Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Feb 06 2023 08:31:11 FOUS30 KWBC 060831 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 330 AM EST Mon Feb 06 2023 Day 1 Valid 12Z Mon Feb 06 2023 - 12Z Tue Feb 07 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Churchill Day 2 Valid 12Z Tue Feb 07 2023 - 12Z Wed Feb 08 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE ARKLATEX AND PORTIONS OF THE SURROUNDING REGION... A positively-titled trough ejecting out of the Four Corners region Tuesday begins to take on a neutral-tilt as it approaches central Texas. Meanwhile, a downstream jet streak over the Ohio Valley strengthens to near 130 kts by late Tuesday/early Wednesday, providing large-scale forcing for ascent across the ArkLaTex region. Deep layer southerly flow ahead of the system will usher higher moisture northward, characterized by precipitable water values near 1.5" (between 2-3 standard deviations above the climatological mean). Late Tuesday night into Wednesday morning the strengthening low-level jet (850 mb flow 30-40 kts) and deep layer lift is expected to produce several clusters of heavy rainfall initially across northeast Texas into northern Arkansas and far southern Missouri. The favorable overlap of strong lift, high moisture, and sufficient instability (MUCAPE of 1000 J/kg) should produce intense rain rates exceeding 2"/hr at times. In addition, deep layer flow being nearly parallel to expected storm motions could allow for training/repeating rounds of heavy rainfall. The ECENS and GEFS members still show decent probabilities for 2"+ totals over the period (with some potential for isolated 3-4 inch amounts), although there was a notable (but minor) shift towards the west of prior runs. As a result, the Slight Risk area was shifted west according, and also once again expanded (this time a bit towards the south) for this cycle. The latest NASA SPoRT 0-40 cm layer soil moisture values remain above the 90th percentile of climatology across a good portion of eastern TX (and 7-day precipitation departures are as high as 300-600 percent of normal across much of northern and eastern TX). Churchill/Bann Day 3 Valid 12Z Wed Feb 08 2023 - 12Z Thu Feb 09 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF THE MIDDLE AND LOWER MS/OH VALLEYS... An upper-level trough will transition to a negatively-tilted configuration as it approaches the Middle and Lower Mississippi Valley on Wednesday. Deep layer southerly flow will remain entrenched ahead of the trough, increasing tropospheric moisture levels across the region with precipitable water values reaching as high as 1.5-1.8 inches. This increase in tropospheric moisture, combined with strong lift and instability (MUCAPE of 500-1000 J/kg), will result in the potential for heavy rainfall with areal average 1-3" amounts (and locally higher) expected. The model spread going into Day 3 remains much higher than usual, as the ECENS and GEFS ensembles indicate a high degree of spread in the expected rainfall patterns (with the GFS/GEFS being the greatest outlier to the north and west, making it difficult to determine the exact location of the higher risk area for flash flooding at this time). The WPC Excessive Rainfall Outlook has therefore depicted a broad Marginal Risk area, covering a region from southern IL/IN southward through western TN and AR, into the state of MS and LA (with some surrounding portions of AL, OK, and TX also included). However, the potential for a Slight Risk area in subsequent outlooks remains fairly high, as models will eventually come into better agreement to pinpoint the greatest area of concern (likely somewhere near the Mid-South). With regard to antecedent conditions, NASA SPoRT 0-40 cm soil moisture values remain elevated across the Lower Mississippi Valley, whereas these soil moisture values are well below normal across the Middle MS and OH Valleys. Churchill Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5jycomvqaPzghmXxG2XoORn8yonwK-3Zp6q0fVp8L5Vl= uMYSmm5y9YfviDoqaYmZo9sdPCUb_EFZp-UWFMVQxULU9ec$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5jycomvqaPzghmXxG2XoORn8yonwK-3Zp6q0fVp8L5Vl= uMYSmm5y9YfviDoqaYmZo9sdPCUb_EFZp-UWFMVQ93-bRPM$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5jycomvqaPzghmXxG2XoORn8yonwK-3Zp6q0fVp8L5Vl= uMYSmm5y9YfviDoqaYmZo9sdPCUb_EFZp-UWFMVQHkD5RSk$=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) .