17 May 2011 AFD

Convection ongoing across Carolinas into Virginia this morning, and convection is expected to continue and intensify this afternoon given some clearing in warm sector and minimal cap. Nearly saturated environment, low-cape/moderate shear environment will result in strong and possibly severe storms. Although damaging wind gusts will be primary concern, low-lcl environment will keep threat of brief/weak tornadoes with initial development of convection primarily over eastern Virginia into eastern North Carolina where low-level cape/stretching potential will exist. Warm front extending sw-ne across northern portions of Virginia will need to be monitored as well with conentrated low-level shear. CI satellite detection possible early in the event before cirrus canopy becomes an issue. Hi-res models forecast banded convection near cold core and initiation of bands with CI detection may prove useful where higher impact areas will evolve. Already some more obvious clusters of CI detection using UAH product are highlighting areas in srn VA/nrn NC where new 12Z SPC 4km WRF is fcstg clusters of convection near short wave to develop early afternoon. CI products may continue to be useful to help identify where these potential severe clusters/bands may develop within the wider scattered shallower convection expected to develop. Value of 3dvar may prove useful as well where low-level vort and updraft fields can help warning forecasters concentrate on regions where low-level cape/shear are maximized. Good opportunity to experiment with utility of many 3DVAR products with shallower convection.  Same with MRMS products. In addition, some  of the nearcast differential theta-e/PW products indicating severe potential through mid to late afternoon over central VA shifting NW into northwestern VA…consistent with local WRFs and SPC WRF ideas.

High plains convection will be possible near developing dryline across eastern Colorado/western Kansas. CI detection will be useful late this afternoon and early this evening as it may take a while for CI once cu develops. Although shear will be increasing through the day, moisture availability will be a concern for more than LP type supercells, especially as storm move off of higher terrain.

Warning ops – our feeling is that initial warning ops, perhaps through at least 21z, should be centered on mid-atlantic region with the option of shifting west to Colorado eastern plains and western Kansas after 21z for possible initiation of isolated/scattered supercells. Greatest value of satellite CI detection and 3dvar fields may be most useful over eastern ops area, although CI detection along with OUN WRF output could be utilized out west. Expecting mainly a hail threat with the LP-type storms in the Plains, and evaluation of some of the MRMS products would be helpful as well.

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