BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Sun, 15 Mar 2026 23:42:45 +0000 ----------------------------------------------------------- FOUS30 KWBC 152342 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 742 PM EDT Sun Mar 15 2026 Day 1 Valid 01Z Mon Mar 16 2026 - 12Z Mon Mar 16 2026 Heavy rainfall is Florida is generally on the wane, and severe=20 convection in the Midwest has been dropping hourly rain=20 amounts/local totals of 0.5-1.25" while remaining quite=20 progressive, which should continue through tonight as the activity dives into the Southeast. The probability of rainfall exceeding flash flood guidance is less than 5 percent. Roth Day 2 Valid 12Z Mon Mar 16 2026 - 12Z Tue Mar 17 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MID-ATLANTIC AND NORTHEASTERN U.S & EXTREME NORTHWEST WASHINGTON... 19z Update: Forecast looks on track. Nothing in the 12z high res guidance supports any changes to the inherited Marginal risk areas. Chenard ...Mid-Atlantic into Northeast... Highly meridional moisture surge will be already ongoing at the start of the forecast period (16.12z) as the leading edge of the Atlantic warm front should be lifting through southern New England and Gulf of Maine. Upstream the highly dynamic cyclone will be well occluded through depth across the north-central Great Lakes with a powerful near 980mb surface low and attendant sharp cold front extending due south across the Mid-Ohio Valley, Cumberland Plateau into the central Deep South. The based of the large scale trough will be lifting northeastward providing solid dPVA to support strengthening deep layer southerly flow further compounding on the initial warm advective surge through out of the Southeast through the Mid-Atlantic. Integrated Vapor Transport (IVT) values will increase from upper hundreds of kg/m/s toward 1250 kg/m/s across the Coastal Plain into southern New England eventually reaching values over 1400 kg/m/s after 00z through S ME due to the combining strength of the LLJ and confluent moisture streams off the Eastern Gulf and Western Atlantic. This brings moisture flux well above 97-99th+ percentiles of moisture flux. Instability will be a limiting factor for vertical development along/ahead of the cold front but some 250-750 J/kg will be available through the central Mid- Atlantic with some localized convergence for scattered showers and thunderstorms prior to the main cold front/squall line to emerge out of the Appalachian terrain by mid-day. These initial cells should be quick moving and limited in total, but any that broaden into stronger isolated super-cells may have capability for locally intense rates prior to the main line. Still, the main focus will be the hourly to sub- hourly 1-1.5+" totals with the main convective line that will have greatest potential for localized, mainly minor flash flooding impacts. Hydrologically, the Northeast remains highly saturated and cold through depth with modest SWE in some remaining snow pack. So, while the rain rates will likely be much lower due to lack of deep unstable/vertical shower activity; the orographic ascent and should remain concerning that any rain on snow will further compound the ongoing hydrologic/stream rises (please refer to National Water Center FHO and Local River Forecast Center forecasts for further river concerns across this region). As such a broad Marginal Risk will remain in place for nearly all of the Northeast (minus areas in south to south-southwest rain shadow areas of far N VT), with an extension of the Marginal into the Potomac River Valley and southern extents of the Megalopolis where those higher rates/short-burst totals may result with localized exceedance of lower hourly FFG values. ...Pacific Northwest... Prolonged warm advection of a moderate positively anomalous moisture stream will be continuing across the extreme northwestern portion of the Olympic Peninsula with a very weak continuation to the northern Washington Cascades. Rates will remain fairly consistent between .25"-.33"/hr allowing for totals to near 3-5" toward the the end of the forecast period with 00z HREF probability of 5" nearing 30%; though 5"/24hr just across the Sound will be near 60%. By late evening/early overnight period, the cold front will be starting to surge southeastward and further direct enhanced moisture flux toward the Olympic Peninsula after 06z, with 1-1.25" Total PWats fluxed on 40-45kts of flow generally resulting in about 750 kg/m/s IVT values, bringing rates locally up to .5" for the best orographic ascent regions. As such, a very small Marginal Risk was included for this AR surge into an area already at above average soil saturation due to recent AR plumes in the last few days/week(s). Gallina Day 3 Valid 12Z Tue Mar 17 2026 - 12Z Wed Mar 18 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF NORTHWEST WASHINGTON... 19z Update: Marginal risk looks on track, thus no changes needed. Chenard At the start of the day 3 forecast period, 18.12z, the strong, prolonged Atmospheric River had recently shifted slightly eastward directing the core of the AR plume centered across Northwest Washington into the northern Cascades, oriented from SW to NE. Deep layer moisture remained well above normal with total PWat values remaining well above 1" with 1.25" reaching the southwest flanks of the Olympic Range. Winds had calmed a tad but remain around or above 40kts through the 850-700mb range favorably orthogonal to the Olympic Range. Freezing levels are well above even the highest peaks, exposing some Snow Water Equivalent (SWE) to the higher WAA southwesterly flow adding to the .25"-.33"/hr rain rates though will be higher earlier in the period as winds slack ever so subtly between shortwave features. Overall IVT values will remain above 500 kg/m/s with peak values over 750 that extend into the northern Cascades as well. As such, 24hr totals will once again be over 3-4" and combined with the snow melt, could further increase stream flows. With lower rates, a Marginal Risk of Excessive Rainfall will remain in place; however, please refer the National Water Center and NWRFC forecasts for stream/river flow/rise information with respect to increasing flooding potential. Gallina Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-BGw8M2MYeRbAmcYtsEkHzM4HGCOn2YumZijl2AYgD2G= 1CYh3-J5poI9tFGFctwcPI5Jv8CPE2oJpLOJK9AKSdmCZKU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-BGw8M2MYeRbAmcYtsEkHzM4HGCOn2YumZijl2AYgD2G= 1CYh3-J5poI9tFGFctwcPI5Jv8CPE2oJpLOJK9AKG1Q3Qgc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-BGw8M2MYeRbAmcYtsEkHzM4HGCOn2YumZijl2AYgD2G= 1CYh3-J5poI9tFGFctwcPI5Jv8CPE2oJpLOJK9AKhoWP73g$=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]