Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Mar 12 2024 20:01:45 FOUS30 KWBC 122001 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 401 PM EDT Tue Mar 12 2024 Day 1 Valid 16Z Tue Mar 12 2024 - 12Z Wed Mar 13 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Oravec/Kleebauer Day 2 Valid 12Z Wed Mar 13 2024 - 12Z Thu Mar 14 2024 ....A MARGINAL RISK OF EXCESSIVE RAINFALL IS IN EFFECT ACROSS PORTIONS OF THE CENTRAL PLAINS AND MID-MISSISSIPPI VALLEY... Sharpening trough out west will aid in the development of a lee surface low within the front range of the Rockies on Wednesday, strengthening through the period with accompanying 85H and 7H low pressures ejecting eastward into the plains. A warm front will develop ahead of the surface reflection across the central plains and Mid-Mississippi Valley, lifting north through the afternoon time frame. A surge of elevated theta-E's will occur south of the warm front with Gulf moisture advecting north thanks to prominent southerly flow ahead of the surface low to the west. Instability fields across guidance have become more robust over the past 24 hrs, along with the addition of the latest CAMs guidance at range in agreement with the global deterministic. Mid-level shortwave ejecting from the southwest within the difluent pattern aloft will help trigger a round of convection across portions of the plains within the confines of the warm front generally positioned over eastern KS into western MO, advancing northward towards the NE/IA border as the boundary continues its northward propagation. Locally heavy rainfall in excess of 1"/hr is becoming more likely with the latest 12z HREF probability fields signaling a stripe of up to 30% probability for exceeding the above interval during the Wednesday evening time frame, along with a 20-30% signal for at least 2"/3-hrs positioned over southeastern NE into northwest MO. This is generally along the warm front where hi-res deterministic has been most bullish in the general placement of the boundary and areal thunderstorm coverage during the initial development tomorrow evening. As we head through the overnight into Thursday AM, there's some discrepancies on the handling of the maturing 85H low as it ejects eastward through KS. The trend has been for a strengthening of the subsequent 85H low in-of central and northern KS which would provide ample support for a band of heavy rainfall to the north of the closed circulation within the developing CCB axis. Convective risks will be much lower due to the lack of sufficient buoyancy more co-located downstream along and south of the warm front. However, the ample moisture available within a broad expanse of 2+ deviations above normal PWATs signifies another local QPF maximum somewhere within the northern periphery of the low-level circulation. As of now, the prime candidate is likely within eastern NE where some deterministic shows north of 1" QPF within a 6-12 hr window after 00z Thursday, even some deterministic eclipsing 2" over the time frame of note. Latest ECMWF ML model output is also fairly consistent in showing a secondary QPF bullseye within the aforementioned zone, capable of localized flood potential within any small towns or urban corridors near Omaha/Lincoln. As of now, have added a MRGL risk encompassing the Quad state area across northeast KS, northern MO, central and southern IA, as well as eastern NE. Recent drought will likely limit some significant impacts within the above corridor, but hard soils from the lack of precip this winter and the threat of training within generated cold pools in the convective area of interest may lead to isolated flash flood returns, especially in any storms that exceed 1.5"/hr or greater.=20 Kleebauer=20=20 Day 3 The Day 3 outlook will be updated by 2030Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!537S_4WmV_jm5JIB9N_W0VaNJ3rTZ1pXHxw_7AV2AJE_= 2O6BY45pN4dlMugxSdhhRTDgvuq23RBG9q-9-kCoOrgkpwg$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!537S_4WmV_jm5JIB9N_W0VaNJ3rTZ1pXHxw_7AV2AJE_= 2O6BY45pN4dlMugxSdhhRTDgvuq23RBG9q-9-kCoIetZd4c$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!537S_4WmV_jm5JIB9N_W0VaNJ3rTZ1pXHxw_7AV2AJE_= 2O6BY45pN4dlMugxSdhhRTDgvuq23RBG9q-9-kCovnngRVE$=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) .