As the heat spreads out across the Southern United States with 100s baking the southern and central plains and mid-90s eventually reaching the Southeast including Atlanta and Charlotte, so a lot of upper level energy will ride the northern periphery of this hot dome and will enhance storminess and the flash flood risk over the Northern Plains today and into the Midwest tonight and tomorrow. Eventually the threat area will extend down into the Mid-Atlantic region.

Through today parcels of energy will ride within a strong upper jet stream, and these parcels will enhance the upward motion beneath, allowing thunderstorms to form from the Rockies and as downright hot, humid air gets forced north ahead of the disturbance, so the atmosphere will be primed late this afternoon from the Dakotas across Iowa and towards Illinois. The strong UPPER level westerly winds overlapping southerly winds will create the necessary rotation for developing storms to transition into supercells. These cells will run ESE and may bow into derechos into this evening as the sun eventually sets and they travel potentially hundreds of miles from North and or South Dakota all the way towards Illinois, possibly threatening the Chicago area overnight.

Here’s the threat area today according to AccuWeather.com.

The once-upper low off California is enhancing high elevation lightning over parts of the Rockies today but as this feature speeds along a powerful 150+mph jet stream, the stage will be set later tomorrow afternoon for a heightened risk of severe weather with possible derechos, hail, damaging winds and tornado risk over Illinois extending into Indiana and Ohio along with flash flooding with 1-3 inch per hour rains.

Here’s the SPC convective outlook with a MODERATE risk extending from east-central Illinois through Indiana into western Ohio tomorrow.

Here’s the risk area for Thursday, notice it has an area outlined over a large area of the east. I wouldn’t be surprised if there’s a moderate risk put out for the Mid-Atlantic.

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The risk eventually extends all the way to the Washington DC-Baltimore area by Thursday.

However the real threat zone is back west with the atmosphere highly conducive for MCS (Mesoscale Convective System) development which is a large thunderstorm complex which typically blows up after dark and can run throughout the night producing damaging winds, hail, flooding rains and derechos which are bows of thunderstorms which can stretch hundreds of miles and are fast moving. Can be very destructive with their straight line winds.

Here is the current temperatures across the nation. Denver has reached 100 this afternoon which is the hottest so early, on record.

No wonder there is a heightened risk of an ‘active’ ring of fire pattern.

Here’s projected highs tomorrow.

Here’s a look at the ECMWF 500mb chart for the next few days.

Note the trough over the East this afternoon and the energy driving SE this afternoon. This will enhance shower and thunderstorm this afternoon and evening over Ohio, Kentucky into West Virginia and Virginia with flooding rain potential.

6 hr

The ridge is forcing the Plains heat and humity as far north as possible but it coming up against resistance across the Dakotas with energy rotating around the hot dome.

The below chart for tomorrow afternoon shows the once upper low off California this past weekend crossing the Northern Plains, enhancing storm development and this features will speed ESE into the Upper Midwest, producing all sorts of storminess and flooding rains.

36 hr

During Thursday this upper disturbance crosses the Midwest towards the Mid-Atlantic where the risk enters the Washington-Baltimore area. Much cooler air pushes into the Northeast where highs will be stuck in the mid-60s in New York City, low 60s in Boston with rain.

60 hr

Just look at the depth of the trough by Friday! Highs go from mid-90s in Atlanta and Charlotte to the low and mid-80s.

90 hr

A lot of rain will fall over the next 72 hours  from the Lower Midwest to Mid-Atlantic.

Here’s the latest ECMWF rainfall total for the next 96 hours. This may be conservative in areas. I wouldn’t be surprised if we see local amounts over 10 inches, especially with ‘training’ storms.

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