Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Oct 24 2023 08:11:46 FOUS30 KWBC 240811 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 410 AM EDT Tue Oct 24 2023 Day 1 Valid 12Z Tue Oct 24 2023 - 12Z Wed Oct 25 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN PLAINS AND OVER PORTIONS OF THE UPPER MISSISSIPPI VALLEY INTO THE UPPER GREAT LAKES... An expansive area of anomalous PW values...2 to 3+ standard deviations above the mean... expected to stretch across the Southern to Central Plains into the Upper Mississippi Valley and Upper Great Lakes region day 1 in the broad southwesterly mid to upper level flow across these areas. There is good model agreement for two primary precipitation areas in this anomalous PW axis. One across the Southern to Central Plains into the Lower Missouri Valley and another in the vicinity of a west southwest to east northeast oriented frontal boundary stretching from the Upper Mississippi Valley into the Upper Great Lakes... ...Southern to Central Plains into the Lower Missouri Valley... The current organized area of rains across the Southern Plains will be lifting farther northeast day 1 into areas from north Texas, across large portions of Oklahoma, save for the Panhandle and southeast OK, and into eastern Kansas and northwest Missouri, associated with lead areas of height falls ahead of the primary strong upstream closed low moving across northern Mexico. The risk area is depicted as marginal with this lead area of precip as this region has been well below average in precip over the past few weeks, with resultant low soil moisture and below average stream flows. We did trim the slight risk area from the previous outlook out of far southeast Kansas into north central Oklahoma. This will be followed by a second surge of heavy precip developing across the Southern High Plains Tuesday afternoon ahead of the aforementioned upstream strong closed low moving across northern Mexico. The slight risk area was drawn from southwest Oklahoma, southwestward into Northwest Texas and toward the Big Bend of Texas to encompass areas that have or will receive potentially heavy rains through 12Z Tuesday and overlap areas that will then see another round of potentially heavy rains moving into the Southern Plains Tuesday night/early Wednesday. The HREF neighborhood probabilities for 1"+ hourly amounts are the most defined with this next surge of heavy precip into far southeast NM and west Texas from approximately 0300 to 1200 UTC Wednesday with probabilities ranging from 20-50%+. In comparison, the HREF neighborhood probabilities for 1"+ hourly amounts for the lead area of precip into the Central Plains and Lower MO Valley top out at 20%+. ....Upper Mississippi Valley into the Upper Great Lakes... Current surface analysis is showing a well defined front stretching along the MN/IA border eastward into southern WI and the southern portion of the L.P. of MI. This front is forecast to remain well defined as it lifts slowly northward day 1. This front will likely remain an active focusing mechanism for overrunning convection from early Tuesday morning as the current area developing along the MN/IA border pushes east northeastward into south central WI and the northern portions of the L.P. into early Tuesday morning. This will be followed by potential for additional organized areas of convection to fire along and north of the front as 30-40 kts west southwest h85 flow continues into the boundary. Simulated hi res radars show potential for additional rounds of convection to move parallel and along and just north of the front, with a period of training with each round. The slight risk area was drawn where the HREF neighborhood probabilities were high for 1, 2 and 3"+ totals from the southeast MN/southwest WI border area, east northeast across north central WI and into the northern L.P. of MI. Hi res models are in good agreement on this axis, reflected by high EAS probabilities of 1"+ amounts, 50-70% and 10-25% for 2"+ amounts through the slight risk area. In areas of training hourly totals of 1-2"+ are possible with potential for more than one round of training during the day 1 period. Oravec=20 Day 2 Valid 12Z Wed Oct 25 2023 - 12Z Thu Oct 26 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN PLAINS... The strong height falls moving across northern Mexico day 1 will be ejecting northeastward into the Southern Plains day 2, continuing the multi day heavy rain event for portions of the Southern Plains. The day 1 axis of above average PW values across the Southern to Central Plains into the Lower MO Valley will continue during the day 2 period with anomalies remaining 2 to 3+ standard deviations above the mean across these regions. This and the overall strong upper dynamics associated with the northeastward ejecting closed low will support potential for additional widespread heavy rains from the Big Bend, northeastward into Northwest TX, much of OK, save for the Panhandle and southeast OK. There are still some differences in this heavy axis, but a continued strong signal for the potential of overlap of heavy rains from the day 1 period and day 2. Only some minor changes to the previous outlook areas, trimming of the west side of the marginal risk and narrowing of the slight risk area. With the potential for heavy rain overlap days 1 and 2, an upgrade to moderate is possible with later issuances, depending upon where the heavy axis occurs day 1. The day 2 slight area continues to=20 match fairly well with CSU first guess fields, although having a slightly different orientation to the axis to match the latest day 2 qpf. ....Upper Mississippi Valley into the U.P. of Michigan... The expected active day 1 convection along the frontal boundary stretching across the Upper MS into the Upper Lakes may begin to refire along this boundary late day 2, early hours of Thursday,=20 as southwesterly low level flow of 30-40 kts restrengthens into this front. This will favor the potential for another round of convection to move parallel to the boundary early Thursday and possibly across areas that received heavy amounts during the day 1 period. This heavy rain will likely continue into the day 3 time period, with a higher threat risk depicted for day 3. For day 2, we continue to show only a marginal risk, but this may need to be increased to slight in subsequent issuances depending on where the training axes set up day 1. Oravec Day 3 Valid 12Z Thu Oct 26 2023 - 12Z Fri Oct 27 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE UPPER MISSISSIPPI VALLEY INTO THE UPPER GREAT LAKES... The well defined front stretching from the Upper Mississippi Valley into the Upper Great Lakes will continue to be the focus for additional heavy rains day 3. The next round of convection moving along and to the north of this front that is expected to begin late day 2, will continue into the day 3 time period as surface low pressure moving along this front helps to maintain strong west southwesterly flow into this front. This will likely support widespread heavy rains from northwest IA, across far southeast MN, much of WI into the northern L.P. of MI and the central to eastern U.P. of MI. The slight risk was narrowed from the old day 4 outlook to match current qpf consensus. There will be potential for training of cells along and north of the front and potential for overlap of day 1 heavy amounts with expected day 3 amounts. This may be especially so from northeast WI into portions of the south central U.P. into the northern L.P. where multi day totals of 3-5"+ are possible. This may be an area where an upgrade to moderate may be necessary with later issuances depending upon how the day 1 qpf axis verifies. Oravec Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8bQhs08aQNyj9AhAI4OdhtdAW86iE4b6BmZgIaLYiQ1-= 9uMe2bN4WPhV8D_hXi_z_eODMO4sA3wdEl29MTtUkHqYMpA$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8bQhs08aQNyj9AhAI4OdhtdAW86iE4b6BmZgIaLYiQ1-= 9uMe2bN4WPhV8D_hXi_z_eODMO4sA3wdEl29MTtUBZJ4yEw$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8bQhs08aQNyj9AhAI4OdhtdAW86iE4b6BmZgIaLYiQ1-= 9uMe2bN4WPhV8D_hXi_z_eODMO4sA3wdEl29MTtUtmY6hp0$=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) .