BBS: TELESC.NET.BR Assunto: HVYRAIN: Excessive Rainfall Discussion De: COD Weather Processor Data: Fri, 17 Apr 2026 15:34:48 +0000 ----------------------------------------------------------- FOUS30 KWBC 171534 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1134 AM EDT Fri Apr 17 2026 Day 1 Valid 16Z Fri Apr 17 2026 - 12Z Sat Apr 18 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM OKLAHOMA THROUGH PORTIONS OF THE MIDWEST... 16Z Update: Minimal changes were made from the previous forecast,=20 with a broad high-end SLGT Risk area from OK through central MO.=20 The SLGT Risk region was expanded ever-so-slightly southwest=20 further into central OK to account for good agreement with ML=20 models (ECAIFS and AIGFS) in handling the tail-end of the cold=20 front, albeit not as impactful.=20 An upper level trough in the northern Plains will pickup a cutoff=20 low in the Southwest, enhancing upper-level divergence due to jet=20 coupling in the Central Plains. A strong cold front will continue=20 tracking southeastward as a result through the central and southern Plains, which will meet a moist Gulf airmass with a relatively=20 robust southerly LLJ. Low-level convergence will be maximized upon=20 this interaction, and with high PWAT anomalies (widespread +3=20 standard deviations across northeast OK, southeast KS, and MO),=20 heavy rainfall is expected. Updated neighborhood probabilities=20=20 remain over 90% to exceed 2" in much of MO and KS, and 60% to=20 exceed 3" in southeast KS. Blanco-Alcala ..Previous Discussion.. A strong cold front tracking southeast across the Plains will run into a moist and unstable air mass driven by a robust low level jet streaming north off the western Gulf and into the Great Lakes. Meanwhile, a strengthening upper level jet will develop across Texas and Oklahoma Friday night that will further enhance lift across the Slight Risk region, particularly the southern part of it. The result will be a series of waves of strong thunderstorms that will feed on the influx of moisture and instability to allow for frequent redevelopment and training as the entire complex of storms pushes southeast. The strongest storms and most persistent rainfall will occur over areas hard-hit in recent days with prior heavy rainfall, so soils in areas from southern Oklahoma to western Missouri are already near saturation and well above normal for soil moisture content for this time of year. Urban areas from Kansas City to Tulsa will be especially vulnerable should persistent heavy rains set up over those metro areas. Meanwhile, a portion of the Ozarks could also introduce a topographic factor to any flooding potential. A higher-end Slight (25-40% chance of flash flooding) is in effect from northwestern Oklahoma through central Missouri. Meanwhile, further north into the Midwest, the storms are more likely to organize into a single line of storms more quickly. However, these areas have even more saturated soils due to more recent rains. When added the urban factor in cities such as St. Louis, Chicago, and Milwaukee, even a shortened period of heavy rainfall could still result in widely scattered instances of flash flooding. The Slight Risk in this area was expanded north up Lake Michigan to Green Bay, but elsewhere remains little changed. Wegman Day 2 Valid 12Z Sat Apr 18 2026 - 12Z Sun Apr 19 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE GULF COAST AND LOWER MISSISSIPPI VALLEY... A strong cold front sweeping south down the Plains will provide the primary forcing for a line of strong thunderstorms to form as the front uplifts a warm and moisture-laden air mass from the Gulf. Due to close proximity to the Gulf, PWATs are likely to spike to between 1.5 and 1.75 inches Saturday evening. This will support thunderstorms capable of very heavy rainfall. The line will generally be progressive, moving south. Further, the Marginal Risk area is generally covering some of the highest FFG areas in the country. Thus, the flash flooding threat is largely focused on the urban factor in areas such as Houston, Beaumont, and Alexandria. Most of the convective activity is expected at or after sunset, so any flooding that occurs will be more dangerous. Wegman Day 3 Valid 12Z Sun Apr 19 2026 - 12Z Mon Apr 20 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR DEEP SOUTH TEXAS... An area of disturbed weather, partially from the remnants of a cold front that swept across much of Texas on Saturday, will impact portions of Deep South Texas Sunday into Sunday night. The air mass will be characterized by summer-like amounts of moisture, with PWATs exceeding 2 inches in a few areas, and over 1.75 inches across much of Deep South Texas. This will support any showers and thunderstorms that form across the area to be capable of very heavy rainfall. However, the forcing for this rainfall will be lacking, resulting in only isolated to widely scattered showers and thunderstorms. Further, the FFGs in Deep South Texas are quite high, so any storms, which should be slow-moving, would need to train or remain over a single area for a while to produce flash flooding. Thus, only isolated instances of flash flooding are expected. Wegman Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6hMhKu6GCT4jxRt2L-VQi9jYa3W3iKJL0zzaWaUG9FnI= tQKh3T3VrR8MK2wDjhAuTBvbtk6gTLbM-qog0QUdcwWEiV0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6hMhKu6GCT4jxRt2L-VQi9jYa3W3iKJL0zzaWaUG9FnI= tQKh3T3VrR8MK2wDjhAuTBvbtk6gTLbM-qog0QUdXKOqrZ8$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6hMhKu6GCT4jxRt2L-VQi9jYa3W3iKJL0zzaWaUG9FnI= tQKh3T3VrR8MK2wDjhAuTBvbtk6gTLbM-qog0QUd7mtAqVg$=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 3.28-Linux * Origin: Capitol City Online (1:2320/107) ----------------------------------------------------------- [Voltar]