Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 02 2023 02:30:35 AWUS01 KWNH 020230 FFGMPD MTZ000-WYZ000-020800- Mesoscale Precipitation Discussion 0407 NWS Weather Prediction Center College Park MD 1030 PM EDT Thu Jun 01 2023 Areas affected...Central Montana... Concerning...Heavy rainfall...Flash flooding likely Valid 020230Z - 020800Z SUMMARY...Slow moving convection along sharpening frontal boundary. Well above normal moisture and saturated grounds will result in likely localized flash flooding conditions through the early overnight period. DISCUSSION...GOES-E WV suite depicts a consolidating, broad but deep layer cyclone over central WY. Toward the north a very sharp and strengthening FGEN signal is manifesting across central MT from near the apex of the Big Horn Mtns to Valley county. Strengthening low level flow on both sides of the boundary (with 20-25kts northerly being orthogonally intersected by broad 25-30kt east-southeast to easterly flow out of eastern MT). A well of instability exists along the boundary as well with 500 J/kg in S MT up to 1500-1750 J/kg across northeast MT. Very deep surface to 700mb moisture with Tds in the 50s to low 60s (across NE MT) combined with the strong moisture flux convergence will allow for the stronger thunderstorms to have an efficient rainfall production (along with hail generation).=20 Currently, initial more elevated cells near Stillwater to Mussellshell county have be very slow moving given the isallobaric component to the deep-layer flow inward toward S WY, generally counteracted by the propagation toward the strengthening inflow/isentropic convergence. Total PWats of 1-1.25" supported 1.5"/hr rates and slow motions up to 1.5-2" locally inducing some spots of 300-450 cfs/smi in MRMS Flash...generally at the lowest levels for localized flash flooding conditions. Weak outflow from these cells has sharpened the frontal zone and reducing cloud bases, similar 1.5-2"/hr rates are probable, with some hints of 2-2.25"/hr rates after 04z, when 850-7H RH peaks with 700mb Tds in the mid 40s to low 50s especially as convective initiation unzips along the FGEN axis into NE MT.=20 Very wet early season with AHPS precip anomalies generally 300-500% of normal has lowered hourly FFG values below 1.25 and 3hr values <1.5". As such, scattered to numerous localized incidents of 1.5-2.5" are likely to induce scattered flash flooding across the area of concern through early overnight period.=20 Only uncertainty seems to be in cell motion, which may appear more chaotic and related to storm scale outflow interacting with other neighboring cells and strong 850 easterly flow generally about opposite to the mean cell motion to the west, bringing Corfidi vectors to very quickly throughout the next 4-6hrs. This may limit duration at a given spot.=20=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7Pbv8M13uWnvTWabYZxObCkH4DguSl1SScATZ4d7GY9KbEcbbZMFL8CY2wUwtexwhvdc= 5ORiOXsUKW6jCQH-NlbmsF4$ for graphic product... ATTN...WFO...BYZ...GGW...RIW...TFX... ATTN...RFC...MBRFC...NWC... LAT...LON 49040598 48840527 47950538 46950586 46060653=20 44770755 45180865 45440938 46600931 48700857=20 49020762=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) .