331 FOUS30 KWBC 051927 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 327 PM EDT Mon Oct 5 2026 Day 1 Valid 16Z Mon Oct 05 2026 - 12Z Tue Oct 06 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE SOUTHERN LOWER TEXAS COAST... ...Lower Texas Coast... 16Z Update: In coordination with local Brownsville WFO and in regards to the latest radar and short term trends in guidance, the SLGT risk was removed and replaced with a small MRGL to account for an isolated flash flood threat near and east of the Brownsville. HREF neighborhood probs for >3" on the latest 12z output continues to show a relatively modest threat for locally heavy rainfall near and just east of Brownsville proper. Heaviest rain has mainly been confined to South Padre Island and the southern most tip of TX leading to lower end threats for flash flooding. Recent CAMs indicate the best potential holding between now and just before the end of the afternoon before fading as the best convergent area and instability will align just off the coast for the overnight period. A few cells may try to sneak in off the nearby Gulf waters, but the prospects decrease just based on the hourly probabilities for >1"/hr. The SLGT risk was downgraded to just a MRGL risk, restricted to mainly eastern Cameron county and coastal Willacy. Kleebauer ...Southeast... 16Z Update: Our cold front is making a bit more of a steady southern progression this morning with the 12z surface analysis depicting the front right along the FL/GA border with an expectation for the front to bisect northern FL by later this afternoon. The threat is dwindling for the northern extent of the previous MRGL risk with the best chances for any locally heavy rainfall occurring now into the early afternoon hours over southern and eastern GA back into southern AL before ceasing by the evening. Best signature for heavy rainfall and totals between 2-4" will reside over the FL Panhandle between Destin to the Big Bend and up through the interior, near and west of Tallahassee. HREF and REFS EAS signatures for >2" are highest within that zone encompassing the Apalachicola Forest and the coastal towns along US98, an area that is traditionally hard to flood due to the sandier soils and the necessity for fairly elevated rates >3"/hr, outside a few towns like Panama City Beach and Apalachicola proper. The threat in those areas remains lower end given the setup and the greatest ascent lifting out of the region through the course of the afternoon. Some indications that convection off the nearby Gulf this evening can send an outflow or two towards land and create a localized area of enhanced rainfall along the immediate coast. This signature is hit or miss within the CAMs, but the threat is certainly non-zero for something like this to occur. PWATs between 2.3-2.5" reside in this area ahead of the cold front, so the environment is ripe for more efficient warm rain processes and potential for locally >2"/hr. In this case, the MRGL for the Panhandle area is more than sufficient. Further east, frictional convergence along the front between Savannah down through Jacksonville to St.Augustine will lead to isolated flash flood concerns along the I-95 corridor as the environment remains ripe with PWATs on the 12z KJAX sounding up at 2.44" this morning with a textbook tall, skinny CAPE signature that correlates positively to heavy rain prospects. HREF and REFS neighborhood probs for >5" are between 40-60% for that coastal area between GA/FL but low EAS probabilities for >2" signal the threat to be more isolated to widely scattered with the best risk tied to those urban zones due to higher run off potential. Some convection along the sea breeze further inland is also plausible with rates between 2-3"/hr at peak intensity, but considering the pulse nature of the convection, storms will have limited time before dwindling in intensity, thus only generating short windows of opportunity to promote flash flooding. The MRGL risk exists over northern and central FL into eastern GA given all of the above. Kleebauer Day 2 Valid 12Z Tue Oct 06 2026 - 12Z Wed Oct 07 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE LOWER TEXAS COAST, FAR SOUTHERN GEORGIA, AND MUCH OF FLORIDA... 20Z Update: Removed the MRGL risk across South TX as the setup remains more prevalent for heavier convection offshore from South Padre Island with the immediate coast the most notable area from an impact standpoint. If trends move back closer to the Brownsville area, then perhaps the MRGL returns, but the trends for less precip inland to the urban centers lends to a removal with the mention of the non-zero threat in far eastern Cameron and Willacy counties. ...Florida and Georgia... 20Z Update: Stalled front across FL will lead to a continued heavy rain threat as pooling moisture and persistent convergence across the Peninsula with modest instability will generate another period of scattered convection for areas north of I-75 in South FL. Models continue to converge on a signal that shows the greatest potential located in-of the immediate coast, mainly for areas like Tampa/Clearwater on the western coast, and the area between Jacksonville to Port St. Lucie on the eastern side of the Peninsula. The reasoning is just due to the frictional convergence pattern along the coast with prevailing easterly winds near the front itself, creating the threat for efficient rain makers wherever they transpire. Models generally signaling locally 2-4" with a threat for higher in any slow-moving thunderstorms that linger over a given area. 12z HREF and REFS EAS fields overlap with modest probs for >2" over the west-central coast of FL where each ensemble depicts the location of the front for Tuesday afternoon and evening. A little more discrepancy over the eastern FL coast with the HREF signaling a threat closer to St. Augustine and the REFS a bit further north into Jacksonville. Given the signal, maintain general continuity in the MRGL risk inherited with just some minor adjustments to the area of north-central FL between Tallahassee and Jacksonville where guidance indicates an areal minimum in the QPF distribution. Kleebauer Day 3 Valid 12Z Wed Oct 07 2026 - 12Z Thu Oct 08 2026 ...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF THE FLORIDA PENINSULA, THE LOWER TEXAS COAST, AND SOUTHWEST TEXAS... 20Z Update: Removed the MRGL risks across both South TX and Southwest Texas given the latest trends in guidance, and in coordination with local offices. Both these areas will see an uptick in the threat as we move later in the week, so be sure to review the D4/5 ERO forecasts for each respective area. Kleebauer ...Florida... 20Z Update: Little change to the previous forecast as the general pattern and convective potential remain on track with run to run continuity based on the latest guidance. Locally heavy rainfall with the best threat along each coast (Tampa/Clearwater on the west coast and St. Augustine to Port St. Lucie on the east coast) will lead to isolated flash flood concerns as the environment in place remains capable in producing rainfall rates between 2-3"/hr in any given cell that initiates. The MRGL risk remains forecast for the period. Kleebauer ..Previous Discussion.. The front over the middle of the Florida Peninsula will end it's slow southward movement on Wednesday and stall out over the area. Fortunately, with the front no longer providing forcing for storms, any rainfall will be driven by cold pools, proximity to other storms, and localized pockets of higher instability. The point is that there will be no organization to the convection, so the flash flooding threat will remain Marginal, contingent on heavy rain impacting an urban or poor-drainage area. Wegman Day 4 and Day 5 Valid 12Z Thu Oct 08 2026 - 12Z Sat Oct 10 2026 ...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF NORTH-CENTRAL AND NORTHEAST GULF COAST... The excessive rainfall risk late this week is related to a disturbed weather area near the tail of a front currently in the Bay of Campeche. High precipitable water values and instability move in to portions of the Gulf Coast and the TX Big Bend on Thursday/Thursday night to produce a Marginal Risk of flash flooding but shift to portions of the north- central and northeast Gulf Coast Friday/Friday night. Ample moisture, effective bulk shear, and instability should lie within the cyclone's environment, in addition to upper level jet dynamics from its existence near a frontal zone. Due to the southwesterly vertical wind shear present, the cyclone's convective structure should be asymmetric, with a bulk of the activity lying to its northeast. Introduced a Slight Risk from southernmost AL across the FL Panhandle and Big Bend to account for its forecast movement and asymmetry. Hourly rain amounts to 3" with local totals to 6" are possible for locations within the risk areas. 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 $$