Flash Flood Guidance
Issued by NWS
Issued by NWS
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
291 AWUS01 KWNH 260721 FFGMPD MOZ000-ARZ000-OKZ000-KSZ000-261200- Mesoscale Precipitation Discussion 0325 NWS Weather Prediction Center College Park MD 320 AM EDT Sun May 26 2024 Areas affected...much of MO...northeastern and eastern KS...far northern AR...far northeastern OK Concerning...Heavy rainfall...Flash flooding likely Valid 260720Z - 261200Z Summary...Isolated to scattered instances of flash flooding becoming more likely through dawn with upscale growth and training of convection resulting in 1-3"/hr rainfall rates. Discussion...Deep convective activity late tonight remains somewhat scattered at this hour across eastern portions of the central/southern Plains into the Mid-MS Valley, though there are a couple of distinct areas where organized activity is starting to take shape: 1) over northeastern KS where semi-discrete cells are becoming more numerous in a west-to-east training orientation), and 2) with ongoing supercells just to the south, near the MO/KS/AR/OK border region, which have tended to remain more discrete and separated (thus far). The broader mesoscale environment is characterized by MUCAPE of 1500-3000 J/kg (with an interesting pocket of more stable air near the KS/MO border), PWATs of 1.3-1.6" (between the 90th percentile and max moving average, per SPC sounding climatology), and effective bulk shear of 30-60 kts. A very strong LLJ (40-60 kts) from the SSW is resulting in strong moisture transport/flux into the region, which should continue to organize convection due to further destabilization amid ongoing height falls from the approaching potent shortwave trough. Taking a look at the hi-res guidance, the activity farther south was largely missed by the entire 00z HREF suite, and only the latest runs of the HRRR (04z/05z/06z runs) have begun to properly assimilate and initialize these storms in the MO/KS/AR/OK border region. This has resulted in an altered depiction of QPF through early morning, with the 05z/06z HRRR suggesting that short-term localized totals will be limited to 1-3" for the northern swath. Earlier runs of the HRRR suggested higher amounts (locally 3-5"), as do the 00z HREF 40-km neighborhood probabilities for 3" exceedance (which are as high as 20-40%). But this development makes sense, as observational trends support a secondary swath of higher QPF to the south in association with upscale growth of convection and training of supercells (which have been capable of 2-3"/hr rainfall rates, compared to only 1-2"/hr with the swath farther north). Therefore the preference is towards the 06z HRRR as it has caught up with these trends, which suggests localized totals of 3-5" with the swath farther south (and is consistent with the exceedance probabilities from the HREF, though displaced just a bit south). As a result, expect for isolated to scattered instances of flash flooding to become more likely through dawn. Churchill ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...EAX...ICT...LSX...LZK...MEG...PAH...SGF...TOP... TSA... ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC... LAT...LON 39929744 39629524 39399318 39259217 38649135 37929091 37618981 36558956 36049027 35859243 35989486 36719629 37989659 38589727 39209783