SPC May 21, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Sat May 21 2022 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NEW ENGLAND TO SOUTHERN TEXAS... ...SUMMARY... Scattered severe thunderstorms capable of producing both damaging winds and large hail should continue through evening from parts of the southern Plains into the lower Ohio Valley, lower Great Lakes and Northeast. ...20Z Update... The primary change made to the Day 1 Outlook was to trim higher severe probabilities behind the convective line across the Mid Mississippi Valley, as convective overturning has reduced surface-based buoyancy. Otherwise, the previous forecast remains on track, with scattered to numerous wind/hail producing thunderstorms developing ahead of the cold front, from New England to the lower Mississippi Valley. Please refer to MCDs 0852-0854 for more information. Likewise, damaging gusts/occasionally large hail may still accompany ongoing storms across the southeast CONUS (more details available via MCDs 0855-0856). ..Squitieri.. 05/21/2022 .PREV DISCUSSION... /ISSUED 1046 AM CDT Sat May 21 2022/ ...Southern Plains to Northeast... A complex and active convective day is anticipated for much of the central and eastern US. Several lines/clusters of strong to severe thunderstorms are expected to intensify by mid-afternoon along a cold front and associated outflow boundaries from southeast Ontario into the Great Lakes region, OH Valley, middle MS Valley and southern Plains. The air mass ahead of the boundaries is quite moist with areas of strong daytime heating already occurring. While large scale forcing mechanisms are generally weak along this broad corridor, numerous thunderstorms are expected. Strong instability combined with sufficient flow aloft and steep low-level lapse rates will result in a risk of locally damaging wind gusts and some hail along the entire frontal zone. Most areas will see multicell storm clusters and lines. However, sufficient low and deep layer shear will likely result in a few supercells moving into northern New England later today with a slightly higher risk of a tornado or two. Please reference recent MCDs #848 and #849 for further short-term details. ...Gulf Coast states into the Carolinas... There is also a broad area of potential for at least isolated strong to severe storms over much of the southern and southeastern US today. Wind fields aloft are relatively weak in most places. However, strong heating, rich low-level moisture, and relatively cool temperatures aloft will promote robust up/downdrafts capable of locally damaging wind gusts and some hail. Read more CHECK UPDATE ZOOM GRAPHIC
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SPC May 21, 2022 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook Day 4-8 Convective Outlook RESENT 1 NWS Storm Prediction Center Norman OK 0359 AM CDT Sat May 21 2022 Valid 241200Z - 291200Z ...DISCUSSION... ...Tuesday/Day 4 to Thursday/Day 6... An upper-level trough is forecast to move into the southern High Plains on Tuesday. Ahead of the trough, a moist airmass will be located across parts of central and east Texas, where moderate instability is expected to develop by afternoon. Thunderstorm formation will be possible over a large part of the southern Plains eastward into the lower Mississippi Valley. An MCS may organize along the northern edge of the stronger instability and pose a severe threat during the afternoon and evening. At this time, there is a large spread in the model solutions concerning where this MCS could potentially form. This combined with the fact that mesoscale influences will be a strong contributor to any severe threat, makes for a lot of uncertainty. There will likely be need for a severe threat area once the model solutions key in on a specific area with greater potential. On Wednesday, the upper-level trough is forecast to move slowly eastward across the southern Plains. A moist and unstable airmass should be in place from the Texas Coastal Plains eastward into the central Gulf Coast states. Moisture advection will also take place across the Ohio and Tennessee Valleys. A potential for strong thunderstorm development will be possible along the northern edge of the stronger instability, somewhere from east Texas eastward into lower Mississippi Valley. Other strong thunderstorms could form ahead of a cold front from the mid Mississippi Valley northeastward into the Ohio Valley. Mesoscale influences and the distribution of instability will again have a strong impact any severe threat that develops Wednesday afternoon. The upper-level trough is forecast to move into the lower to mid Mississippi Valley on Thursday, as a moist airmass remains to the east of the system. Thunderstorm development will be possible over a large area from the central Gulf Coast states northward into the Ohio Valley. Isolated strong thunderstorms will again be possible along this corridor in areas that heat up the most, and in areas where mesoscale factors are favorable. From Tuesday to Thursday, predictability is too low to add a threat area, due to the uncertainties previously mentioned. ...Friday/Day 7 and Saturday/Day 8... On Friday and Saturday, the upper-level system is forecast to move slowly eastward toward the East Coast. Thunderstorms will again be possible each day across a broad area ahead of the system. Although strong thunderstorms will be possible in some areas of the eastern U.S. each afternoon and evening, the range in the forecast is too far out to make any solid conclusions concerning specific threat areas. Read more CHECK UPDATE ZOOM GRAPHIC
