BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Mon, 16 Mar 2026 15:35:41 +0000 ----------------------------------------------------------- FOUS30 KWBC 161535 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1135 AM EDT Mon Mar 16 2026 Day 1 Valid 16Z 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... ...16Z Update... Only modest changes were needed to the ongoing Marginal Risk across portions of the Mid-Atlantic and much of the Northeast. The strong cold front driving the most severe weather is beginning to cross the Appalachians. Ahead of the front, a deep warm, moist air mass is being rapidly advected northward. Thus, storm motions have been very fast, moving at 50-60 mph. These fast storm motions will put a huge damper on any flash flooding potential, as any heavy rains, which will be numerous, will only impact any given location for a brief time, generally under a half hour. For most areas, this simply will not be enough time to materialize much of a flash flooding threat. Thus, the Marginal Risk remains in place.=20 Starting from the south, the Mid-Atlantic region was trimmed from portions of the inherited Marginal in the Shenandoah Valley and the Delmarva Peninsula. In these areas, the flash flooding risk is lower due to higher FFGs. The updated Marginal really focuses on the DC-Baltimore-Philly urban I-95 corridor where the amount of rain needed to achieve flash flooding is lower.=20 Further north, little change north of the Mason-Dixon Line. A bit more of Central NY was added to the Marginal to account for snowmelt potential adding to river levels. Elsewhere, the main flash flooding threat really is for New England. In southern New England (MA/CT/RI), upslope potential off the Atlantic should=20 locally increase rainfall rates as steadier rain begins in that=20 area later this afternoon into this evening. For northern New England (VT/NH/ME), upsloping will combine with snowmelt and less eastward progression of the otherwise fast-moving convection to raise the risk of flash flooding into the Marginal Risk category. Rates will be less than impressive outside of any storms, which will be moving quickly, so this looks like an isolated flash flooding threat that doesn't rise to a Slight Risk level at this time. All this is to say, the severe threat will be the much greater concern area-wide as compared to the flash flooding threat. Wegman Day 2 Valid 12Z Tue Mar 17 2026 - 12Z Wed Mar 18 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF WASHINGTON STATE... Active pattern across the Gulf of Alaska will lead to another AR contribution into portions of the Pacific Northwest as the main IVT surge will adjust south into WA state after impacting neighboring British Columbia the day prior. Looking at IVT values between 500-700 kg/ms across northwest WA state with the surge propagating far enough inland to impact the Northern Cascades. Rainfall amounts between 2-3" will be common in the hardest hit areas, mainly into the Olympic Peninsula, Chehalis River valley, as well as the Cascades to the east of Seattle. Rates will lack vigor to the point for a more substantial impact, so the threat is mainly due to prolonged moderate to locally heavy rain prospects falling over relatively moist soil layer present after being impacted for weeks leading in. The previous MRGL risk was generally unchanged with the threat leaning towards the lower-end of the risk threshold. Areal hydrologic concerns are still viable with river and small stream flooding the most notable potential impacts. Kleebauer Day 3 Valid 12Z Wed Mar 18 2026 - 12Z Thu Mar 19 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF WASHINGTON STATE... Occluded low over the Gulf of Alaska a strong mid-level ridge positioned across the Southwest U.S. will lead to a continued transport of modest IVT into WA state for the D3 period. AR dominated pattern will enhance rainfall prospects for the northern half of WA leading to cumulative rainfall totals breaching 4" in spots within the Northern Cascades, Olympics, and adjacent coastal areas of northwest WA. Real concern is the growing hydrologic factors with river flooding coupled with moderate rainfall posing a problem for areas around the main rivers and tributaries for the aforementioned areas. Flash flood threat remains low due to the rates anticipated with the rainfall as hourly rainfall will remain <0.5"/hr for a majority of Wednesday. However, the coupling of the previous days rain and the already saturated soils will likely lead to some hydro concerns mid-week, so maintained the previous MRGL risk inherited with only some minor tweaks at the southwest edge of the risk. Kleebauer Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-V4VldTjb923MHUevHk1YlyEFX9oyDQJJFbitg7ce-wj= BBtFPCEg1D6vuuZKa-_7ZrgKtMsokQe-4UP3HdoWRYwudHA$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-V4VldTjb923MHUevHk1YlyEFX9oyDQJJFbitg7ce-wj= BBtFPCEg1D6vuuZKa-_7ZrgKtMsokQe-4UP3HdoWE0Z_9DE$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-V4VldTjb923MHUevHk1YlyEFX9oyDQJJFbitg7ce-wj= BBtFPCEg1D6vuuZKa-_7ZrgKtMsokQe-4UP3HdoW2w4NQDM$=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]