Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 191057
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
557 AM CDT Tue Mar 19 2024

.KEY MESSAGES...

- Northwest winds will gust up to around 30 mph today but
  relative humidity will only fall to 30-45%, keeping elevated
  fire danger across the area today.

- A push of cold air Tuesday into Wednesday will result in
  temperatures slightly below normal Wednesday through next
  weekend.

- Confidence continues to increase in chances for precipitation
  late Wednesday night through the weekend.

- High uncertainty remains for the weekend and early next week forecast.
  Those with weekend travel plans will want to continue to
  monitor the latest forecast for the most up to date
  information.

&&

.DISCUSSION...
Issued at 352 AM CDT Tue Mar 19 2024

Mostly quiet conditions begin the day today with clear skies and
elevated winds thanks to the low level jet. Warm air advection (WAA)
is currently aloft ahead of a shortwave trough diving southward
through the area. A cold front tied to this wave is also pushing
through the forecast area and will exit the area around sunrise this
morning. Winds will turn out of the northwest in the post frontal
cold air advection (CAA) regime. Despite the CAA, temperatures will
warm up to the 50s and low 60s along the Missouri River. On top of
the warming temperatures, dew points will also warm behind the cold
front, warming up to the 20s and 30s. This will keep relative
humidity (RH) values only down to 30-45% this afternoon, lowest
along the Missouri River. Despite RH not meeting critical fire
danger levels, northwest winds will gust up to around 30 mph. With
winds meeting critical fire danger thresholds but not RH, elevated
fire danger is expected this afternoon. Although fire headlines are
not anticipated for today, will continue to monitor trends
throughout the day as the previously mentioned CAA may cool mid
level thermal profiles enough to allow for some slightly deeper
mixing to take place. A second shot of CAA pushes into the area
Tuesday evening and night which will result in cold low temperatures
all the way down to the teens and 20s.

Wednesday will be a quiet day as high pressure slides through the
Upper Midwest. 850 mb temperatures between -5 to -10 degrees C will
result in cooler high temperatures only up to the 30s and low 40s.
Winds will also be much lighter at 5-10 mph as they turn out of the
northeast. The surface high will continue to slide off to the east
during the evening and overnight hours. This will result in winds
at the surface and low levels turning out of the southeast. This
will advect in drier air into the low levels which may create some
low level saturation issues. A mid level wave will begin to encroach
on the Northern Plains Wednesday evening and night, strengthening
WAA and frontogenesis (FGEN) between 850-700 mb. This will be our
next chance for precipitation that will mainly come in the forms of
rain and snow. In a shift from yesterday`s forecast, the dry air in
the low levels coupled with the best forcing for ascent residing
northeast of the forecast area has reduced precipitation chances from
Wednesday night through most of Thursday.

While some light precipitation is possible during this period of
time through the day Thursday, it looks to be tied up mainly north
of I-90. As of now, snow accumulations between a few tenths to up to
around an inch are possible. However confidence is only moderate at
30-50% chance for this potential. An inverted trough just north of a
surface low pressure system will push through the forecast area
Thursday evening and night. A cold front will lie within the surface
trough that may be able to spark some better forcing and thus
produce some more snow. Medium range guidance depicts stronger omega
(upward motion) within the dendritic growth zone (DGZ) along with
strong FGEN at 850 mb all under the right entrance region of an
upper level jet streak. BUFKIT soundings do show top down saturation
during this period of time along with a hint of CAPE. With the
ascent within the right entrance region of the upper level jet
streak, some negative EPV may be possible which could support a
narrow but stronger band of snow. This may lead to a couple of
inches of snow mainly along and north of a Chamberlain, South Dakota
to Canton, South Dakota, to Sioux Rapids, Iowa line. South of this
line looks to see more rain then snow given slightly warmer thermal
profiles. Ensembles generally support this possibility as they show a
30-70% chance for snow totals exceeding an inch of snow. the highest
probabilities for accumulating snow continue to reside just northeast
of the forecast area, across northeastern South Dakota and western
Minnesota. Low temperatures Thursday night will fall to the 20s.

Friday will be another quiet but cool day as high temperatures only
warm to the 30s and 40s. Any remaining precipitation will fall
during the morning hours, leaving dry conditions for the afternoon
hours. A thermal gradient will set up along the front range of the
Rocky mountains which will set the stage for the next storm system.

Saturday will begin dry with high temperatures only warming to the
30s across the area. Medium range guidance remains in decent
agreement in a stronger upper level wave ejecting into the plains
late Saturday. This wave will be the main driver of precipitation
chances late Saturday through early next week. However, the
evolution of the synoptic pattern increases in variance into early
next week, making for higher uncertainty about how this event will
shape up. Ensembles continue to support this possibility for a
stronger system as they all show a 40-70% chance for exceeding a
half an inch of liquid precipitation on Sunday. Cluster analysis
also supports this as the most favored cluster shows a 50% chance
for exceeding half an inch of QPF during this same period of time.
Will certainly keep an eye on this system as it could be a stronger
system to impact the region. Chances for precipitation look to
linger through Tuesday before the system finally pulls out of the
area. Will continue to monitor trends with this system.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 556 AM CDT Tue Mar 19 2024

VFR conditions are expected for the TAF period. Clear skies and
elevated winds begin the TAF period. While skies are clear, MVFR/VFR
stratus up in Canada may push into southwest Minnesota this
afternoon. There is some uncertainty as warming temperatures during
the morning may mix out this stratus before it gets to our area.
Good news is that this stratus will avoid all TAF sites.

Winds will remain out of the northwest today with gusts up to 20-25
knots expected. The strongest gusts will reside along and east of
the James River. Winds will wane this evening and begin to turn
northeasterly to end the TAF period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers


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