BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Thu, 28 May 2026 15:58:35 +0000 ----------------------------------------------------------- FOUS30 KWBC 281558 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1158 AM EDT Thu May 28 2026 Day 1 Valid 16Z Thu May 28 2026 - 12Z Fri May 29 2026 ...THERE ARE SLIGHTS RISKS OF EXCESSIVE RAINFALL ALONG THE CENTRAL GULF COAST, CENTRAL KANSAS, AND IN THE OZARKS OF MISSOURI AND=20 ARKANSAS... 16Z Update... Slight Risks were introduced for the 16Z update in parts of the central KS, the Ozarks, and along the central Gulf Coast. The Marginal Risks in the Pacific NW and South FL remain in good shape. ...Central Gulf Coast... The 12Z LIX sounding was effectively a tropical sounding with=20 plenty of MLCAPE present (>2,000 J/kg). Winds within the depth of=20 the cloud layer were almost uniformly out of the south with=20 training thunderstorms a concern from NOLA non north and east along the I-59 corridor. Soils remain highly saturated and primed for=20 flash flooding with rainfall rates that could top 3"/hr in the=20 heaviest thunderstorm activity. Storms are at least moving along at a steady clip, which should help to reduce the areal extent for=20 flash flooding. That said, these storms may exacerbate the flooding the region has experienced in recent days. For these reasons, a=20 Slight Risk was introduced. ...Ozarks & Central Arkansas... A narrow NW-SE corridor of anomalous PWs (>2.0" PWs that top the 99.5 climatological percentile per ECMWF) is caught between a strong ridge of high pressure in the Upper MS Valley and a negatively tilted 850-300mb trough oriented from southern KS to the ArkLaTex. Strong vertical ascent ahead of the 850-300mb trough axis coupled with MLCAPE between 500-1,000 J/kg will give more support to these highly saturated profiles. Area-averaged=20 soundings over northern AR show >85% RH values between 1000-500mb=20 and warm cloud layers >13,000ft this afternoon and evening. Soils=20 are most sensitive in central AR, while the Ozarks are historically a "flashy" area that, even with some drier soil moisture values in southern MO are prone to flash flooding given rainfall rates could surpass 2"/hr. The 12Z HREF does show high chance probabilities=20 (>70%) for rainfall amounts >3" in southwest MO and northern AR,=20 with low chance probabilities (20-35%) for >5" amounts. In=20 collaboration with WFOs in northern AR and southern MO, opted to=20 upgrade to a Slight Risk for the 16Z update. ...Central KS... A pivoting 700mb low rotating through southern KS will direct a=20 plume of highly anomalous moisture for late May/early June over the heart of KS. Per RAP mesoanalysis, PWs are already >1.5" and could surpass 1.75" this afternoon. Central KS is ideally placed just=20 ahead of a negatively tilted 850-300mb trough that is generating=20 excellent upper-level divergence. Additional storms will form this=20 afternoon with HRRR area-averaged soundings showing >500 J/kg of=20 MLCAPE, >85% RH values within the mean 1000-500mb layer, and warm=20 cloud layers up to 12,000ft deep. Wind more uniformly out of the SE are also supporting the potential for training storms, evident=20 from upshear corfidi vectors that are as low as 10 kts. New 12Z=20 HREF probabilities show high chance (>70%) for rainfall totals >3"=20 from Wichita on north and west with low-to-moderate chances=20 (20-40%) for localized amounts >5". Soils in the area are parched,=20 but these kind of rates can still support flash flooding,=20 particularly where repeating rounds of storms occur and in more urbanized settings. In collaboration with ICT, decided to upgrade=20 to a Slight Risk for the 16Z update.=20 Mullinax ---Previous Discussion--- ...Florida... An active sea breeze pattern with weakening steering flow will lead to periods of heavy rainfall across southeast Florida this afternoon. Greatest concern remains over the South Florida metro corridor from West Palm Beach to Miami. Latest HREF is robust with showing greater than 50% probabilities for 3" in 24-hours, with even some modest, albeit localized, probabilities for 5". This correlates well with CAM guidance, with some indicating bullseyes of greater than 3" within the larger QPF footprint. Locally significant rainfall is likely in this relatively classic pattern with ample moisture and instability present. A marginal risk