BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Sun, 24 May 2026 20:00:28 +0000 ----------------------------------------------------------- FOUS30 KWBC 242000 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Sun May 24 2026 Day 1 Valid 16Z Sun May 24 2026 - 12Z Mon May 25 2026 ...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FROM THE CENTRAL GULF COAST INTO NORTH GEORGIA AND ACROSS THE UPPER OHIO VALLEY... 16Z Update... The forecast overall remains on track with some tweaks made to reflect the latest trends on 12Z CAMs. Satellite shows mostly cloudy and overcast skies across a large portion of the eastern third of the CONUS. Large sums of anomalous moisture remain in place in the South and into both the OH Valley and Mid-Atlantic. However, it is where there are breaks in the clouds that will promote a more unstable atmosphere over soils that are highly saturated (WV, eastern OH, western PA) or near the remnant MCV in approaching central AL that remain the focus as showing the best potential for scattered areas of flash flooding. The Slight Risk in the OH Valley was expanded south more into eastern KY where 12Z HREF probabilities show low chances (20-35%) for localized rainfall totals >3". Some zones in eastern KY sport 3-hr FFGs <2", and NASA SPoRT-LIS 0-10cm soil percentiles are >80% in some cases. 12Z soundings are painting a busy picture in the Mid-South and Ohio Valley. The BMX soundings show a weak capping inversion with over 1,500 MUCAPE and a 1.87" PW ahead of the approaching MCV. Farther north, the BNA sounding is highly saturated and shows an even weaker capping inversion. This air-mass in the TN Valley will advect north and east into the OH Valley this afternoon, setting the stage for highly efficient thunderstorms from central TN to as far north and east as the central Appalachians and western PA. Strong differential heating is also underway in central GA and southern SC along the stationary front, which will once again be another trigger for additional strong thunderstorms this afternoon. Latest 12Z HREF brought QPF up in the windward side of the central Appalachians in eastern WV, with some low-to-moderate chance probabilities (30-50%) for >3" of rainfall this afternoon and evening. There are also moderate chance probabilities (40-60%) for rainfall totals >3" from the SC/GA border to the coastal plain of NC. Localized flash flooding is possible in these areas this afternoon and evening. ...Central TX... A Marginal Risk was introduced for the midday update. 12Z HREF probabilities show low chances (10-30%) for localized rainfall totals topping 3" this afternoon and lingering into this evening. There is a remnant mid-upper level circulation over the heart of TX that coincides within an area seeing strong surface-based heating and PWs approaching 1.5". Storm motions will be very slow with ECMWF area-averaged soundings showing mean cloud-layer winds within the Marginal Risk area less than 5 kts. The lack of shear should make these storms more pulse like in nature and shorter in duration, but given the saturated soils in the region (NASA SPoRT-LIS shows >80 percentile 0-10cm soil moisture the farther south you go in central TX) and these storms potentially packing a punch in a brief period of time (1-hr HREF PMM precip rates up to 1.5"), the potential exists for isolated cases of flash flooding this afternoon and evening. Mullinax ---Previous Discussion--- The well defined MCV moving from southeast LA into far southern MS early this morning expected to continue to push northward day 1 across central AL and into north GA. While the organized convection associated with this MCV may weaken early day 1, there is potential for convection to re-fire ahead of this MCV later this afternoon in the axis of much above average PW values, 2 to 2.5+ standard deviations above the mean expected to stretch from the Central Gulf Coast, northeastward through the Southern to Central Appalachians, Southeast and Mid-Atlantic. We added a slight risk from central AL into north GA to account for this convective potential. Farther to the southwest...we made some significant changes to the previous slight risk area across southern MS and southern LA. We suppressed the slight, keeping it just for far southeast LA. The best instability in the wake of the northeastward moving MCV will be over the northern Gulf, suggesting the heaviest precip with the next round of convection also being offshore. We kept the New Orleans metro area in the slight as model consensus is for a narrow axis of heavy rains to extend into far eastern LA. Across FL...the marginal risk was extended south into portions of north central to southwest FL. Model consensus is for another round of active convection forming Sunday afternoon in a general north to south axis. Slow moving cells will again have potential for produce locally heavy rainfall amounts and isolated runoff issues. There will be potential for overlap of yesterday's heavy rainfall amounts with Sunday afternoon's. The biggest runoff threat will continue to be in more urbanized regions. Over the Upper Ohio Valley...added a slight risk area from northeast KY into eastern OH, northwest WV and far southwest PA. Both the HREF and RRFS are showing fairly high probabilities, 25-50%+ for 3 hour precip amounts exceeding FFG values this afternoon into early evening. Favorable right entrance region jet dynamics in the above mentioned axis of anomalous PW values will support potential for heavy precip and localized runoff issues. Oravec Day 2 Valid 12Z Mon May 25 2026 - 12Z Tue May 26 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL GULF COAST TOWARD THE SOUTHERN APPALACHIANS... 