Wednesday, May 2, 2012

Update on Northern Plains / Midwest Severe Threat for Today/Tonight...

Above is the latest severe weather outlook with respect to damaging wind potential from the Storm Prediction Center (SPC) in Norman, OK.  Severe thunderstorm winds are possible anywhere within the yellow shaded swath on the image, with an elevated risk within the red and lavender shaded areas, which includes the cities of North Platte, Grand Island, Lincoln, Omaha, Norfolk, Sioux City and Sioux Falls.

Very large hail, perhaps in excess of 2 inches in diameter in some cases, is likely late this afternoon into this evening within the red shaded and black hatched area on the image below:

This elevated risk of very large hail generally applies to the same cities listed above for the elevated damaging wind risk.

While a tornado will be possible with most any severe storm that forms in this region later today and into this evening, the highest probability lies within the brown shaded area on this image:

A large complex of thunderstorm activity moved Southeast over Iowa overnight, and is now diminishing over portions of northern Missouri and northern Illinois.  

The atmosphere is already starting to recover behind this activity over Iowa, with an unstable airmass likely to be in place across this region once again by late afternoon.

Meanwhile, the atmosphere over central and eastern Nebraska is destabilizing rapidly, with mostly sunny skies and increasing moisture from the South:

Thunderstorms are likely to form over central Nebraska by mid to late afternoon, and increase in both coverage and intensity as they move and develop Eastward into the late afternoon and evening hours.  Large to very large hail, damaging winds and a few tornadoes can be expected with this activity.

Later this evening and into tonight, this activity is likely to congeal into one or more complexes of thunderstorm activity, with the main threat becoming damaging winds as the complex moves Eastward across much of Iowa again overnight.

Very heavy rainfall is also possible again tonight, particularly as the activity organizes into a larger complex over Iowa.  This will likely lead to a significant flash flooding threat, particularly in areas that received heavy rain last night and/or early this morning.

If you live across this region, please pay attention to the weather this afternoon and evening.  Make sure to identify your best sheltering options, and prepare them so that you can move there quickly if threatening weather is observed or a warning is issued.  If you live in Eastern portions of the region, including much of Iowa, the primary threat of severe weather is likely to occur tonight, so make sure that you have a way to receive weather warnings at night.

Elsewhere, a threat of severe weather will exist within the broad area from the central and northern Plains to the Delmarva region along the East Coast, as indicated by the yellow shaded area on the top image.  Please see this post from earlier this morning for more information on the overall threat.

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Anthill_Goddess said...

We made out pretty well last night (other than one heck of a gust right as the storm got to us that sent a box from a mile away flying past my house!)...hoping and praying we'll slide by pretty easily with this one, too! I absolutely HATE these multiple day threats...I can't be away with the kids for THAT long! *Laughs* Thanks for keeping an eye on all of us, Rob!

Rob White said...

Glad you made out okay last night!

Could be a late start today depending on how long the cap holds. Just keep an eye across the river to the West and we should know by late evening how it's coming together...