Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1200 AM CST Sun Jan 22 2017 Valid 221200Z - 231200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF SOUTH CENTRAL THROUGH SOUTH GEORGIA INTO NORTHERN FLORIDA... ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE SOUTHEAST STATES... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A LARGE PART OF THE SOUTHEAST STATES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A LARGE PART OF THE SOUTHEAST STATES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE SAN FRANCISCO BAY AREA... ...SUMMARY... Severe thunderstorms accompanied by a risk for damaging winds, large hail and tornadoes (a few of which could be strong) are expected across parts of the Southeast today into this evening. A more marginal threat for a few severe storms with damaging wind gusts is expected around the San Francisco Bay area into nearby portions of the Sacramento and San Joaquin Valleys. ...Southeast States... Thunderstorms will likely be ongoing generally along and north of warm front from northern AL through northern and central GA and SC. Initial low-level jet associated with lead impulse will continue through the eastern Carolinas and offshore early in the day. Early storms along the warm front should continue advancing north. By mid day this front should extend from a surface low in south central AL through south-central and southeast GA and will move farther north during the afternoon. Rich boundary-layer moisture resides along the Gulf Coast region with dewpoints in the upper 60s to around 70F. An intense 60+ kt secondary low-level jet is forecast to develop by late morning into afternoon from northern FL into southern GA within exit region of a progressive upper jet. The coupled jet structure will contribute to very large low-level hodographs and strong deep shear in vicinity of warm front as well as in warm sector. Initial severe threat will probably evolve along and just ahead of the cold front across southern Alabama into the FL Panhandle as forcing for ascent within the upper jet exit region interacts with warm sector. Supercells and bowing segments with large hail and damaging wind will be the initial primary threats, but a few tornadoes will also be possible. The environment will become increasingly supportive of supercells with low-level mesocyclones and tornadoes as the secondary low-level jet strengthens and the boundary layer destabilizes from southeast AL into south central and southern GA as well as northern FL. Additional storms will likely develop along the eastward-advancing cold front including potential for supercells with bowing segments capable of large hail, a few tornadoes and damaging wind. Potential complicating factor with northward extent into the Carolinas and GA is impact of ongoing convection on destabilization potential, but will maintain at least an enhanced due the expected northward progression of the warm front. Additional storms will likely develop along the cold front farther south across the FL Peninsula during the afternoon and evening where vertical wind profiles will support organized severe storms. ...San Francisco Bay area... Exit region of an intense (110-130 kt) westerly 500 mb jet streak will spread southward across the region later today. Cooling aloft should contribute to at least weak destabilization in the moist post-frontal onshore flow regime. Strong deep shear will be in place, and model guidance suggests a forced low-topped convective band could spread inland across the San Francisco Bay area, accompanied by the risk for strong wind gusts. Other, more discrete, convective cells could form ahead of this band, across nearby portions of the interior valleys, perhaps with some risk for a brief/weak tornado. ..Dial/Picca.. 01/22/2017Read more
from SPC Forecast Products http://ift.tt/s7Jkvo
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