Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jun 03 2025 23:10:29 FOUS30 KWBC 032309 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 709 PM EDT Tue Jun 3 2025 Day 1 Valid 16Z Tue Jun 03 2025 - 12Z Wed Jun 04 2025 ....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF SOUTHEAST KANSAS... ....19Z Special Update... A Moderate Risk upgrade was introduced with this update for portions of southeastern Kansas. A training line of heavy thunderstorms has set up along and south of I-35 in and east of Wichita is producing areas of considerable flash flooding. Rates in the convection currently are over 2 inches per hour, and showing no signs of weakening. The line of storms is nearly stationary, with=20 additional convection forming southwest of the area which are=20 likely to train over these same areas over the next several hours.=20 Localized totals of 7 inches have already fallen in the hardest hit areas. It's likely some areas will exceed 10 inches of rain before the line eventually moves off to the east. Additional significant flash flooding, including Flash Flood Emergencies, are likely over the next several hours. Please see MPD 351 at wpc.ncep.noaa.gov/metwatch/metwatch_mpd_multi.php?md=3D0351&yr=3D2025 for additional details. Wegman Day 2 Valid 12Z Wed Jun 04 2025 - 12Z Thu Jun 05 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDWEST, MIDDLE MISSISSIPPI VALLEY, SOUTHERN PLAINS, THE FOUR=20 CORNERS/DESERT SOUTHWEST, AND THE SOUTHEAST... ....2030Z Update... Changes to the Day 2 ERO for this cycle were relatively minor. Expanded the Four Corners Marginal Risk on the western side to encompass parts of eastern California and southern Nevada. HREF probabilities for exceeding 3 and 6 hour FFG guidance are scattered through much of the Southwest once again Wednesday. However, the HREF mean etc. shows lower instability compared to today (Tuesday) and support aloft is not quite as strong, so held off from a Slight Risk, but expect possibly isolated to scattered flash flooding, but possibly less focused. Another area to watch for a potential=20 Slight is the southern High Plains, for nocturnal convection that=20 may produce heavy rain rates before 12Z Thursday, but looks to ramp up specifically Thursday/Day 3 period. Meanwhile, expanded the=20 Marginal Risk in south-central Texas for some Wednesday morning=20 ongoing convection. The Southeast to Florida Marginal Risk remains=20 similar to the previous outlook. Tate ....Previous Discussion... ....Four Corners into Central/Southern High Plains... Another active day of showers and thunderstorms expected as the upper low over northern Baja fills and ejects northeast atop the Four Corners. The accompanying ascent will move into continued anomalous PWs which will exceed the 99th percentile (per NAEFS). This will fuel widespread convection capable of localized rainfall rates of 0.5"/hr (or at times higher). Storms will likely move slowly beneath the upper trough, leading to a longer duration of heavy rain. Although total rainfall will be modest in most areas (as reflected by relatively low 24-hr probability from ECENS/GEFS for 1" exceedance), where the heavy rain impacts sensitive terrain features or urban areas instances of flash flooding could result. Probabilities have also increased a bit (particularly from the new 00z ECENS suite) further east into the Central/Southern High Plains and the MRGL risk has been expanded accordingly. Should models come into better agreement, additional expansion may be needed further south into West TX (and with additional CAM guidance and agreement, an upgrade to SLGT may also be needed). ....Southern Plains and Mid-Mississippi Valley to Great Lakes... The cold front from D1 will continue its trek eastward on Wednesday, but will start to slow and become aligned more west to east as its tail gets pulled northward by an approaching shortwave over the Four Corners region. Shortwaves embedded within the flow will continue to race northeast, especially from Missouri to Michigan, which is where the greatest concentration of thunderstorms is expected on D2 (though some models are also indicated potential for isolated convective development farther southwest into portions of the Southern Plains). Storm motions along the front are likely to be progressive, lifting off to the northeast on 0-6km mean winds of 20-30 kts, but weaker Corfidi vectors aligned both to this mean wind and the front suggests a potential for training. As rainfall rates peak above 1"/hr within favorable thermodynamics, this could result in stripes of heavy rainfall with ensembles indicating 10-40% chance of exceeding 1" and up to 10% probabilities for exceeding 2" (with the new ECENS being the most aggressive). The inherited MRGL risk was maintained (and expanded a bit southwest) with this update. ....Southeast... Guidance continues to be somewhat aggressive with=20 a wave of low pressure potentially developing along an inverted=20 trough shifting northeast along the