Flash Flood Guidance
Issued by NWS
Issued by NWS
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932 AWUS01 KWNH 061700 FFGMPD MTZ000-WYZ000-062300- Mesoscale Precipitation Discussion 0230 NWS Weather Prediction Center College Park MD 1259 PM EDT Mon May 06 2024 Areas affected...Portions of Eastern Montana and Northeastern Wyoming Concerning...Heavy rainfall...Flash flooding possible Valid 061659Z - 062300Z SUMMARY... The comma-head region of a deepening cyclone will feature steady rainfall with embedded thunderstorms capable of producing flash flooding. DISCUSSION...Low-level moisture inflow into portions of the upper High Plains is advecting an air mass with dew points into the 50s into this typically dry part of the country. This is being driven by a developing strong low-pressure system threatening to break monthly low pressure records in the western Dakotas. The moisture feed into the storm originates in the Gulf, and is advecting into the area on up to 50 kt winds in the lower levels. Meanwhile, as is typical with mature storms, dry air aloft making up the comma is ending the precipitation further east into the western Dakotas. The dry air aloft is enhancing potential instability, which has allowed for a few thunderstorms to develop on the dry-slot/comma-head interface. These storms have caused greater than an inch per hour rainfall rates, which have already caused some localized flash flooding. CAMs guidance suggests additional thunderstorm development is likely, as noted by the line extending north of the Black Hills. The storms are most likely to form along the eastern edge of the precipitation shield, or as the current line shows, extending as a band of storms into the dry slot. Should the storms move over flood sensitive areas, additional flash flooding is possible. Wegman ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...BYZ...GGW...RIW...UNR... ATTN...RFC...MBRFC...NWC... LAT...LON 48340694 48170640 48010622 48050624 47650605 46740561 45920545 44590520 44280563 44190675 44250714 44730778 45910816 46410823 46950826 47430803 48110748