SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Wed Apr 14 2021 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM WEST-CENTRAL TEXAS TO THE CENTRAL GULF COAST... ...SUMMARY... Isolated strong to severe storms are possible from west-central Texas eastward along the central Gulf Coast. Locally strong gusts and hail will be the main hazards with this activity. ...Synopsis... Satellite imagery currently shows two well-defined upper lows, one over the western Great Basin and the other over the Upper Great Lakes. Expectation is for these lows to gradually move eastward today, beginning the Day 2 Period (i.e. 12Z Thursday) centered over the central Great Basin and southwestern Quebec. Surface low associated with the eastern upper low will likely be centered just off the Mid-Atlantic coast early Thursday, with an associated cold front extending southwestward from this low through another low off the MS/AL coast and into South Texas. Central and eastern portions of this front will likely remain progressive throughout the day before stalling Thursday evening. In contrast, the western portion of the front over the western Gulf and south TX will likely remain stationary throughout the day before returning northward as a warm front Thursday evening through Friday morning. ...Central Gulf Coast through FL Panhandle/Northern FL... This is some uncertainty regarding the position of the cold front early Thursday morning, particularly given the expectation for augmentation of this boundary by storm outflow. Even so, modest warm-air advection is anticipated across this boundary, contributing to scattered thunderstorms from southern LA into the western FL Panhandle early Thursday morning. Steep mid-level lapse rates will exist over the region, as will moderate westerly flow aloft. Resulting combination of vertical shear and buoyancy could result in a few stronger storms capable of hail and/or damaging downburst winds. Elevated storm character should preclude any tornado threat. Surface-based storms are possible along the front Thursday afternoon as it traverses the northern FL Peninsula. Warm temperatures aloft and resulting convective inhibition will likely temper updraft strength within most storms. However, vertical shear will remain strong enough to support rotation/organization of a few updrafts, with large hail and/or damaging gusts possible with these more robust embedded storms. ...West-Central TX to the Middle/Upper TX Coast... A stalled frontal boundary will likely be in place from just off the southeast TX coast back westward through South TX, eventually intersecting lee troughing off the higher terrain of the southern High Plains and northeast Mexico. Deepening of this lee troughing is anticipated throughout the day, with surface southeasterly winds strengthening in tandem. More southerly low-level flow will also increase at the same time. Resulting increase in isentropic ascent will augment the ascent attendant to a subtle shortwave through expected to move across TX. All of these factors will contribute to showers and thunderstorms across much of the southern Plains. Given the steep lapse rates and strong deep-layer vertical shear, a few stronger storms are possible, with large hail as the primary severe risk. Guidance is beginning to hint at a corridor of modestly higher severe potential, from central TX into southeast TX, where storms may begin to encounter slightly higher dewpoints and the northward moving warm front. However, uncertainty regarding frontal position and storm timing remains too high to delineate higher probabilities within this corridor with this forecast. Lastly, conditional risk of supercells capable of large hail exists near the Del Rio vicinity with any storms that can develop over the higher terrain of northeast Mexico and then move eastward. ..Mosier.. 04/14/2021
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