Subj : HVYRAIN: Excessive Rainfa To : All From : Mike Powell Date : Sat Feb 10 2024 08:47:00 FOUS30 KWBC 100830 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 330 AM EST Sat Feb 10 2024 Day 1 Valid 12Z Sat Feb 10 2024 - 12Z Sun Feb 11 2024 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE GULF COAST STATES TO THE SOUTHEAST U.S... Convection capable of producing heavy rainfall will develop today from portions of the Gulf Coast that spreads east/northeast with time as large scale ascent increases ahead of a vigorous upper makes its way out of the southern Rockies. Between enhanced flow of Gulf moisture and increasingly diflent flow aloft...the model QPF of 1 to 3 inches with isolated maximum amounts over 4 inches seem to be reasonable along a quasi-stationary front extending across the region. With more CAMs becoming available, made a few minor adjustments to the previously issued ERO but the overall forecast reasoning has changed little. Bann Day 2 Valid 12Z Sun Feb 11 2024 - 12Z Mon Feb 12 2024 ....THERE IS A MARGINAL RISK AREA OVER PORTIONS OF THE SOUTHEAST U.S. ON SUNDAY... Guidance continue to depict an areal footprint of QPF across the Gulf states and into the Southeast U.S. during this period as one shortwave scoots eastward early in the period and cyclogenesis occurs vigorous shortwave trough continues to head towards the north/northeast followed by deep layered cyclogenesis over the southern Plains and southern Mississippi Valley. This reinvigorates the on-shore flow of Gulf moisture and results in the flow aloft becoming increasingly difluent. While there is some overlap with a northwest to southeast stripe in Alabama where 14-day rainfall amounts of a couple inches was observed...the axis of heaviest rain should generally be over areas that have had little or no rainfall recently. With WPC deterministic QPF generally below 2 inches...felt a Marginal risk area still adequately covers the risk of excessive rainfall. Bann Day 3 Valid 12Z Mon Feb 12 2024 - 12Z Tue Feb 13 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHEAST U.S.... There is a continuing threat of excessive rainfall on Monday...mainly over the Carolinas...as the large scale system moves over parts of the Tennessee Valley. At the surface...one area of low pressure forms and heads northeast over the far eastern TN/OH Valleys while a second area of low pressure forms over parts of the Carolinas...supported by the coupling of upper level jets and the associated vertical velocities supported by the upper level divergence. It is this component which results in the continued risk of excessive rainfall over the Southeast from Monday into the early-morning hours on Tuesday. Precipitable water values increase to values at or slightly above 1.75 inches ahead of a cold front sweeping across the region. Deterministic QPF from the GFS and UKMET seem better than the ECMWF and Canadian and tend to be aligned with the WPC deterministic amounts. Given high FFG numbers...especially where spaghetti plots of model QPF are 2 or 3 inches overlap...will keep the Marginal carried by the WPC Medium Range Desk yesterday. Bann $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .