704
FXUS63 KFSD 260749
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
249 AM CDT Thu Sep 26 2024

.KEY MESSAGES...

- Dry conditions are expected through the period. Above average
  high temperatures in the 80s is expected through the weekend.

- Breezy southerly winds and lowering relative humidity levels
  will result in elevated fire danger for locations west of the
  James River Today.

- Increasing winds along with periods of near to above average
  temperatures could bring additional chances for fire danger
  throughout the duration of next week.

&&

.DISCUSSION...
Issued at 248 AM CDT Thu Sep 26 2024

Clear and quiet conditions begin the day today. Like what we have
seen the past few days, patchy shallow fog has a low possibility
(<=20% chance)of developing this morning, mainly around bodies of
water. Should any fog develop, it will quickly burn off as mixing
increases as the sun rises. This afternoon will feel closer to
Summer rather then Fall as above average high temperatures persist.
Temperatures warmed closer to the NBM 95th percentile yesterday. As
such, have pushed today`s highs closer to the NBM 95th percentile.
Widespread highs in the 80s is expected but locations along and west
of the James River should see high temperatures reach up to around
90 degrees F this afternoon. With such warm temperatures in place,
dew points are expected to lower a bit more as drier air is mixed to
the surface, resulting in lower relative humidity (RH) values across
the area. The lowest RH values will come along and west of the James
River where RH values will fall to about 20-25% The surface pressure
gradient (SPG) will tighten across the area as a surface ridges
slides southeast of the forecast area. The tightened SPG along with
stronger winds aloft will bring a return of breezy winds to the
area, strongest along and west of the James River where gusts up to
around 30 mph is expected. The good news about the winds is that the
strongest winds reside around 850 mb. Mixing above 850 mb will not
result in any stronger winds being transported to the surface. The
very warm temperatures, low humidity, and breezy winds will lead to
elevated fire danger this afternoon along and west of the James
River. While Red Flag conditions look to be met, fuels are still
green enough to only have moderate to a small area of high fire
danger this afternoon. And chance for fire danger will come to an
end this evening as mixing ceases. Low temperatures will fall to the
50s overnight.

The SPG relaxes on Friday as another surface ridge slides into the
Northern Plains. 850 mb temperatures will cool a bit, down to the
upper teens to about 20 degrees C. Mixing this to the surface will
result in high temperatures into the 80s across the area. With a
relaxed SPG in place, light winds are expected. With light winds and
above average temperatures in place, Friday will be another gorgeous
day across the area! Low temperatures will again fall to the 50s
overnight.

Upper level ridging remains squeezed across the Northern Plains for
the weekend between the Jet Stream across southern Canada and a
vertically stacked low pressure system across parts of the Midwest.
This will allow for above average temperatures to persist with highs
in the 80s along with light winds and thus beautiful conditions for
the weekend!

Medium Range guidance remains in decent agreement in a stronger
shortwave trough amplifying as it passes through the Northern Plains
early next week on Monday. This wave will drag a dry cold front
through the region as well which will bring fall like conditions
back to the forecast area after it passes through. High temperatures
look to lower to the 70s up to the low 80s. The Fall like conditions
look to be short lived though as surface high pressure quickly races
through the region on Tuesday, delivering a true Fall like day with
highs in the 60s, before another shortwave trough takes aim at the
Northern Plains on Wednesday. Medium rang guidance is in decent
agreement in this wave this far out but the timing of the waves
differs. However warm air advection (WAA) ahead of the wave looks
to bring a return of above average temperatures to the forecast
area. The GFS, Euro, and Canadian ensembles show a 30-60% chance for
high temperatures to exceed 80 degrees F.

The warm conditions look to be accompanied by breezy winds which may
bring elevated fire danger back to the forecast area. The Hot-Dry-
Windy-Index (HWDI) supports this as it shows about 50% of its
members pointing to elevated fire danger conditions. Something to
continue to monitor heading into next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1005 PM CDT Wed Sep 25 2024

VFR conditions are expected to continue this TAF period. Taking
a look at satellite imagery, clear conditions continue as a
weak surface high continues to work its way eastwards. Expect
these conditions to continue overnight hours with light and
variable winds potentially promoting some patchy valley fog.
Breezy southerly winds will return by Thursday afternoon as the
SPG tightens leading to wind gusts up to 30 mph mostly west of
I-29 to end the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...Meyers
AVIATION...Gumbs