Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Oct 07 2025 08:15:28 FOUS30 KWBC 070815 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 415 AM EDT Tue Oct 7 2025 Day 1 Valid 12Z Tue Oct 07 2025 - 12Z Wed Oct 08 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF KENTUCKY, MIDDLE TENNESSEE, THE UPPER OHIO VALLEY, AND NEW MEXICO... ....Mid-South through the Upper Ohio Valley and Central Appalachians... A weak mid-level vorticity maxima (currently over far northeastern Arkansas) will trek east-northeastward across Kentucky through=20 most of the day. This feature will likely maintain at least some of its organization given persistent convection near and east of its=20 center and sufficient downstream instability. Areas of 1-3 inch=20 rainfall totals are expected with this feature, and an uptick in=20 convective coverage should occur later today as surface heating=20 promotes destabilization within a moist airmass downstream of the=20 feature. Slow cell movement and localized training/backbuilding are both expected to prompt areas of excessive runoff through the=20 forecast period especially within the Slight Risk area. Later today, height falls from a larger scale trough centered over Hudson Bay will aid in additional convection along a front that will sweep through the region. Storms may redevelop across Kentucky and Tennessee, although the degree of coverage will be heavily=20 modulated by the degree of lingering instability behind the initial wave of daytime convection expected across those areas. A pool of=20 at least 1.5 inch PW values should remain - supporting heavy=20 rainfall with any lingering convection through the evening hours. Additional convection is expected along the aforementioned cold front across New York State and western New England. Storm motions should be relatively fast (30+ knots), limiting any heavy rainfall to any localized areas of training that can materialize. Additionally, antecedent dryness/drought should limit excessive runoff potential. A Marginal risk extends to western Pennsylvania and vicinity - although this risk seems a bit too isolated farther northward to include or expand in any probabilities at this time. ....New Mexico... A southwestward moving cold front will stall close to the higher terrain across central New Mexico today through tonight. Upslope flow behind this front and weak mid/upper waves traversing the state will both initiate deep convection within a sufficiently moist airmass (0.7-1.25 inch PW) for heavy rainfall. Storm motions across northern portions of the state may be quick enough to limit rainfall, yielding a mostly isolated flash flood threat in areas=20 that are sensitive (i.e., burn scars, low-lying areas). Central and southern portions of the state should experience slower storm=20 motions and perhaps multiple rounds of convection from afternoon=20 through the overnight hours. Given increase in convective coverage=20 and potential for local 3+ inch rainfall totals occurring=20 perilously close to sensitive areas/burn scars, a Slight Risk was=20 introduced with the expectation of at least a few instances of=20 excessive runoff given the scenario. Cook Day 2 Valid 12Z Wed Oct 08 2025 - 12Z Thu Oct 09 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF NEW MEXICO AND EASTERN ARIZONA... Some continuation of heavy rainfall potential will exist across New Mexico during the early morning hours of the D2/Wed forecast period. During the day, an increase in insolation/destabiliztaion should promote development of isolated to scattered thunderstorms initially along terrain/ridgelines near the Arizona/New Mexico border and across the southern Rockies. Storms will drift slowly/erratically while producing brief heavy rainfall. Typical low spots/sensitive areas will experience a flash flood threat with this activity. Coverage of flash flood potential should be sparse enough to warrant continuation of a Marginal Risk and associated probabilities. Cook Day 3 Valid 12Z Thu Oct 09 2025 - 12Z Fri Oct 10 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS A LARGE PART OF THE SOUTHWEST... Models are consistent in depicting a dramatic increas in atmospheric moisture content across the Colorado River Valley from both Hurricane Priscilla and the Gulf of California. Widespread 1-1.75 inch PW values are expected by midday Thursday. This=20 moisture will combine with deep southwesterly steering flow and=20 weak mid-level waves aloft to produce several areas of=20 precipitation throughout the forecast period (including the=20 overnight and early morning hours). A close inspection of point=20 forecast soundings from model data casts some doubt on the extent=20 of instability developing within the moist axis due to widespread=20 cloud cover. Any daytime destabilization within the region will=20 likely lead to stronger convection and an increased risk of flash=20 flooding. Trends in instability will be monitored for possible=20 upgrades in parts of the Marginal Risk area in later outlooks. Cook Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8216NDDt0pvM6YTMTYszZyVcIfwfbBSVcCDMcYi21jq3= U6Q03jnHx9hRbiqYUPYeUcOQWv1120qteRSaLHkDjFOmrPg$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8216NDDt0pvM6YTMTYszZyVcIfwfbBSVcCDMcYi21jq3= U6Q03jnHx9hRbiqYUPYeUcOQWv1120qteRSaLHkDqTsE9Yc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8216NDDt0pvM6YTMTYszZyVcIfwfbBSVcCDMcYi21jq3= U6Q03jnHx9hRbiqYUPYeUcOQWv1120qteRSaLHkDi-aInFQ$=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .