Sunrise 6:15 AM   Sunset 8:32 PM Moonrise 2:46 AM   Moonset 1:00 PM

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FXUS63 KFSD 022330 AFDFSD

Area Forecast Discussion National Weather Service Sioux Falls SD 630 PM CDT Thu May 2 2024

KEY MESSAGES

- Low level stratus continues to clear from west to east this afternoon, allowing for sunshine to return. Isolated showers remain possible north of I-90 through sunset.

- Rain returns Friday afternoon and continues through Saturday morning. Rainfall amounts between a quarter to up to a half an inch are expected. Ponding on roads along with minor stream and river flooding are again possible.

- A strong low pressure system looks to bring renewed storm chances on Monday but details are uncertain as of now.

DISCUSSION
Issued at 328 PM CDT Thu May 2 2024

Current satellite shows low level stratus beginning to clear from west to east this afternoon, allowing sunshine to return. The edge of the stratus is currently sitting over I-90 but will continue to push east for the rest of the daylight hours. A weak boundary has sparked a few weak showers along highway-14 but could continue to produce light showers down to about I-90 through sunset. Minimal rain is expected from the showers. A weak surface ridge will slide through the area this evening and night which will allow for light winds and low temperatures to fall to the upper 30s to low 40s overnight.

Friday begins on the quiet side but rain chances will return to the area as a cold front tied to an upper level wave pushes into the area. Cloud cover will gradually build in but 850 mb temperatures up between +3 to +7 degrees C should allow for highs to warm to the upper 50s to about 70 degrees. Rain looks to begin for locations towards central and south central South Dakota after noon as the front initially pushes into the forecast area. This front will be highly frontogenetic and result in strong lift along it. Vertical cross sections also show strong omega (upward motion) and negative equivalent potential vorticity (EPV) above the front. This signals that a tight band of rain will develop right along the front. The front will be a bit slow to move southeastwards as it looks to reach the I-29 corridor around midnight. As the front hits the interstate, the frontogenetical forcing will wane a bit leading to a more diffuse and weaker rain band. However, a mesoscale convective system (MCS)
looks to develop in Nebraska and push eastwards through the night.
While the MCS looks to stay south of the area, the MCS's northern precipitation shield looks to connect with the weaker rain band and bring additional rainfall to locations along and east of I-29. Still some uncertainty though as the MCS evolution is not definite just yet. Slight shifts in its track can result in more or less rain for this area. As of now, between a quarter of an inch to up to around a half an inch is expected generally along the James River Valley.
Isolated higher amounts are possible. East of the James, rainfall totals look to be closer to around a quarter of an inch. This can still change though depending on the track of the MCS. Ensemble guidance shows parts of northwest Iowa with a 30-40% chance for exceeding a quarter of an inch, therefore continuing this chance.
While this is not as much rain compared to our last event, saturated soils will yield the potential for ponding on roadways along with minor flooding on some rivers and streams.

Any chance for rain will come to an end Saturday morning, leaving dry conditions for the rest of the weekend. Highs will remain in the 60s and lows will fall to the 40s and 50s, warmest Sunday night. The next chance for rain will come on Monday as a strong upper level wave ejects from the Rockies into the Plains. Medium range guidance is very consistent in this wave taking on a negative tilt as it pushes into the Northern Plains. This will result in strong upper level divergence and set the stage for more rain chances. Ensembles show a near 100% chance for exceeding a tenth of an inch of rain and a 30-60% chance for exceeding half an inch of rain. The ensembles also show a 30-60% chance for exceeding 500 J/kg of CAPE, suggesting the potential for thunderstorms. CIPS analogs do have some probabilities for strong to severe storms, highest across the central Plains. However, mesoscale details remain highly uncertain at this time. As such, have left model blended PoPs but this system will continue to be monitored over the coming days. Outside of storm chances, Monday will be a warm day with highs in the upper 60s and 70s with lows falling to the 40s.

The same upper level wave will occlude and spin over the Northern Plains through the middle of next week. This will keep chances for rain going throughout this period of time along with near seasonal highs in the 60s.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
Issued at 630 PM CDT Thu May 2 2024

MVFR cloud deck continues to push eastward, allowing VFR conditions to largely return across our area. Should see breezy W/NW diminish quickly after sunset, with light winds forecast to prevail through the overnight period. Otherwise, will see a cold front dive southeastward across the region Friday afternoon and evening, causing winds to shift to the northwest in it's wake. Rain chances will return as this boundary pushes through, which may result brief periods of reduced cigs and vsbys.

FSD WATCHES/WARNINGS/ADVISORIES
SD...None.
MN...None.
IA...None.
NE...None.

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