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
41
42
43
44
45
46
47
48
49
50
082 AWUS01 KWNH 022303 FFGMPD ILZ000-MOZ000-IAZ000-KSZ000-030430- Mesoscale Precipitation Discussion 0542 NWS Weather Prediction Center College Park MD 702 PM EDT Tue Jul 02 2024 Areas affected...Northeast KS...Northern MO...Southeast IA...Nortwest IL... Concerning...Heavy rainfall...Flash flooding likely Valid 022300Z - 030430Z SUMMARY...Upstream development across recently saturated soils in NE KS with rates of 2-3"/hr and potential axes of training pose likely flash flooding conditions over the later evening. Downstream maturing squall line to continue to track east-southeast with similar 2-3"/hr rates and localized 3-5" totals through 03z. DISCUSSION...GOES-E WV suite depict mid to upper level warming across central NEB with a subtle anti-cyclonic arched cirrus banding indicative of a subtle upper-level jet streak across SE NEB into SW IA; both suggestive of increased digging of the polar shortwave providing DPVA and right entrance ascent across Eastern KS and downstream. 22z surface analysis denotes this response with an amplifying wave lifting through central KS northeastward and backing surface winds across NE KS. Additionally, this has backed the LLJ just a bit with 30-35kts of increasing confluent flow across the Lower Missouri Valley. Deep moisture pooling has increased total PWat values into the 2.25" range and the combination of factors has seen recent convective initiation across NE KS (and a bowing line across south-central KS). Expect further convective development/expansion along the frontal zone with some back-building of the upwind portion of the squall line across N MO. This will provide an area of favorable deep layer unidirectional flow parallel to the convergence axis to support short term training. Given the parameters, of 2500-3000 J/kg across N MO and adj. KS; rates of 2-3"/hr are probable and with training streaks of 3-5" are possible before cold pools and upstream shortwave support forward propagation generally after 01-02z. Recent heavy rainfall over the region, has resulted in lowered FFG values of 1-1.5"/hr and below 2.5"/3hr which are likely to be exceeded resulting in broad axes of flash flooding conditions perhaps in and around the Kansas City Metro area (though more probable to the north and east given current trends). Further east into the Mississippi Valley... Regional RADAR and visible imagery depict a mature squall line extending from north-central MO/south-central IA starting to march into E IA and far SW WI. The warm front has surged northward along the southern edge of the eroding clouds in S WI. However, a pre-frontal surface wave developed downstream of the southern stream shortwave across central IA, but that wave is starting to accelerate northeastward and height-falls is starting to bow the QLCS out across SE IA. This will intersect and become more parallel to the 925-850mb moisture flux convergence channel and with upstream warm advection/backing influence from approaching polar shortwave; better moisture flux convergence will exist from the nose of the bowing segment in SE IA/N IL back southwest into northern MO. As noted, higher instability into the 3000 J/kg range, total Pwat to 2.25-2.4" and 25-30kts of inflow should support highly efficient rainfall production with 3"/hr rates likely. Training will become a bit less likely given strength of southeasterly propagation, but spots of 3-5" are likely across NE MO/SE IA/far NW IL. Recent WoFS solutions continue to shift this bulls-eye south and east with each run, but there is a consistency of of the mean values in this range, though 90th percentile values are in the 7-8" maximum ranges at the nose of pressing bow with spots of 4-5" across northern MO. This is further south of the 12z/18z Hi-res guidance, but given the trends, there is increasing confidence that portions of this area will see considerable rainfall totals and flash flooding conditions, even though soils have been drier they are still at 40-55% of capacity through 40cm. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...DMX...DVN...EAX...ICT...ILX...LOT...LSX...TOP... ATTN...RFC...ABRFC...MBRFC...NCRFC...NWC... LAT...LON 42389008 42368897 41868852 40848891 39479109 38549368 38109619 38829697 39639600 40029499 40509344 41169201