Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jun 09 2025 00:58:07 FOUS30 KWBC 090057 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 857 PM EDT Sun Jun 8 2025 Day 1 Valid 01Z Mon Jun 09 2025 - 12Z Mon Jun 09 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE SOUTHERN=20 PLAINS TO THE GULF COAST...AS WELL AS THE MID-ATLANTIC... 01Z Update... ....Southern Plains to the Lower Mississippi Valley...=20 A cluster of heavy thunderstorms over the TX Panhandle and=20 Northwest TX this evening will further develop into a forward=20 propagating bowing line (or lines) that last through the night and=20 reach the Gulf Coast Monday morning. High shear should allow the existing supercells to persist and congeal into organized MCSs.=20 Corridors of heavy rainfall in these MCS cases tend to occur in=20 the left bookend vortex, along the upshear flank of the cold pool, and with repeating cells which in this case would be activity=20 developing ahead of the main organized system.=20 Recent HRRR and RRFS runs are in decent agreement with widespread coverage of 2-4" across NW and North TX (upshear flanking side of the activity), southern OK and Northwest LA (left bookend of activity) through 12Z. This forward propagating system should increase forward speed late tonight, allowing it to at least approach the upper TX coast by 12Z.=20 Therefore, the Slight Risk was expanded a bit south in TX and LA with the Marginal extended to the Gulf Coast including the Houston metro. For further information on TX flooding potential this evening please see MPD 405 and further downstream MPDs overnight. ....Central Gulf Coast... Convection that fired on the outflow from morning heavy thunderstorms over central MS/AL continues this evening with 30kt bulk shear helping maintain supercell segments over southern AL. An approaching impulse from TX should allow westward propagation of this activity which CAMs have shown all day today. The 23Z HRRR=20 keys in on central MS to Mobile AL as the greatest heavy rain risk corridor (2-5") which is a bit farther west than previous runs.=20 Therefore, the Slight Risk was expanded west through southern MS. ....Mid-Atlantic and Central Appalachians... Shrank western end of Slight Risk where activity has waned with the cold frontal passage west of the Appalachian Crest. Maintained the Slight Risk over the rest of the Mid-Atlantic where activity is ongoing. Please see MPD 404 for further info. ....Midwest... Pre-cold frontal activity is progged from recent HRRRs to redevelop overnight as it shifts east. Given lower FFG over central/eastern IN and southeast MI, the Marginal Risk is expanded up through the Detroit area. Robust activity over central MO this evening is progged to shift over southern IL overnight, so the Marginal Risk was expanded there too. Lamers/Jackson Day 2 Valid 12Z Mon Jun 09 2025 - 12Z Tue Jun 10 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN PORTIONS OF PENNSYLVANIA AND NEW YORK...AS WELL AS THE GULF COAST... ....Northeast and Ohio Valley... Convective lines are expected to develop Monday just ahead of a=20 strong, steadily advancing cold front over the eastern Great Lakes=20 and Ohio Valley, and eventually advancing into the interior=20 Northeast (PA and NY in particular). A narrow plume of PWs around=20 1.5 inches and moderate instability should support heavy rain rates on the order of 1-2 inches per hour in the most intense activity.=20 The Slight Risk was maintained but retracted a bit to be focused=20 primarily in Pennsylvania and southern New York. The model QPF=20 signal was reduced a bit in eastern Ohio and West Virginia. Greater confidence in the possibility of training thunderstorms or=20 convective rain bands exists over PA and NY where the deep layer=20 mean wind will be more parallel to the cold front orientation.=20 Further southwest into portions of SE OH, WV, KY, TN, the HREF and=20 experimental RRFS ensemble both show a scattering of low chances of rainfall exceeding flash flood guidance on a 1-hr or 3-hr basis,=20 but overall ensemble mean QPF is lower and the mean wind is more=20 crosswise to the cold front. This suggests convective lines should=20 be more progressive and any flash flooding impacts may be more=20 isolated. ....Gulf Coast and Southeast... A Slight Risk was introduced from SE MS into S AL, SW and C GA,=20 and the FL Panhandle. Multi-model ensemble QPFs show the greatest=20 chances of 2+ inches of rainfall now increasingly concentrated in=20 this area. Scattered clusters of thunderstorms are expected to=20 develop by Monday afternoon across the Gulf Coast region in an=20 environment characterized by strong instability and PWs around 2=20 inches. The availability of deep moisture and favorable instability would support very heavy rain rates. While hi-res models differ a=20 bit on the details, they all generally show clusters and lines of=20 thunderstorms developing in west-east oriented bands along=20 mesoscale boundaries. Some of these boundaries may be related to=20 convection from the day and night prior, or increasingly the=20 arrival of a synoptic cold front from the northwest. Any lines that are oriented in this fashion would be more parallel to the deep=20 layer mean wind and could create corridors of training convection=20 and swaths of localized heavy rainfall. ....West Texas and New Mexico... For now, a broad Marginal Risk was maintained in these areas as=20 any concentrated areas of heavy rainfall would likely be highly=20 dependent on the convective evolution from Sunday afternoon into=20 Monday morning across the region. A forward propagating MCS across=20 S OK and N TX should push an outflow boundary somewhere into C TX,=20 and that could become a feature that focuses renewed convective=20 development on Monday. Broad low-level east to southeast flow from=20 the coastal plain all the way into W TX and E NM should cause PWs=20 to gradually increase, and support scattered convection well into=20 C/E NM during the afternoon hours. Some hi-res models show this=20 activity in NM coalescing into a MCS and pushing southeastward into W TX during the evening and overnight, and existing boundaries=20 would be important to that process as well. It's possible a Slight=20 Risk may be needed in future outlook updates. Lamers Day 3 Valid 12Z Tue Jun 10 2025 - 12Z Wed Jun 11 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF WEST TEXAS AND SOUTHEASTERN NEW MEXICO... ....West Texas, Texas Hill Country, and Southwest New Mexico... Greater confidence exists in a heavy rainfall event on Tuesday=20 (compared to Monday) in SE NM and W/C TX. A shortwave ejecting out=20 of the Desert Southwest will push through NM early Tuesday and=20 approach the Slight Risk area over the aforementioned region. The=20 combination of abundant deep moisture, with PWs generally above the 90th percentile for early June, strong instability, the=20 approaching shortwave, and upper level divergence will favor=20 widespread thunderstorm activity. Deep layer mean winds will not be particularly strong, around 10-15 knots, which should favor slow=20 eastward propagation with time. It seems most likely that=20 convective initiation will occur closer to the Sacramento,=20 Guadalupe, and Davis Mountains from SE NM into far W TX, near the=20 nose of a low-level moisture transport maximum. Slow propagation of convective clusters could then lead to flash flooding issues from=20 near those areas, to eventually as far east as the Edwards Plateau=20 and Texas Hill Country. Lamers Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6T0Kd9WHtsIfx4H6PpFJlFXDZSS_BfMo6l5ag1VabOpv= guYdiFaJkDf772HTn_b6iid2KwLTPDil6Fs_NKTWPJcdVuc$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6T0Kd9WHtsIfx4H6PpFJlFXDZSS_BfMo6l5ag1VabOpv= guYdiFaJkDf772HTn_b6iid2KwLTPDil6Fs_NKTWWQ0-tEQ$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6T0Kd9WHtsIfx4H6PpFJlFXDZSS_BfMo6l5ag1VabOpv= guYdiFaJkDf772HTn_b6iid2KwLTPDil6Fs_NKTWiu4v8L4$=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .