Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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
298 FXUS63 KDMX 271149 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 649 AM CDT Mon May 27 2024 ...Updated for the 12z Aviation Discussion... .KEY MESSAGES... - Marginal risk for severe weather across the north and east. Damaging winds are the primary concern. - Additional showers and storms Tuesday for the south and east, but less in coverage and intensity compared to Monday. - Dry midweek followed by rainy period Thursday night into the weekend. Some signal for extended dry, warm period beginning sometime next week. && .DISCUSSION... Issued at 313 AM CDT Mon May 27 2024 Northwest flow settled in across the state with a shortwave upstream in the Dakotas. Ahead of the wave is a weak boundary that produced light showers in South Dakota and Nebraska overnight. Expect these showers to hold together in the north this morning. Rain will increase in coverage in the afternoon as the influence of the shortwave arrives, and once again with convective characteristics. Storms will form primarily in the eastern half of the state. MUCAPE values around 1000 J/kg will build in by the afternoon with fairly straight hodographs. As mentioned in the previous discussion, more favorable shear values are displaced in the south in the afternoon, but storms that can tap into the better shear will become more organized. The primary concern with the storms remains damaging winds with DCAPE values exceeding 500 J/kg over generally the southern half of the state. Cannot rule out sparse hail, but enough dry air in the column will limit hail development. As mentioned in previous discussions, funnel clouds will be possible beneath the vorticity generated from the shortwave. Additionally, if the boundary can reignite in the southeast this afternoon like some CAMs have, there is a nonzero landspout potential as the surface boundary provides near surface vorticity and stretching potential. The NST parameter doesn`t highlight this because the aforementioned shear values are canceling out the parameter there. Due to the low moisture content, rainfall amounts will generally remain under 0.20" for the day. High pressure begins to influence the weather on Tuesday, but not before one more shortwave ushers in a quick burst of rain into the same area as Monday. This time it will be with even less moisture. Plenty of deep layer shear will be present, but CAPE values look to be under 500 J/kg in the afternoon. At most for now, expecting at least some thunder showers in the south and east, but there isn`t enough instability or kinematics at play for strong storms. Trends will be monitored. Have lowered highs in the north Tuesday as the cooler air from the high pressure airmass invades the north in the afternoon, keeping that area in the upper 60s. A much welcomed dry period will settle in by midweek with upper level ridging displacing moisture to our south and west. The Gulf begins to open back up on the back side of the ridge late Thursday. A series of shortwaves originating from a longwave trough will keep the weekend weather rainy. Some instability may sneak into the southwest Saturday afternoon. Looking ahead at ensemble guidance, there are hints that an upper level ridging pattern will build in sometime next week, eventually bringing warmth and drying conditions. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 646 AM CDT Mon May 27 2024 Tempo at KFOD for fog for the first hour. Showers and some thunderstorms to move across northern terminals through the morning. Have left as VCSH due to lack of confidence in thunder holding together. Later, introduced VCTS for afternoon thunderstorms. Left KDSM and KOTM with VCSH due to lack of confidence. Northwest winds with 25kts possible in the afternoon. Rain and storms cease after sunset, leaving VFR for the remainder of the period. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Jimenez AVIATION...Jimenez