Sunrise 5:53 AM   Sunset 7:48 PM Moonrise 7:55 PM   Moonset 5:42 AM

  Print   HELP   Reset   Save   Recall

FXUS63 KUNR 231059 AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 459 AM MDT Tue Apr 23 2024

KEY MESSAGES

- Warm, dry, and occasionally breezy weather continues through Wednesday

- Unsettled weather returns late this week. Chances for showers and thunderstorms returning by Thursday and continuing into the weekend.

DISCUSSION
(Today Through Monday)
Issued at 333 AM MDT Tue Apr 23 2024

500mb analysis depicts positively tilted shortwave skirting past the region to the northeast with a 100kt jet streak directly overhead at 300 mb. At the sfc, a sfc low sits over the Great Lakes region with high pressure centered over the Canadian Rockies. This has allowed a pressure gradient to set up across the region which has resulted in some breezy west-northwest winds, especially over northwestern SD. However, these winds aren't much to write home about, generally 10 to 15 mph gusting to 20 to 25 mph at times. Skies over the region are mostly clear with temperatures largely in the 30s to low 40s.

Our marginally breezy conditions will continue into the morning hours, especially towards central SD where 850 mb winds of 30kts may mix down to the sfc after sunrise. South central SD could see some gusts 30 to 40 mph in the morning hours with winds diminishing in the afternoon as the shortwave moves out of the region.

Upper level ridging builds into the region by Wednesday with vigorous return flow advecting warmer temperatures into the region. LLJ will form over western SD Tuesday night into early Wednesday, leading to a breezy Wednesday over much of the western SD plains. South central SD could see some low end advsy level gusts Wednesday afternoon. In addition, RHs over northeastern WY will plummet into the mid-teens. However, winds over northeastern WY will be fairly light which will preclude any fire wx concerns at this time.

Upper low will swing through the four corners region late Wednesday into Thursday with lee cyclone developing over the central plains late Thursday evening. This will bring us our next chances for showers and storms. NAM depicts 1000 J/kg CAPE over the region Thursday afternoon, though shear is rather meager and may preclude any widespread severe threat at this time. Rain chances continue through Friday as the sfc low crosses the region.
As of now, it looks like south central into central SD will get the bulk of the QPF with GEPS/ENS having the highest probs (40-60%) of total precip accumulation of 1+" over south central SD by Saturday afternoon.

Another shortwave and lee cyclone will follow right on the heels of the first system, impacting the region late Saturday and continuing our rain chances through the weekend. There's a little more uncertainty with the track of this system (and thus uncertainty about how much precip we may get out of it) though recent deterministic GFS runs have kept the bulk of the QPF over south central SD and the most recent ECMWF run has the system tracking further south and east and missing the CWA all together.
Either way, we're on track for an unsettled and dreary weekend.

AVIATION
(For the 12Z TAFS Through 12Z Wednesday Morning)
Issued At 459 AM MDT Tue Apr 23 2024

VFR conditions will continue through the TAF period.

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,