Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1248 AM CDT Mon Jul 13 2020 Valid 131200Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EASTERN COLORADO AND NORTHWEST KANSAS INTO CENTRAL NEBRASKA... ...SUMMARY... Severe thunderstorms are possible from the central High Plains into parts of the Upper Midwest this afternoon into tonight. Severe gusts, possibly significant, large hail and a couple of tornadoes are the threats with the stronger storms. ...Synopsis... A mid-level shortwave trough initially over WY/MT at daybreak will move through the base of a larger scale trough and reach the Red River Valley of the north by late afternoon and subsequently into northwest Ontario overnight. Farther east, a mid-level ridge will move east into the Great Lakes while a larger scale trough moves from the East Coast into the western Atlantic during the period. At the surface, a cool front will push east across much of the Dakotas during the day with the trialing portion of the boundary arcing southwestward into the central High Plains to an area of weak low pressure. A lee trough/dryline will extend southward into the south-central High Plains. ...Central High Plains... Strong heating will steepen low-level lapse rates and models are suggesting storm initiation by the early afternoon across southern WY and the high terrain of northern CO. Isolated to scattered storms will develop/spread east into the central High Plains during the afternoon from the NE Panhandle southward into northeastern NM. The southern fringe of strong mid-level flow will encompass areas generally near and north of I-70. Forecast soundings show very steep surface to 500mb lapse rates on the western periphery of a moisture reservoir over KS/NE. Supercells and severe multicells capable of large to very large hail will initially be the threat before additional storm development/upscale growth into several broken bands of storms. Large CAPE (2000-4000 J/kg MLCAPE), very steep tropospheric lapse rates, a wind profile for organized storms, and a linear mode evolving all suggest the potential for a swath of severe gusts (60-80 mph) potentially evolving across the central High Plains during the late afternoon/evening. ...Eastern Dakotas into western Wisconsin... Strengthening southerly low-level flow will contribute to the advection of a moist boundary layer into the Upper Midwest during the day. Scattered thunderstorms are forecast during the mid to late afternoon. The strength of the low- to mid-level flow will favor supercell development with the stronger storms as they mature in the moist/unstable sector. Appreciable low-level shear (200 m2/s2 0-1 km SRH) and moist low levels imply a few tornadoes are possible with the more intense mesocyclones. Models suggest a cluster or two will evolve with damaging gusts transitioning towards the primary hazard with time. ...Eastern OK into western LA... A remnant MCV owing to thunderstorm activity this morning across OK may focus a risk for thunderstorms this afternoon near residual outflow over eastern OK/Arklatex region. Although predictability is low at this time, it appears some risk for a cluster or two may evolve from southeast OK into western LA during the day within a moist/unstable axis. Isolated damaging gusts will be the main threat with these storms before this potential activity weakens by early evening. ...New England southward through the Carolinas... Scattered thunderstorms are forecast during the midday into the afternoon across southern New England. Some multicellular storm organization may lead to a risk for damaging gusts. Farther south, it appears storm coverage is in question across parts of the Mid-Atlantic states. It appears another area of greater storm coverage and potential for isolated damaging gusts may evolve within a very moist airmass across parts of the eastern Carolinas during the afternoon with this activity diminishing by the early evening. ..Smith/Lyons.. 07/13/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
No comments:
Post a Comment