BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Sun, 15 Mar 2026 00:34:11 +0000 ----------------------------------------------------------- FOUS30 KWBC 150033 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 833 PM EDT Sat Mar 14 2026 Day 1 Valid 01Z Sun Mar 15 2026 - 12Z Sun Mar 15 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. ...Southern Florida... Isolated to widely scattered showers and thunderstorms formed this afternoon and appear to be in decline now, which exhibited hourly=20 rain amounts to 2" and local totals to 3" not far from Belle Glade. The 18z HREF appears to have a better handle on the current state=20 of FL convection than the 12z REFS. Overnight, the piece of the=20 polar front that's been languishing near the southern peninsula and the coastal front across the central peninsula lift northward,=20 with low-level flow becoming southerly by Sunday morning. This is=20 not the usual synoptic pattern for overnight heavy rainfall for the southern peninsula but it can concentrate convection just offshore eastern FL near the Gulf Stream -- the 12z REFS and 18z HREF=20 guidance shows very low to low chances for 3"+ totals over the=20 southern peninsula during the early morning hours, which appears to support that idea. The ERO has been left blank as the chances for=20 flash flooding still appear less than 5 percent. Roth Day 2 Valid 12Z Sun Mar 15 2026 - 12Z Mon Mar 16 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Some consideration was given to a Marginal risk across portions of the OH and TN valley where strong to severe convection is likely Sunday afternoon into the overnight. Working against a flash flood risk is the quick movement of the cold front and squall line leading to only a short duration of heavier rain rates. High res models currently cap hourly rainfall in the 0.75" to 1.25" range, which is below FFG. Given the intense nature of convection, it will only take some brief training or cell mergers to get rainfall towards 2", which would be enough for localized flash flooding. We will continue to monitor, but for now will keep no areas in the ERO with the risk still considered below 5 percent. Chenard Day 3 Valid 12Z Mon Mar 16 2026 - 12Z Tue Mar 17 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE NORTHEASTERN U.S... 19z Update: Only change to the inherited Marginal risk was to expand it a bit farther southwest into portions of the Mid- Atlantic and more into upstate NY. In general, two day rainfall of 1-2" is expected, with quick moving convection Monday afternoon/evening capable of dropping a quick 1" of rain within an hour. This may be enough for localized, mainly minor, flash flood impacts. Chenard ...Previous Discussion... Highly meridional setup expected this weekend, carrying into early next week as a powerful cyclone materializes over the Midwest and Great Lakes sending a strong cold front migrating west to east for areas east of the Mississippi. Ahead of the front, a strong warm air and deep moisture advection regime will couple to send PWATs surging between 2-4 standard deviations above normal for areas east of the Appalachians on Monday along with modest instability of MUCAPE between 500-1000 J/kg over the Mid Atlantic and 200-400 J/kg as far north as Central New England. Increased forcing at both the surface with the approach of the cold front, as well as favorable upper dynamics comprised of textbook diffluent flow aloft within the RER of a 160kt jet will allow for quite the developing QLCS structure off the lee-side of the Appalachians, pushing east into the Piedmont, eventually to the coastal plain the end of the period. Current QPF forecast is generally between 1-2" with a maxima focused over Southern New England thanks to a multi-round setup of heavy rain over that area. Setup will be relatively progressive, but rates between 1-2"/hr at peak intensity should spur some issues for flash flooding across the urban corridor along I-95. Add in snow and ice melt across New England with the expected heavy rain and the prospects for flash flooding will increase thanks to the anomalous setup. Will be monitoring the trends in QPF closely as the forecast is still outside the CAMs window. Convective nature of the precipitation should provide some opportunity for local maxima during the evolution on Monday and Monday night. Maintained general continuity from the previous forecast of a broad MRGL encompassing eastern PA up through Northern New England. Did make some minor adjustments on the northern fringes as heaviest precip does look to avoid some areas of far northern New England, including the Champlain Valley up through northwest ME where guidance has reflected a general min in the QPF distribution. Stay tuned over the coming days as this setup has merit for a potential upgrade across parts of the Northeastern CONUS. Kleebauer Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-oOZdeSl-m5qfpXAU1GOLp2opGUpD3oYEfJuDSfKC2CT= MpUo-JrkcO5BZIG8mHFnqrnfubzCUinia3QQGaEA-tNt4q8$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-oOZdeSl-m5qfpXAU1GOLp2opGUpD3oYEfJuDSfKC2CT= MpUo-JrkcO5BZIG8mHFnqrnfubzCUinia3QQGaEA205TsBM$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-oOZdeSl-m5qfpXAU1GOLp2opGUpD3oYEfJuDSfKC2CT= MpUo-JrkcO5BZIG8mHFnqrnfubzCUinia3QQGaEApfZ1jFw$=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: Capitol City Online (1:2320/107) ----------------------------------------------------------- [Voltar]