034
FXUS63 KFSD 052245
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
545 PM CDT Sat Oct 5 2024

.KEY MESSAGES...

- Critical fire danger continues across the entire area this
afternoon. A Red Flag Warning remains in effect until 8 PM this
evening.

- Little to no precipitation and above average high temperatures is
expected for next week. Weaker winds will allow for lower chances
for fire danger.

&&

.DISCUSSION...
Issued at 310 PM CDT Sat Oct 5 2024

Breezy to windy conditions continue across the area this afternoon.
Should see winds slowly wane through the rest of the afternoon hours
before a larger drop off occurs after sunset as the boundary layer
stabilizes. However, breezy winds will persist through the overnight
hours as the surface pressure gradient (SPG) remains tight across
the forecast area. Gusts up to about 25 mph are expected tonight.
The breezy winds will keep low temperatures a bit above average in
the mid to upper 40s.

Surface high pressure will be sliding into the area tomorrow. While
winds won`t be calm they will be much lighter then today. However,
gusts up to around 25 mph is possible, mainly east of I-29. These
winds will reside ahead of the surface high, where the tightest SPG
will lie. 850 mb temperatures will cool to the single digits. Mixing
this to the surface will result in a seasonable day with high
temperatures in the 60s across the area. However, dew points will be
in the 20s and 30s, contributing to low RH and potential fire
danger. More details are discussed in the fire weather section
below. The surface high will still reside over the forecast area
through the overnight hours, allowing low temperatures to fall to
the 30s to upper 40s. This may allow for some areas of frost to
develop. Confidence in this potential is low to moderate (30-40%
chance) though as drier air still resides across the area. If frost
were to develop, it would most likely develop in valley where lows
may drop a bit more.

Upper level ridging persists across the southwestern CONUS to begin
the work week. This will result in continued northwest flow aloft.
However warm air advection (WAA) will push 850 mb temperatures back
up to the teens aloft. This will result in a return to above average
temperatures with highs in the upper 60s and 70s. This could be
slightly mitigated though by wildfire smoke aloft. Latest HRRR
vertically integrated smoke shows smoke aloft beginning to enter the
forecast area early Monday morning. Still a bit too early to say how
thick the smoke will be but will continue to monitor this potential.
Low temperatures will fall to 40s overnight.

The same upper level ridging over the southwestern CONUS will
amplify for the middle and end of next week. This will allow for dry
conditions to persist across the Northern Plains. Ensembles also
support this as they all show a straight zero percent chance for a
hundredth of an inch of rain or more. However, ensembles also
support the potential for above average temperatures as they all
show a broad 50-90% chance for high temperatures to exceed 80
degrees F. All this to say that next week will be warm and dry. The
good news is that pressure gradients do not look to be that steep
given the ridging in place. This should result in lighter winds
across the region and reduce the potential for fire danger.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 542 PM CDT Sat Oct 5 2024

Northwest winds will weaken some after sunset although may still
see occasional gustiness. Depending how much surface winds
weaken, LLWS may be possible, mainly for FSD/SUX. Otherwise,
northwesterly winds will again gust between 20-25 kts after
sunrise on Sunday with a weakening trend by the second half of
the afternoon.

&&

.FIRE WEATHER...
Issued at 310 PM CDT Sat Oct 5 2024

A cold front continues to push through the area this afternoon.
Southwesterly gusts ahead of the front will turn to out of the
northwest behind the boundary. Gusts between 30-45 mph are being
observed with the strongest gusts occurring across central South
Dakota. Dew points continue to fall behind the front, from the 50s
ahead of the boundary to the 30s behind it. With temperatures that
have warmed to the 70s and 80, relative humidity (RH) values are
falling behind the front with values down to teens to the low to mid
20s. The low RH and stronger winds have indeed resulted in critical
fire danger conditions across the area this afternoon. Winds will
drop off more abruptly as the boundary layer stabilizes after sunset
this evening. With a tighter surface pressure gradient (SPG)
residing across the area, winds will not go calm but remain breezy
through the overnight hours. Despite the breezy winds, RH will
increase, thus putting an end to the fire danger today.

Sunday presents another day of potential fire danger. This potential
is more uncertain though as surface high pressure will be sliding
through the forecast area. The tightest SPG will reside ahead of it
and thus will also be the same area where the strongest winds will
lie. Winds will be out of the northwest with gusts up to around 25
mph. With dew points remaining in the 20s and 30s, low RH values are
possible, down to about 20-25%, even though high temperatures will
only warm to the 60s. The lowest RH and strongest winds will reside
east of I-29. While this could result in critical fire danger
conditions in this area, there looks to be only minor overlap of the
strongest winds and lowest RH as the surface high will be relaxing
the SPG. Thus, the strongest winds will be weakening as RH drops to
or below 25% during the afternoon hours. Will closely monitor trends
for needing fire headlines tomorrow.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning until 8 PM CDT this evening for SDZ038>040-
     050-052>071.
MN...Red Flag Warning until 8 PM CDT this evening for MNZ071-072-
     080-081-089-090-097-098.
IA...Red Flag Warning until 8 PM CDT this evening for IAZ001>003-
     012>014-020>022-031-032.
NE...Red Flag Warning until 8 PM CDT this evening for NEZ013-014.

&&

$$

DISCUSSION...Meyers
AVIATION...Kalin
FIRE WEATHER...Meyers