Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 172016
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
316 PM CDT Sun Mar 17 2024

.KEY MESSAGES...

- Winds will be light for Monday afternoon out of the southwest.
  However, humidity levels remain low, 20-25%. This will result
  in High to Very High grassland fire danger Monday afternoon.
  High to Very High grassland fire danger persists through
  Wednesday.

- Colder air drives south Tuesday into Wednesday. This has a
  high chance of bringing near to below normal temperatures
  from Wednesday through next weekend.

- A more active weather pattern will set up by Thursday through
  next weekend. Model agreement is still poor so low confidence
  in timing of precipitation and related impacts. Those with
  weekend travel plans will want to begin to monitor the
  forecast as precipitation is more favored to be snow than
  rain.

&&

.DISCUSSION...
Issued at 310 PM CDT Sun Mar 17 2024

THIS AFTERNOON: Clouds will continue to thin out, and we will have a
mostly clear night. Gusty winds quickly subside after sunset. Lows
tonight will be mid to upper teens.

MONDAY: The surface pressure gradient (SPG) eases as surface high
pressure builds in from the northwest overnight. By sunrise winds
will be northwesterly around 5-10 mph with occasional gusts of
15 mph. As the high pressure moves southeast after noon, winds
will become westerly, then southwesterly. Conditions will be
very dry at the surface with dew points in the single digits,
and the corresponding relative humidity (RH) in the 20-25%
range. Bufkit soundings and ensemble cloud models indicate
afternoon mid to upper level stratus development. This could
work to limit highs somewhat to the 40s and low 50s. Though
grassland fire conditions will be in the High to Very High
category, the cooler temps and lighter winds should limit rapid
fire growth. But caution is still advised with sources of
ignition, as fuels are cured and ready to burn. Lows for Monday
night will be in the upper 20s to mid 30s.

TUESDAY: As a northern stream clipper system digs from the Canadian
Prairie into the Great Lakes Monday night, a cold front slides
through early Tuesday. This brings notably cooler air aloft for
Tuesday, but we should see one last mild day with highs in the 50s
and some 60s.

Expect stronger winds Tuesday than Monday with breezy northwest
winds gusting in the 20s Tuesday afternoon. High to very high fire
danger persists Tuesday afternoon across the region as gusty winds
combine with humidity levels below 30%. Model profiles suggest an
afternoon cumulus field would likely develop before we could mix
down enough dry air and stronger winds to develop critical fire
weather conditions, but this will be something to continue to
monitor given recent propensity to mix drier/windier than expected.

WEDNESDAY: A northwesterly upper jet streak pushes a colder, drier
Arctic High into the Northern Plains Tuesday night into early
Wednesday. Despite weakening winds, this should drop temperatures
into the teens and 20s Wednesday morning. Cold air advection aloft
and northerly flow during the day will make for a chilly day with
highs remaining colder than normal for this time of year - in the
30s to mid 40s. Even drier air brings continued elevated fire danger.

THURSDAY: A low to moderate (30-60%) chance for snow develops late
Wednesday night through Thursday as a mid level wave brings a band
of snow somewhere in the Northern Plains. At this stage, ensemble
guidance favors snow accumulations residing north of a line from
Huron and Madison SD to Windom MN with the heaviest amounts (maybe
up to a few inches of snow) even further north in North Dakota, far
northeast South Dakota, and west central Minnesota. However, there
will certainly be minor shifts in the system track over the next few
days. This combined with complex forcing associated with both an
inverted sfc trough and mesoscale Fgen forcing suggest those
traveling will want to monitor this period.

FRIDAY AND BEYOND: The Northern Plains is favored to remain on the
cool side of a quasi-stationary thermal gradient draped from the
Northern Rockies into the Central Plains and Ohio Valley/Southeast
next weekend. Although northwest flow turns more zonal by Friday,
proximity to the northern jetstream favors near to below normal
temperatures through the weekend.

As a longwave trough treks into the West, an early look into next
weekend and the following week favors periods of moderate or
occasionally high chances for precipitation. Precipitation during
this period is favored to be snow moreso than rain, but there is
very poor agreement in timing the progression of a complex series of
upper waves or details at this time.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1225 PM CDT Sun Mar 17 2024

Light flurries along and east of the James River Valley will
continue for the next couple hours and then dissipate. No
accumulation is expected and therefore no impacts are expected.
VFR over southeastern South Dakota, mix of MVFR and VFR over
southwestern Minnesota and northwestern Iowa. Expect clouds to
begin to lift over the next few hours and ceilings will increase
to VFR. Clouds will begin to scatter out late afternoon into
the evening. Winds will be gusting out of the northwest at 30-35
mph with some stronger gusts up to 40 mph until after sunset.
Winds decrease and become light, turning westerly to
southwesterly by the end of the period.

&&

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

&&

$$

DISCUSSION...AJP
AVIATION...AJP/BAP


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