Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jun 01 2023 08:09:48 FOUS30 KWBC 010809 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 409 AM EDT Thu Jun 01 2023 Day 1 Valid 12Z Thu Jun 01 2023 - 12Z Fri Jun 02 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN-CENTRAL PLAINS AND MUCH OF EAST-CENTRAL MONTANA INTO NORTH-CENTRAL WYOMING... ....Central and Southern Plains... Based on continued CAM trends and short-term wet antecedent soils, maintained an adjusted Slight Risk area largely based on the new HREF and associated neighborhood exceedance probabilities (suggesting high odds of localized 2" exceedance across the region). This includes a small portion of northeast NM, much of the TX/OK Panhandles, and into north-central OK and south-central KS. Another active day of convection looks likely, with some additional lift being provided by the northward moving aforementioned mid-upper low and associated vort max. While convection overall should be less organized than on Day 2, there could be multiple rounds of heavy rainfall with convection likely still lingering from overnight into the morning, in addition to the anticipated initiation from daytime heating in the afternoon/evening. Further increasing confidence, the latest machine learning CSU First-Guess fields continue to depict a broad Slight Risk area as well. ....Northern/Central Rockies and Plains... Things start to get a little more interesting across the Northern Rockies and High Plains today, as a remnant mid-upper low and associated vorticity maxima eject northward from the Four Corners region. This should provide broad ascent via DPVA, along with modest diffluence aloft and sufficient instability (rising to 750-1500 J/kg of SB CAPE, per the HREF). The 00z HREF also suggests relatively high neighborhood probabilities for exceedance of both 2" and 3", with the best probabilities over south-central MT (near and west of Billings). PWATs are expected to increase to as high as 1.25" (which is +3.0 SD, or approaching the 95th percentile climatologically per the GEFS.. near or above the max moving average per TFX and GGW sounding climatology). Have once again maintained (and modified) the inherited Slight Risk and this area based on the new guidance. Farther south into the Central Rockies and into the Great Basin, any flash flooding is expected to be localized with much less organized convection (and largely tied to small-scale terrain forcing). Machine learning CSU First-Guess fields are also depicting a broad Slight Risk for this area (though offset seemingly a bit too far east). ....Central and Southern Florida... Continued the Marginal Risk for much of central/southern FL going into today, given the potential for a surface low to become more coherent and track toward this area. Aloft, a very slow-moving upper-trough over the Gulf will finally make its way directly overhead the Florida Peninsula with the strength/track of its surface reflection still uncertain. This should act to enhance typical diurnal convective activity across the region, with strong mid-level lapse rates allowing for more intense updrafts with tropical-like rainfall efficiency (given PWATs ~2.0" and wet bulb zero heights of ~15K feet). There may be a banded type feature as well oriented from northwest to southeast, which may allow for some training of heavy rates as well. Any localized flooding impacts are most likely across urbanized metro areas with poor drainage. Churchill/Pereira/Hurley/Fracasso 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!_X6pP2OciR9WaJr8j-fZd-wiVZWEa4o7nUtERTGb-bnp= GpHeEM3X2FiJpOVKRnqku56lHH33dxDHyU8MXOY1M7Z5uao$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_X6pP2OciR9WaJr8j-fZd-wiVZWEa4o7nUtERTGb-bnp= GpHeEM3X2FiJpOVKRnqku56lHH33dxDHyU8MXOY1FoOjq68$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_X6pP2OciR9WaJr8j-fZd-wiVZWEa4o7nUtERTGb-bnp= GpHeEM3X2FiJpOVKRnqku56lHH33dxDHyU8MXOY1rhcE3sI$=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) .