891 FOUS30 KWBC 160819 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 419 AM EDT Fri Oct 16 2026 Day 1 Valid 12Z Fri Oct 16 2026 - 12Z Sat Oct 17 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF CENTRAL/SOUTH FLORIDA AND WEST TEXAS... Locally heavy to potentially excessive rainfall will be possible today across portions of the central and southern Florida peninsula given the moist and unstable airmass in place and expected slow storm motion. The Marginal Risk continues to highlight the area where the HREF and REFS both generally show higher (greater than 50 percent) probabilities for accumulations exceeding 3 inches. Bann Day 2 Valid 12Z Sat Oct 17 2026 - 12Z Sun Oct 18 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG PORTIONS OF THE FLORIDA EAST COAST... Showers and thunderstorms...some capable of producing localized downpours that result in flooding...should develop along and ahead of a cold front making its way southward across the Florida peninsula on Saturday. Both the HreF/RRFS guidance develop low-end probabilities of flash flood guidance near the front during the time of maximum diurnal heating. Rainfall rates of locally 2-3"/hr within any convective cores suggest isolated totals of 4-6" are very much plausible. The previous MRGL risk was maintained with no adjustment. Bann Day 3 Valid 12Z Sun Oct 18 2026 - 12Z Mon Oct 19 2026 ...MARGINAL RISKS OF EXCESSIVE RAINFALL EXIST FOR THE GOLD COAST OF FLORIDA SUNDAY... ...FL Gold Coast... A well defined cold front is expected to press southward before stalling south of Florida on Monday. Moderate to strong post- frontal on-shore flow Low level flow will focus moisture flux convergence in proximity of the front. Strong boundary layer convergence maxima likely along the east central coast of Florida, which would be strongest overnight will support potential for locally heavy rains from well defined rain bands that may train for periods early Sunday. There has been a subtle southward shift in the placement of the rainfall compared with previous model runs...but spaghetti plots from the ECMWF Ensembles and the GEFS ensembles still indicate that some potential lingers for 3+ inch amounts during the period. Consequently...shrunk the Marginal risk area somewhat but did not remove it. Bann Day 4 and Day 5 Valid 12Z Mon Oct 19 2026 - 12Z Wed Oct 21 2026 ...MARGINAL RISKS OF EXCESSIVE RAINFALL EXIST FOR PORTIONS OF THE EAST COAST MONDAY INTO WEDNESDAY MORNING... ...Eastern NC/Southeast VA... The guidance is trending more towards an occluded low not far off the Southeast Coast, which could have some interior convection as -18C air at 500 hPa moves over 28-29C sea surface temperatures during the short range period and perhaps a convective comma head/TROWAL which feeds off additional instability from the western subtropical North Atlantic. Wet solutions are now shown on the 00z Canadian and 00z ECMWF, with the 00z GFS barely off the coast with its heavy rain signal Monday/Monday night before it ejects the cyclone northeast due to a slightly stronger shortwave moving through Atlantic Canada. The 00z ECMWF AIFS and 00z AIGFS are supportive of their control/operational runs respectively. Since support appears to be slowly increasing and spread generally decreasing. left the Marginal Risk from continuity for coastal NC/VA for Monday/Monday night and introduced a new MRGL for a similar locale Tuesday/Tuesday night. ...Southwest... There was consideration for a Marginal Risk for portions of southeast and central AZ to the southeast and eventually east of a deep layer cyclone/"outside slider" moving west of CA, but the atmosphere didn't appear to be sufficiently saturated with 0.75-1" precipitable water values in an environment with 5640-5670 decameter 1000-500 hPa thickness. MU CAPE also appears skimpy, with only small pockets of 250 J/kg forecast by the 00z GFS and 100 J/kg by the 00z ECMWF. While the threat for flash flooding/ excessive rainfall may be non-zero, did not feel it was up to the Marginal Risk threshold so left risk areas out, for the time being. This can be re-evaluated in later cycles. Roth 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 $$