textproduct: Sioux Falls
This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.
KEY MESSAGES
- Rain chances increase towards the 50-80% level Sunday evening and continue into mid-day Monday.
- Rainfall amounts continue to trend lower, with most areas seeing a tenth to a quarter inch. Some pockets of higher amounts are possible, especially south of a line from Sioux City to Estherville.
- Temperatures moderate to around average for early November as we dry out for the rest of the week.
- The next risk for light rain arrives by next weekend.
DISCUSSION
Issued at 234 PM CST Sun Nov 3 2024
Taking a look at satellite water vapor we can see the approaching trough over the Rockies, and the ongoing convection over the southern and eastern Plains. At the surface south-southeasterly flow continues to bring north moisture from the Gulf and warm air advection, keeping afternoon highs on the warm side for this time of year, in the 50s to low 60s. Overnight, clouds and mixy winds in the boundary layer will help keep our lows very warm for this time of year, in the 40s to 50s. That's 15 to 20 degrees above average!
Tonight, we expect a surface low to move northeast out of Colorado/Nebraska. As it does so it will drag a cold front across our region. This cold front will help to focus the available energy (300-700 J/kg MUCAPE) to form some stronger showers and possibly a thunderstorm or two. CAMS models are beginning to pick up on the possibility of the front helping to organize showers and thunderstorms into a slightly more organized, but broken, line that moves through early Monday morning. As mentioned in the previous discussion, QPF amounts have continued to trend down slightly. North of a rough line from Chamberlain to Watertown, and south of a line from roughly Wayne NE to Marshall MN look to have the highest probability of seeing at least 0.1 inches of accumulation. This same area has only a 10-20% probability of seeing at least 0.5". Areas in the middle have about a 70-90% probability of seeing 0.1". So, not a significant rainfall, but most should see at least measurable rain. Dry and cool air filters in behind the front, causing the rain to end from west to east in the afternoon. Highs for Monday will be slightly cooler, but still above average, in the 50s. Clearing skies overnight and light winds will allow us to cool down to about average for this time of year, in the upper 20s to 30s.
An embedded shortwave coupled with positive vorticity advection will trigger another round of showers beginning late Monday evening. These showers look to be focused over central Iowa, but the western edge of the precipitation may reach into our northwestern Iowa counties. Showers are expected to be east of our area by Tuesday afternoon. An additional tenth to a quarter of an inch is possible south of a rough line from Sioux City to Windom MN. Highs for Tuesday will be average to slightly below average for early November, in the low 50s and upper 40s, with lows in the upper 20s to low 30s.
Things dry out for a few days beginning Wednesday. Meanwhile we watch as an extended upper trough becomes a closed upper low over the desert southwest. The associated surface low slowly moves east through the Rockies over the next few days. This will keep up us in a mostly southerly to southeasterly flow at the surface. Ushering in warm air advection and allowing Gulf moisture to pool through the Plains ahead of the system. Early Thursday, a weak shortwave in the midlevel flow could trigger some light showers over central South Dakota. These showers are not expected to produce much precipitation with only a 20-50% ensemble probability of measurable rain (0.01 inches). Late Friday to early Saturday the surface low will move out over the southern plains and accelerate to the northeast, bringing the next chance for rainfall. There remains high uncertainty in track and precipitation totals. At this time temperatures look to be warm enough that any precipitation that does fall will most likely fall as rain. But there is plenty of time for things to change, so please remain weather aware if you have travel plans that weekend.
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
Issued at 515 PM CST Sun Nov 3 2024
MVFR and lower visibility with IFR and lower ceilings continue through much of the period. Periods of showers expected, with drizzle/mist/fog as well. Some rumbles of thunder are possible for the area, and have included TSRA mention in PROB30 groups at all 3 TAF sites. Improvement in conditions is anticipated toward mid day Monday as stratus begins to lift and precipitation moves east.
Light east to southeast winds will transition to northwesterly as a cold front moves through overnight and early Monday. Winds increase with gusts 20 to 25 knots to end the period.
FSD WATCHES/WARNINGS/ADVISORIES
SD...None. MN...None. IA...None. NE...None.
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