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
583 AWUS01 KWNH 220046 FFGMPD MIZ000-WIZ000-MNZ000-220500- Mesoscale Precipitation Discussion 0300 NWS Weather Prediction Center College Park MD 846 PM EDT Tue May 21 2024 Areas affected...far eastern MN into WI and the U.P. of MI Concerning...Heavy rainfall...Flash flooding possible Valid 220044Z - 220500Z SUMMARY...Despite an overall progressive nature for many locations, Heavy rain with embedded areas of training may produce localized 2-3 inch rainfall totals across portions of the Upper Midwest tonight. Localized to scattered areas of flash flooding may result through 05Z. DISCUSSION...GOES East water vapor imagery at 00Z showed a well defined, negatively titled shortwave trough over northern IA, tracking toward the northeast. Radar imagery and surface observations showed a commahead region of mostly stratiform rainfall but with embedded convection, producing hourly rainfall of 0.5 to 1 inch to the southeast of St. Cloud and St. Paul through 0030Z, located within a deformation axis to the N and NW of a vorticity max over IA. Weak elevated instability up to 500 J/kg was seen on the 00Z SPC mesoanalysis over eastern MN into northwestern WI. Farther south and east, a line of severe thunderstorms was tracking through west-central WI with a secondary line over south-central WI. Convective activity over WI is expected to continue in a mostly progressive manner off toward the northeast with mean storm movement of 40-50 kt toward the northeast within MLCAPE of 1000-2000 J/kg. However, the orientation of heavy rainfall echoes will support short term training at times with 1-2 in/hr rainfall rates. The majority of this activity should clear WI by about 04Z. Back to the west, a pivoting axis of deformation will allow slower movement of embedded moderate to heavy rain from far eastern MN into northwestern WI and western portions of the U.P. of MI. Here, localized 2-3 inch totals with rainfall rates possibly exceeding 1 in/hr on a localized basis at times within weak instability but a strong dynamically forced regime ahead of the upper trough will be favored. Anomalous moisture will help to support heavy rain with the 00Z sounding from GRB indicating an anomalous precipitable water value of 1.53 inches, near the climatological max for mid to late May according to the SPC sounding climatology. Otto ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...ARX...DLH...GRB...MKX...MPX...MQT... ATTN...RFC...NCRFC...NWC... LAT...LON 47718843 47468731 46578652 45658671 44108768 43038857 42858962 43219045 43999102 44529217 44599310 44829361 45469369 46519316 47389171 47698980