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000
FXUS63 KFSD 210746
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
246 AM CDT Sun Apr 21 2024

.KEY MESSAGES...

- Scattered showers and very isolated thunder will return Monday morning
  into Monday afternoon, possibly lingering near the Missouri
  River into Monday night. Overall any precipitation should
  remain spotty and on the lighter side.

- 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 both days.

- A chance for some frost on Wednesday morning as high pressure
  settle south.

- A bit better chance for rain and thunderstorms Thursday into
  Friday with EC and GFS ensemble output indicating an increased
  20-40 percent chance for an inch or more of rainfall, the
  better chances towards the latter part of this period. There
  is a small chance for severe storms during this time as well,
  especially Thursday night into Friday morning.

&&

.DISCUSSION...
Issued at 245 AM CDT Sun Apr 21 2024

A pleasant Spring day on tap today with highs generally 60 to 65 and
winds mainly below 20 mph. Dry air will see some low relative
humidities of 20 to 25 percent, but with recent rains, some greenup
underway and winds mainly less than 20 mph fire weather should
remain in the moderate category. Some high fire danger may exist in
localized areas that have not had as much rain the past week or so.

A west northwest oriented jet races into SD on Monday with low
pressure expected to track east along the Canadian border. This will
bring a quick moving area of mid level warm advection through, but
at this time moisture will be a problem. The place to look for any
precipitation potential looks like it will be in the 700 to 600 mb
layer where a little moisture and some very weak instability with an
EML around 7-8 C could drive some showers and very isolated thunder.
Timing wise, this weak instability and elevated moisture should come
through areas west of I-29 on Monday morning and areas near and east
of I-29 from late morning into the afternoon. A small tail of
instability may lag across northwest IA towards the Missouri River
which may allow a little development into Monday night.

Otherwise on Monday with this system passing, wind will be a
concern. Southerly flow ahead of this wave with marginally deep
mixing may allow wind gusts of 40 to 50 mph near and east of a
Ivanhoe to Vermillion line, beginning in the morning. Right now with
relative humidity around 40 percent and fuels beginning to green,
expect a high fire danger. Farther west in central SD, northwest
winds will strengthen a bit in the afternoon as a front passes. This
will be another area to watch, but for now relative humidity values
should come up just a bit short of criteria with winds right around
what would be necessary for critical fire danger.

Tuesday will see the tail end of the upper level wave drop southeast
through the area. With some low and mid level moisture more weak
instability will be possible and could result in some isolated
showers. The other concern on Tuesday will be strong northwest winds
which could approach advisory criteria. Fire weather will also be a
concern with afternoon relative humidity of 30 to 40 percent.

Tuesday night into Wednesday night should see mostly quiet weather
as upper level ridging moves through. Surface high pressure will
move through on Tuesday night and may allow for some frost
development with lows in the 30s. Otherwise rebounding southerly
flow will allow for a seasonally mild day with highs around normal
and winds mostly less than 20 mph.

Models are in a bit better agreement today on the system expected
Thursday night into Friday. Upper level low pressure should deepen
to the southwest of the area bringing a strong increase in southerly
flow, especially around the LLJ. Suspect that this will bring some
elevated instability with fairly substantial forcing and may allow
for a few severe storms. If Friday ends up with low pressure
overhead we could see a repeat of April 16th with isolated small
tornadoes. But, still a long ways to go until this threat
actually materializes, so only a small chance for now.

Friday night into next weekend still remains fairly uncertain, but
for now troughing to the west is fairly well agreed upon, so at
least a chance for an active period into next weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1029 PM CDT Sat Apr 20 2024

VFR throughout the period. As a surface high pressure is moving
across portions of the region, winds become slightly variable
overnight for a couple hours, but will remain with a westerly
component before winds increase tomorrow morning out of the
northwest. The northwesterly winds will become southwesterly from
west to east throughout the day tomorrow with winds remaining on the
light side. Will likely see some LLWS Sunday night into Monday due
to directional and speed shear, most likely for areas south and east
of a line from Chamberlain, SD to Mitchell, SD to Brookings, SD.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Freeze Warning until 8 AM CDT this morning for SDZ055-056-061-
     062-066-067-069>071.
MN...Freeze Warning until 8 AM CDT this morning for MNZ071-072-080-
     081-089-090-097-098.
IA...Freeze Warning until 8 AM CDT this morning for IAZ001>003-
     012>014-020>022-031-032.
NE...Freeze Warning until 8 AM CDT this morning for NEZ013-014.

&&

$$

DISCUSSION...08
AVIATION...APT