Multi-Day Severe Threat, Surge Of Summer, Big 7 Day Heartland Rains

Written by on May 28, 2013 in United States of America with 0 Comments

The Plains is entering an increasingly primed environment for severe weather with multiple tornadoes possible today, tomorrow and Thursday. The trough is beginning to carve out with the main upper disturbance roaring in on a powerful Pacific jet. It’s as that trough gets carved out, the atmosphere is being forced to ‘lift’ out ahead over the Southern and Central Plains. Cool air is overlapping increasing warm, moist air with dew points rising into the 70s as far north as Illinois and Wisconsin will provide plenty of bouyancy and with varying wind speeds and direction with height, all the ingredients as expected since way back last week, are now coming together.

Today will be a bigger day for severe weather than yesterday but it’s tomorrow when I think we’re likely to get the bigger and more violent storms as all the ingredients merge over the Plains.

Here’s the 500mb vort max for tomorrow afternoon. Note the deep trough and ridge out ahead with pulses of energy racing NE in between.


Below is the 250mb winds or jet stream winds and you can see the high levels of energy racing into the base of the trough from off the Pacific. The area to watch for dangerous storms developing is on the south east side of the trough. That’s where your strongest upward motion is and also where winds diverge or spread out in the upper levels and converge at the surface. The spreading apart of winds aloft, forces air to rise and in doing so, winds are pulled in from all directions at the surface underneath.


These speed maxes which round the base of the trough, simply enhance instability.

Check out this surface instability lifted index chart for tomorrow afternoon. The greatest values or areas where the greatest ‘lift’ within the atmosphere can be found is through the heart of Kansas and Nebraska.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s the CAPE values or another measure of enhanced upward motion within the atmosphere.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

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Surprise surprise the SPC now has a moderate risk over this very area for tomorrow.


The severe risk with tornado development possible if not likely will extend into Thursday.

SPC risk area for Thursday


Watch out for pesky thunderstorms over parts of the Northeast tomorrow as a warm front is drapped across the region. Note the slight risk issued by the SPC for tomorrow.

Warm, humid air lifted north up against the front is what will spark the storms over the Northeast tomorrow.

Big 7 Day Rain Totals

Rainfall has been prolific over Iowa down into Missouri over the past 5 days and unfortunately, there is a lot more to come over the same area in the next 5 days. Near stationary frontal boundary and persistent, heavy thunderstorms lifting north into the area will keep the heavy, flooding rain potential going.

Just look at what the QPF is printing out in just the next 5 days. We may see local 6-8 inch amounts on top of 4-8 inches already over Iowa.


2-4 Day Surge Of Summer Into The Northeast

I have had temperatures reaching 90 or greater in the DC to Boston corridor since early last week and it would appear we will see perhaps 1 day of 90 in Boston, 2 in NYC and maybe 3 from Philly down to DC before cooler weather returns next week.

Thursday should make 90 in DC, Baltimore and may get close in Philly but Friday and Saturday look likely to produce 90 all the way to NYC and Boston.

Here’s the ECMWF 850 temps for Friday




The upper 80s/low 90s may extend into Monday of next week while cool, Canadian air drops down over the Great Lakes. This will eventually wipe out the heat and humidity over the Northeast while hot air rebuilds Out West. In fact we could see some record heat over Southern and Central California extending east into the Great Basin by as early as this weekend.

Here’s the ECMWF for Monday which shows one last day of near or above 90 up the I-95 while a cool shot drops into the Midwest, heat builds over the Southwest with 90 possible in LA, may get close to 110 in Phoenix, 105 in Vegas.


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