SPC Convective Outlooks

SPC Apr 9, 2020 0600 UTC Day 1 Convective Outlook (Do, 09 Apr 2020)
SPC 1200Z Day 1 Outlook Day 1 Outlook Image Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1220 AM CDT Thu Apr 09 2020 Valid 091200Z - 101200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE TEXAS COASTAL PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MID-ATLANTIC INTO SOUTHEASTERN NEW YORK... ...SUMMARY... Severe thunderstorms associated with very large hail and damaging wind gusts are expected from the southern Texas Hill Country onto the Texas Coastal Plains this afternoon and evening. Damaging wind gusts may also occur around midday in the Washington D.C. and New York City vicinities. ....Southern Texas Hill Country/Texas Coastal Plains... At mid-levels, heights will fall as a low-amplitude upper-level ridge because much less amplified. A subtle shortwave trough will move eastward through the ridge across central and east Texas. At the surface, a cold front will move southeastward across the Texas Hill Country today. The boundary will be a focus for convective development this afternoon and evening. Ahead of the front, surface dewpoints in the lower 70s F will aid strong destabilization as surface temperatures warm. MLCAPE is forecast to reach the 3000 to 4000 J/kg range by afternoon. Increasing low-level convergence along with large-scale ascent associated with the shortwave trough, will help storms to develop early this afternoon across southern parts of the Texas Hill Country. This convection is forecast to grow upscale, moving east-southeastward into the Texas Coastal Plains late this afternoon into this evening. In addition to the strong instability, RAP forecast soundings this afternoon across the Texas Coastal Plains show strong speed shear in the mid-levels. 0-6 km shear is forecast to be in the 45 to 50 kt range with 700 to 500 mb lapse rates near 7.0 C/km. This should be favorable for supercells with large hail. Hailstones greater than 2 inches in diameter will be possible with the more dominant storms close to localized maxima in instability. 0-3 km lapse rates are forecast to peak near or above 8.5 C/km in the late afternoon. This will be favorable for damaging wind gusts with supercells and intense multicell line segments. The greatest potential for severe storms is expected to be from between Corpus Christi and San Antonio northeastward to the Houston area. The severe threat could impact the immediate Texas Coast during the evening as the cold front approaches. ...Southeast New York/Mid-Atlantic/Carolinas... An upper-level trough will move quickly eastward into the upper Ohio Valley this morning. An associated 100 to 120 kt mid-level jet will move through the base of the trough with the exit region of the jet overspreading the Mid-Atlantic region. At the surface, a cold front will advance quickly eastward across the central Appalachians this morning. Surface dewpoints ahead of the front should be in the mid to upper 50s F, allowing for weak instability to develop. As strong large-scale ascent moves into the region form the west, low-topped thunderstorms should initiate and move quickly eastward toward the coast. Due to very strong wind speeds in the low to mid-levels, this convection should be able to produce damaging wind gusts. Although the greatest threat should be from the vicinity of Washington D.C. to near New York City, marginally severe wind gusts will also be possible in southern New England and southward into Virginia and the Carolinas. ..Broyles/Cook.. 04/09/2020 Read more
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SPC Apr 9, 2020 0600 UTC Day 2 Convective Outlook (Thu, 09 Apr 2020)
SPC 0600Z Day 2 Outlook Day 2 Outlook Image Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1223 AM CDT Thu Apr 09 2020 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST NM INTO WEST TX... ...SUMMARY... Some threat for isolated strong thunderstorms may evolve on Friday into Friday night across west Texas and southeast New Mexico. Hail would be the primary hazard with any severe activity. ...Synopsis... The cutoff upper low over the Southwest is forecast to begin moving eastward on Friday afternoon into Friday night. A deep upper trough over the eastern CONUS should continue moving eastward. At the surface, low pressure is forecast to gradually deepen across the central High Plains by afternoon, while a ridge moves southeastward from the central Plains into the Southeast. ...West TX into southeast NM... Low-level flow is forecast to veer to southeasterly across central/south TX into west TX/eastern NM on Friday, as the ridge shifts eastward. As this occurs, low-level moisture over the western Gulf will begin to advect northwestward, as a surface trough becomes an effective dryline somewhere over west TX or eastern NM. Uncertainty remains regarding the magnitude of low-level moisture return by Friday afternoon/evening. If sufficient moisture can advect northwestward, then isolated surface-based thunderstorm development will be possible across some portion of west TX and perhaps into southeast NM. Any such development would pose some hail risk. Some hail threat may also evolve from elevated convection later Friday night across a broader portion of west TX, as moisture continues to slowly increase beneath steep midlevel lapse rates. Hail would be the primary hazard with any such activity. ..Dean/Dial.. 04/09/2020 Read more
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