FL/GA/SC coasts. While NHC=20 continues to indicate a 10% probability of tropical or sub-tropical development with this feature, regardless of whether a circulation forms or not, there continues to be increasing confidence that=20 heavy rain will spread across the FL Peninsula and then rotate=20 onshore the GA/SC coasts on Wednesday. There also has been a clear=20 model trend of potential increased convective development farther=20 inland to the FL Panhandle and into southeast AL and southwest GA=20 (likely due to a stronger closed low and the associated dynamics),=20 so the MRGL was expanded to reflect this. With PWs progged to=20 exceed 2", above the 90th percentile, supported by warm cloud=20 depths that may exceed 15,000 ft, efficient rainfall rates of=20 1-2"/hr will be likely in any showers/thunderstorms. It certainly=20 remains possible that the heaviest rainfall in association with the potential surface low will remain just offshore, but impressive=20 moisture convergence from Jacksonville, FL to Charleston, SC should support waves of heavy rainfall regardless of development of this=20 system. Additionally, plentiful tropical moisture across the rest=20 of the FL Peninsula and a shortwave continuing to pivot across the=20 Gulf could enhance rainfall over much of Florida Wednesday, and the MRGL was maintained accordingly (with the exception of the FL=20 Keys, which were removed due to model consensus that convection=20 will be pulling away northward by 12z Weds). Churchill/Weiss Day 3 Valid 12Z Thu Jun 05 2025 - 12Z Fri Jun 06 2025 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE SOUTH-CENTRAL PLAINS... ....Central Great Basin to Central/Southern Plains into the Ohio Valley... Thursday/Day 3 should see a similar pattern as Wednesday/Day 2,=20 with a broad positively tilted trough axis across the West and=20 shortwaves moving through. Pacific moisture (continuing to be over=20 the 90th percentile for PWs) will stream northeastward just ahead=20 of the trough to produce scattered convection across the central=20 Great Basin toward the central Rockies, so expanded the Marginal=20 Risk into these areas with the axis just a bit north of the=20 previous couple of days.=20 Farther east, an initial shortwave will force convection in the=20 southern High Plains Wednesday night into Thursday morning. Then a=20 renewed low level jet will push moisture and instability a bit=20 farther north into Oklahoma/Kansas Thursday night and likely=20 sustain convection that originates in Colorado, leading to heavy=20 rain rates. For this issuance, combined both these areas into the=20 Slight Risk. There continues to be some model spread in heavy=20 rainfall placement and with which MCS may lead to the heavier=20 totals, with most recent ECENS probabilities of exceeding 1" and 2" focused in Oklahoma whereas GEFS probabilities are centered in=20 Kansas. So more refinements may be necessary in future cycles.=20 Expanded the Marginal farther south in West Texas for convection=20 with heavy rain rates just east of the dryline. To the east, moisture pooling along a meandering front may lead to locally heavy rain across the Mid-Mississippi Valley and Ohio=20 Valley toward the Lower Great Lakes region. A Marginal Risk remains in place for these areas. Considered a Marginal Risk stretching=20 into northern New England near/ahead of the front where above=20 normal moisture and instability are likely, but model QPFs were not very heavy. There is likely a nonzero probability though so will=20 continue to monitor. ....Southeast/Carolina Coast... Model guidance indicates a low pressure system potentially just=20 onshore in the Carolinas near the Atlantic coast on Thursday. This=20 system is most likely to be frontal but with a low end chance of=20 becoming tropical or subtropical per NHC. Heaviest rainfall totals=20 are forecast to stay offshore. However, wraparound moisture will=20 stream into coastal areas with PWs above the 90th if not 95th=20 percentile. Instability though generally looks to remain below 1000 J/km west of the low, which may limit rain rates somewhat. Per=20 coordination with the Morehead City (MHX) WFO, antecedent=20 conditions are wetter than normal along coastal areas due to recent rain. So will continue to monitor this area for a Slight Risk=20 eventually, but will await better model convergence and see if=20 instability increases. Expanded the preexisting Marginal west a bit per some 12Z models that were farther inland. Tate/Churchill Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!9RRhsR4EkagdCoYQqdj0O0dd5clmSKq3mp582ziBPr8L= SCjqxdEEAxwvRm8PZpxlEhmy-5BC9ylBeA7pC5M-LyMcub0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9RRhsR4EkagdCoYQqdj0O0dd5clmSKq3mp582ziBPr8L= SCjqxdEEAxwvRm8PZpxlEhmy-5BC9ylBeA7pC5M-O3pTwJM$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9RRhsR4EkagdCoYQqdj0O0dd5clmSKq3mp582ziBPr8L= SCjqxdEEAxwvRm8PZpxlEhmy-5BC9ylBeA7pC5M-naPUuo0$=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) .