Weak upper-level flow and warm temperatures at the surface and aloft will rule the U.S. roost over the next few days, leading to patterns of severe weather more akin to those that prevail in late spring and early summer. Scattered clusters of high wind, large hail, and heavy rain can be expected, but the tornado threat will be on the low side through the coming weekend.
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| Figure 4. WU depiction of severe weather risk areas as designated at midday Thursday, May 10, by the NOAA/NWS Storm Prediction Center for Days 1 and 2 (left to right), or Thursday and Friday, May 10-11, 2018. |
Late Thursday morning, the NOAA/NWS Storm Prediction Center upgraded a small patch of western Nebraska to an enhanced risk of severe weather, with a slight risk encompassing most of the state plus eastern Wyoming. Photogenic, rotating supercells are possible as storms develop, but moisture may be too skimpy to produce the lower thunderstorm bases needed to support significant tornadoes. More likely, these storms will congeal into a wind- and hail-producing complex that rolls across Nebraska late Thursday night.
Severe storms are also possible along the Eastern Seaboard, where a slight risk extends from northeast North Carolina to southeast New York. The biggest threat is pockets of severe wind gusts above 50 knots (57 mph).
Friday looks like an instant reply across the Central Great Plains, with the risk areas shifted southeastward. SPC has a Day 2 slight risk from northeast Colorado to parts of Iowa and Missouri along with a cold front where moisture will be pooling beneath weak upper-level winds. There could be another localized enhancement of supercell risk on the High Plains, this time toward northeast Colorado.
A sharp dry line will be in place through the weekend from the Central Plains southward into West Texas. Often the dry line is a hotbed of supercell production in May, but this time a strong cap of mid-level warm air will keep the dry line largely storm-free until perhaps early next week.
Temperatures at the surface will be soaring as well. Wednesday was only the third time that Death Valley, California, has hit 116°F this early in the year (the other two times were on May 3 and 5, 1947). Record heat is possible on Thursday in Colorado, where Denver could notch its fourth-earliest 90°F reading in 146 years of recordkeeping (the earliest is April 30, 1992).
- Friday: St. Louis (91 degrees); Little Rock (91 degrees); New Orleans (91 degrees); Nashville (90 degrees)
- Saturday: Lubbock (90 degrees); Louisville (90 degrees); Washington, D.C. (93 degrees)
- Sunday: New Orleans (90 degrees); Atlanta (90 degrees); Charlotte (93 degrees)
- Monday: Memphis (91 degrees); New Orleans (91 degrees); Atlanta (91 degrees)
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| Figure 5. Highs of midday Thursday, May 10, 2018, for Friday-Sunday, May 11-13. |