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SPC May 21, 2022 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Sat May 21 2022 Valid 231200Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF TEXAS... ...SUMMARY... Isolated wind damage and large hail will be possible across parts of central Texas Monday afternoon and evening. Marginally severe storms with strong wind gusts and hail could also occur across parts of north and east Texas. ...Texas... An upper-level trough is forecast to move eastward into the southern and central High Plains on Monday. At the surface, a trough is forecast to develop across central Texas. Ahead of the surface trough, a moist and unstable airmass will be in place with surface dewpoints from the upper 60s to the mid 70s F. In response, moderate instability is expected across much of the moist sector by afternoon. Although thunderstorm development will be possible across a large portion of the southern Plains, the strongest convection is expected along the western edge of the moderately unstable airmass. Thunderstorms are forecast to increase in coverage during the afternoon and move eastward into the stronger instability across the Texas Hill country and north Texas. Forecast soundings Monday afternoon, near the axis of strongest instability, have MLCAPE peaking in the 2500 to 3500 J/kg range. 0-6 km shear is forecast to range from about 30 knots in north Texas to around 40 knots in the Texas Hill Country. This combined with steep low to mid-level lapse rates should be sufficient for an isolated severe threat. Wind damage would be the greatest of the threats if an organized line segment can develop. If cells remain more discrete, then supercell development will be possible. At this time, the models show the best severe-weather parameters over southwest and central Texas, where there could be a slightly greater potential for wind damage and isolated large hail than further to the north. If tomorrow's model runs continue to show more potential for severe storms in central and southwest Texas on Monday, then a slight could be added in an upcoming outlook. ..Broyles.. 05/21/2022 Read more CHECK UPDATE ZOOM GRAPHIC
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SPC May 20, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Fri May 20 2022 Valid 202000Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR A SMALL PART OF EASTERN PENNSYLVANIA INTO NEW JERSEY... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF LOWER MICHIGAN...AND OKLAHOMA INTO NORTH TEXAS... ...SUMMARY... Severe thunderstorms are expected to be most concentrated over portions of the northern Mid-Atlantic states, Lower Michigan, and a small part of the southern Plains this afternoon and evening. ...20Z Update... Have trimmed severe probabilities behind a small cluster of thunderstorms over eastern PA. Damaging winds should continue to be the main threat with this activity as it spreads into NJ over the next couple of hours, but a tornado or two also remain possible. See Mesoscale Discussion 842 and 843 for more information on the near-term severe threat across this area. An intense supercell producing a tornado is ongoing at 1958Z over northern Lower MI. The 19Z sounding from APX shows a favorable environment for continued thunderstorm organization, and it appears plausible that this supercell will persist across the rest of northern Lower MI over the next hour or so. A threat for tornadoes, large to very large hail, and damaging winds should persist with this supercell in the short term, and with any other intense thunderstorms that can develop. Still, weak large-scale ascent will probably tend to limit overall coverage through the rest of the afternoon, with the overall severe threat probably remaining fairly isolated. See Mesoscale Discussion 844 for additional details on the near-term severe threat across northern Lower MI. Elsewhere, little to no changes were made to the outlook. ..Gleason.. 05/20/2022 .PREV DISCUSSION... /ISSUED 1126 AM CDT Fri May 20 2022/ ...Mid Atlantic Region... A well-defined MCV is noted on satellite imagery over southwest PA. This feature will track eastward today across PA, northern MD, and into NJ, fostering the development of severe thunderstorms. Destabilization ahead of the MCV, combined with strong low and mid-level wind fields near the circulation will promote the development of supercell and bowing structures capable of damaging winds, large hail, and a few tornadoes. Given the rapid eastward motion of the activity, it should move off the NJ coast well before dark, ending the severe threat. ...MI... A strong surface cold front currently extends from southern WI northward into upper MI. This front will cross Lake Michigan this afternoon and move into lower MI by early evening. Thunderstorms are expected to form in vicinity of the front and move across parts of the northern Lower MI. Forecast soundings suggest favorable parameters for large hail in the stronger storms, along with the possibility of isolated tornadoes. ...OK/TX... A cold front is sagging southward across OK today, and should stall for awhile this evening before progressing into TX overnight. A strengthening southerly low-level jet atop the boundary will lead to scattered thunderstorms in a very unstable air mass. Storms may be supercellular with large hail and damaging winds. A tornado or two cannot be ruled out before activity becomes more linear after dark. ...FL... A moist boundary layer is present today across the FL peninsula, along with pockets of strong heating. Scattered thunderstorms have begun to form over south FL, and this activity is expected to build northward through the day. Relatively cool temperatures and modest westerly flow aloft will promote a few organized multicell storm clusters capable of gusty/damaging winds or perhaps hail. Read more CHECK UPDATE ZOOM GRAPHIC
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