SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Tue Jul 06 2021 Valid 061630Z - 071200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF FLORIDA...NORTHEAST STATES...UPPER MIDWEST...AND NORTHERN HIGH PLAINS... ...SUMMARY... Tornadoes are possible through tonight, mainly over the western and central Florida Peninsula, in association with Tropical Storm Elsa. Scattered damaging winds are expected this afternoon through early evening over parts of the Northeast States as well as the Upper Mississippi Valley. Isolated severe storms may also occur across a portion of the northern High Plains. ...Florida Peninsula... The National Hurricane Center continues a generally northward forecast track for Tropical Storm Elsa just to the west of the Florida Peninsula through tonight; consult NHC for the latest Elsa forecast details. Accordingly, the corridor of strongest low-level shear/SRH accompanying Elsa will slowly spread north from the Florida Keys and coastal southwest Florida across western and central portions of the Florida Peninsula through Wednesday morning. Outer banded convection will tend to be located within a modest SRH environment through this afternoon, which may tend to temper a greater tornado threat with eastward extent toward the east coast of the Peninsula. Intermediate bands should have somewhat greater potential to produce brief tornadoes owing to an enlarged low-level hodograph. This tornado risk appears greatest late this afternoon into tonight across the southwest to west-central/central portions of the Florida Peninsula. ...Northeast States and southern New England... In the wake of a shortwave trough exiting the coast of northern New England, a belt of moderately strong west-northwesterly winds will persist across the region. Initially, convection will continue to develop and intensify in the lee of the Lower Great Lakes through early evening, and subsequently eastward to a lee surface trough across the Delaware Valley into southern New England. A plume of moderate MLCAPE from 1500-2500 J/kg is anticipated within these regions. The enhanced lower/mid-level flow will support some organized multicell clusters capable of downbursts/wind damage. Storms are expected to reach and impact much of the Northeast Megalopolis by late afternoon/early evening. ...Montana/northern High Plains... A remnant MCV/subtle mid-level impulse over east-central Montana at midday should influence thunderstorm development later this afternoon in conjunction with moist low-level upslope flow/differential heating near the higher terrain/mountains of north-central/east-central/southeast Montana and northeast Wyoming as well as the Canadian Front Range. Coincident with 50s F dewpoints, steep mid-level lapse rates and strong effective shear owing to 35-40 kt 500-mb west-northwesterly winds atop weak low-level easterlies will foster potential for a few discrete supercells. At least isolated instances of severe-caliber hail and wind are expected particularly across east-central/southeast Montana into northeast Wyoming, while additional storms may develop/move into north-central Montana via the Alberta Front Range. ...Southern Minnesota to south-central Wisconsin/Lower Michigan... A belt of likely MCV-enhanced mid-level westerlies, as noted in the 12Z observed sounding from Aberdeen SD, appear to be developing eastward per late morning WSR-88D VWP data from Minneapolis and La Crosse WI. These stronger westerlies will tend to overlie, in a parallel orientation, a roughly west/east-oriented frontal boundary and surface wave. As clouds thin and more appreciable heating occurs particularly along/south of the front, thunderstorms are expected to develop and gradually intensify through mid/late afternoon. Some supercell structures could initially occur, particularly across parts of west/southwest Wisconsin into central Wisconsin to the east-northeast of the weak surface wave. Storms should otherwise tend to develop into east-southeastward moving clusters, including some embedded bowing segments, by early evening with damaging winds as the primary risk. Some of the strong/severe storms could develop into northern Iowa and/or Lower Michigan this evening. ..Guyer/Lyons.. 07/06/2021 Read more LIVE: spc.noaa.gov
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