Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jun 15 2023 08:05:47 FOUS30 KWBC 150805 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 405 AM EDT Thu Jun 15 2023 Day 1 Valid 12Z Thu Jun 15 2023 - 12Z Fri Jun 16 2023 ....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTHEAST AND WYOMING... Lower Mississippi Valley through the Southeast... The series of impulses that have ridden the westerly subtropical jet and provided lift a persistent west to east oriented low level frontal zone over the Southeast continues this morning. Brief ridging builds in later today from the west which should provide a short break in activity, though a shortwave trough currently crossing into New Mexico from Arizona is poised to trigger organized activity that progresses over the lower MS Valley late tonight. Regarding morning activity, the western edge to the impulse series looks to be entering southern AR. Training convection extends east from southern AR across north-central MS and over southern AL. Much of this activity should continue a southeast progressive trend through the rest of the morning with the main threat areas after 12Z expected to be in a zone from central MS through the western FL Panhandle. Pooling of 1.75 to 2" PWs persists through this corridor extending north from the eastern Gulf Coast with abundant instability and deep layer shear maintaining organized activity to repeat over this already saturated section of the Southeast (as well as get into newer areas farther south such as around Mobile Bay. The Slight Risk extends from central MS down to the MS/AL Gulf Coast and east across southern AL/GA and far northern FL. Southern Plains... Mid-level ridging this morning primes OK into northeast TX for heavy and progressive convective activity this evening into the overnight. A marginal risk is warranted to be maintained over these areas with expansion farther south over the Red River where several inches have fallen over the past three days. Intermountain West onto the Great Plains... An upper trough digs south over the northern Rockies this morning in the wake of the departing upper low into the Canadian Prairies, connecting a trough axis through southern CA. Lee-side cyclogenesis off the WY Rockies will draw Gulf-sourced moisture up over the High Plains and promote heavy rain (good potential for 1"+ hourly rainfall) over central through southeastern WY where a Slight Risk is maintained. A QPF axis over UT into the CO Rockies, similar to yesterday is expected with maintenance of the marginal risk there. Farther east on the northern Plains, Gulf moisture drawn up around the lee-side low and slowing cold front allows for increased PW around 1.25" (1.5 sigma above normal) and diurnally enhanced development of locally heavy thunderstorms. Slower southwesterly mean flow should allow some cell mergers, continuing to warrant a marginal risk over much of the Dakotas. Southern Sierra Nevada... Weak instability combined with PW of 0.75 to 1" (2 to 3 sigma above normal) will support locally heavy rainfall rates in diurnal convection. Some instances of flash flooding are possible, particularly in areas where soils are overly saturated from multiple recent days of rain and in rugged terrain warranting maintenance of the Marginal Risk. Jackson 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!63AGkBa06RfMItBvipaMGMFxmwp-1ddMzrAA5GGRebw4= mjaqbYEomHCjCX0GTCOFEfVfu1x7EcEADa2sENTTPxMnCjU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!63AGkBa06RfMItBvipaMGMFxmwp-1ddMzrAA5GGRebw4= mjaqbYEomHCjCX0GTCOFEfVfu1x7EcEADa2sENTTrtOX8iY$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!63AGkBa06RfMItBvipaMGMFxmwp-1ddMzrAA5GGRebw4= mjaqbYEomHCjCX0GTCOFEfVfu1x7EcEADa2sENTTVBqzkBg$=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) .