remains in effect across Southeast Florida. ...Washington/Oregon... A deep upper level low over the West will allow for a broad axis of diffluent flow across the interior Northwest. Precipitable water values 1-1.5" are in the 90-90th percentile, and with sufficient instability, should support convection capable of producing heavy rainfall. Flooding and flash flooding are a concern for mainly the more vulnerable areas - urban, small stream, and low lying areas. HREF 24-hr probabilities for greater than 3" are between 40-70% for especially the Oregon cascades. Given the favorable environment though, a marginal risk extends all the way from far northern California northward to the eastern half of Washington state. A previous marginal risk for parts of the northern Rockies was trimmed out for this update given the lack of QPF signal. Santorelli Day 2 Valid 12Z Fri May 29 2026 - 12Z Sat May 30 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF THE NORTHERN ROCKIES AS WELL AS MUCH OF THE SOUTHEAST TO MIDDLE MISSISSIPPI VALLEY... ...Eastern Washington to Northern Rockies... A marginal risk is in place across far northeast Washington to northwest Montana due to an increase in the heavy rainfall signal for this period as the upper low over the West on Day 1, pivots slightly northeastward, placing this region in an area with better upper forcing and advection of moisture. The presence of anomalous moisture and some instability may present a threat for localized heavy rainfall and flash flooding, especially for burn scar locations within this region. ...Middle Mississippi Valley to the Southeast... Strong Canadian high pressure pressing in from the north will allow for a slow moving cold front to press south over the course of Thursday into Friday with convection likely to spawn along and ahead of the front and dry air advecting behind the front leading to a quick cutoff of activity. The front will arc back into the Tennessee Valley to Middle Mississippi Valley, supported by the persistent troughing over the south-central Plains. A moist and unstable environment near and south of this front will support scattered convection, with some heavier cells likely within the pattern. It is still too hard to pick out any discernible areas of interest, so maintained a very broad marginal risk over this area which is quite wet and will continue to be in the Day 1 period. Santorelli Day 3 Valid 12Z Sat May 30 2026 - 12Z Sun May 31 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE NORTHERN ROCKIES TO HIGH PLAINS AND THE SOUTHEAST... ...Northern Rockies to High Plains... The upper level low over the West during the Day 1 and 2 periods will weaken and shift northeastward, moving over the Northern Rockies to High Plains region on Day 3/Saturday. Moisture anomalies will continue to be in the 90-90th percentile, supporting moderate to heavy rainfall, with widespread QPF greater than 0.5-1" likely across western and central Montana. There may not be a lot of instability to work with, so any flood or flash flood threats should be mainly localized with particular attention to burn scar locations. A fairly broad marginal risk is in place across much of western and central Montana, into parts of northern Wyoming as well. ...Southeast... Same story as Days 1 and 2, with ample moisture and instability present near and south of a cold front that may stall over the region on Saturday supporting convection, across much of the Southeast. Some of this region, especially western parts of South Carolina and into the Appalachians has been very wet as of late and is well primed, so may be more favorable for flooding concerns. The marginal risk though continues towards the coast due to the presence of a weak frontal wave in the region. The Marginal Risk extends from the Southeast coast, westward into northeast Alabama and southeast Tennessee. Santorelli Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4fwOagQdvMAvdhwdiWuACYpzSRpajxTud1ZSNHEoICMB= KaGZTX_8w1-Yt_3v1NQmkPXRbOI22hCVWe1Tb7hPMHp2Yok$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4fwOagQdvMAvdhwdiWuACYpzSRpajxTud1ZSNHEoICMB= KaGZTX_8w1-Yt_3v1NQmkPXRbOI22hCVWe1Tb7hPRCwgUmM$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4fwOagQdvMAvdhwdiWuACYpzSRpajxTud1ZSNHEoICMB= KaGZTX_8w1-Yt_3v1NQmkPXRbOI22hCVWe1Tb7hPZvQTtL8$=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]