Sunrise 6:33 AM   Sunset 8:18 PM Moonrise 4:17 PM   Moonset 4:25 AM

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FXUS63 KFSD 201112 AFDFSD

Area Forecast Discussion National Weather Service Sioux Falls SD 612 AM CDT Sat Apr 20 2024

KEY MESSAGES

- Below freezing temperatures are expected again tonight into Sunday morning, potentially creating some frost/freeze concerns across portions of the area.

- More light rain chances (20%-50%) will return by Monday.
However, only light accumulations are expected.

- Monday and Tuesday will be the next windy days and while many of the fuels are beginning to green up with the recent rains, afternoon relative humidity will likely fall to about 30 to 35 percent in some locations, leading to a high fire danger in a few locations.

- A bit better chance for rain and thunderstorms Thursday into Friday with EC and GFS ensemble output indicating a 10-20 percent chance for an inch or more of rainfall.

DISCUSSION
Issued at 313 AM CDT Sat Apr 20 2024

A little relief from the excessive wind today, although there will still be some gusts around 25 mph. The surface pressure gradient gradually slackens through the afternoon as high pressure builds across the Western High Plains, so winds should be a little less gusty towards late afternoon. Temperatures aloft are just a smidge warmer, so highs should be a couple of degrees higher than yesterday, so still on the cooler side.

High pressure builds into the area tonight so lows may be at their coolest with a little better chance for some patchy frost.
Regardless, will likely need another freeze warning for tonight into Sunday morning. Sunday should be a pleasant day with lighter winds and highs in the 60s.

Sunday night into Monday low pressure aloft deepens over southern Canada with a lead wave expected to eject onto the Northern Plains late Sunday night into Monday. This will bring some broad mid level warm advection through which may aid in generating scattered showers. Generally westerly warm advection lacks a bit of moisture and this case is no different. So then there is more reliance on the elevated mixed layer to generate some instability and for now that looks to be a challenge as well. Not completely out of the question for a few showers but rainfall amounts should be spotty and on the light side. There will be some stronger winds as this system passes which comes as no surprise and gusts should be somewhere from about 30 to 40 mph. Fire weather should not be a major problem, but will need to watch the trends in fuels and potential afternoon relative humidity, but for now green up is happening with the recent rains.

Cold advection spills into the area on Tuesday as the tail end of the system moves east. With the cold air aloft moving through some very weak instability will be possible which could trigger a few showers, but once again the amounts should be light. Otherwise with the cold advection mixing will be strong and with the potential for 35 to 40 knot winds in the mixed layer it should Be a very windy day. Will once again need to pay attention to fire weather concerns as well as the potential for wind advisory criteria.

Tuesday night through Wednesday night should be mostly dry as upper level ridging moves through and troughiness develops to the west.
The next system of interest moves into the area Thursday into Friday and should bring the next better chance for rain and potentially a few thunderstorms. Temperatures Wednesday into Friday should be near or a few degrees above normal and with a warmer EC Ensemble temperatures may end up another 3-5 degrees warmer than forecast.
That will be a trend to watch with the GFS potentially running on the cool side.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
Issued at 610 AM CDT Sat Apr 20 2024

While there will be some periods of scattered clouds, areas north of the Missouri River will see mostly cloudy conditions through the day, with clouds generally around 5-6 kft. After sunset clearing is expected. Northwest winds will gust around 25 mph at times, but will begin to diminish by mid afternoon.

FSD WATCHES/WARNINGS/ADVISORIES
SD...Freeze Warning until 7 AM CDT this morning for SDZ055-056-061- 062-066-067-069>071.
MN...Freeze Warning until 7 AM CDT this morning for MNZ071-072-080- 081-089-090-097-098.
IA...Freeze Warning until 7 AM CDT this morning for IAZ001>003- 012>014-020>022-031-032.
NE...Freeze Warning until 7 AM CDT this morning for NEZ013-014.

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