Severe Weather: Tornado watch for Denver NOW!!!p152

Lots of flooding over the next 5 days in several states and down the Mississippi river valley to the delta.

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Day by day

Friday: Severe storms will be most concentrated in Nebraska, extending northeastward from a surface low expected to be near North Platte by evening. The NWS/NOAA Storm Prediction Center is warning that a couple of strong tornadoes are possible, and very large hail can be expected as well. Southward along a dry line into Kansas, storms will be more scattered, even isolated, but they could be very intense wherever they pop up.

Further south into Texas, a “cap” of very warm air one to two miles high will likely keep a lid on most severe weather until after dark, when a strong upper impulse moves across. Models agree that an arcing line of intense overnight storms with large hail and high winds will develop in southwest Texas, perhaps holding together long enough to reach the Dallas-Fort Worth and Austin areas by late morning.

Saturday: Severe storms will be widespread along the frontal zone from Iowa to Texas and Louisiana, but there remain questions about how the day will evolve. Models are suggesting that morning thunderstorms could develop from Oklahoma into Missouri, and any rain-cooled air from these storms may reduce instability later in the day along the lagging frontal zone. Still, it appears that Saturday afternoon will likely bring a renewed round of severe weather in eastern Oklahoma and eastern Kansas, eventually morphing into a squall line stretching from Iowa to Louisiana that should reach the Mississippi River overnight Saturday night. One or more corridors of persistent training storms may develop along the front from eastern Kansas to Wisconsin.

Sunday: Sunday should be the quietest of the next several days, although strong winds could occur with thunderstorms along the leading cold front as it pushes across Illinois into Michigan and Indiana. Late on Sunday night, the next big impulse from the upper low will begin moving into west Texas, and intense overnight storms could develop depending on how quickly low-level moisture returns to the area.

Monday: A major outbreak of severe weather, including significant tornadoes, looks quite possible as an especially potent upper-level impulse heads into the southern Plains. The strong winds and cold air aloft will lead to a widespread zone of favorable wind shear and high instability. The storms will likely be most intense and concentrated from southern Kansas to north and northwest Texas, especially across Oklahoma. Model agreement on this scenario is reflected in the fact that SPC has consistently highlighted the elevated risk on this day ever since last Tuesday. Because conditions will be favorable for supercells well ahead of the front/dry line, potentially tornadic storms could range across a broad area.

The other serious concern for Monday is a band of intense upward motion and torrential rain expected to develop with the upper impulse as it heads from Oklahoma across southeast Kansas into Missouri. GFS model output suggests that 3” – 6” totals could fall in a short period across already-saturated soils, and local amounts could be higher.

Depending on how the western trough evolves, more severe weather may erupt later in the week across the Plains and Midwest, and more heavy rain may fall. Flood concerns are likely to mount as we approach Memorial Day weekend.
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Mesoscale Discussion 0649
NWS Storm Prediction Center Norman OK
0155 PM CDT Fri May 17 2019

Areas affected...Parts of southwest into central Nebraska and western Kansas

Concerning...Severe potential...Watch likely

Valid 171855Z - 172100Z

Probability of Watch Issuance...80 percent

SUMMARY...The risk for supercells capable of producing large to very large hail and a couple of tornadoes appears likely to increase through 3-5 PM CDT.

DISCUSSION...A plume of warm and capping elevated mixed-layer air remains over much of the central and southern Plains. However, the leading edge of stronger mid-level height falls associated with amplified upper troughing is already spreading through much of the high Plains. And an area of lower/mid tropospheric cooling and forcing for ascent associated with at least one embedded perturbation appears to be in the process of pivoting northeast of the Front Range.

In advance of this feature, insolation is contributing to moderate to large CAPE of 2000-3000 J/kg, mainly focused near/east of a deepening cyclone within lee surface troughing, across western Kansas into southwest and central Nebraska. Latest model output suggests that with additional surface heating and cooling aloft, inhibition probably will weaken sufficiently to allow for the initiation of thunderstorms as early as the 20-22Z time frame.

Strongest low-level convergence appears focused near a surface front/sharpening dryline intersection near/west of North Platte NE, where stronger 2-hourly surface pressure falls are now evident. This is where the initiation of sustained discrete supercells and subsequent upscale convective growth appears most certain, with at least isolated to widely scattered supercells possibly forming along/just ahead of the dryline, southward across western Kansas.

In the presence of strong deep layer shear, large to very large hail appears the primary initial severe weather risk. However, at least relatively weak/brief tornadoes also appear possible, and tornadic potential probably will increase near/northeast of the triple-point low, across southwest Nebraska, as southerly 850 mb flow strengthens and low-level hodographs enlarge closer to 18/00Z.

..Kerr/Hart.. 05/17/2019

The severe storms have begun: [link to radar.weather.gov (secure)]

Here's the live big picture interactive map: [link to radar.weather.gov]

be a long night it is so hot in Texas today right kind of fuel

Dan is headed right at it: [link to www.severestudios.com (secure)]

Ohio storms now going severe, too: [link to radar.weather.gov (secure)]

Phillipsburg, KS about to get blasted: [link to radar.weather.gov (secure)]

Saturday is the full moon. Serious Weed-chestra in the hood today, but I'll do it the moment the grass is dry on full moon day, because that storm hits at 3pm here boom!

[link to twitter.com (secure)]

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
409 PM EDT Fri May 17 2019

Valid 00Z Sat May 18 2019 - 00Z Mon May 20 2019

...Severe thunderstorms likely for the Plains states west of lower and mid-Mississippi Valley during the weekend...

...Heavy rain and some flash flooding will be possible across portions of the Great Plains and Midwest...

...Much cooler than normal temperatures will continue for much of the western U.S. and the northern Plains...

A series of cold and energetic upper-level troughs will continue to bring active weather from the northeastern Pacific into the western U.S. This will allow unsettled weather and very chilly temperatures to continue for much of the West and into the northern Plains. In fact, the higher elevations of the Intermountain West and the northern Rockies will be cold enough to see accumulating snow, while valley locations will see a chilly rain. Areas in the northern High Plains could even see rain changing to wet snow before tapering off Saturday night. High temperatures in some
locations will be as much as 20 to 30 degrees below normal for Friday and Saturday, and this very cool and unsettled pattern should last generally through the weekend across the West.

Meanwhile, energy ejecting from the lead upper-level trough is currently edging its way into the Great Plains. This will trigger the formation of a couple of low pressure waves moving across the central Plains along a front, setting the stage for fairly widespread heavy showers and thunderstorms to move generally eastward across the Plains toward the Mississippi Valley during the weekend. The Storm Prediction Center has highlighted a fairly large area of Slight to Enhanced Risk of severe weather mainly west of the Mississippi Valley for the weekend. In addition, heavy rainfall will likely result in flash flooding issues in these areas and further north into the upper Midwest.