textproduct: Memphis

KEY MESSAGES

Updated at 1150 PM CDT Fri Apr 4 2025

-Severe storms and excessive rainfall are expected to continue through Saturday night. -A Moderate Risk of severe weather is in effect through tonight for portions of northeast Arkansas and the Missouri Bootheel.

-An Enhanced Risk of severe weather is in effect for much of the Mid-South through Saturday night.

-A High Risk of excessive rainfall is in effect through Saturday night. Total rainfall amounts of 10 to 15 inches along and north of I-40 are likely. This is not your average flood risk. Generational flooding with devastating impacts are possible.

UPDATE

Issued at 748 PM CDT Fri Apr 4 2025

A few storms were able to develop across the CWA this afternoon and have lingered into the evening. This activity has largely waned with the loss of diurnal heating and lack of large scale forcing for ascent. Convection is much more organized just to our north and west from central AR into the OH Valley. This activity will propagate eastward into the CWA over the next several hours, gradually overspreading northeast AR and the Bootheel through approximately midnight. Some of this convection will be severe as the near storm environment remains favorable for strong, rotating updrafts. MLCAPE is forecast to remain near 2000 J/kg with ample deep-layer shear and 0-1 km SRH on the order of 300-400 J/kg. Some of the WoFS ML products and UH probabilistic data highlight this greatest potential for supercells across Clay, Greene, Dunklin, and Pemiscot Counties, but the area will expand a bit south and east with time. The current watch really doesn't cover this time frame so another watch cannot be ruled out after midnight.

Also of significant concern is the potential for a significant hydrologic event overnight. The initiating boundary extends southwest to northeast, roughly parallel 850-300 mb steering flow, suggesting the likelihood of training cells. Right-moving supercells could potentially propagate east off the boundary given the Bunkers RM vectors. Storms could congeal into more of a messy QLCS mode overnight with a potential for mesovortices and tornadoes, in addition to damaging wind and large hail. Rainfall amounts over the next 24-36 hours could be similar to what we've already seen in many areas over the past 2 days given the training convection and ridiculous rainfall rates. Additional rainfall amounts of 3-6" are expected, but a band of higher amounts is likely somewhere along or north of I-40 appears likely. CAM guidance suggests higher end amounts of 8-10" in some areas (based on HREF LPMM products). This flash flood threat has a high ceiling and will need to be watched closely.

MJ

DISCUSSION

(This evening through next Thursday) Issued at 143 PM CDT Fri Apr 4 2025

Another day, and another round of severe weather as we continue through an extremely active weather episode. A large upper trough continues east today and is gradually picking up speed. To its east and closer to the surface, a cold front extends south through central Texas with a warm front lifting north from the Arklatex through the Midsouth into the Ohio River Valley. A warm, tropical airmass will then move into the region and persist through the next 36-48 hours, producing heavy rain, severe thunderstorms, and significant flooding.

The severe weather threat this afternoon will be characterized by two rounds: warm sector cells and a QLCS overnight. Strong southerly flow and upper height falls have allowed the retreat of yesterdays cold air mass. Rapid destabilization is already under way across our northern counties where upwards of 4000 J/kg of SBCAPE are possible by midafternoon. The upper low to the west will bring increasing upper winds and allow for 0-6 km bulk shear in excess of 50 knots, favoring supercells and strong bowing line segments within the QLCS. ESRH is currently lackluster (100-200 0-3 km) but is expected to increase into the evening and along the warm frontal zone. Therefore, any storms that are able to form in the open warm sector that reside through the evening or interact with the warm front will pose a threat for all severe hazards, especially across West Tennessee, East Arkansas, and the Missouri Bootheel. However, there is still uncertainty in the coverage, longevity, and location of warm sector storms going into this afternoon and evening.

More severe weather is likely tomorrow as a cold front and western upper low pass over through the region. A forced line and the potential for prefrontal cells exist once again. However, convection today will likely shove instability further south towards the TN/MS border with 2000+ J/kg MUCAPE to the south. High ESRH, especially in the lowest 1 km, will be high and streamwise. Therefore, storms will rotate and organize quickly. Storm mode is expected to be a line with embedded mesovortices/mesocyclones that will have the potential to produce tornadoes and damaging winds. Prefrontal cells are still possible tomorrow but extensive cloud cover might preclude sufficient surface instability to break through any capping. Storms are expected to leave the area by Sunday afternoon with a few showers behind the front that are not expected to add much rainfall.

Alongside the severe weather, significant and possibly destructive flash flooding is likely starting today that will last into Sunday across much of the Midsouth. PWATs currently sit above the 99th percentile (1.8"-2") here and upstream towards the Gulf. Strong integrated moisture transport and training convection will aid in very heavy, long-lasting rain rates starting this afternoon. Mean storm motion is not expected to change much between tonight and Saturday evening. Expect north/south bands of significant rainfall. Furthermore, much of the region has already experienced 4-7 inches of rain. These saturated soils will fail to contain new rainfall accumulations which are expected to be as high as 6-10 inches through Sunday over western Tennessee, Arkansas, and extreme northern Mississippi. Any areas that have already experienced this rainfall will flood quickly. So heed warnings immediately!

The upper pattern will then slow down after the upper trough exits to our east. Northwest flow is expected to prevail over the region for several days, with high pressure as the surface. This regime will keep cooler than average temperatures around through Tuesday with temperatures expected to warm into Wednesday and Thursday ahead of a new upper surface low to our northwest. Moisture is expected to be scoured off the Gulf as far south as the Yucatan Peninsula. Therefore, significant moisture return is unlikely as continental air is recycled into the CONUS. Some showers could occur Thursday afternoon as the upper system responsible for the surface low passes through, but no significant threat for severe weather is anticipated at this time.

AVIATION

(06Z TAFS) Issued at 1201 PM CDT Fri Apr 4 2025

TSRA remains the primary forecast concern over the next 24 hours. Latest radar trends suggest TSRA chances at MEM will increase by 09Z and continue for several hours. This may stabilize the atmosphere sufficiently to limit strong wind potential associated with the final push of TSRA in the early afternoon. Too soon to say at this point. In any case, TSRA will be the rule through all TAF sites but TUP through the night and the morning daylight hours.

PWB

MEG WATCHES/WARNINGS/ADVISORIES

AR...Flood Watch through Sunday morning for ARZ009-018-026>028-035- 036-048-049-058.

MO...Flood Watch through Sunday morning for MOZ113-115.

MS...Flood Watch through Sunday morning for MSZ001>005-007-008- 010>014-020.

Flood Watch through Sunday afternoon for MSZ006-009-015>017- 021>024.

TN...Flood Watch through Sunday morning for TNZ001>004-019>022- 048>055-088>092.