Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Oct 25 2023 16:14:44 FOUS30 KWBC 251614 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1213 PM EDT Wed Oct 25 2023 Day 1 Valid 16Z Wed Oct 25 2023 - 12Z Thu Oct 26 2023 ....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN PLAINS AND EASTERN KANSAS... ....16Z Update... Main adjustments this forecast cycle are the expansion of the Moderate further east across TX/OK with an inclusion of the DFW metroplex, as well as an addition of a Moderate risk over portions of eastern Kansas where heavy rainfall over the course of last night and this morning have lead to ongoing flooding south of Topeka. On these inclusions can be found below.... ....Central Texas into south central Oklahoma... Large scale forcing ahead of a deep shortwave trough centered over northern Chihuahua has aided in a line of heavy rainfall focused over west-central TX extending up into KS. Across the southern plains, rainfall rates have been observed consistently between 1-2" at peak intensity, but the slow forward progression of the main precip field has caused training of these heavier cells over portions of the area. Flash flood warnings have already been issued across the Concho Valley within the San Angelo urban area as observations have shown a general 1.5-3" of rain within the span of a few hrs. This is a trend that will continue to the east with increased convective coverage anticipated later this afternoon and evening with the initiation of the LLJ. Anomalous moisture field of 2-3 standard deviations above normal will persist across much of TX into OK which will enhance the heavy rainfall threat where convective impacts occur. 12z HREF probabilities are very high for neighborhood exceedance of 3" (70-80%) total, as well as 5" neighborhood exceedance (20-40%) across portions of central TX and southern OK. Upscale growth of the convective footprint will expand eastward overnight with hi-res guidance now depicting a greater impact into the DFW metro area which has a higher propensity for flooding due to the vast expanse of impervious surfaces within the urban corridor. Even the conservative EAS probability for exceeding 3" of rainfall has upwards of 20% across the Dallas metro and near 30% for the Fort Worth area. Rates of 1-2"/hr over several hrs will cause heightened flash flood concerns over the area, and with support from the Dallas/Fort Worth WFO, have elected to expand the Moderate further east to cover the northern sections of the I-35 corridor including the DFW metroplex. Rainfall totals of 5-8" with locally higher will be possible from the Edwards Plateau into north TX with much of the rainfall occurring within 3-5 hr intervals as the precip shield advances eastward. ....Eastern KS... A stalled frontal boundary over KS into MO with enhanced mid-level forcing and persistent southwesterly flow has allowed for a band of very heavy rainfall across portions of eastern KS, mainly northeast of Wichita and south of Topeka. Rainfall totals in excess of 8" have been reported across portions of Lyons county within the Topeka CWA forcing road closures out of Emporia. Another wave of moderate to heavy rainfall is forecast across the region later this afternoon and evening with the main axis of precip exiting after 06z. Considering the already saturated grounds within the corridor of expected rainfall, and with collaboration from the local Wichita/Topeka WFO's, have added a Moderate risk to the highly sensitive areas that were impacted overnight into this morning. Convective pattern will improve slightly once again as instability gradient that was pushed south from the area cold pool will return back the area of interest. 12z HREF probabilities for rainfall rates of 1"/hr or greater lie within the 25-30% range, but this is more than sufficient to cause problems for areas that cannot take much more rainfall. Embedded shortwave within the mean flow causing the secondary uptick will shift to the northeast with heavy rain potential focused over Kansas City and points north which allowed for the expansion of the SLGT risk as well from a previous update.=20=20 Kleebauer Day 2 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... ....Upper Mississippi Valley into the Upper 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 2. The next round of convection moving along and to the north of this front that is expected to begin late day 1, will continue into the day 2 time period as surface low pressure moving along this front helps to maintain strong west southwesterly flow into this front. This will support potential for additional heavy rains from northern IA, across far southeast MN, central to southern WI into the northern L.P. of MI and the southern U.P. of MI. The model consensus for the day 2 qpf axis has shifted southward from previous runs and has resulted in less overlap of areas that have received heavy rains over the past 24 hours and the day 2 qpf axis. The new day 2 outlook has also trended southward with the marginal and slight risk areas by about 40-60 miles. ,...Eastern Texas... Large scale dynamics will be weakening across the Southern Plains day 2 as the closed low ejecting northeastward day 1 continues to weaken as it presses into the Central Plains and Mid Mississippi Valley region. However, an axis of anomalous PW values ..2 to 3+ standard deviations above the mean... will persist across eastern TX. Model consensus is for moderate to heavy amounts in this anomalous PW axis. This expected precip will be mostly to the southeast of the expected day 1 heavy amounts. For this reason,=20 kept any risk at marginal. This marginal agrees well with the latest day 2 CSU first guess fields. Oravec Day 3 Valid 12Z Fri Oct 27 2023 - 12Z Sat Oct 28 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE SOUTHERN PLAINS INTO THE LOWER ARKANSAS RIVER VALLEY... ....Northeast Texas, southeast Oklahoma into northwest Arkansas... The anomalous PW axis across eastern Texas on day 2 will begin to lift northeastward ahead of the strong cold front sinking southeastward through the Central to Southern Plains during day 3. This front is expected to slow its southeastward push toward the end of the day 3 period becoming nearly stationary from northeast Texas into northwestern Arkansas. Precipitation should become more active along and ahead of this front late Friday afternoon into the early hours of Saturday when well defined frontal convergence and favorable right entrance region jet dynamics enhance uvvs in the anomalous PW axis. The model consensus is for a narrow axis of potentially moderate to heavy totals along this front from northeast Texas into southeast Oklahoma and northwest Arkansas. There may be some overlap of day 1 heavy precip and day 3 amounts across portions of northeast Texas into southeast Oklahoma. The threat level was maintained as marginal from the old day 4, but may need to be upgraded to slight in later issuances depending upon where the observed heavy amounts on day 1 occur. Oravec Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-8NFF2uA8KIW5P5nRCUCyCdg8-8SxGsjxZfUsUmwbO1X= hqJaxaGxTB8tBp_sNh--jLoLRfBRYYL9TylK3AaMW5dOwRs$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-8NFF2uA8KIW5P5nRCUCyCdg8-8SxGsjxZfUsUmwbO1X= hqJaxaGxTB8tBp_sNh--jLoLRfBRYYL9TylK3AaMwCwgUT8$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-8NFF2uA8KIW5P5nRCUCyCdg8-8SxGsjxZfUsUmwbO1X= hqJaxaGxTB8tBp_sNh--jLoLRfBRYYL9TylK3AaMCSKRDQA$=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) .