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Posted At: March 31, 2008 @ 9:14 AM

Posted By: Reed Timmer

A tornado watch has been issued for much of eastern OK, southeast KS, southwest MO, and northwest AR from 8:45 am until 4:00 pm this afternoon as the cold front/dryline combo begins to move eastward.  Storms are already firing along the front from northern OK northeastward, and these storms will have the chance of producing tornadoes, especially after noon.  0-1 km helicities are currently in the 300-400 m2/s2 range with CAPEs of 2000 J/kg and no CIN in Oklahoma.  Stay tuned for updates as this severe weather outbreak unfolds.

Posted At: March 31, 2008 @ 1:45 AM

Posted By: Reed Timmer

An outbreak of severe weather is likely across parts of the Central U.S. today (Monday), especially over eastern OK, northeastern TX, western AR, and Southwest MO, beginning early afternoon as a massive trough ejects from the Rocky Mountain region.  While widespread large hail and severe straight-line winds will be the main threats today, there will be a window during early- to mid-afternoon for tornadic supercells across Eastern OK as a dryline/cold front move east.  A potential limiting factor for tornadoes is the rapid eastward movement and weakening of the low-level jet with time as the afternoon progresses, due to the initial shortwave forecast to eject towards the Great Lakes during the day.  However, 35+ knot 850 flow is forecast to prevail in the storm environment just east of the dryline over Eastern OK for at least a few hours until 21z, when the best low-level flow may propagate east of the storms.  The SPC has issued a moderate risk for this area (see below):


As seen below in the GFS forecast 850 mb flow for 18z tomorrow, a strong 40+ knot low-level jet will still exist over the warm sector east of the dryline/cold front in Eastern OK into southeast KS, MO, and AR (where tornadoes will also be possible with any discrete storms).  However, by 00z the western edge of the LLJ is forecast to be near the AR/OK Border, slightly east of the storms.  Our plan is to target a window between 18 and 22z in central/eastern OK, where and when tornadoes will be most likely.

The GFS forecast 6-hr precip. for 00z tomorrow shows a very large area of convection stretching from IL south to TX.  The storms in MO northward will likely be more linear in nature, with embedded supercells and bow echoes.  Given very strong low-level flow, tornadoes will be possible with any of these storms as well.  Further south across eastern OK, where the WNW-ly upper flow is more perpendicular to the boundary, supercells will be the primary storm mode.  If the LLJ lingers further west through the evening, then the tornado threat will be enhanced further.  Stay tuned for updates!