FOUS30 KWBC 061601 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1201 PM EDT Tue Oct 6 2026 Day 1 Valid 16Z Tue Oct 06 2026 - 12Z Wed Oct 07 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF FLORIDA AND FAR SOUTHEASTERN GEORGIA... 16Z Update... No significant changes were made to the previous forecast. The HREF/REFS continue to indicate widespread amounts 1-3 inches are likely within the Marginal Risk area, with higher probabilities for heavier totals focused along the coastal regions. This includes the First Coast, where northeasterly flow on the north side of the stalled front is expected to support localized heavier amounts. Urbanized and poor drainage areas in and around the Jacksonville metro are more likely to see instances of flash flooding. Pereira Previous discussion... A very slow-moving front will sag southward from Georgia and Alabama into north Florida today. A very dry and refreshingly cool air mass lies north of the front, while a very tropical, moisture- rich air mass lies south of it. This large discrepancy between air masses means the front is strong, and will effectively uplift the tropical air mass, resulting in more of the same for north Florida. Very slow-moving tropical showers with occasional embedded thunderstorms will continue today. A widespread 1 to 3 inches of rain is expected over much of north Florida. The flooding potential remains Marginal. While soils are saturated from prior days' rains, the flat terrain, generally low rainfall rates due to marginal instability, and swampy areas should all continue to handle most of the rain well. Thus, the isolated flooding threat is really targeted towards urban and poor-drainage areas. Like yesterday, there could be localized areas where heavier rain rates from training storms could cause more widely scattered instances of flash flooding, but those should be largely hit and miss. Wegman Day 2 Valid 12Z Wed Oct 07 2026 - 12Z Thu Oct 08 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE FLORIDA PENINSULA... The cold front sagging south into north Florida will stall out near the Big Bend and the First Coast on Wednesday, becoming a stationary front. The contrasting air masses on either side of the front will remain extremely different, with dry air to the north, and very soupy air to the south. Thus, the front will remain a very effective boundary for the tropical air mass south of the front to leverage to produce lift and locally heavy rain. The southward progress of the front will allow the I-10 corridor to get a break, relatively-speaking. While rain will the a threat there, the amounts will be significantly lower than further south, as dry air intrudes on north Florida. Meanwhile, on Wednesday the front will more intensely target the I-4 corridor, especially on the Gulf Coast side, where the heaviest rainfall amounts (1-3 inches) are most likely. Meanwhile on the Atlantic side, expect a general 1-2 inches of rain. The format of the rain remains the same. Slow- moving showers with embedded thunderstorms. Most of the time the rain rates will be light, but where storms train, very localized heavier amounts to 6 inches are possible. Flat terrain and sandy soils, even if saturated, should limit the flash flooding threat once again to urban and poor-drainage areas. The rainfall amounts needed to get more significant flooding will be few and far between. Wegman Day 3 Valid 12Z Thu Oct 08 2026 - 12Z Fri Oct 09 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF FLORIDA... The front that stalled across Florida on Wednesday will begin to retreat northward as a warm front on Thursday. Thus, the swath of heaviest rainfall will return to much of north Florida, though the Panhandle may escape the heaviest rains for one more day. For the most part, it's a rinse-and-repeat pattern. The front remains a distinct dividing line between the soupy, tropical air mass to the south, and a much drier one to the north. Thus, more of the same is expected again on Thursday. Expect slow-moving showers and light rain for most areas most of the time. However, there will be embedded thunderstorms that if there is training or sufficient time for a single cell to be parked over a given area, isolated flash flooding is possible. Thus, the Marginal Risk remains in place, much like the prior 2 days. This will be the last day of this pattern, as the circulation associated with AL92 begins to make its way northeast across the Gulf from the Bay of Campeche. Thus will spur on a much more widespread and significantly heavier rainfall threat into the Gulf Coast for Friday into the weekend. Wegman Day 4 and Day 5 Valid 12Z Fri Oct 09 2026 - 12Z Sun Oct 11 2026 ...A SLIGHT RISK OF EXCESSIVE RAINFALL ALONG PARTS OF THE NORTHERN GULF COAST ON FRIDAY EXPANDS ACROSS THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS AND SOUTHEAST OVER THE WEEKEND... The guidance is beginning to converge on a rather wet pattern Friday into the weekend across central and eastern portions of the Gulf Coast and areas inland across the Lower MS Valley, Lower TN Valley, and Southeast. A big reason for this will be the possible development and track of a tropical cyclone this week, though other more synoptic-scale details will factor in as well. At this point (4-5 days out), uncertainties (spatial and temporal) exist not only with the possible tropical development, but also with the possible interaction (and timing) of this system being absorbed by the upper trough pivoting across the Lower MS Valley over the weekend. The 00Z 10/6 operational ECMWF was faster than the GFS in terms of this extratropical transition, while the CMC was slowest and farthest west. Given the timing and areal spread in the guidance, including the AI models (00Z 10/6 EC-AIFS even faster than the operational ECMWF), while we feel confident ramping up the ERO risk areas on Days 4-5 (high-end Slight by Day 5), per collaboration with the WFOs along the northern Gulf Coast, we opted to hold off on a Moderate Risk at this point. This is consistent with the messaging from the local WFOs as well as with the current Key Messages from the NHC. Forecast confidence in a swath of at least 3-7" of rainfall continues to grow per the latest global QPF trends, though the potential for more (or less) will be highly dependent on the speed of the Gulf system and extratropical transition with the approaching upper trough. For further details regarding the potential of tropical cyclone development in the Gulf, please refer to the latest Tropical Weather Outlook from the NHC. Hurley 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 $$