Quantitative Precipitation Forecast
Issued by NWS
Issued by NWS
864 FOUS30 KWBC 140054 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 854 PM EDT Mon May 13 2024 Day 1 Valid 01Z Tue May 14 2024 - 12Z Tue May 14 2024 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR COASTAL PORTIONS OF THE CENTRAL GULF COAST... 01Z Update...The strong convection that has been over coastal portions of Texas this afternoon has moved off the coast, with the exception of some supercells across Deep South Texas that should exit the region by 9 pm CDT. Therefore, the existing Marginal and Slight Risk areas over southern Texas and western Louisiana have been trimmed back to account for current radar trends. Farther east, the existing Moderate Risk area over the central Gulf Coast has been scaled back to include just the coastal counties from far southeastern Mississippi to the western Florida Panhandle. The latest CAM guidance suggests the best instability will not make much northward progress, but an incoming MCS from Louisiana tracking across areas with heavy rainfall earlier today support maintaining a broad Slight Risk area and the coastal Moderate Risk. A small Slight Risk area has been added for portions of southeast Missouri and northeast Arkansas to account for a stronger signal in the CAM guidance for swaths of heavier rainfall later tonight that would be indicative of some convective training, with QPF maxima on the order of 2-3 inches through 12Z. There are also some signals in the HREF guidance for some instances of flash flood guidance exceedance across this region. The previous forecast discussion is appended below for reference. Hamrick ------------------------ ...Gulf Coast... A powerful MCS continues to work east along a stationary front over the central Gulf Coast this morning with particularly heavy rain as noted in MPD 264 which is out until 18Z. This MCS will push the frontal boundary to or south of the Gulf Coast, but there is still confidence on more scattered activity to continue along the Gulf Coast this afternoon ahead of a cold front from the central US low that sweeps east from Texas tonight. The Moderate Risk was shrunk toward the central Gulf Coast while also expanding east a bit more over the FL Panhandle on account of radar trends and the 12Z CAM consensus. Convective activity ahead of this cold front has initiated over south-central TX east of Del Rio with a now organized multi- cell cluster of heavy thunderstorms that are moving east over the San Antonio metro as noted in MPD 265 which is out until 2130Z. This south-central TX activity will push east to the Houston metro this afternoon along with other development along the stationary boundary just inland from the Gulf Coast. The Marginal and Slight Risks in TX were stretched east to account for this activity and 12Z CAM consensus for its development. ...Mid-South and Southeast... The Marginal Risk was able to be trimmed based on update positioning of the prefrontal activity on the west side and the 12Z CAM consensus for heavier rain over the Southeast. Much of the Day 1 Marginal over the southeast was removed based on increased confidence on less rainfall this afternoon over the far southern Appalachians as well as with timing for overnight activity approaching the TN Valley overnight. The cold frontal convection will have a fast forward speed across Arkansas and southern Missouri. Should the convection move over a particularly sensitive area, isolated flash flooding is possible. ...Portions of the Midwest... Maintained the Slight from KC to Chicago though this is certainly low end given 12Z CAM QPF progs of generally 1-2" with local 3" through this swath which follows the warm frontal interface ahead of the developing low over Kansas and eventually southern Missouri. Convection in the warm sector will collide into the warm front, which will remain largely stationary. This in turn may result in localized training along that boundary. Further monitoring of localized flash flood concerns for sensitive areas such as the St. Louis metro area. Jackson Day 2 Valid 12Z Tue May 14 2024 - 12Z Wed May 15 2024 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR A PORTION OF NORTH FLORIDA... 21Z Update... ...North Florida... Organized convection is crossing north Florida this afternoon with the main focus a bit farther south than previously progged. The 18Z HRRR places 1-4" through this evening in a stripe north of Tampa and south of 30N. The next round of heavy thunderstorms is organizing over east Texas this afternoon and will track east overnight, crossing north Florida early Tuesday. The 18Z HRRR has a stripe of 1-5" over north Florida also contained between Tampa and 30N. Given this overlap risk of heavy rain, the Slight Risk was shifted south to the northern Florida Peninsula. With 2" PW and unilateral SW flow allowing repeating activity,any storms will be capable of rates of 2 inches per hour. ...Portions of the Southeast, Mid-Atlantic, and Ohio and Tennessee Valleys... Mid-level low pressure shifts east from Missouri to the central OH Valley with the associated cold front pushing across the Southeast through Tuesday night. Prefrontal conditions of PW 1.5 to 2 sigma above normal and sufficient instability warrant a continued Marginal Risk for localized flash flooding (mainly for cell mergers and training). 12Z guidance has increased confidence on a more progressive front which allows less of AL/GA to need a Marginal and a focus more over the southern Apps/Carolinas into Virginia. The northern end of the Marginal was shifted south a bit into Maryland based on progs for heavier QPF tracks in the 12Z/18Z consensus. Further north and west, the parent low and associated upper level cold air will result in widely scattered convection for the Ohio/Tennessee Valleys. Instability will be modest, but a PW anomaly warrants continued Marginal Risk for localized areas where cell mergers or training occur. Jackson Day 3 Valid 12Z Wed May 15 2024 - 12Z Thu May 16 2024 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE SOUTHERN PLAINS AND TEXAS AS WELL AS A PORTION OF NORTH FLORIDA... 21Z Update... ...Southern Plains... The next trough crosses the northern Rockies Tuesday night with lee-side troughing over the TX Panhandle through central OK on Wednesday. Convection develops on the leading edge of return flow associated with an LLJ that will move north along the west Texas dryline is expected to be isolated to widely scattered in coverage Wednesday afternoon, becoming more numerous by Wednesday night across north Texas and western Oklahoma and back over eastern Colorado. Other activity over south-central TX could also develop and spread east, so the Marginal Risk further increases in size for now. A targeted Slight is possible once the heaviest corridor is honed in on. ...Northeast Florida... The trailing end of a cold front will slowly progress south over the Florida Peninsula on Wednesday. South of the front, abundant Gulf moisture will stream eastward along the boundary, providing a focus for convection to develop. Thus, a small Marginal remains for the northern Florida Peninsula due to ongoing convection in the morning getting into the Tampa Bay metro up through Orlando. Jackson Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt