Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Fri Jul 10 2020 Valid 101200Z - 111200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE NORTHERN AND CENTRAL PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM COASTAL NEW JERSEY INTO COASTAL NEW ENGLAND... ...SUMMARY... Several clusters of severe storms are expected over parts of the northern and central Plains this afternoon into tonight. Large to very large hail and damaging wind are likely, and a few tornadoes are possible. ...Northern through central Plains regions... The northern and central Plains will remain within belt of modest westerlies today. A low-amplitude shortwave trough currently moving through the Pacific Northwest will reach the northern High Plains by late afternoon and continue through the Dakotas this evening accompanied by a cold front. A minor impulse will precede this feature and move through SD during the morning. Warm front will become established and extend from a weak surface low over southwest SD southeastward through eastern NE and KS. Dryline will extend southward through western NE into eastern CO. A cold front will approach the western Dakotas by late afternoon. Easterly low-level winds will persist north of the warm front and in advance of the cold front across the Dakotas into northeast WY and eastern MT maintaining a corridor of surface dewpoints from the upper 50s to low 60s F beneath steep lapse rates. The atmosphere in this region will likely become moderately to strongly unstable as the boundary layer warms with 2000-3500 J/kg MLCAPE likely by mid afternoon. Storms are expected to develop along the cold front as it interacts with the destabilizing boundary layer across eastern MT and northeast WY. Other storms will develop farther south near triple point over southwest SD into northwest NE. Vertical wind profiles with veering in the lowest 2 km and 50+ kt effective bulk shear will support supercells capable of large to very large hail and damaging wind. A few tornadoes are possible, especially with storms developing near warm front across SD into northern NE. Some of the storms may eventually grow upscale into lines and clusters and spread east and southeast posing a risk for more widespread wind damage. Though some uncertainty remains, potential will exist for a longer lived severe MCS to organize across SD or NE and move southeast along instability gradient into the overnight, supported by a strengthening southwesterly low-level jet. Have expanded the SLGT risk southward for the possibility of this scenario and farther southward expansion through eastern KS and western MO might be necessary if more confidence is gained in later outlooks. ...Northeast and southern New England coastal areas... Tropical storm Fay is forecast by the National Hurricane Center to continue moving northward, and the center should be located near the central NJ coast by early this evening. Shear in the 0-1 km layer will increase from coastal NJ through coastal southern New England later today where near-surface dewpoints will reach the low 70s F. Best tornado threat with low-topped supercells will evolve during the afternoon into the early evening if some surface heating can occur between outer rainbands. ..Dial/Lyons.. 07/10/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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