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Area forecast discussion 
National Weather Service Sioux Falls South Dakota
633 am CDT sun Mar 29 2015

Short term...(today and tonight)
issued at 433 am CDT sun Mar 29 2015

Winds and impact on fire weather capture full concern for short term
portion of the forecast.

Leading upper energy racing through the eastern County Warning Area early this
morning...taking spotty light showers quickly with it. Southerly low
level jet winds remain quite strong...with surface gusts 40 to 50
miles per hour in parts of SW Minnesota as showers pushed through...along with some
Buffalo Ridge enhancement. To the west...surface frontal boundary
marked on satellite by a narrow band of clouds east of the James
River Valley back toward Lower Brule area. Leading pressure rises
starting to collapse more southward through a bit of
stabilization in clear slot has allowed lesser winds for a time in
much of southeast South Dakota.

However...winds will get another boost this morning as main upper
trough currently swinging through northwest South Dakota races
east/southeast early this morning. Secondary area of pressure rises
will aid the 40-55kt northwesterly jet in drastically increasing
winds during the early to middle morning period...roughly accompanying
increase in lower clouds. These clouds...and an area of light
rainfall...will make a stronger southward push than previously
expected during the morning. While lower to middle level frontogenetic
precipitation band looks to make inroads east/southeast...will be
undergoing a gradual dissipation as it shears through around middle to
late morning. Therefore...expect a limited southward push to a lower
end measurable precipitation threat...probably no further south than
I 90. Total rainfall will be fairly minimal...several hundredths at
most across parts of east central South Dakota and northern SW Minnesota.

Winds will certainly become strong enough to support a Wind
Advisory...but will even have to watch the Buffalo Ridge area for
outside chance of High Wind Warning conditions as middle mixed layer
winds get close to strong enough later morning and midday. Winds
will start to drop off first in the west by early to middle
afternoon... with dropoff slowed a bit by mixing.

Things should rapidly quiet down this evening as surface ridge drops
into the Central Plains. With dry airmass...expect that lows tonight
may dip toward cooler end of guidance envelope...especially lower
spots...with typical weakening gradient favoring southwest
decoupling. Increase in higher clouds about the only thing to put
the brakes on radiative cooling.

Long term...(monday through saturday)
issued at 433 am CDT sun Mar 29 2015

Dry and warm conditions are expected for Monday/Tuesday...and have
favored warmer side of guidance for afternoon highs both days given
strong mixing potential Monday...and lack of widespread moisture of
late to keep the soils moist...which should aid in warming even in
slightly less favorable mixing on Tuesday. The breezier winds and
low humidity levels Monday will lead to very high fire danger across
the forecast area...with only moderate to high fire danger Tuesday
as surface ridge brings much lighter winds to the region.

Cold front still on track to push through the forecast area on
Wednesday...preceded by increasing low level moisture and gusty
southwest winds. Nose of elevated instability extends into the
central/eastern County Warning Area by daybreak Wednesday. Fairly Stout cap to
overcome...but cannot rule out some altocumulus castellanus showers Wednesday morning.
Better chance of precipitation will be ahead of the surface front Wednesday
afternoon...and this should be focused across the southeast half of
the County Warning Area. European model (ecmwf) on the slower side with timing...and have thus far
favored the faster GFS/Gem. Should be a decent thunder potential
with both GFS/European model (ecmwf) showing cape values greater than 1000j/kg ahead
of the boundary.

Broad middle level trough remains over the region Thursday...then
begins to shift eastward for Friday/Saturday. Main question for
precipitation chances late in the week will be how far south wednesday's
cold front will push through the plains as a secondary wave tracks
out of the central rockies. Gem remains farther north...and thus
spreads fairly decent chance of rain into the southern half of our
forecast area Thursday night/Friday. 00z European model (ecmwf) has trended farther
south like the GFS...keeping our area pretty much dry through the
latter part of the week. Will hang onto some low probability of precipitation in the south
to account for uncertainty.


Aviation...(for the 12z tafs through 12z Monday morning)
issued at 633 am CDT sun Mar 29 2015

Very strong northwest winds will generate the greatest aviation
hazard today. Winds will increase behind a secondary cold front
pushing into the James Valley around 12z. Winds will gust to
around 40 knots at times into early afternoon...before winds start
to slowly diminish west to east. Band of clouds featuring some light
precipitation will likely wrap a period of MVFR ceilings into khon
and kfsd during the morning...but skies will rapidly clear later
morning to midday with strong subsidence.


Fire weather...
issued at 433 am CDT sun Mar 29 2015

Not quite as straightforward issues with fire weather today. Some
of the strongest winds may actually occur during the later morning
as area of lower clouds moves through...and relative humidity likely to get a bit
of a boost with secondary area of very light rainfall sliding
through east central South Dakota and SW Minnesota middle to late morning. Any clouds
and precipitation will come to a quick demise by late morning...leaving
sun and wind to work on the rest of the day.

Decided to go with the red flag warning in those areas where lowest
humidity gets close to or exceeds 20/25 percent criteria...with
strong winds the deciding factor on pushing marginal conditions.
Despite fact that lowest humidity and strongest winds will be
somewhat off timed in the Lower Brule areas. Elsewhere...after
coordination call have maintained watch for east central South Dakota...SW
Minnesota...and Iowa Great Lakes area in northwest Iowa where lowest humidity is
much more highly in question...currently expected to remain 30 to 38
percent. Also have wild card of morning rainfall moving through the
northern and eastern fire weather zones. Albeit expectations of very
light precipitation...should be sufficient with wind and subsidence
to alter fine fuels fast enough to matter. Extreme fire danger today
for all areas.

Westerly flow on Monday should favor strong mixing...resulting in
afternoon wind gusts to around 25 miles per hour or slightly higher...along
with minimum humidity levels from 20 to 25 percent over much of the
the areas. Fire danger will be very high throughout the area...but
could approach extreme if winds become slightly stronger than

Strong pre and Post-frontal winds on Wednesday will lead to very
high fire danger at some point during the day throughout the County Warning Area.
The fire danger should decrease across northwest Iowa during the
afternoon as the front moves in and brings a decrease in winds and
increase in precipitation threat though. Deep northwest flow will dominate
across the area Thursday which should again be favorable for mixing
down some higher wind gusts and lower dew points in the afternoon.
This will lead to another day of very high fire danger for most


Fsd watches/warnings/advisories...
South flag warning from 1 PM this afternoon to 7 PM CDT this
evening for sdz255-256-258.

Wind Advisory until 7 PM CDT this evening for sdz040-055-056-061-

Wind Advisory until 1 PM CDT this afternoon for sdz038-039-050-

Fire Weather Watch from 1 PM CDT this afternoon through this
evening for sdz257.

Minnesota...Wind Advisory until 7 PM CDT this evening for mnz071-072-080-081-

Fire Weather Watch from 1 PM CDT this afternoon through this
evening for mnz900. flag warning from 1 PM this afternoon to 7 PM CDT this
evening for iaz300.

Wind Advisory until 7 PM CDT this evening for iaz001>003-012>014-

Fire Weather Watch from 1 PM CDT this afternoon through this
evening for iaz301. flag warning from 1 PM this afternoon to 7 PM CDT this
evening for nez249.

Wind Advisory until 7 PM CDT this evening for nez013-014.



Short term...Chapman
long term...jh
fire weather...Chapman/jh

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