Flash Flood Guidance
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Issued by NWS
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825 AWUS01 KWNH 041753 FFGMPD MNZ000-NDZ000-042100- Mesoscale Precipitation Discussion 0396 NWS Weather Prediction Center College Park MD 152 PM EDT Tue Jun 04 2024 Areas affected...Red River Valley of Northwestern Minnesota & Adj North Dakota... Concerning...Heavy rainfall...Flash flooding possible Valid 041755Z - 042100Z SUMMARY...Short-term window for northward training/repeating of developing thunderstorms capable of 1.5-1.75"/hr rates. Scattered spots up to 3" in 1-2 hours pose localized flash flooding concern before front presses eastward more rapidly. DISCUSSION...GOES-E WV suite depicts an anomalously deep (2-2.5 std. dev) closed low across southern Canada with a strong 110-120kt Pacific jet diving south across the northern High Plains supporting a secondary shortwave across central SDAK. A short 90kt jet south to north jet streak across NDAK supports dual dynamic strengthening of the lower levels with DPVA and right entrance ascent over the Red River Valley. A strong surface wave is analyzed along the SD/ND/MN boarder with a slow moving front connected up to the triple point low along the Canadian boarder (with the warm front across the northern MN toward Lake enhanced front near DLH. Isallobaric backing 925-850mb flow within the warm sector is providing moisture flux convergence along the stalled/slow moving front through the Red River Valley. As such, convective overturning has begun. MLCAPE to 1500 J/kg support strong updrafts; though that confluent low level flux north of the inflection helps to pool moisture to near 1.5" TPW with mid to upper 60s Tds. This should support hourly rates of 1.5-1.75"/hr, though updrafts/downdrafts may be narrow. Deep layer steering is fairly parallel to the boundary and the 500-1000 thickness suggest propagation vectors to be generally aligned at the front. This will be short-lived as the shortwave continues to progress and forward progression of the front will begin in earnest over the next few hours. This may allow for a window of 1-3 hours of training cores in proximity of the front and through the naturally lower FFG values near the River Valley. As such, spots of 2-3" are possible which may result in a spot or two of possible flash flooding conditions. Thereafter, updrafts should broaden/strengthen but forward (eastward) propagation may limit totals to 1.5-2" mainly in a sub-hourly to hourly nature, this will move into higher FFG and risk of flash flooding should likewise decrease into the north woods of MN. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...FGF... ATTN...RFC...NCRFC...NWC... LAT...LON 49489513 48999453 48109463 47219507 46249567 46089696 46509711 47609685 48969607 49079540