BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Wed, 27 May 2026 07:13:24 +0000 ----------------------------------------------------------- FOUS30 KWBC 270713 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 313 AM EDT Wed May 27 2026 Day 1 Valid 12Z Wed May 27 2026 - 12Z Thu May 28 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHEAST TEXAS, CENTRAL GULF COAST, AND AREAS OF THE OHIO VALLEY=20 TO CENTRAL APPALACHIANS... ...Texas to Central Gulf Coast... Radar this evening is pretty telling with the current evolution over TX revealing quite the complex of thunderstorms migrating=20 eastward out Hill Country into the I-35 corridor. These storms will continue to shove eastward with assistance from both a relatively=20 solid mean steering flow and outflow propagation stemming from the=20 organized convection. Aloft, two notable features are depicted via=20 WV satellite and UA analysis across the Southern Plains. The first=20 is a well-defined negatively tilted trough oriented over NM into=20 the TX Panhandle that will be slow to deviate from its current positioning over the course of the D1, even some prospects of the upper pattern closing off across the Panhandle area of TX/OK which would allow for some general enhancement of organized convective clusters under the primary circulation stemming from any upper low (ULL). In any case, this general upper pattern across the=20 region will entice broad cyclonic flow across the south-central=20 portion of the CONUS leading to convective development around the=20 periphery of the trough/ULL with an extension of activity likely to be situated from southeastern CO, across KS and OK, and eventually swinging back into the Lower Mississippi Valley. Instability maxima will still be located further to the south and east within closer proxy to the Gulf, however the upper levels and generally above normal PWAT anomalies over the entire scope of the Southern Plains should still act as a favorable environment for locally heavy rainfall leading to some flash flood prospects over the arcing area referenced above.=20 That said, one of the wild cards at play in this setup is the=20 maturation/development of any MCV structures that would locally=20 enhance convective episodes and likely trigger a more beneficial=20 low-level convergence pattern capable of better flash flood=20 prospects. This has been an output via some of the CAMs this=20 evening, most notably the HRRR where MCV development across OK=20 would trigger some locally enhanced precip maxima located within=20 the broad cyclonic presence. These features are tough to forecast=20 in the short term with more of a nowcasting component likely to be=20 instituted before committing to anything more concrete in the=20 forecast, so this will bear watching over the course of the D1. The more notable feature of interest for this evening and carrying through the D1 will likely be the evolution of a trailing vorticity maxima ejecting out of Coahuila this evening with the current radar/sat composite indicating a cluster of thunderstorms currently migrating east out of the Mexican state. The current MCS over Texas has a defined southern edge arcing back into south TX with a strong cell currently situated above 50 miles to the east of Laredo. Recent 00z CAMs indicate the Mexican disturbance following the tail end of the complex over TX and focusing on a heavy rain core trailing across south TX with a due east push of the mid-level disturbance. Consensus on heavy rainfall for the period will begin across southeast TX with the highlight likely to start around Corpus Christi and surrounds with moderate to heavy rain lingering across the Upper TX coast. As the outflow from the current complex shoves east, the environment will become stabilized behind the complex leading to a weakening convective regime as the disturbance to the south begins to enter into the region. There's some discrepancy on the specifics of the convective placement as we step through the morning, but the trends are for the immediate TX Gulf coast into southern LA as being the most notable areas of interest with the evolution of expected heavy rainfall during the D1. This is reflected well within the neighborhood prob fields off the latest HREF signaling >3" running between 40-70% across the entire stretch from Port O'Connor all the way towards New Orleans. Downstream prospects are more in due part to the continued southerly flow continuing to advect deep moisture into the region allowing for an environment capable of producing heavy convection during peak afternoon heating. The migration of the outflow on the northern edge of the current complex will likely skirt the southern portion of LA with some models maintaining its presence as far east as southeastern LA before it finally dwindles. In any case, the environmental favorability in the period lies within that coastal plain where elevated theta_E's lend to a heightened threat for heavy rainfall in anything that crops up with hourly rates likely to reach 2-3"/hr in the heavier cell cores.