Area Forecast Discussion
Issued by NWS Sioux Falls, SD
Issued by NWS Sioux Falls, SD
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
816 FXUS63 KFSD 272310 AFDFSD Area Forecast Discussion National Weather Service Sioux Falls SD 610 PM CDT Mon May 27 2024 .KEY MESSAGES... - Scattered showers and thunderstorms continue through the late evening hours tonight for areas of southwestern Minnesota and northwestern Iowa. There is a Marginal (level 1 of 5) risk for severe weather in this area. The greatest threat is damaging wind gusts of 60 mph and hail up to the size of a quarter. - A second round of showers and thunderstorms are possible for the same area Tuesday morning. Severe weather is not expected at this time. Most areas will stay dry. - Wednesday is expected to be dry. Multiple chances for showers and thunderstorms return Thursday through the weekend. - Temperatures will be near average for this time of the year. Breezy conditions ease tonight. Wednesday afternoon through Thursday afternoon is also expected to be breezy. && .DISCUSSION... Issued at 222 PM CDT Mon May 27 2024 TODAY-TONIGHT: Water vapor imagery shows a well defined upper low pressure system moving southeast across our area. This low is responsible for the scattered showers and thunderstorms this afternoon over southwestern Minnesota and northwestern Iowa. There exists a Marginal (level 1 of 5) risk for severe thunderstorms over this same area. Model guidance indicates a broad range of available potential energy, with MUCAPE varying from 500 to around 1500 J/kg. A deep, dry subcloud layer will provide ample time for evaporative cooling that could enhance downdraft strength into the 60 mph range. Low freezing levels between 6000 and 7000 ft AGL could support hail formation up to the size of a quarter. This wave should be east of the region around midnight. Breezy northwest winds will decrease this evening, becoming light and variable overnight. Lows will be in the 40s. TUESDAY: A second, weaker wave on the back side of the upper low brings another round of scattered showers and thunderstorms for early Tuesday morning. The latest guidance indicates most of the showers forming in the early morning hours east of I-29. While severe storms are not expected at this time, there is enough weak instability available for a few rumbles of thunder. Showers clear the area by early afternoon. Winds increase through the day, reaching around 10-15 mph sustained, with gusts up to 25 mph. Winds will initially be northerly, then shifting east through the evening and overnight, eventually becoming southeasterly for Wednesday. Highs for Tuesday will be a touch on the cool side thanks to the northwesterly winds and CAA, in the mid 60s to mid 70s. Lows will again be in the 40s. WEDNESDAY: A weak ridge builds in for Wednesday. Clear skies and WAA help us warm into the low to upper 70s. Meanwhile, a low pressure trough is digging southward over the Rockies. As it pushes east it will compact the SPG, bringing breezy conditions for Wednesday afternoon. Winds will peak in the afternoon, with the strongest winds west of the James River Valley. Sustained around 15-20 mph with gusts 25-30 mph. The breezy winds progress eastward overnight, spreading into southwestern Minnesota and northwestern Iowa by Thursday morning. THURSDAY AND BEYOND: By Thursday afternoon, a negatively tilted upper trough ejects out over the northern Plains, bringing the next chance for widespread showers and thunderstorms. Cloudy skies and showers will limit highs into the low to mid 70s for Thursday. Ensembles indicate a high (80- 90%) chance for widespread quarter inch of rain, and a moderate chance (60-90%) of a half an inch. At this time, the better dynamics for severe weather stay to our south, but there is a lot of time for this to change as the wave evolves. Several successive waves will follow this one through the early part of next week, indicating multiple chances for rain. However, confidence is low due to high model uncertainty. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 610 PM CDT Mon May 27 2024 VFR throughout the period. Scattered showers and thunderstorms along and east of I-29 are decreasing in coverage and intensity, with breezy W/NW winds similarly decreasing in intensity throughout the rest of the evening hours. May see another round of weak showers overnight into the morning hours, but coverage looks to be scattered at best. Semi-breezy N/NW winds will develop throughout the morning hours, decreasing during the late afternoon hours. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...AJP AVIATION...APT