are trying to break the line apart when it reaches the western slopes, including the HRRR, other are not (the NMM versions for example). I tend to think we’ll see some winds make it at least partially through, but we’ll see if they get east of the Blue Ridge with the initial line overnight, or it takes redevelopment tomorrow.

    By the way, our bow echo yesterday morning in far SW VA was really a strong shear NO CAPE event (no thunder by the time it reached our border, but nice bow echo and plenty of wind damage).

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