Severe Storm Outlook Narrative (AC)
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Issued by NWS
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702 ACUS01 KWNS 190550 SWODY1 SPC AC 190548 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1248 AM CDT Wed Jun 19 2024 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHERN HIGH PLAINS REGION...LOWER GREAT LAKES-NEW ENGLAND...AND OVER SOUTH TEXAS... ...SUMMARY... Locally strong gusts and marginal hail may occur with storms over the southern High Plains, with a couple of strong gusts also possible from the lower Great Lakes region into New England. A brief tornado or two may occur over parts of southern Texas tonight in association with Potential Tropical Cyclone 1. ...Discussion... Dominant East Coast upper ridge is forecast to build west into the mid MS Valley later today as the primary belt of westerlies retreats north of the international border. This westward expansion will encourage the tropical system over the western Gulf basin to move into northeast Mexico, considerably south of the Rio Grande Valley. Convection that developed in association with frontal zone Tuesday afternoon/evening has weakened considerably, but continues along a corridor from the upper Great Lakes, southwest across IA into the Oklahoma Panhandle. Latest model guidance suggests this activity will be ongoing at the beginning of the period, along with widespread convective debris. While an embedded disturbance or two may evolve from this activity, it`s not entirely clear how substantial subsequent development will be given the weak environmental shear and modest instability. The greatest risk for robust updrafts will be across the southern High Plains into southern NM where strong boundary-layer heating and orographic influences will be favorable for a few strong to potentially severe thunderstorms. Another region where a few strong storms are possible is across the lower Great Lakes into New England. While upper ridging will dominate this region, scattered convection will once again develop from portions of the Ohio Valley, northeast into New England as surface temperatures warm through the mid 80s to near 90F. Convective temperatures will be breached and thunderstorms should develop within a seasonally moist environment with PW values in excess of 1.75 inches. Gusty winds are the primary concern with this weakly sheared convection. Low-level shear will increase markedly during the latter half of the period across south Texas along the northern fringe of the western Gulf basin tropical system. This feature may evolve into a tropical cyclone before it moves inland well south of the lower Rio Grande Valley. While this system will remain at low latitudes, 850mb flow is expected to increase across south TX such that sustained updrafts will likely rotate. High PW and strong low-level shear favors some low risk for a tornado or two, especially during the latter half of the period. ..Darrow/Thornton.. 06/19/2024 $$