=20 Considering the complex evolutions referenced above for both areas of interest, the highest probabilities aligning with the Upper TX and Central Gulf coast allows for a continued SLGT risk positioning in these locations with a broad MRGL encompassing the overall cyclonic pattern oriented over the Southern Plains to Lower Mississippi Valley. Will still need to monitor the evolution closely as deviations in the outflow positioning, or the introduction of either closed ULL reflections or MVC's over the Southern Plains could very well aid in additional upgrades in any areas encompassed by these features.=20 ...Ohio Valley to Central Appalachians... Latest surface analysis over the Ohio Valley to Mid Atlantic indicates a defined quasi-stationary front bisecting northern KY through southern WV into central VA with pockets of showers currently migrating northeast within the mean flow around a broad ridge extension off the Atlantic seaboard. This frontal alignment and lingering mid-level vorticity analyzed over the Ohio Valley will lead to scattered to widespread convective regime over the course of today with a heightened threat for locally heavy rainfall occurring by late-morning and afternoon as environmental destabilization takes shape. The frontal placement will be important with regards to eventual convective initiation as this will become a focal point for any future development over the course of the afternoon. Model consensus is the boundary wavering slowly to the north during the morning as a weak disturbance begins to ride along the boundary leading to some minor regional amplification and a slow push north of the front to about the latitude of I-70. A sweeping trough exiting out of Ontario will also help tighten an axis of confluence across the Midwest and=20 Ohio Valley by later in the afternoon, enticing a squeeze of the=20 thermal gradient and regional instability axis that aligns with the frontal placement.=20 Instability markers by the afternoon hours will run between=20 2000-3000 J/kg for MUCAPE with weak shear presence leading to=20 scattered to widespread thunderstorm initiation along and south of=20 the front with generally modest cell motions to the southeast after development. PWAT anomalies will sit firmly within +2 standard=20 deviations above climo within the proposed area of impact, a factor that will correlate to strong cell cores capable of heavier downpours with hourly rates between 1-2"/hr. Previous periods of=20 rainfall in the last three to four days have really brought down=20 the areal FFG markers for all 1/3/6 hour thresholds with a vast=20 majority of places along the Ohio River basin and points north=20 running <1"/hr in the hourly exceedance indicator. This points to=20 any heavier convective impacts could cause issues with the remnant=20 soil moisture and hydrologic concerns that are lingering after the=20 last event. This is especially true for eastern OH, southwest PA,=20 and western WV where complex topography only exacerbate the=20 potential in these zones. The latest 00z HREF continues to paint a favorable concept of heavier rain prospects along and south of I-70 with a corridor of heavier rainfall likely to occur over southeast IN through southern OH into northwest WV. EAS probs for >1" are actually pretty elevated (50-80%) in the zone along I-79 over towards the Appalachian front in WV with modest probs of 25-40% located along the aforementioned line extending through IN/OH. A lot of the flash flood focus will likely correlate with the hourly rates and overlap of heavy rain over areas still saturated from previous periods. Considering the antecedent conditions and=20 expected widespread convective regime along the front, the SLGT=20 risk was maintained for an increasing threat for flash flooding during the period. ...Northern Rockies... Relatively buoyant environment within a deep, anomalous moisture presence across the Northern Rockies along with regional ascent provided by sheared vorticity maxima maneuvering through the area will allow for another round of widely scattered convection to materialize across the Lewis Range in northwest MT. Instability and regional forcing will be a bit less than the previous period, however sensitivities remain from remnant burn scars present=20 within the mountainous terrain in the aforementioned area which is=20 a cause for concern for any cells that happen to occur over the=20 burn scars themselves. Hourly rates between 0.5-1"/hr in the=20 stronger cell cores would be capable of providing localized flash=20 flood impacts over those more sensitive grounds and this setup will maintain the prospects given the anomalous moisture presence as=20 PWATs remain above the 90th percentile over the entire stretch of=20 the Northern Rockies. The previous MRGL risk inherited was=20 maintained given the relative continuity.