Area forecast discussion
National Weather Service Sioux Falls South Dakota
1100 PM CDT Monday Jun 17 2013
Update...
issued at 1043 PM CDT Monday Jun 17 2013
Quick update to include 20 probability of precipitation across the Highway 14 corridor.
Convection under upper short wave is mainly diurnally driven and
continues to weaken...however cannot rule out some elevated
showers/thunderstorms reaching the east central South Dakota and southwest
Minnesota zones tonight. Any storms should continue to be non
severe with MUCAPES of just a few hundred j/kg accompanying the
short wave.
Update issued at 618 PM CDT Monday Jun 17 2013
Isolated to scattered thunderstorms continue to develop along 1000 j/kg
MLCAPE axis across southwest South Dakota this evening. With short
wave over North Dakota pushing southeast...these storm could
persist and will likely follow the instability axis southeast
through south central South Dakota and the MO river this evening
and tonight. Have introduce probability of precipitation into the forecast accordingly.
Isolated large hail is possible with these storms this evening.
&&
Short term...(this evening through tuesday)
issued at 344 PM CDT Monday Jun 17 2013
A very quiet and pleasant period as high pressure moves in then
shifts east of the area. Marginally breezy conditions this afternoon
will diminish fairly rapidly this evening then become very light
overnight. This should allow for some fairly cool radiational low
temperatures. Models indicate weak shortwave tracking along the
Missouri River valley tonight. With relatively dry
environment...did not add mention of probability of precipitation this time...but lifting
from near 800mb indicates the outside chance of thunderstorms
early Wednesday morning. For now...left forecast dry but evening
crew may need to update. Will lower lows a bit and aim for lower
to middle 50s in most locations. With mostly sunny skies and dry
conditions on Tuesday will go fairly warm...lower to middle 80s. Went
below guidance on dew points through the day as guidance has been
overdoing that a bit lately and also ramped up temperatures in the
morning more quickly as that has also been the trend lately and it
looks like that should hold true for tomorrow.
Long term...(tuesday night through monday)
issued at 344 PM CDT Monday Jun 17 2013
Models continue to indicate the potential for isolated convection
across central South Dakota in warm air advection aloft early
Wednesday morning. Have continued 20 percent chance probability of precipitation west of
the James River Valley. Models indicate a shortwave will traverse
the forecast area on Wednesday creating a chance for showers and
thunderstorms. Right now...NAM is slightly further south than the
GFS taking the wave across the South Dakota/Nebraska border into
northwest Iowa through the evening hours. While wind shear appears
to be fairly unimpressive on Wednesday...tall thin cape profiles and
light winds in the middle levels of the atmosphere suggest the
potential for heavy rain exists. Precipitable water values are not extraordinarily
high ranging from 1.3-1.4 inches...but are still up towards the 75th
to 80th percentile for this time of year.
Precipitable water continues to increase towards the weekend as
strong unimpeded southerly flow originating in the Gulf continues
Thursday into Friday. Models continue to indicate the potential for
convection Thursday into Friday with unstable environment and
shortwaves tracking across the area ahead of an approaching upper
level low from the west. Have tried to concentrate probability of precipitation closer to
the surface front moving through the region Friday night through
Sunday. Front should gradually progress south through the
weekend...but with upper wave located well to the north there is
little in the way of forcing to drive the front south beyond
convection. Ahead of the front...atmosphere appears to be fairly
capped and should be warm and sticky with temperatures near 90 and
dew points near 70. With decent lapse rates from 500-700 mb and
modest wind shear in the middle levels...the potential for severe
weather over the weekend increases with threats being mainly large
hail and damaging winds.
&&
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1100 PM CDT Monday Jun 17 2013
VFR conditions with variable winds at or below 10 kts expected
through the taf period. Isolated showers/thunderstorms moving south-
southeast across the region through 10z-12z. Due to isolated nature
of the storms...unlikely that they will affect taf locations and have
not included any mention of precipitation in 06z tafs.
&&
Fsd watches/warnings/advisories...
South Dakota...none.
Minnesota...none.
Iowa...none.
NE...none.
&&
$$
Update...
short term...08
long term...
aviation...jh
