Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 031136
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
536 AM CST Sun Mar 3 2024

.KEY MESSAGES...

- Elevated to Critical fire weather conditions are expected on
  Sunday due to the arrival of gusty westerly winds and very low
  relative humidity levels.

- Temperatures remain 10-20 degrees above normal through
  Wednesday, with some potential for a slightly cooldown (still
  above normal) by next weekend.

- Precipitation risks remain low through Wednesday, with a more
  focused risk for rain or snow on Thursday. Probabilities of
  significant precipitation (>.50) remain low (10%).

&&

.DISCUSSION...
Issued at 239 AM CST Sun Mar 3 2024

THIS MORNING:  Surface low pressure over north central Nebraska
continues to track to the northeast at 2am.  East of the surface
low, and lingering frontal boundary into western Minnesota,
temperatures remain in the 40s.  Into central South Dakota, some
stratus and fog has develop and may slide southeast towards Huron
this morning.

TODAY:  The greatest weather risks for today are focused on
critical fire weather conditions in areas west of I-29, and
especially along and west of the James River.  See separate fire
weather discussion for further details.

Surface low pressure will track towards far northeastern South
Dakota by mid-morning, pushing a surface front into southwest
Minnesota and northwest Iowa by mid-day.  Strong low-lvl cold
advection will begin in central South Dakota by mid-day, with sharp
surface heating through all areas west of the James. This will serve
to significantly enhance the low-lvl lapse rates, with mixing
depths up to 700 mb likely west of the James. Temperatures after
a bit of a slow warm-up this morning, should rise into the
upper 50s in most locations afternoon. Deeper mixing models such
as the RAP/HRRR indicate the potential for near advisory to
advisory level winds for a few hours early in the afternoon west
of the James River. Further east, we`ll see more of a strong
persistent gradient wind, with occasional gusts above 30 knots.
Given the brevity of the highest wind gusts, will hold off on
any advisory ATTM.

TONIGHT: Winds will weaken through the night as mid-lvl clouds
thicken.  Soundings continue to show a fairly deep layer of elevated
moisture AOA 700 mb moving through the area, with weak 700:500
dPVA within the right entrance of the upper jet by early
Monday. The sub-cloud layer remains significantly dry however,
so will limit PoPs to very isolated 20% probabilities with more
widespread sprinkle/flurry potential.

MONDAY-TUESDAY:   Northeast surface winds are expected Monday, but
with dry ground and persistent warm low-lvl temperatures, highs may
still climb into the upper 40s to 50s. A weak 700 mb trough slides
through the Dakotas on Tuesday, with a narrow focused area of
lift moving through central and northern South Dakota during the
day. Further southeast in the Tri-State area, highs again climb
into the 40s and 50s.

WEDNESDAY-FRIDAY:  There still remains quite a bit of uncertainty
with the forecast for the second half of the work week.  Medium
range guidance continues to show a deeper trough tracking from the
Northern Rockies across the southern Canadian provinces by Thursday
and Friday.  The increased southwesterly flow through the Plains
will try to bring moisture northward ahead of a north to south cold
front over the Dakotas by Wednesday night.  The biggest uncertainty
with this setup revolves around the northward moisture transport
towards the area.  The GFS/ECMWF/CMC all suggest a secondary wave
lifting out of the Southern Plains that could provide some
interference with the northward moisture advection. Subtle timing
differences with this secondary as noted in ensemble data are likely
the reason for the large spread in probabilistic QPF numbers
through the Plains. 00Z guidance does suggest that probabilities
for meaningful QPF greater than 0.50" are likely to stay
focused south of the CWA. All that said, will continue to focus
the highest PoPs locally within the Thursday timeframe as the
front moves east through the area. Temperatures after the wave
passes through will cool down closer to seasonal normals near 40
degrees for a couple days.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 532 AM CST Sun Mar 3 2024

Locally dense fog and stratus has developed near an area of
surface low pressure where temperatures have fallen below
freezing. Model guidance is poorly resolving this area of
moisture, leading to a less confidence first 6 hours of the TAF
for HON. It`s possible the stratus and fog may begin to advect
northeast as the flow turns southwesterly, However it`s also
possible that as the surface low moves northeast by 14Z, the
increased mixing may dissipate the fog completely, with just an
area of stratus moving northeast.

Elsewhere, VFR conditions are prevailing with a southeast wind.
Eventually through the day winds will turn southerly and then
westerly with gusts over 25 to 35 knots at times. The strongest
winds will be west of I-29.

VFR conditions continue into tonight, with an increasing mid-lvl
cloud deck and occasional sprinkles/flurries after midnight.



&&

.FIRE WEATHER...
Issued at 245 AM CST Sun Mar 3 2024

Widespread elevated fire weather conditions are expected Sunday
afternoon, with areas along and west of the James River likely
to see critical conditions. These conditions will be due to the
passage of surface low pressure and the developing strong winds
mixing down by mid-day through the afternoon. Potential for
gusts over 30 mph remains high, with some model data indicating
potential for gusts up to 45 mph. While still slightly mis-
matched with the highest winds, dew points will also begin to
drop significantly by mid-afternoon. The resultant relative
humidity values may fall below 25 percent in many areas west of
I-29, with potential for RH values near 15 percent in the
Missouri River valley.

The HRRR experimental wildfire potential data suggests that the
most critical fire weather conditions are likely to be found
southwest of the James River valley and especially into south
central South Dakota where RH values may fall near 10%.

The positive today may be that strong wind gusts will begin to
weaken after 4pm, however sustained winds of 20-25 mph may keep the
fire danger risk critical through 6pm.  Have issued a RFW for areas
with the greatest overlap of low RH and strong winds, but it is
possible that areas along the Missouri River may fall out of RFW
criteria before the expiration.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from noon today to 6 PM CST this evening for
     SDZ038-050-052>054-057>061-063>066-068>070.
MN...None.
IA...None.
NE...Red Flag Warning from noon today to 6 PM CST this evening for
     NEZ013.

&&

$$

DISCUSSION...Dux
AVIATION...Dux
FIRE WEATHER...Dux


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