Storm Prediction Center Jan 2, 2017 2000 UTC Day 1 Convective Outlook (original) (raw)

Categorical Graphic

Probabilistic Tornado Graphic

Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.

Probabilistic Damaging Wind Graphic

Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.

Probabilistic Large Hail Graphic

Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.

SPC AC 022004

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK 0204 PM CST Mon Jan 02 2017

Valid 022000Z - 031200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST LOUISIANA...CENTRAL AND SOUTHERN MISSISSIPPI...SOUTHERN ALABAMA AND THE WESTERN FLORIDA PANHANDLE...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK FROM THE CENTRAL GULF COAST STATES TO CENTRAL AND SOUTHERN GEORGIA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EXTENDING FROM PORTIONS OF THE MID SOUTH AND TENNESSEE TO SOUTHERN SOUTH CAROLINA...

...SUMMARY... Severe thunderstorms are expected through the afternoon and evening from eastern Louisiana across much of the central Gulf Coast States to portions of central and southern Georgia. All severe hazards will be possible including damaging winds and tornadoes, especially across portions of southeast Louisiana and central and southern Mississippi through southern Alabama and the western Florida Panhandle.

...Lower MS Valley to central Gulf Coast States... Early afternoon radar imagery and lightning data showed a bowing line of storms moving into southwest MS and southeast LA, with a second area of thunderstorms located well east of the bowing line across southeast MS into the western FL Panhandle to central and eastern AL, and adjacent northwest GA. The air mass across the Slight and Enhanced severe risk areas remains moderately unstable and sufficiently sheared for discrete rotating updrafts, primarily with storms across the warm sector. Strengthening southerly low-level winds across much of the Enhanced risk area with an additional increase in midlevel flow (from the southwest to west) will maintain favorable effective srh of 200-400 m2/s2 for a continued tornado threat. Meanwhile, WSR-88D VWPs indicated strengthening westerly inflow jet into the bowing line of storms, supportive of a continued likelihood for damaging winds from central and southern MS to southern AL this afternoon and evening. The western extent of the severe probabilities and categorical risk areas have been trimmed east to account for the progressive eastward convective trends.

The tornado probabilities have been reduced some across northern AL into TN, where storms should tend to remain elevated.

...Central and southern GA into southern SC... A destabilizing air mass along and south of the wedge front combined with strengthening southwesterly 500-mb flow, given the approach of the lower MS Valley shortwave trough suggests any storms developing within this region will have the potential to become severe. Given these factors and model indication for storms in southern AL and the FL Panhandle to develop to the east-northeast into Georgia this evening, the severe probabilities and categorical Slight and Marginal risk areas have been expanded to the east.

..Peters.. 01/02/2017

.PREV DISCUSSION... /ISSUED 1028 AM CST Mon Jan 02 2017/

...Gulf Coast states and Tennessee Valley... Considerable strong/severe convection is moving eastward across western Louisiana and extreme southeast Texas, in advance of a strong upper short-wave trough progressing eastward over central Texas. Embedded within the cluster is a bowing line segment that has been producing occasional wind damage reports this morning.

Additional storms are continuing downstream from this activity over eastern Mississippi and western/northern Alabama, in association with a weaker short-wave trough and within a coupled upper-level jet structure where divergence aloft is maximized. This activity is resulting in widespread cloud cover that will likely limit diurnal heating and destabilization north of the I-20 corridor.

Surface analysis and visible satellite imagery indicate an east-west coastal warm front extending from southwest Louisiana into the northwest Florida, with richer low-level moisture /surface dew points around 70 degrees/ and warmer temperatures to the south of the front. This boundary may lift farther north this afternoon but substantial progress inland will likely be impeded by ongoing convection and clouds.

Current indications are the eastward-moving QLCS over western Louisiana will progress across the lower Mississippi Valley this afternoon with a continuing threat for primarily damaging wind gusts. Several tornadoes will also be possible, especially with any embedded rotational couplets that may develop and near the intersection of the advancing QLCS and the warm front. In addition, any persistent semi-discrete cells developing downstream from the line may also pose a tornado threat given the clockwise-turning low-level hodographs evident in recent VAD profiles at LCH, LIX, and MOB radars.

Other severe storms will be possible northward into parts of the Tennessee Valley where strong vertical shear may compensate for weaker instability. A few damaging wind gusts and marginally severe hail will be the primary threats.

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