Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu May 11 2023 01:30:24 AWUS01 KWNH 110130 FFGMPD MNZ000-NDZ000-110500- Mesoscale Precipitation Discussion 0256 NWS Weather Prediction Center College Park MD 929 PM EDT Wed May 10 2023 Areas affected...Central to Northeast NDak...Ext Northwest MN... Concerning...Heavy rainfall...Flash flooding possible Valid 110130Z - 110500Z SUMMARY...Slow moving thunderstorms capable of 1-1.5"/hr rates crossing wet grounds and low FFG pose possible localized flash flooding risk into early overnight period. DISCUSSION...GOES-E WV suite depicts a compact but fast moving shortwave crossing central Manitoba with an associated surface low which drapes a cold front across northeast ND from KD55 to 5H5 to HZE where the synoptic ridge across the central US becomes the dominating feature. A subtle shortwave over-topping the US ridge across SW MN as helped to delay/stall the boundary across central North Dakota, though still within a regime of southerly low level flow to allow for increased moisture to reach to the Canadian boarder along the cold front. Surface Tds into the upper 50s along with solid day time heating has supported modest instability to build and with strengthening LLJ and favorable orthogonality with the front has supported sufficient moisture convergence to initiate convection along the boundary. Deep layer ridge has helped 500-1000 thickness ridge along the frontal zone, reducing forward propagation vectors while still having some weak bulk shear up to 25-30kts to allow for some weak organization of thunderstorms. Mean steering flow is 20-25kts just a few degrees east of parallel to the boundary to allow for some repeating/cross tracks if convection can be dense enough along the frontal zone. This would pose the best risk for isolated flash flooding conditions; however, given the ample moisture and depth/strength of the updrafts, hourly rain rates and totals up to 1.5" are probable.=20 The snowy winter has left the upper layers of the soil fairly saturated with NASA SPoRT LIS 0-40cm relative soil moisture values over 65% for much of the area becoming higher in the Red River Valley. As such, the low FFG values (less than 1.5"/hr) with 3-6hr FFG below 2" are within reach a single stronger downdraft core. As such, localized flash flooding is considered possible as the line slowly slides eastward before diminishing with sufficient remaining instability/loss of solar heating over the next 3-4 hours.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-pYeEbxT3ASWKBdTN_XshatnHCEQmxQedyvvc2No0o14B5cZJAssmSbvsn902OmJINm-= 44XaY-deifnZ9vZ6ykopsSg$ for graphic product... ATTN...WFO...BIS...FGF... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 49059731 48909627 48169763 47689893 47250057=20 47440090 47800042 48339947 48979828=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) .