Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun May 28 2023 08:02:12 FOUS30 KWBC 280802 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 401 AM EDT Sun May 28 2023 Day 1 Valid 12Z Sun May 28 2023 - 12Z Mon May 29 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE BLUE RIDGE OF NORTH CAROLINA AND FAR SOUTHWEST VIRGINIA, PARTS OF SOUTHWEST NEBRASKA SOUTH OF THE SAND HILLS, AND FROM PORTIONS OF NORTHWEST TEXAS SOUTH TO THE RIO GRANDE RIVER.... ....Central Appalachians into parts of the Mid Atlantic... The surface low will migrate onshore near the northern SC shores this morning, then weaken while drifting slowly northward and becoming vertically stacked across NC. Even though the surface cyclone and 850 mb inflow will weaken substantially, periods of heavy rain producing showers are likely, especially on the western edge of the mid-level circulation from the higher elevations if western NC to nearby southwest VA. For areas farther east, additional organized north-south bands of convection are possible in eastern NC Sunday morning within an environment of 1.5" PWATs. Despite some of this rain falling atop soils that are almost guaranteed to be fully saturated from the previous day's rainfall, the coverage and intensity suggest a MRGL risk is sufficient to cover the excessive rain risk for most of the region. Other isolated instances of localized heavy rain are possible across central NC and southwest VA into far eastern KY-TN associated with low level fgen and ~500 J/kg of MUCAPE, supporting a Marginal Risk. More organized convection falling atop sensitive terrain is possible across the Blue Ridge of NC and into southwest VA, where 1.5-3" of additional rainfall is likely per the latest guidance (including the 06Z HRRR), due in large part to the additional upslope enhancement. This heavy rain falling atop soils saturated from Day 1 and into the inherently flashy terrain could result in more scattered instances of flash flooding. 12z HREF neighborhood probabilities depict 20-35% chances for 2" of rain in 6 hours into Saturday evening, which provides enough confidence to maintain the previous risk area. Per collaboration with WFO's RNK, RLX, and LWX, given the guidance trends (limited instability and less intense short-term rainfall rates), have trimmed the northern portion of both the Slight and Marginal Risk areas across central and southern WV-VA. ....Rio Grande Valley northward through the Northern High Plains... A persistent and slow moving pattern driven by a trough to the west and ridge to the east will promote another day of scattered to widespread showers and thunderstorms from Texas to the Dakotas. Localized rainfall totals of 1-3" are possible throughout much of the Marginal Risk area, though a more elevated risk for flash flooding will be across parts southwest NE as well as parts of the TX Big Country south to the Rio Grande River, including the Edwards Plateau and western portions of the Hill Country and South TX Brush Country. This is due to the potential for additional heavy rain (more organized convection) during Day 1, along with the antecedent wet soils given the recent heavy rainfall. Across TX, PWATs are expected to peak between 1.75-2.--" along the Rio Grande River Valley while MUCAPE also increases to 2000-2500 J/kg per the 00Z HREF. Shortwave approaching out of northern Mexico and potential lingering surface boundaries from previous day's MCS activity could provide focus for development and brief training of higher rain rates in this area. FFGs across the Edwards Plateau and surrounding regions are very low (1-2"/hr and 1.5-2.5"/3-hr). Per the 00Z HREF, probabilities between 25-50% of QPF exceeding 3" during Day 1 are scattered throughout the Slight Risk area. Hurley/Snell Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5nbxRvYMGnMIX9gjLNQbRaOM3YPbfUySIStRxSBbV7yG= FBl5tD9IT4ZTtKTuSiy2sjWuYuf1vC6-MJEexZf7h8qTWOo$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5nbxRvYMGnMIX9gjLNQbRaOM3YPbfUySIStRxSBbV7yG= FBl5tD9IT4ZTtKTuSiy2sjWuYuf1vC6-MJEexZf7o9jsqxs$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5nbxRvYMGnMIX9gjLNQbRaOM3YPbfUySIStRxSBbV7yG= FBl5tD9IT4ZTtKTuSiy2sjWuYuf1vC6-MJEexZf79NhuEcs$=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .