Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed May 17 2023 04:32:37 AWUS01 KWNH 170432 FFGMPD MTZ000-170830- Mesoscale Precipitation Discussion 0306 NWS Weather Prediction Center College Park MD 1230 AM EDT Wed May 17 2023 Areas affected...Central MT Concerning...Heavy rainfall...Flash flooding possible Valid 170430Z - 170830Z SUMMARY...An isolated threat for some runoff problems and potential flash flooding may exist over the next couple of hours across portions of central MT to the east of Great Falls. DISCUSSION...The late-day GOES-W IR/WV satellite imagery shows a mid-level trough with multiple vort centers situated over central and western MT. This energy over the last couple of hours has been working in tandem with a relatively unstable boundary layer with MLCAPE values of as much as 500 to 1000 J/kg to foster a few small-scale clusters of showers and thunderstorms. More recently, radar imagery has been showing some tendencies for this activity to begin aligning itself in a general north/south fashion across portions of southern Liberty, Chouteau, and eastern Cascade counties. This alignment and localized training of convective cells is currently focused east of the greater Great Falls, MT area. Meanwhile, surface observations show a cold front making steady progress toward central MT from the northwest in connection to stronger height falls/troughing dropping south through south-central Canada. This cold front will likely promote a swath of somewhat stronger surface convergence in vicinity of the current complex of convection and may result in some additional upscale growth of this activity over the next couple of hours. The relatively slow cell-motions, cell-training activity, and potential for some additional expansion of the convective coverage may promote a 2 to 3 hour window of seeing excessive rainfall totals. The PWs across the region are running 1.5 to 2 standard deviations above normal, and with the instability and larger scale forcing nearby, there will likely be areas of convection with rather intense rainfall rates that could exceed 1.5 inches/hour. Over the next few hours, some spotty storm totals of 2 to 4 inches may be possible, and this might result in some runoff concerns and potential for isolated flash flooding. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-Bg8t1hBtK8D_IoIE9oOgnIx8g68zdn6xcJtt6v4e7vv0fnE8WqG7fUw_JH9oDfUTTtQ= bTl4RRPG1zdOg-S5TqxkXeo$ for graphic product... ATTN...WFO...TFX... ATTN...RFC...MBRFC...NWC... LAT...LON 48441131 48211066 47611014 47120993 46901006=20 46831044 46941075 47401135 48211183=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) .