Day 1 Outlook - Wind (Today and Tonight)

Day 1 Outlook - Hail (Today and Tonight)

Day 1 Outlook - Tornado (Today and Tonight)

Day 2 Outlook (Saturday and Saturday Night)

Day 3 Outlook (Sunday and Sunday Night)
Now let’s take a look at the specific details of why this threat exists starting with today. Below are images from today’s 12Z NAM model run showing what the scenario may look like come this evening.

Precipitation

Dewpoint Temperatures and Surface Winds

850 mb (Low-Level Jet) Winds

250 mb (Jet Stream) Winds

500 mb Relative Vorticity

CAPE

EHI
Today and tonight thunderstorms are expected to break out in a fairly unstable environment across mainly Nebraska, South Dakota, North Dakota, and Minnesota. Dewpoint temperatures will be generally greater than 55 but as high as the low 70s in some areas which will really aid in creating a moist and unstable environment. 850 mb winds will generally be pretty weak but the storms will get some help from faster winds in the jet stream reaching up to 90 knots in some spots. The trough associated with the surface cold front will still be positively tilted and positive vorticity advection will be somewhat on the low end. Taking a look at CAPE values, some areas may see values reaching above and perhaps beyond 4000 J/kg but most areas will remain between 1000 and 3000 J/kg. The last image shows us that EHI values may become pretty high with values above 6 in some areas. If this turns out to be the case we may see a small tornado threat this afternoon and evening. In fact, today may pose the best chance for tornadoes as this trough pushes across the northern portions of the country. Overall, most storms will pose a damaging wind and perhaps some large hail threat. Today will likely pose the least risk of severe weather this weekend. That being said though, there will definitely still be severe weather today and tonight across the Northen Plains, as depicted by the SPC’s outlook percentages.
Below are images from today’s 12Z NAM model depicting what conditions could be like come Saturday evening.

Precipitation

Dewpoint Temperatures and Surface Winds

850 mb (Low-Level Jet) Winds

250 mb (Jet Stream) Winds

500 mb Relative Vorticity

CAPE

EHI
Saturday I expect the severe weather to start firing up even more. The reasons behind this can be seen in the graphics above. First off, dewpoint temperatures will top out generally higher than the day before with values at and above 65 and perhaps as high as the upper 70s. Surface winds will be about the same magnitude out of the south but winds at the low-level jet level will be stronger with some areas potentially seeing these winds hit 40 knots. Winds in the jet stream will also be stronger, peaking above 100 knots across northwest Wisconsin on Saturday evening. The jet stream will also be aligned in a way now that the right rear quadrant should provide some extra lift for thunderstorms to form and become stronger. The trough will also slowly start becoming more neutral in nature and positive vorticity advection will become stronger, especially across the more northern portion of the nation. We also see that CAPE values will be generally the same as the day before with some areas topping out at and above 4000 J/kg. The last measure, EHI, will once again present some fairly high values mainly across Illinois and Indiana so we may see a slight tornado threat across this area as well as somewhat but to a lesser extent to the north of these regions. Once again, the main threat on Saturday and Saturday night will be damaging winds and some large hail.
Below are images from today’s 12Z NAM model depicting what conditions could be like come Sunday evening.

Precipitation

Dewpoint Temperatures and Surface Winds

850 mb (Low-Level Jet) Winds

250 mb (Jet Stream) Winds

500 mb Relative Vorticity

CAPE

EHI
Sunday and Sunday night will likely present the largest threat for severe weather out of the three days. Once again we will see high dewpoint temperatures from the mid 60s to as high as the mid 70s with nice southerly surface winds, helping to increase the moisture content of the air even more. Winds at 850 mb will be the strongest out of any of the three days with some areas just north of New York in Canada, seeing these winds peak at above 60 knots. The jet stream winds will once again be strong, topping out at above 100 knots, and placing that right rear quadrant right across a portion of the threat region. Our trough by now will likely have tilted negative which will help enhance that threat of severe weather as it makes this tilt towards negative on Sunday. 500 mb positive vorticity advection will likely remain fairly strong, especially across the northern portions of the threat area. CAPE values may be lower on Sunday but it is the current thought that the strengthening of upper air processes will outweigh this. Still, CAPE values will generally be above 1000 J/kg which will be enough instability for these storms to maintain themselves. EHI values will generally remain below 2 with some pockets being a little higher so the tornado threat should be pretty low. However, this does not mean that an isolated tornado risk cannot be ruled out. Once again though, the main threats will be damaging winds and some large hail.
This weekend will surely lead to multiple severe weather reports, including some large hail, perhaps a couple tornadoes, and what will likely be some widespread damaging wind reports. Please remain aware this weekend across the northern portions of the Plains, Midwest and Northeast.