Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 03 2023 08:32:35 FOUS30 KWBC 030832 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 431 AM EDT Mon Jul 03 2023 Day 1 Valid 12Z Mon Jul 03 2023 - 12Z Tue Jul 04 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE NORTHEAST AND MID-ATLANTIC, THE UPPER MIDWEST/NORTHERN PLAINS, THE MID-SOUTH, AND SOUTH FLORIDA... ....Appalachians and Mid-Atlantic into New England... Models still linger sufficient moisture to keep modest precipitation amounts across the region as a system slowly pulls away to the East Coast. Additional rainfall amounts after the start of the outlook period at this morning are not expected to be overly impressive, but wet antecedent conditions leading up to this time period could still yield areas with isolated flooding or problems in regions of poor drainage. Therefore, the Marginal risk area in this part of the country was maintained (with expansion southward into both the Appalachians, to account for lingering morning precipitation, and farther south into the Mid-Atlantic, due to a small window of opportunity for afternoon storms to locally exceed 3"). ....Montana/Wyoming Eastward to Northern Minnesota... A cold front will drop south across the Northern Plains today and tonight as the parent surface low pressure remains well north of the US/Canadian border. This front should provide a focus for showers and thunderstorms from south-central Montana and northern Wyoming eastward across South Dakota/Nebraska and into the Upper Midwest. Moisture pooling along and ahead of the front combined with divergence aloft from an upper level jet will create an environment favorable for storms to produce locally heavy rainfall, although highest precipitable water values only look to be modestly above 1.25 inches which may limit rates and any associated excessive rainfall potential. No major changes were needed with this forecast update. ....Mid-South... A lingering frontal boundary extending from the Mid-Atlantic to the Lower Tennessee Valley, pooling 1.75-2.00 inch PWs combined with a subtle shortwave ejecting across the central/southern Plains should allow for slow-moving storms to develop across the ArkLaMiss and extending into central/northern Alabama. Minimal low-to-mid level flow is likely to limit storm motion and could result in localized flash flooding concerns and rainfall amounts up to 2-3" within a relatively short period of time. The inherited Marginal Risk area was expanded a bit, based on the 00z HREF QPF footprint (and associated HREF 3" neighborhood exceedance probabilities as high as 20-40%). ....South Florida... A Marginal Risk area was maintained for portions of South Florida to account for slow moving cells that develop in response to sea breeze convergence, with the potential for 1-2 inches of rainfall to fall within a 30-minute time period for affected areas (with localized totals in excess of 3" possible in only an hour or so). The best coverage for convection is likely to be within the typical 18Z-00Z time period, and poor drainage/metropolitan areas are most at risk for localized flash flooding. Churchill/Bann/Hamrick 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!_7nLrWmzgh6oHXac7sWO9x3oIkAbIrQfMVYl3o30R54q= GlESqoct1sSHLTk3l7RN7-UJobOJdQ84idSbwK2ET0NNANg$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_7nLrWmzgh6oHXac7sWO9x3oIkAbIrQfMVYl3o30R54q= GlESqoct1sSHLTk3l7RN7-UJobOJdQ84idSbwK2EEHyF7Ok$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_7nLrWmzgh6oHXac7sWO9x3oIkAbIrQfMVYl3o30R54q= GlESqoct1sSHLTk3l7RN7-UJobOJdQ84idSbwK2EYFRrgxU$=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) .