ChaserTV

The severe weather threat will be a bit less panoptic today, as Canadian high pressure dominates parts of the middle CONUS following a few days of active weather across the Upper Mississippi River Valley into the Great Lakes.  As you can see above the SPC has several areas outlined for a slight risk for severe weather, though the greatest risk that exists over the most optimal chasing terrain will be found across the Northern Plains as a shortwave currently centered over the Rockies continues to progress eastward today.

Ongoing convection across parts of the Dakotas should diminish through early afternoon, as ample instability germinates across parts of the Dakotas into far SE MT.  As the shortwave approaches, adequate SBCAPE, moisture and favorable 0-6 km shear profiles will enhance the threat for supercells, with large hail and damaging winds being the primary severe weather threats today.  By 00z the SPC SREF progs downdraft CAPE AOA 1000 J/KG across portions of NW SD/W ND and far E/SE MT, with LI values <-4 and mean 700-500 MB lapse rates >= 7.0 C, while EBS values should range on the order of 30-40 kts across the same region.

However, forecast soundings do indicate some favorable 0-1 km directional shear, so a few tornadoes may also be possible (12z BIS radiosonde is below for environmental reference).  Current thinking is that a few discrete cells may erupt by 21z over parts of the western Dakotas and possibly far ESE MT, but the activity should organize into an MCS and progress ESE across the Northern Plains overnight.

JLR

The main severe weather threat today exists across the parts of the central and eastern Corn Belt region and into the southern Great Lakes as a shortwave continues to move eastward with an ancillary cold front progressing southeastward across the risk area.  Convergence along the front as it progresses southward, combined with ample instability AOA 2000 J/KG across the region (spasmodic values > 3,000 J/KG are possible), should provide the synergist for convective development this afternoon.  Weaker forcing and rather mediocre 0-3km shear profiles of 20-30 kts should assuage a widerspead severe weather outbreak of any substantial, high impact over a broad area.

Latest 12z radiosonde data indicates largely unidirectional shear profiles exist across the region, with marginal mid and low level lapse rates <6 C/km and SFC-6 km shear profiles at 25-40 kts.  However, PW values at numerous sites currently sit at 1.5-2.0 .in, adumbrating a threat for heavy rainfall with some of these storms, though damaging winds remain the primary threat, with downdraft CAPE values progged (per SREF) to be AOA 500-1000 J/KG across much of the region.  Current thinking is that convection will initiate early this afternoon as the frontal boundary progresses southeastward and interacts with the unstable airmass ahead of the front.  While damaging winds will remain the primary hazard, a brief tornado or two is also possible.

Be sure to check back with ChaserTV to see if any live streams are available.  Remember that you can also follow us on Facebook and Twitter for the latest breaking severe weather updates.

JLR

The Northern Plains will once again become active today, with a more appreciable threat for severe weather across a broader area from the eastern Dakotas into the northwestern Great Lakes region.  A shortwave centered over the Prairie Provinces of west central Canada will progress eastward towards the central Canadian Shield.  H25 flow of ~ 100 kts will exist coterminously with strong westerly H5 flow of ~ 60 kts as a vort max approaches southeastern MB late this afternoon.

A concomitant surface low will move into WC ON by early afternoon, with an ancillary cold front extending from near YHD to ABR by 18z.  SW H85 flow of 30-40 kts will continue to anneal throughout the afternoon, as strong WAA in advance of the CF engenders SBCAPE values on the order of 2000 – 3000 J/KG, with LI values progged to be < -6C across the region and SFC-500 mb shear values AOA 55 kts across a broad swath from NC MN to SW ON.   While 700 mb temps of 10C – 12C will be found across the region, CIN should erode in advance of the front in association with strong forcing.  This strong forcing coupled with adequate low level moisture, instability and low level WAA courtesty of a strengthening SW H85 flow will provide the impetus for the development of deep convection.

Ample speed shear, with a 20 kt increase between 850mb and 250 mb per KDLH forecast SKEW-T via RUC guidance (the 12z observed sounding at INL is posted below), and suitable directional shear engender the threat for rotating updrafts and perhaps some discrete activity early in the evolution of this event.  While tornado potential exists courtesy of these favorable shear profiles, there is also an attendant threat for damaging winds, with mean downdraft CAPE >=1000 J/KG present across much of the area per SREF, and large hail.  Ongoing, elevated convection relatively along and north of I-94 should begin to clear the area through 17z, allowing for atmospheric recovery in the wake of diurnal heating.  Current thinking is that convection will re-initiate by late afternoon ahead of the front, with discrete supercells likely early in the evolution of the event, before transitioning more to a linear mode and moving ESE across the region.  The impact of this morning’s convection as it pertains to remnant OFBs will have to be watched, as any such boundaries will likely enhance tornado potential later this afternoon, should the atmosphere be able to recover across the risk area.

As always, be sure to check back with ChaserTV to see if any live severe weather streams are available from this area.  Additionally, you can follow us on both Facebook and Twitter for the latest breaking severe weather news and updates of noteworthiness.

JLR

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