Another round of strong to severe storms appears to be in the making for many of these same areas as we head into this weekend. A cold front extending from a Low centered just north of Minnesota will drape back across the Plains on Saturday morning, shown below. The advancement of this front will result in the triggering for strong to severe storms as it enters unstable and moist air ahead of this system.
The image above shows where this front will be on about Sunday morning and the below image then shows about where it will be come Monday morning.
The 12Z NAM model shows what the precipitation may look like come Friday evening as this front begins its push across the northern Plains.
CAPE values in advance of the front will be above 1000 J/kg with pockets above 3000 J/kg.
EHI values will also be quite nice with many areas in Minnesota recording values at or above 3. This is the result of good low level turning of the winds with height which means if supercells can form, there may be some tornado threat on Friday.
For these reasons, the SPC has highlighted a region across the eastern Dakotas and most of Minnesota in their Day 3 Outlook as being at a slight risk for severe storms. The main threat at this time appears to be some large hail but mainly damaging wind gusts. If supercells can get going out in front of the cold front however, we may see a few tornadoes.
On Saturday, the front will continue pushing east and even though the SPC has not highlighted an area for severe weather risk at this time, they do mention that a risk will likely be present across portion of the Midwest and Great Lakes. Below the 12Z NAM model shows what the precipitation may look like come Saturday evening with storms stretching from Michigan into Illinois and back across the Plains.
CAPE values and EHI values will once again be fairly high, with CAPE values looking much like Friday’s CAPE values but EHI values being somewhat less spread out but potentially packing areas of higher values above 6. This once again would result in a mainly damaging wind threat but a few tornadoes may not be out of the question in the areas with stronger EHI values.
Check out what hodographs may look like across central Indiana come Saturday evening. If this ends up being the case, a few tornadoes would definitely not be out of the question.
The risk of severe weather in general will also probably be worse on Saturday than it was on Friday due to the strengthening of winds aloft and better moisture across these areas. Below are images from the 12Z NAM model showing the winds at 250 mb, 850 mb, and dewpoints with surface winds. A 100 knot plus jet streak will likely be centered across the Wisconsin and Minnesota border with an 850 mb low-level jet with winds approaching 50 knots from Illinois into Michigan.
Dewpoints will also be high from the mid 60s into the low 70s across these areas. Surface winds will be mainly out of the south in front of the cold front which will aid in bringing this moist air in and help the inflow into these thunderstorms as winds could be as strong as 20 knots at the surface Saturday evening.
Storms will continue throughout Saturday night before we get to what will likely be the main event from this cold front on Sunday across the Northeast. While this event is still five days out, the SPC has highlighted an area on their Day 4 to 8 Outlook meaning that they expect a 30% chance or greater of severe weather within 25 miles of a point on Sunday and Sunday night.
The 12Z GFS model depicts this event probably a bit differently than the NAM will depict it come this time tomorrow when the NAM begins to send predictions for an event this far out. This is based on the fact that the GFS depicts the Friday and Saturday events slightly different, mainly with not as much moisture being pushed north as the NAM thinks it will. Despite this, here is what the CAPE may look like come Sunday evening and below that are images depicting 250 mb winds, 850 mb winds, and surface winds and dewpoints.
CAPE values will be above 1000 J/kg and a 100 knot jet streak will be in place north of the threat area with the right rear quadrant being placed over the threat area. Additionally, an 850 mb low-level jet will become quite strong with areas of 50 knot plus wind and widespread dewpoints at and above 70. All of these conditions along with what should be some good positive vorticity advection, will result in what should be a pretty substantial severe weather threat come Sunday. The main threat will likely be damaging winds.
This cold front will definitely be something we should all keep an eye on this weekend as it sparks strong and severe thunderstorms. This is still an evolving situation so the exact locations which may come under a threat due to these storms is still somewhat unknown. Below is my threat map depicting where I think the threats may be come Friday (shaded in brown), Saturday (shaded in yellow), and Sunday (shaded in red).