Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, 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
44
822 FXUS63 KUNR 242301 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 501 PM MDT Wed Apr 24 2024 .KEY MESSAGES... - Thunderstorms with heavy rain expected Thursday afternoon and evening, with some hail and gusty winds. - Widespread rain will develop Friday morning and continue through Sunday, bringing abundant moisture to the area. - Warmer and drier weather expected early next week. && .DISCUSSION...(This Evening Through Wednesday) Issued at 240 PM MDT Wed Apr 24 2024 Low amplitude upper ridge axis is slowly crossing the central to northern Rockies, ahead of a split trough extending along the Pacific Coast. A weak upper low is crossing southern to central California and will push northeastward toward Colorado tonight and Thursday. Surface high pressure has pushed into the Great Lakes region, with strong return flow now over the area. Temperatures are currently in the 60s to mid 70s. One last quiet night is expected tonight before the unsettled, wet pattern develops. Theta E advection tonight and tomorrow will bring dewpoints into the upper 40s/low 50s across western South Dakota by Thursday afternoon. With temps reaching into the 70s across most areas, forecast soundings suggest SBCAPE values to 1500 J/kg. The best 0-3 SRH seems to be mismatched with the strongest instability. The strongest shear will be over central SD, where gusty SE winds are expected...and weakest across northeast WY. Severe weather will be limited by just weak shear across the Black Hills/far western SD. However, there is enough instability for storms to produce hail and gusty winds...and a few perhaps producing large hail...as they push eastward off the Black Hills into increasingly better shear. PWATs are in the 150% range in the early afternoon, then increasing to 175-200% by late afternoon/evening. Models suggest the stronger storms may produce over an inch of QPF through the evening. The storm system will become better organized and strengthen Thursday night/Fri morning as it pushes into western Nebraska. Wrap-around precip will fill in across the CWA, especially over western SD, where a band of heavier precip is expected. Northerly winds will develop, which will bring upslope enhancement to the northern Black Hills area. Right now it looks like half an inch to an inch of QPF will fall on Friday across portions of western SD, with locally higher amounts over the northern Black Hills. A second system will dig across the Four Corners region late Friday and lift into the central Plains Saturday into Sunday. As precip wanes from the first system, redevelopment is expected with this second system Saturday into Sunday. This system will be farther east, which could bring the highest QPF to south central SD into East River on Sunday...but some uncertainty remains with this track. It does look like light rain will continue to fall over the rest of the area through much of the weekend. Breezy northeast winds may bring slight upslope enhancement across the northern to eastern foothills Saturday into Sunday morning. By Sunday afternoon, much of the forecast area could see QPF amounts of 1 to 2 inches...maybe even 3 inches across some spots. Drier weather will finally move in late Sunday into Monday...with warming temperatures for the first half of the week. && .AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening) Issued At 449 PM MDT Wed Apr 24 2024 Isolated showers, and possibly a thunderstorm, may occur near the SD/NEB border early this evening. Isolated showers are then possible over northeastern Wyoming, the Black Hills area and southwestern South Dakota tonight through Thursday morning. Showers and thunderstorms will increase in coverage and intensity after 20Z on Thursday afternoon. VFR conditions will continue overnight with areas of MVFR CIGS developing over south central South Dakota after 11Z on Thursday morning and continuing through the Day. Mainly VFR conditions are expected over the rest of the area with LCL MVFR conditions possible with the stronger showers and thunderstorms on Thursday afternoon. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...13 AVIATION...10