20Z Update... Some adjustments were made to the eastern periphery of both the inherited Marginal and Slight Risks in the South with the latest QPF being a little wetter in southern AL, southern GA, and the FL Panhandle. This aligns well with where the greatest source of instability is likely to be.=20 Biggest change was to introduce a Marginal Risk in eastern NM and=20 western TX. ECMWF SATs show a narrow 200 kg/m/s southerly IVT in=20 advance of the approaching upper low over AZ. PWs jump to 1" over=20 the plains of eastern NM, but approach 0.75" in the Sacramento,=20 Guadalupe, and Davis Mountains. All PWs in these areas are likely=20 to surpass the 90th climatological percentile. On top of the=20 synoptic scale forcing and ample moisture, sufficient MUCAPE >500=20 J/kg will support rainfall rates that could range between=20 1-1.5"/hr. There is a Flood Watch for areas downstream of the South Fork and Seven Cabins burn scars in the Sacramento, indicating the flash flood potential that could occur near burn scars as well. Latest HREF probabilities do show low chance probabilities (20-35%) for rainfall totals >2" within the Marginal Risk area, particularly just east of the Sacramento Mountains. Mullinax ---Previous Discussion--- An axis of anomalous PW values, 2 to 2.5+ standard deviations above the mean, will persist from the Central Gulf Coast, northeastward across the South, Southeast and Southern Mid-Atlantic day 2. The closed low over the eastern portions of the Southern Plains toward the Lower MS Valley will move only very slowly north northeastward day 2, keeping a favorable broadly upper diffluent pattern to its east in this anomalous PW axis. This will support widespread scattered convection and potential for widespread moderate to heavy precip totals. There is a typical amount of model qpf spread, but consensus for potential for widespread moderate to heavy totals. There will likely be overlap between the day 1 and day 2 heavy precip areas, although low confidence at the moment with details. No significant changes made to the previous outlooks areas. Minor adjustments made to fit the latest model qpf consensus. Oravec Day 3 Valid 12Z Tue May 26 2026 - 12Z Wed May 27 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL GULF COAST TOWARD THE SOUTHERN APPALACHIANS AND ACROSS THE SOUTH CENTRAL TEXAS... 20Z Update... The rationale with the inherited Slight Risk in the Southern Plains remains in good shape. There was an increased number of model members that showed Excessive Rainfall potential just out ahead of the negatively-tilting 200-500mb trough axis ejecting out of NM. This places more of northwest TX (encroaching upon the TX Panhandle) within an axis strong forcing aloft within a narrow corridor of >1.25" PWs, which is above the 90th climatological percentile. Latest guidance also show the potential for up to 1,000 J/kg of MUCAPE as far north as the TX Panhandle. Some portions of West TX, even as far north as the Cap Rock, have dealt with localized flash flooding in recent days, and sensitive soils in the area are unlikely to recover fast enough for a setup that could feature 1.5-2.0"/hr rainfall rates at their peak. For these reasons, the Slight Risk was extended farther north into northwest TX. The setup continues to be one that residents in the TX Hill Country will want to monitor in the coming days. While there remains some uncertainty in the exact location of the heaviest precipitation,=20 rainfall rates topping 2"/hr are possible as far south as Laredo and south of San Antonio. Soils remain most sensitive along the I-35 corridor on north to the Edwards Plateau. The flash flood=20 threat could start as early as Tuesday afternoon, but latest=20 ensemble guidance is indicating the heaviest rainfall rates are=20 favored to occur overnight Tuesday.=20 Mullinax ---Previous Discussion--- Not a lot of changes to the wet pattern from the Central Gulf Coast, northeastward across the South, Southeast and Southern Appalachians. The axis of anomalous PW values, 2 to 2.5+ standard deviations above the mean, will persist across this area in a region of persistent south southwesterly mid to upper level flow on the east side of the weak mid to upper low moving north through the Lower MS Valley. Expect another day of widespread scattered convection and widespread moderate to heavy rainfall totals. With not much changes overall to the large scale pattern, a slight risk was maintained in a similar region as during the day 2 period. There may again be overlap in heavy rain areas day 3 with day 1 and 2, which may lead to a upgrade in threat categories in future issuances. Mid to upper level troffing developing across the Southwest during day 2 will be pushing height falls into the Southern Plains day 3. Increasingly active convection likely across the Southern Plains day 3, with model consensus for widespread moderate to heavy totals. Not a lot of changes made to the previous slight risk area over south central TX. This region has seen several rounds of heavy precip over the past week, lowering FFG values and increasing threat of additional runoff issues. There is a lot of spread with qpf details, but a strong signal for heavy rainfall totals day 3 across this area. Oravec Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_yb6RxxStd-3bbrX2eP2Nr2Vasu_JF684PyED86wPN9Y= DOUg9_Pxu6cO_hSvGsTj82nVgBI-EXA8tquuzpK3DxW3G1g$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_yb6RxxStd-3bbrX2eP2Nr2Vasu_JF684PyED86wPN9Y= DOUg9_Pxu6cO_hSvGsTj82nVgBI-EXA8tquuzpK3jMGfA70$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_yb6RxxStd-3bbrX2eP2Nr2Vasu_JF684PyED86wPN9Y= DOUg9_Pxu6cO_hSvGsTj82nVgBI-EXA8tquuzpK3oeNkH1k$=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]