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FXUS63 KFSD 041930 AFDFSD

Area Forecast Discussion National Weather Service Sioux Falls SD 230 PM CDT Sat May 4 2024

KEY MESSAGES

- Conditions will continue to trend warmer into the early parts of the week with highs returning to upper 60s and low 70s by Sunday.

- Winds may near and/or exceed advisory levels Monday morning and afternoon in areas along and west of I-29.

- A few strong to severe storms will be possible Monday afternoon and evening, with the greatest severe threat currently focused along and south of the Missouri River and Highway 20 corridor.

- Periodic rain chances continue for much of the upcoming week, with highs in the 60s to lower 70s.

DISCUSSION
Issued at 228 PM CDT Sat May 4 2024

REST OF THE AFTERNOON/TONIGHT: A warm and quiet day continues.
Taking a look at satellite imagery across the area, mostly clear conditions this morning have given way to developing cumulus field this afternoon mostly due to some elevated instability. Efficient mixing along with a tightening SPG has led breezy northwesterly winds across portions of the area with a few sites reporting sustained wind between 10-20 mph with gusts up to 30 mph this afternoon. Expect the marginally breezy conditions to continue into the evening hours before diminishing as a surface high approaches from the northwest moves overhead. Otherwise, lingering cold air advection (CAA) and northwesterly surface winds will lead to temperatures slightly below our seasonal normal as highs approach the upper 50s to low 60s for the day. By tonight, winds will likely decouple becoming more variable after sunset as the surface high moves overhead. Lastly, as temperatures decrease into the upper 30s to low 40s overnight; a shrinking dewpoint depression could potentially lead to a few patchy area of fog developing mostly over portions of northwestern IA. Nonetheless, with high resolution guidance only showing 10-20 percent confidence in any isn't too excited about those chances

SUNDAY: By Sunday, another warm and quiet day will be on tap as the upper-level portion of the ridge moves overhead. Light and variable winds in the morning will become breezy southeasterly winds by the afternoon as the SPG tightens. Wind gusts between 20-30 mph will be possible with the strongest winds expected west of the James River.
Looking aloft, some weak warm air advection (WAA) will mix into the mid-levels by the afternoon hours helping our overall temperatures slightly increase from the previous day. As a result, highs should peak in the upper 60s to low 70s for the day. By Sunday night, our attention pivots to the Rockies as an upper-level wave ejects into the Central and Northern Plains leading to our next precipitation chances from Monday onwards.

MONDAY: Upper level trough over the Rockies ejects northeastward toward the Northern Plains Monday, causing showers and storms to return to the forecast. While precipitation will be likely by mid- morning in areas west of the James River, expect more widespread chances to prevail during the afternoon and evening as the sfc low pressure deepens over the western Dakotas. As alluded to in the previous discussion, SPC's Day 3 Outlook does include a Slight Risk (Level 2 of 5) along the MO River Valley, with a Marginal Risk (Level 1 of 5) encompassing those areas north up to the I-90 corridor. In regard to dynamics, latest guidance continues to show MU/MLCAPE around 500 to 1000 J/kg depending on what model you look at. That being said, ensembles remain less than excited, with both the Euro/GFS only showing a 10-20% probability of seeing CAPE greater than or equal to 1000 J/kg. Nonetheless, there will be a fairly robust S/SE LLJ overhead, with winds ranging between 40 to 50 kts, resulting in highs in the 60s to lower 70s and dewpoints in the mid 50s to lower 60s. CIPS analogs and CSU machine learning probabilities also give us a 10-15% of severe weather, so don't want to completely rule things out just yet despite instability being on the lower side.

In terms of accumulations, confidence continues to grow that we will see another round of meaningful rainfall across much of the area, as soundings reveal a tall and skinny profile. Latest QPF estimates would suggest accumulations between half an inch to an inch, especially in areas that see convection. In addition to the storm potential on Monday, it will also be quite windy, with areas along and west of I-29 approaching advisory level winds in the morning and early afternoon hours as the SPG tightens overhead. Will continue to monitor trends in the event that headlines are needed. Otherwise, expect showers and storms to continue eastward overnight, allowing largely quiet conditions to return by daybreak Tuesday.

TUESDAY THROUGH FRIDAY: Upper level low continues to spin and wobble over the Northern Plains through mid-week, resulting in a persistent wave train across our area. Thus, expect low-end PoPs (<40%) to continue at least through Friday. Winds also look to be fairly breezy each day, with gusts between 20 to 30 MPH possible each afternoon. In regard to temperatures, will see highs to rise into the 60s to lower 70s during this time, with overnight falling into the 40s.

SATURDAY: Dry conditions look to return heading into the weekend as the aforementioned upper level low pushes eastward, causing northwesterly flow to set up overhead. Highs in the 60s will still remain common.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
Issued at 1214 PM CDT Sat May 4 2024

Mostly VFR conditions with occasional MVFR ceilings are expected for this TAF period. Taking a look at satellite imagery, a cumulus field has developed across most of the area in response to some elevated instability with parts of northwestern IA dealing with lingering stratus from this morning's cold front. As the surface high continues to move into the area this evening, expect conditions to begin to clear from west to east. Otherwise, breezy northwesterly winds will continue through the late afternoon before diminishing as the surface high moves overhead tonight. Lastly, some high resolution guidance has started to hint at some patchy fog developing across northwestern IA overnight. However, confidence is still low in occurrence so far.

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

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