=20 Kleebauer Day 2 Valid 12Z Thu May 28 2026 - 12Z Fri May 29 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS, NORTHERN ROCKIES, LOWER MISSISSIPPI VALLEY, AND SOUTHEAST FLORIDA... ...Plains to Lower Mississippi Valley... A bit of an omega block pattern is shaping up across the CONUS with a broad upper trough axis fixated over the Central and Southern Plains with with ridging in place over the top. This will cause a rather chaotic flow under the mean trough with deep moisture and several smaller mid-level perturbations basically "stuck" under the the overall trough axis. Ample instability with deep moisture presence will certain be a cause for continuing at least a scattered heavy rain footprint across areas under the influence of the trough. Scattered elevated probabilities between 30-60% exists for localized amounts >2" from KS all the way into the Southeast U.S. with the maxima split between KS and the Central Gulf coast. The two areas are different in the reasoning as the primary center of the trough will be fixed over KS leading to the best upper forcing pattern and stagnant flow remaining parked over the area as we move through D2. Pending the amount of rain that falls over the course of D1, a targeted upgrade is possible, but maintained the MRGL and will reassess as we move forward in future updates to see if an upgrade is warranted. The Central Gulf coast will remain in a favorable instability maxima with weak flow likely a component that could lead to isolated heavy totals stemming from slow-moving convection. The area from the Upper TX coast over through southern GA has been leaning wet over the past week, so antecedent conditions are a little more unforgiving for these types of setups. In any case, the threat remains modest, at best, so the MRGL risk was sufficient for the pattern with any upgrades likely to stem from more near term sampling of the radar trends. ...Florida... Active sea breeze pattern with weakening steering flow will lead to a period of heavy rainfall across the southeast FL coast on Thursday afternoon. Consensus within guidance is for an active period between 18-00z Thu/Fri that would allow for heavy convection with slow forward propagations to impact the South Florida metro corridor from West Palm Beach down to Miami. Latest 00z HREF is modestly robust with the signature for at least 3" off the neighborhood probabilities with a steady 60-90% output along the southeastern coast of FL with the maxima generally confined to the Miami Metro up to West Palm Beach. This correlates strongly with what has been advertised via regional and global guidance the past few days with the deterministic CAMs even indicating some 4-6" bullseye's within the main QPF footprint. This is a relatively classic pattern capable of locally significant rainfall within a deep moisture presence as PWAT anomalies sit between +1 to +2 standard deviations within the various ensemble packages. A MRGL risk remains in effect for the period across the South Florida metro corridor.=20 ...Northern Rockies... Maturing ULL over the west coast will allow for a broad axis of diffluent flow across the interior northwest with the highlight of scattered convection likely to pivot further west into eastern WA, northern ID, and the western slopes of the Northern Rockies. Signals are not as prevalent compared to previous periods, however the environmental conditions are still favorable, especially when it comes to PWAT anomalies still generally running between the 90-95th percentile across northeast WA into northern ID. Burn scar remnants will likely be the most susceptible to seeing impacts, so the threat remains low-end and generally localized. Maintained continuity from the previous forecast with a MRGL risk in place across the aforementioned areas.=20 Kleebauer Day 3 Valid 12Z Fri May 29 2026 - 12Z Sat May 30 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHEAST U.S... Strong Canadian high pressure pressing in from the north will lead to a persistent quasi-stationary turned cold front to press south over the course of Thursday into Friday with convection likely to spawn along and ahead of the front with dry air advecting behind the front leading to a cutoff of activity. Jury is still out on specifics with the placement of the front generally over the Carolina's by Friday morning with slow push south as the day wears on. Frontal alignment is more of a arcing back into the Tennessee Valley as the persistent troughing in the South-Central Plains will likely maintain some southerly flow for areas along and west of the Mississippi. Anywhere within proximity to this front will be subject to various convective outputs with some heavier cells likely intertwined in over the pattern. No discernible areas of interest are present at this juncture, however the environmental favorability likely points to the best chances occurring across=20 the Southeast into the lower Tennessee Valley. A broad MRGL is=20 forecast for the above areas through the Lower Mississippi Valley. Kleebauer Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!83IdOxNqj5XiuOidgDhWctuiMl81zG38y_OF47G8OhYl= 77XXATImHkmS7N6EYCBC0zUlUsgNlBTgrPGnnRjl3qAqAds$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!83IdOxNqj5XiuOidgDhWctuiMl81zG38y_OF47G8OhYl= 77XXATImHkmS7N6EYCBC0zUlUsgNlBTgrPGnnRjl214-Nv8$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!83IdOxNqj5XiuOidgDhWctuiMl81zG38y_OF47G8OhYl= 77XXATImHkmS7N6EYCBC0zUlUsgNlBTgrPGnnRjlaxhCRdc$=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]