South Mississippi flooding update: WPC Discussion

Author: || Published: 12/28/2018 at 1:01am

Here is another upadte from the Weather Prediction Center regarding the overnight flooding risk:

Mesoscale Precipitation Discussion 1073
NWS Weather Prediction Center College Park MD
1151 PM EST Thu Dec 27 2018

Areas affected…southeastern LA into southern MS and central AL

Concerning…Heavy rainfall…Flash flooding likely

Valid 280450Z – 280950Z

Summary…Dangerously high additional rainfall totals of 5-7 inches expected from southeastern LA into southern MS and central AL through 10Z. This will only worsen ongoing flash flooding across these areas.

Discussion…04Z radar imagery showed 2 to 3 southwest to northeast oriented axes of heavy rain located from central LA into western GA. Training was occurring across LA, MS and western AL where 850 mb flow was closely aligned with 850-300 mb layer mean flow supporting weak Corfidi Vector motions, versus farther east across eastern AL/western GA where 850 mb flow was backed relative to 850-300 mb mean flow helping allow slow movement of heavy rain axes toward the east. Observed rainfall of 10 to 11+ inches in Marion and Walthall Counties in southern MS is aligned close to KLIX dual pol estimates.

Water vapor imagery through 04Z showed an inflection point over central LA, located between a weak mid-upper level shortwave over TX and a departing shortwave over the Mid-Mississippi Valley. As the weak shortwave over east-central TX continues to advance toward the northeast through 12Z, only weak mid-upper level height falls are expected across LA/MS which should only allow a small eastward movement to the ongoing axes of heavy rainfall among an otherwise unchanged environment. Given MLCAPE values of 500-1000+ J/kg are forecast to maintain across the central Gulf Coast, and little change is anticipated in 850 mb direction/magnitude, many of the same locations experiencing major flash flooding are expected to continue to receive 1-2 in/hr rainfall rates, locally higher, over the next few hours with localized maximum additional totals of 5-7 from southeastern LA into western AL. This includes the metropolitan areas of New Orleans and along the I-59 and I-20 corridors. A broad 1-3 inches is expected outside of the local maxima which could cause flash flooding/flooding over already saturated soils.

Here is a look at the radar as of 12:05am


Author of the article:


Nick Lilja

Nick is former television meteorologist with stints in Amarillo and Hattiesburg. During his time in Hattiesburg, he was also an adjunct professor at the University of Southern Mississippi. He is a graduate of both Oregon State and Syracuse University that now calls Houston home. Now that he is retired from TV, he maintains this blog in his spare time.