Sunrise 5:19 AM   Sunset 8:20 PM Moonrise 5:42 PM   Moonset 3:47 AM

  Print   HELP   Reset   Save   Recall  New

FXUS63 KUNR 200416 AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1016 PM MDT Sun May 19 2024

KEY MESSAGES

- Widespread showers late Monday/Monday night. Locally heavy rain over south central South Dakota.

- Active pattern continues through the end of the week and into the holiday weekend.

DISCUSSION
(This Evening Through Sunday)
Issued at 240 PM MDT Sun May 19 2024

Current surface analysis shows low pressure just east of the Black Hills, with warm front extending east across southern SD and a cold front trailing to the southwest across WY. A surface trough/dryline extends south from the low across the central into southern high Plains. Upper level analysis shows a pair of low pressure systems over southern Canada, with a shortwave trough across the northern Rockies into the northern high Plains.
Additional energy extends further south across the Rockies. Skies are variably cloudy with showers and storms developing early this afternoon across eastern WY, southwest SD, and the NE panhandle.
Temps are mostly in the upper 60s to around 80 degrees across the area, warmest over far southern SD. Winds are gusty from the south to southeast across a good portion of south central SD.

A fairly active afternoon/early evening is in store for portions of western into central SD as the surface low moves slowly east near the I-90 corridor during this time. Most of the short range models and CAMS show storms continuing to develop near and along the surface trough as it moves east through the late afternoon and early evening. A severe thunderstorm watch was issued earlier this afternoon for most of southwest into central SD until 02z. Latest analysis shows moderate buoyancy ahead of the low and to the south of the warm front across locations mostly east of the Black Hills at this time, with MLCAPE values to around 1000 j/kg to the southeast of the Black Hills. Shear is modest in most areas, with the more favorable values either behind the front to the north and west or well south/southeast across the central Plains. However, they could be sufficient for at least short-lived supercells or some more organized multicells to develop. Activity is starting to focus relatively quickly along the surface trough over southwestern SD as it tracks east into central SD by the early evening. Main time period for severe storm potential across southwest SD will be from now until about 5 or 6 PM MT, with areas further east toward central SD mostly from 4 to 7 PM MT (5 to 8 PM CT). Strong wind gusts and at least marginally severe hail will be the main threats from any severe storms, with wind likely becoming the bigger threat late this afternoon and early evening. A few lighter showers/thundershowers could linger later into the evening across western SD, but remaining activity should end by midnight.

After a brief period of quiet weather later tonight into Monday morning, showery weather develops for Monday afternoon into Tuesday as a larger trough moves across the western US and active southwesterly flow develops from the Rockies into the Plains.
Showers still look to be most numerous across southern portions of the forecast area, I-90 and southward, with some thunder also possible. At least some locally heavy rain is possible across south central SD, probabilities of an inch or more at or above 50 percent, as the heaviest rainfall likely tracks from northern NE to southeast SD. There could even be a little bit of snow across the highest elevations of the Black Hills later Monday night into Tuesday morning. Highs Monday and Tuesday will drop back to below average levels, mostly in the 50s and 60s.

The rest of the week and the holiday weekend looks to be unsettled at times with near seasonable temperatures as near zonal flow brings occasional shortwave disturbances across the Rockies and Plains. The best and most widespread chances for showers and storms later in the week looks to be Thursday afternoon into Friday. There is some potential for stronger storms later Thursday across at least eastern portions of the CWA The weekend looks seasonably warm, with highs in the mid 60s to mid 70s.

AVIATION
(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1013 PM MDT Sun May 19 2024

Breezy northwesterly winds will continue behind cold front overnight, gusting to over 35 kts on portions of the SD plains.
Winds will gradually decrease Mon morning. VFR conditions can be expected overnight into Monday. Chances for showers will increase from west to east across northeast WY and southwest SD during the late morning and afternoon on Monday, with local MVFR conditions expected in the afternoon.

UNR WATCHES/WARNINGS/ADVISORIES
SD...None.
WY...None.

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Rapid City, SD,