SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1212 PM CDT Sun Aug 01 2021 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk of severe thunderstorm appears negligible across the U.S., Monday through Monday night. ...Discussion... The most prominent short wave trough impacting the U.S. during this period appears likely to accelerate east-northeast of New England by early Monday. This is expected to occur as an even stronger upstream perturbation digs southeast of Hudson/James Bays, before turning eastward across northern Quebec by Monday night. While the stronger westerlies may begin to trend at least a bit more zonal across eastern Canada, models indicate that larger-scale mid/upper troughing will persist east of the Rockies through the Atlantic Seaboard, within a much weaker flow regime across the southern mid- and subtropical latitudes. Some further amplification of the troughing is possible across the Gulf Coast region, in response to digging smaller-scale perturbations to the east of large-scale ridging initially encompassing much of western North America. Downstream of quasi-stationary troughing off the Pacific coast, strongest mid-level level ridging appears likely to persist across the lower Colorado Valley into the Great Basin. To the north and east of this axis, at least a couple of weak perturbations will contribute to suppression of the ridging, while very slowly continuing to progress through the broader anticyclonic regime. ...Rockies and areas to the west... A plume of monsoonal moisture along and east of these perturbations appears likely to provide the primary focus for diurnal thunderstorm development across the Intermountain West and Rockies. However, there may be sufficient residual low-level moisture to the east of the Oregon Cascades to support a few thunderstorms, and perhaps a developing cluster of storms late Monday, aided by large-scale forcing for ascent downstream of the offshore troughing. While (as is typically the case) there is potential for thermodynamic profiles across each of these areas to become at least locally supportive of isolated downbursts and/or perhaps marginally severe hail, the risk for organized severe weather appears low and severe probabilities, in general, still less than 5 percent. ...East of Rockies... The leading edge of substantive low-level cooling and/or drying appears likely to reach the Gulf and south Atlantic Coast states by early Monday. Some continuing southward progression toward the northwest Gulf coast appears probable through early Tuesday, with some northward return possible across the Carolinas. While daytime heating may contribute to sufficient CAPE to support scattered vigorous thunderstorm development within the moist air mass during the day, this heating is forecast to be more modest than prior days. With modest to weak lower/mid tropospheric lapse rates a limiting factor, coupled with the generally weak flow and shear, severe weather probabilities associated with the risk for downbursts and damaging surface gusts still appears less than 5 percent at the present time. ..Kerr.. 08/01/2021
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