Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Aug 01 2023 23:00:07 AWUS01 KWNH 012300 FFGMPD MNZ000-SDZ000-NDZ000-020400- Mesoscale Precipitation Discussion 0829 NWS Weather Prediction Center College Park MD 659 PM EDT Tue Aug 01 2023 Areas affected...Southern ND...Northwest MN...Far Northern SD Concerning...Heavy rainfall...Flash flooding possible Valid 012300Z - 020400Z SUMMARY...Additional strong thunderstorms containing excessive rainfall rates as high as 2"/hr could produce areas of flash flooding, especially in areas where training thunderstorms occur. DISCUSSION...22Z surface analysis showed a frontal boundary extending from eastern MT all the way to a surface low located in far northwest MN. There is also a warm front oriented N-S that has helped spark storms over northwest MN. Visible satellite also depicted an outflow boundary propagating north into southern ND that was already beginning to trigger new thunderstorms. The atmosphere sports plenty of instability (MLCAPE of 1,000-2,500 J/kg) and moisture content (PWs of 1.25-1.5", highest values over the Red River of the North). The special 20Z BIS sounding showed that while there were dew points in the upper 60s, still quite a bit of mid-level dry air was present. This should help to cap the heavy rain threat to an extent. However, it also showed a strong 200-300mb jet aloft with increasing sfc-6km shear (easterlies in the sfc-3km layer, westerlies 3-6km layer). This kind of sheared environment will support storms capable of containing healthy mesocyclones, which in the presence of upper 60s to low 70s dew points and PWs that are near the 90th climatological percentile can still be efficient rainfall producers. Over the next few hours, the 850mb jet over SD will strengthen out of the south and intersect the stationary front over ND. Meanwhile, 850-300mb winds will be oriented quasi-parallel to the front, suggesting storms forming along the front and other potential outflows could result in training storms. It is worth noting the 850-300mb winds are progressive (20-30 knots), so cases where flash flooding have the best odds of occurring would be where training storms takes shape. The 18Z HREF shows 1-3hr QPF > 1-3hr FFGs topping out around 20% within this MPD's time frame. The setup could favor possible training in select areas along or just ahead of the cold front, especially as storms in western ND approach ongoing storms in eastern ND and western MN. AHPS also shows some parts of southern ND and western MN have picked up 300-400% of normal rainfall in the past 7 days as well. Flash flooding is possible this evening with poor drainage areas, more urbanized communities, and locations with more saturated soils most at-risk. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4h1Xlj68XLVqtIKel7NNz0z2uwOjWliHBAY6qmFynq0ALNJJB9dwB7H4d2MZoQn93K_l= XL9lUyILpP2Zrb3kdYu8f9M$ for graphic product... ATTN...WFO...ABR...BIS...FGF... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 47980146 47629973 47639766 47809531 46929495=20 46239549 45809769 46010056 46980202=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) .