Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 30 2023 08:30:35 FOUS30 KWBC 300830 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 429 AM EDT Fri Jun 30 2023 Day 1 Valid 12Z Fri Jun 30 2023 - 12Z Sat Jul 01 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE CENTRAL PLAINS... ....Central High Plains to the Appalachians/Northeast... Introduced a Slight Risk of excessive rainfall over portions of the Central Plains within a broader Marginal Risk area that spans from the Rockies Front Range and adjacent High Plaines eastward into the Tennessee Valley. An upper trough moving out of the West is expected to trigger additional storms west from near the Rockies Front Range across the Plains. The thermal and moisture profiles suggest that convection should be efficient rainfall producers and fairly modest forward speed suggest that flooding may be a concern given some of the rainfall observed on Thursday.=20 Farther east...mid-level energy will continue to move across the top of the ridge centered over the lower Mississippi Valley and the Southeast, likely to help initiate additional rounds of showers and storms from the Mid-Mississippi Valley into portions of the Ohio Valley as embedded shortwave troughs interact with an axis of deeper moisture. A Marginal Risk was maintained to highlight an increasing threat for heavy rains to spread back into portions of the Northeast that were recently impacted by heavy amounts. Mid-level energy and deeper moisture will be directed northeast into the region ahead of a low centered north of the Great Lakes and usher in renewed PWs near 1.75 inches. Given limited confidence...tried to be more targeted in the areal coverage of the Marginal but still covers at least some potential for moderate to heavy amounts to begin to develop across some parts of Pennsylvania and New York that were recently impacted with heavy amounts and where FFGs remain relatively low. Bann Day 2 Valid 12Z Sat Jul 01 2023 - 12Z Sun Jul 02 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE MID MISSISSIPPI INTO THE LOWER OHIO VALLEY... ....Central Plains to the Northeast... Models continue to present a good signal for widespread moderate to heavy rainfall developing ahead of a well-defined trough moving from the central Plains into the mid Mississippi Valley. Deep southwesterly flow ahead of the trough is expected to draw ample moisture (precipitable water values of 1.5-2 inches) into a region of large-scale ascent. The models suggest an environment favorable for redeveloping storms and west-east training, increasing the threat for heavy accumulations. The main change to yesterdays Day 3 outlook was to expand the Slight Risk northward where a few of the operational models got some support from the 2+ inch amounts from the SREF and GEFS. This included some areas that may be impacted by heavy amounts in Days 1 and 2.=20 Meanwhile, downstream energy is likely to contribute to at least locally heavy amounts and isolated flash flooding concerns across the Ohio Valley into the central to southern Appalachians.=20 Farther to the north, southwesterly flow ahead of a slow-moving trough over the Great Lakes will continue to channel deeper moisture into the Northeast, fueling the potential for the recurrence of heavy rains and flooding concerns for portions of the area. Bann Day 3 Valid 12Z Sun Jul 02 2023 - 12Z Mon Jul 03 2023 ....There is a Marginal Risk of Excessive Rainfall Over Portions of the Eastern United States... A trough making its way eastward from the Tennessee Valley eastward will tap deeper moisture over the eastern United States to produce showers and thunderstorms on Sunday and Sunday night.=20 There was a large spread of model solutions as to where the heavier rainfall amounts will occur within a broader shield of rainfall. Upper level difluence/divergence ahead of an upper level trough and some frontogenetical forcing in an atmosphere with precipitable water values of 1.75 to 2+ inch will support local 2+ rainfall amounts over the Northeast U.S...where flash flood guidance has been suppressed by locally heavy rainfall during the preceding week. Farther south...the synoptic scale forcing looks to be weaker but the instability could also produce flooding as a result of some intense downpours. The model spread really limits confidence and precluded the issuance of a Slight risk area at this point. Bann Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!76XHG200npSNFmcYBF5KVSh6Aknpy6r58cAb680GSAAh= YOzt4sIzIqYAhXBHzRZuh7YoD2WNIyDla8yaPmEOd2Jbrec$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!76XHG200npSNFmcYBF5KVSh6Aknpy6r58cAb680GSAAh= YOzt4sIzIqYAhXBHzRZuh7YoD2WNIyDla8yaPmEONVgXZfU$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!76XHG200npSNFmcYBF5KVSh6Aknpy6r58cAb680GSAAh= YOzt4sIzIqYAhXBHzRZuh7YoD2WNIyDla8yaPmEOoaPlj1M$=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) .